sustainability

Article Advanced Techniques for Fast and Accurate Heritage Digitisation in Multiple Case Studies

Iñigo Leon * , José Javier Pérez and María Senderos Department of Architecture, University of the Basque Country UPV/EHU, Plaza Oñati 2, 20018 Donostia-San Sebastián, Spain; [email protected] (J.J.P.); [email protected] (M.S.) * Correspondence: [email protected]; Tel.: +34-943-01-7192



Received: 30 June 2020; Accepted: 24 July 2020; Published: 28 July 2020


Abstract: All elements of heritage are exposed to more or less predictable risks. Even though they are in a good state of conservation with economic support for their repair or maintenance, they can suffer sudden accidents leading to their imminent destruction. It is therefore necessary to safeguard them in all scenarios, regardless of the respective scale or state of conservation. That process must at least be based on complete and accurate 3D digitisation. The evolution of devices, software/hardware and platforms nowadays allows such information to be gathered in a sustainable manner. Various existing resources were tried and compared at several heritage sites of different scales with dissimilar risk and protection, following the guidelines of different ICOMOS (International Council on Monuments and Sites) committees. Each case study addresses the choice of digitisation techniques and the characteristics of the end product obtained. The most suitable modality for each situation is analysed, depending on different factors such as accessibility and risks faced. Although the 3D laser scanner is clearly a very fast and very accurate resource, automated photogrammetry is one of the more accessible and affordable resources; along with the potential of UAVs (unmanned aerial vehicles), this enables the digitisation to be sustainably completed.

Keywords: heritage; 3D laser scanning; automated photogrammetry; unmanned aerial vehicle (UAV); 3D model; building information modelling (BIM)

1. Introduction On 15 April 2019, the images of fire destroying the cathedral of Notre Dame in Paris were seen around the world. Other examples, such as the fire at the National Museum of Brazil in September 2018 [1], or the destruction of the Bamiy¯ an¯ Buddhas in Afghanistan, helped raise immediate awareness about the fragile state of many heritage sites. The risks they face are, in many cases, unpredictable, sometimes intentional and sometimes accidental. However, in any case, such losses highlight the need to establish preservation strategies, which must begin with accurate and sustainable digitisation of the heritage asset. The aim is to generate replicas of the heritage asset via 3D models with as little investment and in as short a time as possible. Even in the most well-conserved cases, such heritage assets face challenges of different natures which can become a real or hypothetical continual threat. A heritage asset may have sufficient economic backing to take care of maintenance and future renovations, yet in many cases it does not possess a thorough and accurate 3D model. The case of Notre Dame is a clear example of the lack of foresight in the building’s digital record. For this iconic Gothic cathedral, whose construction began in 1163 and ended in 1345 [2,3], there was no 3D digital model accurate enough to rebuild the features destroyed in the 2019 fire (the roof and spire, among others). Although there are three-dimensional captures of certain renovations using 3D laser scanning technology [4], they were never meant to provide a complete and accurate digital rendering to safeguard the asset in the future against eventual, sudden,

Sustainability 2020, 12, 6068; doi:10.3390/su12156068 www.mdpi.com/journal/sustainability Sustainability 2020, 12, 6068 2 of 29 unpredictable and catastrophic events with immediate and destructive impact. After the fire, the work done in 2010 by the Belgian art historian Andrew Tallon, is practically the only option that can be used to document the destroyed elements [5]. In 2010, a digital survey was conducted using a high-precision laser scanner, positioning the device at approximately 50 stations inside and outside the cathedral, obtaining 360◦ images that enabled the digital model to be mapped in colour, resulting in a quality model. However, the objective in this case was different; it was not meant to ensure effective and exact reconstruction in the wake of the disaster. Architectural heritage is threatened by two categories of risks: the unpredictable ones and the predictable ones associated with the intrinsic features of the heritage asset. Disasters have occurred in fortuitous circumstances caused by humans or due to forces of nature, which can affect any heritage asset, even when in a good state of conservation with means to preserve it. However, other risks stemming from human action must not be forgotten, such as intentional destruction of heritage or heritage buildings threatened by rapid urban expansion of cities. It is estimated that more than 50% of the population lives in urban settlements and that in 2030, virtually 60% of people will live in cities [6,7]. The fast pace of global population growth means that they suffer from pressures of the property market, which demands free space to build more housing. However, the most obvious risk for heritage is probably the lack of means for the respective preservation and the deterioration over time due to aging and lack of maintenance. It is hard to protect all heritage spread around the world to the same extent and at the same time. Some historic buildings and monuments are apparently at much more risk than others, so a scale of priorities must be established if the aim is to optimise resources to achieve effective and sustainable preservation [8]. However, even in cases without obvious risk, it is indispensable to have sufficient information on hand to preserve these heritage sites before they deteriorate or are destroyed. Digitisation can enhance understanding of the cultural heritage and respective values, while new tools enable better management and control of heritage as well as appropriate conservation. Moreover, publicising heritage via formats that actively explain its meaning and value helps raise public awareness; this is the surest way to preserve it. At present, the respective documentation should be based on obtaining a 3D model with sufficient textured geometric information, to which additional information (alphanumeric, video or virtual) can be added to ensure effective and sustainable preservation. To safeguard and protect in the long term, there are now state-of-the-art techniques based on massive point capture, enabling fast and accurate digitisation that can be adjusted to different economic circumstances, even when there is no management plan for the asset. The main aim of the research was to try and to analyse different devices, software and platforms, both to capture the 3D reality and for dissemination or museum exhibition of the heritage to preserve. The latest market trends were worked with, especially modern automated resources that enable universal dissemination with open access as well as sustainable preservation and management of the heritage [9,10]. Several heritage sites of different scales were studied, with various protection levels and disparate degrees of conservation and risk. This was done following the guidelines of different scientific committees of ICOMOS (International Council on Monuments and Sites) and other international organisations devoted to disseminating the theory, methodology and technology applied to conserving, protecting and enhancing the value of cultural heritage. The pros and cons for each case were compared so that the most efficient workflow in each type of heritage asset analysed could be chosen. It was verified that the particular constraints of each heritage asset generate unique problems that require the mastery of different resources with specific features, which in many cases must be used in a combined manner. Ultimately, it can be stated that modern non-invasive universal resources are available on the market, enabling a 3D model of the object analysed to be obtained quickly and with precision. This facilitates the sustainable preservation of any heritage element. Sustainability 2020, 12, 6068 3 of 29

2. Materials and Methods Bearing in mind the previously mentioned aim of the research, four heritage sites or monuments were chosen, situated in the Basque Country in southwest Europe, classifying them in three groups: heritage sites, heritage built of wood and heritage buildings embedded in the urban fabric. The selected heritage asset was described, indicating the risks it faces. Based on this problem, the kind of documentary record needed for each case could be determined. The purpose of the documentary record was also analysed, along with the choice of techniques most appropriate for each situation and the difficulties for the respective realisation.

2.1. Heritage Sites The Managing Cultural World Heritage manual of UNESCO sets out basic guidelines for developing heritage management plans. Its central core provides a common framework for documenting heritage management systems, establishing a series of processes, among which data collection, including in monitoring processes, is fundamental. The manual warns that such systems must be able to deal with risks deriving from unpredictable events such as natural disasters or damage generated by human destructive action [11]. At the same time, the International Committee on Interpretation and Presentation of Cultural Heritage Sites (ICIP) of ICOMOS considers interpretation and presentation to be part of the overall process of conservation and management of cultural heritage, and establishes that graphic information sources should be based on systematic and detailed data analysis [12]. For all these reasons, the new digital techniques for data collection and three-dimensional rendering may, in coming years, become an indispensable tool for development of the processes that make up heritage site management systems [13]. Although the record from geographic information systems (GISs) already forms a part of such management systems, including digital terrain data, area demarcations, cadastral information, landscape types and accessibility, etc. [14], the new digital techniques hugely expand the operative scenario for data gathering, largely limited by the traditional tools—topographical instruments, photography, video and 2D/3D planimetrics. Beyond reliable and comprehensive data collection, such records must be converted into information that can be integrated in a system accessible to all agents involved in the respective management [11]. In this regard, the last few years have witnessed the irruption of BIM (building information modelling) technology applied to the documentation of built heritage. Architects, along with archaeologists, conservationists and engineers, have considered this technology a disruptive force able to change the way that heritage is documented and administered [15]. Consequently, proposals based on collaborative HBIM (historical building information modelling) technology, accessible and interoperable via internet and enabling integration and management of indicators of different formats, have become increasingly common [16]. HBIM’s implementation is conceived as being an integrated process of information-gathering, 3D modelling and database design [17], wherein the capture of geometric information is established as a step prior to the modelling. In this regard, data acquisition using massive point-capture technology, which basically includes close-range photogrammetry and TLS (terrestrial laser scanner), resulted in an advance that has been extensively studied [18–21]. However, the dissemination in recent years of automated applications for planning and control of UAV (unmanned aerial vehicle) photography operations and the novel appearance of dynamic TLS-captures signifies a new enlargement of the panorama of the heritage documentation phase.

Salt Valley of Añana. World Heritage Candidate in 2013 The use of both data-capture techniques was studied in the Salt Valley of Añana, included in UNESCO’s indicative list of World Heritage candidates in 2013. The aim was to obtain a three-dimensional rendering of the site (3D shape reconstruction) as a step prior to the 3D modelling, enabling development of a BIM model to improve its management system. Sustainability 2020, 12, 6068 4 of 29

The Salt Valley of Añana is one of Europe’s best conserved interior salt production complexes [22], recognised by the United Nations Food and Agriculture Organisation (FAO) as being Europe’s first Globally Important Agriculture Heritage System (GIAHS) (Figure1). Since the first Salt Valley Master Sustainability 2020, 12, x 4 of 29 Plan was produced (2000–2004), its main goals have been to recover and conserve its material and techniques,environmental and heritage,develop initiativ re-establishes th saltat boost production social, tourism using traditional-related and and economic sustainable development techniques, of theand region develop. The initiatives architecture that boostof the social,salt evaporation tourism-related beds, andgenerated economic over development centuries, has of e thexceptional region. Thevalue architecture owing to ofits the adaptation salt evaporation to the beds,site and generated because over the centuries, original hasforms, exceptional functions, value mate owingrials toand its techniquesadaptation to of the traditional site and because construction the original compris forms,ing this functions, enormously materials rich and sustainable techniques heritage of traditional have beenconstruction maintained comprising [23]. this enormously rich sustainable heritage have been maintained [23].

Figure 1. PanoramicPanoramic view view of of the the Añana Añana Salt Valley: Basque Country, Spain (Source: Basotxerri).

The salt works encompass an area of approximately 15 ha, occupied by a group of wooden buildings in the form of stepped terraces that house the salt production beds beds,, served by an intricateintricate system of channels,channels, shapingshaping anan exceptional exceptional and and very very geometrically geometrically complex complex landscape. landscape. Indeed, Indeed, one one of ofthe the main main problems problems of theof the documentary documentary process process applied applied in thein the framework framework of theof the master master plan plan was was the theuse ofuse a two-dimensional of a two-dimensional geographic geographic information informatio systemn system [24] that [24] was that unable was to unable depict thatto depict geometric that geometriccomplexity. complexity. The plan The therefore plan therefore required required the production the production of a 3D Autocadof a 3D Autocad model, model, for which for which it was itnecessary was necessary to collect to andcollect represent and represent discrete discrete data for data three for years. three Due years. to itDue being to a it vector being standard,a vector standard,this model this does model not permit does not interrelationship permit interrelationship between geometric between data geometric and information data and information during the duringmonitoring the monitoring process, thereby process, hampering thereby thehampering implementation the implementation of basic information: of basic stateinformation: of conservation, state of conservationmaintenance, work, maintenance production, work, cultural production, and tourism cultural impact, and and tourism environmental impact, and analysis, environmen etc. tal analysis,The etc. study begins with the assumption that the combination of UAV data collection and the SfM (structureThe study from begins motion) with automated the assumption photogrammetry that the combination method facilitates of UAV heritage data collection documentation and the SfM due (structureto the simplicity from motion) of the process automated and photogrammetry the extent of the workingmethod facilitate range [25s, 26heritage]. The documentation study centres on due an toassessment the simplicity of the of operability the process and and eff theectiveness extent o off the automatedworking range flight [25,26] mode. appliedThe study to takingcentres photos on an assessmentvia UAV and of thethe noveloperability appearance and effectiveness of dynamic of TLS-capture the automated in an flight environment mode applied where to the taking complexity photos viaof the UAV respective and the novel geometric appearance configuration of dynamic (extent TLS of-capture the group, in anmultiplicity environment of where elements the complexity and levels, pathwayof the respe limits)ctive makesgeometric it extremely configuration difficult (extent to capture of the data group, using multiplicity photogrammetry of elements techniques and levels, and TLS,pathway which limits) require makes instrument it extremely stationing. difficult The to capture UAV used data is using a DJI photogrammetry Phantom 4 pro model, techniques equipped and withTLS, awhich 20 Mpx require effective instrument CMOS 1” stationing. sensor and The a focal UAV distance used is of a 35 DJI mm, Phanto whichm reduces4 pro model, radial equipped distortion withand improves a 20 Mpx the effective metric CMOSquality 1” of sensorthe SfM and restitution a focal distancemethod [ of27 ]. 35 The mm, UAV which is controlled reduces radial by a programmabledistortion and improves application the (DJI-GS metric Pro),quality which of the enables SfM rest configurationitution method of the [27] flight. The mission UAV is by controlled means of bynavigation a programmable based on satelliteapplication positioning (DJI-GS (GNSS).Pro), which enables configuration of the flight mission by means of navigation based on satellite positioning (GNSS). With the aim of documenting the entire group of salt work structures, as well as part of the surrounding area, a grid composed of 44 square sectors measuring 71 m per side with an area of 0.5 ha was created, establishing a low-altitude (20 m) flight parameter to ensure accuracy of the model (Figure 2a) [28]. This altitude provides a GSD (ground sampling distance) factor of 0.5 cm/pixel with 75% frontal and lateral overlap between photos. Using a Leica TCR 407 total station, four ground control points (GCPs) were established per sector in UTM (Universal Transverse Mercator) Sustainability 2020, 12, 6068 5 of 29

With the aim of documenting the entire group of salt work structures, as well as part of the surrounding area, a grid composed of 44 square sectors measuring 71 m per side with an area of 0.5 ha was created, establishing a low-altitude (20 m) flight parameter to ensure accuracy of the model (Figure2a) [ 28]. This altitude provides a GSD (ground sampling distance) factor of 0.5 cm/pixel with 75% frontal and lateral overlap between photos. Using a Leica TCR 407 total station, four ground Sustainability 2020, 12, x 5 of 29 control points (GCPs) were established per sector in UTM (Universal Transverse Mercator) coordinates, using 35 35 cm targets. The CPGs were positioned based on the following criteria: First, the placement coordinates,× using 35 × 35 cm targets. The CPGs were positioned based on the following criteria: First, theof targets placement 1, 2, 3of and targets 4 on 1, the 2, edges3 and of4 on each the sector, edges close of each to the sector, vertices close of to the the delimiting vertices of square, the delimiting ensuring square,the greatest ensuring possible the greatest distance possible between distance them inbetween the XY themplane; in second,the XY plane; their staggeredsecond, their arrangement staggered arrangewith respectment towith the respectZ axis, tryingto the toZ axis, ensure trying the maximum to ensure possiblethe maximum elevation possible difference elevation between difference targets between1 and 4 and targets locating 1 and the 4 other and targetslocating 2 theand other 3 equidistantly. targets 2 and This 3 was equidistantly. done to guarantee This was the done highest to guaranteehorizontal the and highest vertical horizontal precision and of the vertical model precis [29]. ion of the model [29]. BearingBearing in in mind mind the the need for accurate documentation of of the vertical structural supports and and masonrymasonry walls walls that that support support the the wooden wooden frameworks frameworks on on which which salt salt is is produced, produced, and and considering considering that that thethe exclusive exclusive use use of of nadir nadir shots shots offers offers less less precise precise results, results, particularly particularly in in geometric geometric description description of of the the vertical planes [30], the use of nadir shots (Gimbal angle of 90 ) and oblique shots (Gimbal angle of vertical planes [30], the use of nadir shots (Gimbal angle of −–90°◦) and oblique shots (Gimbal angle of 45 ) was combined. One nadir shot and four oblique shots were thus done per sector, with the latter –−45°◦) was combined. One nadir shot and four oblique shots were thus done per sector, with the latter aligalignedned to to the the four four trajectories trajectories that join the vertices of each sector with its centre (Figure2 2bb,c).,c).

(a) (b) (c)

FigureFigure 2. ((aa)) Work planningplanning inin 44 44 sectors; sectors; ( b()b Flight) Flight configuration configuration in in one one of theof the sectors sectors with with DJI-GS DJI- Pro;GS Proalso; also position position of 4 of targets 4 targets and an thed the station; station (c); Planning(c) Planning of shootingsof shootings in onein one of theof the sectors, sectors, from from top top to tobottom: bottom: 1. 1. Shooting Shooting overlap, overlap, 2. 2.Nadiral Nadiral shootingshooting/G.P.A.:/G.P.A.: −9900º/C.A.:º/C.A.: 0º, 0º, 3. Oblique Oblique shooting/G.P.A. shooting/G.P.A.:: − −4455º/C.A.:º/C.A.: 45º, 45º 4., 4.Oblique Oblique shooting/G.P.A.: shooting/G.P.A.: −45º/C.A.:45º/C.A.: 135º, 135 5. ºOblique, 5. Oblique shooting/G.P.A.: shooting/G.P.A.: −45º/C.A.:45º/ 225º,C.A.: − − − 6.225 Obliqueº, 6. Oblique shooting/G.P.A.: shooting/G.P.A.: −45º/C.A.:45 º315º,/C.A.: 7. 315Orthophoto,º, 7. Orthophoto, (G.P.A: Gimbal (G.P.A: GimbalPitch Angle; Pitch C.A: Angle; Course C.A: − Angle)Course (Source: Angle) (Source:Authors). Authors).

DueDue to to the the extremely extremely d diifficultfficult access, access, and and the the narrowness narrowness and and the the low low clearance clearance of of many many of of the the spacesspaces situated situated under under the the salt evaporation beds beds,, data collection using photogrammetric techniques oror TLS that require tripod stationing is pra practicallyctically undoable. The The capture capture of of the the pillars, beams beams and and structuralstructural frameworksframeworkshidden hidden under under the the beds beds was was therefore therefore done done using using a Leica a BLK2GO Leica BLK hand2GO scanner, hand scanner,just released just released on the market on the in market 2020. Thisin 2020. 3D laserThis scanner3D laser captures scanner imagescaptures and images point and clouds point in motionclouds inand mo real-time,tion and real using-time, SLAM using (simultaneous SLAM (simultaneous localisation localisation and mapping) and mapping) technology technology to record itsto record course itsthrough course the through space [ the31– 33 space]. The [31 scanner–33]. The combines scanner double-axis combines double LiDAR,-axis a 4.3 LiDAR, Mpx a360 4.3◦ panoramic Mpx 360° panoramicviewing system, viewing a 12 system, Mpx high-resolution a 12 Mpx high camera-resolution for detailed camera photos for anddetailed an inertial photos measurement and an inertial unit measurementthat enables self-navigation, unit that enables capturing self-navigation, 420,000 pts capturing/s, with a 420,000 capture pts/ ranges, with of 0–25 a capture m. The range performance of 0–25 m.of theThe system performance based on of SLAMthe system technology based oonffers SLAM relative technology precision offers of 6–15 relative mm and precision absolute of positioning 6–15 mm andprecision absolute of 20 positioning mm for maximum precision scans of 20 ofmm 2 min for maximum (Figure3). scans of 2 min (Figure 3). SustainabilitySustainabilitySustainability 20202020 20, ,201122,, 1,x2 6068 , x 6 6of 6 of29 of 29 29

(a) (b) (c) (a) (b) (c) Figure 3. (a) BLK2GO ready to start the itinerary; (b) Capture in motion of wooden structures under FigureFigurethe salt3. 3. ( a(pansa) )BLK2GO BLK2GO (c) Capture ready ready display to to start start in the real the itinerary;- itinerary;time on any (b (b) )mobileCapture Capture device in in motion motion (Source: of of Authors).wooden wooden structures structures under under thethe salt salt pans pans (c (c) )Capture Capture display display in in real real-time-time on on any any mobile mobile device device (Source: (Source: Authors). Authors). Four itineraries of less than two minutes were executed, computing a course with a total length ofFour Four 75 m iitinerariestineraries in a previously of of less less delimitedthan two minutes area of 0.125 werewere executed, ha,executed the aim,computing computing being to adetermine a course course with with the a equipment’sa total total length length of of75 75performance m inm ain previously a previously with delimited respec delimitedt toarea scanning of area 0.125 of ha, range 0.125 the aim and ha, being the power aim to determine and being thereby to thedetermine evaluaequipment’ste the the equipment’s performance method’s performancewithoperability respect to with(Figure scanning respec 4). ranget to and scanning power range and thereby and power evaluate and the thereby method’s evalua operabilityte the (Figure method’s4). operability (Figure 4).

FigureFigure 4. 4.Scan Scan path, path, real-time real-time pointpoint cloud,cloud, and detail photo photo position position (Source: (Source: Authors). Authors).

2.2.2.2. Heritage HeritageFigure Built Built 4. of Scanof Wood W oodpath, real-time point cloud, and detail photo position (Source: Authors). InIn its itsprinciples principles for conservation for conservation of heritage of heritage built of built wood, of the wood, ICOMOS the ICOMOS International International Committee 2.2.onCommittee WoodHeritage (IIWC) B uilton of Woodrecognises Wood (IIWC) the recognises importance the of importance the documentary of the documentary process to tackle process the increasingto tackle the loss ofincreasing historicIn its wooden principles loss of historic structures for conservationwooden due structures to their of vulnerability heritage due to their built vulnerability to climate of wood, conditions, to the climate ICOMOS conditions, natural International and natural specific Committeetoand the surroundings, specific on Wood to the surroundings,and(IIWC) to the recognises destructive and to the the actionimportance destructive of humans. of action the documentary It of also hum highlightsans. It process also the highlights importanceto tackle the the of increasingeducationalimportance loss programmes of historic education wooden foral awareness,programmes structures recognition for due awareness, to their and vulnerability understanding recognition to and ofclimate theunderstanding respective conditions, values ofnatural the and andculturalrespective specific significance. tovalues the surroundings, and The new cultural digital significancand techniques to thee. destructive The for three-dimensional new digital action techniques of hum geometricans. for It rendering threealso - highlightsdimensional and visual the geometric rendering and visual depiction may help minimise the effects of that vulnerability and importancedepiction may of help education minimiseal programmes the effects of for that awareness, vulnerability recognition and prove to and be fundamentalunderstanding in policies of the prove to be fundamental in policies meant to conserve and sustainably develop that heritage [34]. respectivemeant to conservevalues and and sustainably cultural significanc develope. that The heritage new [digital34]. techniques for three-dimensional Despite its small territorial extent, the Basque Country retains substantial heritage built of wood, geometricDespite rendering its small and territorial visual depiction extent, themay Basque help minimise Country the retains effects substantial of that vulnerability heritage built and of comprising the carpentry work used in the structures, frameworks and ceilings of nearly a hundred provewood, to comprising be fundamental the carpentry in policies work meant used to conserve in the structures, and sustainably frameworks develop and that ceilings heritage of [34] nearly. churches and several hundred farmsteads [35–37]. Some authors have highlighted the singular nature a hundred churches and several hundred farmsteads [35–37]. Some authors have highlighted the ofDespite Basque itscarpentry, small territorial not just in extent the Spanish, the Basque and French Country context retains [36, substantial38] but also heritage as the repository built of wood, of a compsingularrising nature the carpentry of Basque work carpentry, used in not the just structures, in the Spanish frameworks and Frenchand ceilings context of [nearly36,38] a but hundred also as churchesthe repository and several of a veryhundred archaic farm traditionsteads [35 in–37 the]. Some European authors scope have [39 highlighted]. The origin the singular of this wooden nature of Basque carpentry, not just in the Spanish and French context [36,38] but also as the repository of a Sustainability 2020, 12, 6068 7 of 29

Sustainability 2020, 12, x 7 of 29 heritage was traditionally situated in a period between the end of the 15th century and the first half ofvery the 16tharchaic century tradition [40 in], the coinciding European with scope the [39] territory’s. The origin pacification of this wooden [41,42 heritage] and itswas profound traditionally urban transformationsituated in a period [43]. Somebetween investigations the end of the have 15th corroborated century and thisthe first idea, half dating of the such 16th structures century [40] to, the firstcoincidin half ofg thewith 16th the centuryterritory’s [44 pacification]. However, [41,42] recent and research its profound has indicated urban transformation dates that go [43] back. Some to the mid-15thinvestigations century have [45 ],corroborated proposing athis revision idea, dating of the such historiographical structures to the bases. first half of the 16th century [44]Despite. However, the recognition,recent research protection has indicated and awareness dates that of some go back paradigmatic to the mid examples-15th century [46], this[45], is a proposing a revision of the historiographical bases. very vulnerable heritage, threatened by multiple factors and basically characterised, in the case of the Despite the recognition, protection and awareness of some paradigmatic examples [46], this is a churches, by disuse and vacancy caused by the secularisation of the Catholic religion [47]. Additionally, very vulnerable heritage, threatened by multiple factors and basically characterised, in the case of the the numerous examples, their dispersal in the territory and the system governing privately owned churches, by disuse and vacancy caused by the secularisation of the Catholic religion [47]. property make it very hard to manage plans and investments that guarantee effective protection of Additionally, the numerous examples, their dispersal in the territory and the system governing suchprivately heritage. owned To that property vulnerability make itmust very be hard added to the manage general plans lack and of an investments accurate documentary that guarantee record ofeffective geometric protection and dimensional of such heri naturetage.that To thatcould vulnerability support the must asset’s be reconstruction added the general in the lack event of an of an unpredictableaccurate documentary disaster or record accident. of geometric and dimensional nature that could support the asset’s reconstrAn exampleuction in of the three-dimensional event of an unpredictable rendering disaster (3D shapeor accident. reconstruction) is shown, using digital techniquesAn example applied of to three the polychrome-dimensional wooden rendering frame (3D covering shape reconstruction) the interior of is the show churchn, using of San digital Andr és detechniques Ibarrangelua applied in Biscay. to the polychrome wooden frame covering the interior of the church of San Andrés de Ibarrangelua in Biscay. The Church TheThe Church Basque Autonomous Community concentrates more than 60 examples of churches with aestheticThe ceilings Basque of Autonomous wood or charpente Community apparente concentrates [48] in more an area than of 60 just examples over 1600 of churches km2. The with origin ofaesthetic these ceilings ceilings is of associated wood or charpente to the scant apparente financial [48] means in an availablearea of just to over many 1600 rural km2 temples. The origin to coverof theirthese chapels ceilings with is associated stonework to the vaults, scant sofinancial they had means to useavailable wood to [35 many]. Barring rural temples occasional to cover exceptions, their mostchapels cases with are stone situatedwork in vaults modest, so parishthey had churches to use wood or chapels [35]. Barring in small occasional settlements exceptions, far from most major urbancasescentres are situated and mainin modest communication parish churches arteries. or chapels They arein small generally settlements buildings far from without major continuous urban use.centres Hence, and in main most communicat cases, this ision a hidden arteries. heritage, They are barely generally known buildings and insu withoutfficiently continuous valued by use.society. Moreover,Hence, in the most high cases degree, this ofis territoriala hidden heritage, dispersal barely and theirknown location and insufficiently outside the valued main tourism by society. routes makesMoreover, it hard the to high generate degree financial of territorial income; dispersal this is and a major their inconvenience location outside that the hinders main to eurismfforts routes to revert makes it hard to generate financial income; this is a major inconvenience that hinders efforts to revert this situation. All this makes it a heritage group with a high degree of vulnerability. this situation. All this makes it a heritage group with a high degree of vulnerability. The church of San Andrés de Ibarrangelua is one of the most representative examples of this The church of San Andrés de Ibarrangelua is one of the most representative examples of this heritage. It counts a large polychrome wooden frame that covers the inside of the five-section nave, heritage. It counts a large polychrome wooden frame that covers the inside of the five-section nave, divided by four large diaphragm arches (Figure5a). The ensemble displays a rich and very striking divided by four large diaphragm arches (Figure 5a). The ensemble displays a rich and very striking polychromepolychrome repertoire repertoire in which in which iconographic iconographic elements elements from Christianfrom Christian tradition tradition and Italian and Mannerist Italian adornmentMannerist areadornment represented are represented (Figure5b). (Figure 5b).

(a) (b)

FigureFigure 5. 5.( a(a)) Polychrome Polychrome cocofferedffered ceiling of of the the church church of of San San Andrés André des de Ibarra Ibarrangelu,ngelu, Basque Basque Country, Country, Spain.Spain. (b ()b UAV) UAV (unmanned (unmannedaerial aerial vehicle)vehicle) inside flig flightht (Source: (Source: Authors) Authors).. Sustainability 2020, 12, 6068 8 of 29

Considering that close-range photogrammetry allows geometric recording of the heritage asset at low costSustainability and an 2020 acceptable, 12, x level of accuracy [49] and that the graphic environments of virtual8 of 29 and immersive reality can improve accessibility, awareness and understanding of the respective values [50], Considering that close-range photogrammetry allows geometric recording of the heritage asset it was decided to apply that methodology for the purpose of achieving three specific objectives: at low cost and an acceptable level of accuracy [49] and that the graphic environments of virtual and Toimmersive establish reality a low-cost can improve working accessibility, method awareness that is not and technically understanding complex, of the resp withective a high values degree • of[50] automation;, it was decided to apply that methodology for the purpose of achieving three specific objectives: To recordTo establish and document a low-cost the working heritage method asset inthat order is not to technically have a geometric complex, digital with a model high degree that supports of • its conservation;automation; To boostTo record awareness and document and knowledge the herita ofge heritage asset in values order byto have means a geometric of graphic digital depiction model techniques that • supports its conservation; based on virtual representation and immersive experience.  To boost awareness and knowledge of heritage values by means of graphic depiction techniques A Nikonbased D3400 on virtual photographic representation camera and withimmersive a CMOS experience. sensor, 23.5 mm 15.6 mm, 24.2 effective Mpx × was used,A with Nikon a NikonD3400 AF-Sphotogr Nikkoraphic camera f/1.8 G with objective. a CMOS The sensor, SfM processing23.5 mm × 15.6 software mm, 24.2 used effective was ReCap Photo,Mpx with was option used, towith make a Nikon use ofAF the-S Nikkor free educational f/1.8 G objective. licence The for SfM free pro processingcessing software of up used to 100 was photos and theReCap paid Photo, licence with for option processing to make up us toe of 300 the photos. free educational licence for free processing of up to 100 Takingphotos and into the account paid licence the size forof processing the study up object to 300 (30 photos.14 m), the photo shoot was divided into five × rectangles,Taking each into corresponding account the size to one of the of thestudy vaulted object sections(30 × 14 m covering), the photo the shoot nave, was with divided each rectangleinto five rectangles, each corresponding to one of the vaulted sections covering the nave, with each measuring approximately 6 14 m. The photo shoot was arranged using, as a reference, the parameters rectangle measuring approximately× 6 × 14 m. The photo shoot was arranged using, as a reference, the of average focus distance (10 m) and overlap between consecutive shots (horizontal/vertical 60%). parameters of average focus distance (10 m) and overlap between consecutive shots Each(horizontal/vertical rectangle was thus 60%). divided Eachinto rectangle a grid wa withs thus an divided interval into of 1.5a grid m thatwith determinesan interval of the 1.5 stationing m that of eachdetermines shot. Based the on stationing that grid, of fiveeach staticshot. Based sequences on that were grid, done five static using sequences a tripod: were one done orthogonal using a shot sequencetripod: and one four orthogonal 45◦ oblique shot sequence shots, perpendicular and four 45° oblique to the fourshots sides, perpendicular that define to the each four of sides the rectangles that (Figuredefine6). Aeach total of ofthe 200 rectangles photos (Figure were thus 6). A obtained total of 200 for photos each vaultedwere thus section obtained and for 1000 each photos vaulted in all, providingsection a and ratio 1000 of photos 2.38 photos in all, providing/m2. Using a ratio a Leica of 2.38 TCR photos/ 407m2 total. Using station, a Leica twoTCR GCP407 total control station, points weretwo established GCP control for eachpoints of were the vaultedestablished sections for each at localof the coordinates,vaulted sections using at local as reference, coordinates characteristic, using featuresas reference of the vaults’, characteristic polychrome features work, of the withvaults’ the polychrome aim being work, to scale with thethe photogrammetricaim being to scale the model. photogrammetric model. The static photo shoot was completed with a series of UAV-captures that The static photo shoot was completed with a series of UAV-captures that enable detailed orthogonal enable detailed orthogonal depictions of the polychrome work situated on the vertical planes of the depictionsdiaphragm of the arches. polychrome work situated on the vertical planes of the diaphragm arches.

FigureFigure 6. Shooting 6. Shooting methodology methodology and planning planning (S (Source:ource: Authors. Authors. Reference Reference image: image:Ars Lignea. Ars Las Lignea. Las iglesiasiglesias de madera del del País Pa íVasco)s Vasco).. Sustainability 2020, 12, 6068 9 of 29

Considering that virtual reality, 3D graphics and digitised objects no longer require any expensive equipment or specialised viewing hardware [51], after processing the photoset and obtaining a textured 3D digital rendering model (3D shape reconstruction), it was implemented in various formats accessible to the non-specialised public. The opportunities offered by virtual viewing web platforms were specifically studied, along with multiplatform viewing formats such as interactive PDF3D or viewing systems included in OS operating systems such as the interactive 3D viewer of Microsoft Windows 10.

2.3. Heritage Buildings Embedded in the Urban Fabric Each typological case study of heritage has its concrete risk, though there is one common problem that affects those heritage buildings that have become constricted with the urban fabric due to urban expansion caused by the increasing population. As this is a common issue that affects the whole world, it impacts buildings diversely, depending on their intended use and, above all, on the kind of ownership maintained. Social and economic change requires more and more buildable ground, and real estate pressure, above all, places buildings at risk that are not publicly owned. Within this common block, two very different cases will be studied, which affect the choice of methodology for the capture of reality in 3D: a 16th-century religious building converted into a museum and a 20th-century industrial building.

2.3.1. 20th Century Industrial Heritage: The Case of NCO (Nueva Cerámica de Orio) The Basque Country is one of the most important industrial zones in western Europe. Its location next to France on the Cantabrian coast, the existence of iron deposits and the strategic port of Bilbao have made it a reference in steelmaking. The Vizcaya Bridge, also called the Hanging Bridge of Portugalete, declared by UNESCO to be part of the World Heritage, is one example of Industrial Revolution iron architecture [52,53]. Along with this important industry, other production sectors such as textiles, paper and metallurgy have also developed. In the province of Gipuzkoa, a mountainous coastal region, industry was dispersed among urban centres some distance from each other. Their location was strongly influenced by the area’s orography, with chains of mountains surrounding the flat areas along valley floors [54]. This specificity entails a number of associated risks. The doctrine of the International Committee for the Conservation of the Industrial Heritage (TICCIH), which advises ICOMOS, highlights the importance of cataloguing, recording and researching industrial remains whose preservation is sought, stressing the need to protect them by taking sufficiently strong legal measures. Construction pressure nevertheless generates a lack of protection for many such buildings (Table1). The abundance of industrial buildings with heritage or architectural value makes it impossible to economically sustain such spaces [55]. The legal protection of some factories safeguards them in the first instance, though their disuse leads to much deterioration.

Table 1. Industrial heritage buildings in the province of Gipuzkoa only.

DOCOMOMO AVPIOP * EKOB * Registered 11 20 79 Protected 3 7 10 * Basque Associations for the protection of industrial heritage.

The demographic increase places these industrial buildings at risk. On the one hand, factories and workshops originally situated outside towns have become embedded in the urban fabric, and their coveted location means they are in danger. On the other, there is the risk of only protecting buildings with architectural value, demolishing the industrial complexes they pertain to. As expressed by the Nizhny Tagil Charter, these isolated buildings lose the value of being the “evidence of activities which had [ ... ] profound historical consequences” [56]; only the aesthetic value is maintained, due to the Sustainability 2020, 12, 6068 10 of 29

Sustainability 2020, 12, x 10 of 29 quality of their architecture. This decontextualisation considerably lowers the industrial heritage value industrial heritage value and impacts the public appeal and interest. It must not be forgotten that the and impacts the public appeal and interest. It must not be forgotten that the heritage value of these heritage value of these industrial complexes reflects social habits that make up the culture of the place industrial complexes reflects social habits that make up the culture of the place [56]. [56]. The case selected for this comparative study manifests one of the problems mentioned. It is the The case selected for this comparative study manifests one of the problems mentioned. It is the Nueva Cerámica de Orio (NCO) factory, situated between a fluvial channel and a national highway on Nueva Cerámica de Orio (NCO) factory, situated between a fluvial channel and a national highway the outskirts of a small coastal town (Figure7). The municipality’s urban expansion absorbed the lot on the outskirts of a small coastal town (Figure 7). The municipality’s urban expansion absorbed the where it was situated, leaving it totally constricted. This complex, formed by the factory, offices and lot where it was situated, leaving it totally constricted. This complex, formed by the factory, offices laboratory, enjoys general protection; the factory is the building with the most architectural value [57]. and laboratory, enjoys general protection; the factory is the building with the most architectural value The machinery is preserved, as well as the brick furnaces and chimneys, and the production process [57]. The machinery is preserved, as well as the brick furnaces and chimneys, and the production is easily understandable. The usual production of refractory material ended some time ago, though process is easily understandable. The usual production of refractory material ended some time ago, the building continues to be used as a warehouse. It enjoys a high degree of protection, but is still a though the building continues to be used as a warehouse. It enjoys a high degree of protection, but is high-risk heritage asset due to acceleration of its progressive deterioration. The flooded roof is not still a high-risk heritage asset due to acceleration of its progressive deterioration. The flooded roof is sufficiently impermeable, whereby water penetrates the building and runs along the façades. The old not sufficiently impermeable, whereby water penetrates the building and runs along the façades. The steel windows (very much used at the time) are rusted, and the process has sped up deterioration of old steel windows (very much used at the time) are rusted, and the process has sped up deterioration the façades. The objective of the digitisation work is consequently linked to the need for an urgent and of the façades. The objective of the digitisation work is consequently linked to the need for an urgent absolutely necessary intervention. and absolutely necessary intervention.

FigureFigure 7.7. Factory of Nueva CerCerámicaámica dede OrioOrio (NCO).(NCO). BasqueBasque Country,Country, SpainSpain(Source: (Source: Authors).Authors).

AllAll thesethese pathologiespathologies havehave resultedresulted inin aa buildingbuilding whosewhose morphologymorphology hashas changedchanged comparedcompared toto thethe originaloriginal edifice.edifice. UnlikeUnlike thethe previouslypreviously indicatedindicated cases,cases, thisthis isis notnot aboutabout undertakingundertaking anan exhaustiveexhaustive digitaldigital surveysurvey of the asset in it itss current current state, state, as as there there is is no no interest interest in in preserving preserving the the deformations deformations it itpresents, presents, which which,, in in many many cases cases,, measure measure several several centimetres. centimetres. The The aim aim is to is preserve to preserve the thevalues values of the of theoriginal original construction, construction, and and,, for that for that purpose purpose,, repair repair and andrenovation renovation will willbe nec beessary. necessary. Exhaustive Exhaustive data datacollection collection should should therefore therefore be accompanied be accompanied by a by restoration a restoration based based on documentary on documentary study study of the of thebuilding. building. The Theresearch research was wasable ableto obtain to obtain the project the project drawings drawings produced produced in 1941 in; 1941; they are they still are well still- well-preservedpreserved and andare arean indispensable an indispensable tool tool for for studying studying and and understanding understanding the the building, building, even thoughthough evidentevident didifferencesfferences betweenbetween thethe planplan andand whatwhat waswas eventuallyeventually builtbuilt have have been been verified. verified. TheThe NCONCO isis privatelyprivately owned,owned, withwith scantscant resourcesresources toto maintainmaintain oror investinvest inin it,it, andand isis openopen toto realreal estateestate interestsinterests that that could could enable enable its its renovation renovation and and reuse. reuse For. For all all these these reasons, reasons the, the preservation preservation of the of heritagethe heritage asset asset by means by means of a fastof a and fast accurate and accurate digital digital survey survey is indispensable, is indispensable, although although there are there barely are anybarely financial any financial means means for such for an such undertaking. an undertaking The digital. The di documentarygital documentary record record aims toaims define to de af 3Dine BIMa 3D consistent BIM consistent with its with original its original state, for state, subsequent for subsequent repair of the repair building, of the and building to achieve, and exhaustive to achieve documentationexhaustive documentation of the current of state, the current accurately state, compiling accurately the pathologiescompiling the to determinepathologies which to determine elements mustwhich be elements replaced must and whichbe replaced repaired. and Consideringwhich repaired. the secondConsidering aim, above the second all, for aim restoration, above all of, thefor restoration of the façades, it was deemed necessary to obtain textured 2D scale elevations, which will enable collapses and other pathologies to be studied. The digital survey was completed by the Sustainability 2020, 12, 6068 11 of 29 façades, it was deemed necessary to obtain textured 2D scale elevations, which will enable collapses and other pathologies to be studied. The digital survey was completed by the collection of video and photographic data to completely document the heritage asset, as the building presents areas of difficult visual access. The geographical features, the current use linked to a large accumulation of material inside, the lack of financial resources and the sorry state of conservation conditioned the techniques to use (Tables2 and3). Given the complexity of the model used and the diverse parameters a ffecting it, a survey was conducted in various phases, combining different techniques.

Table 2. Restrictions in outside data collection.

Legislation Activity in Geometric Characteristics of Climatology Exterior Access Restrictions Surrounding Area Complexity Materials Controlled Very complex due Reinforced Very rainy, with Uneven but UAV flight in to geometry of the concrete, flooded fog and mist, complicated. urban area. Residential area. surroundings and flat roof, steel complexity of North façade Need to block the interior windows. Large data collection. very difficult. road. Permits. structure. deformations.

Table 3. Restrictions in inside data collection.

Geometric Characteristics of Building Activity Interior Access Interior Lighting Complexity Materials Complex. Large Uneven. Well-lit Very complex, because Actively used. Reinforced concrete. amount of material. areas and others the structure is Abundant stored Deterioration of Existence of poorly lit. Capture adapted to the material. structural elements. inaccessible spaces. is complicated. furnaces.

In the first phase, a direct capture of specific points was produced, with total station, laser distance measurement and sketch done on site (Figure8a). For this purpose, a Leica Geosystems model TCR-407 total station was used. The work was done with typical deviation parameters (ISO 17123-4) with 5 mm + 2 ppm prism (IR), using a global coordinate system. Due to the difficult access to many points, the measurement was finished with a Leica D2 laser measurement device with typical measurement precision of 1.5 mm at 10 m. This enabled a reliable base to be obtained, in order to begin producing ± the BIM model. In the second phase, a survey was conducted using automated photogrammetry, using both the Nikon D-3400 digital camera and the Phantom 4 Pro UAV employed in previous work (Figure8b,c). These buildings situated in the urban fabric have an added complexity when using UAVs, because, in many cases, the buildings are founded in zones catalogued as CTR (controlled airspace), an extensive reserved control area around airports so that take-off and landing operations can safely proceed. In such areas, express permission from the responsible authority is required. In this case, the building is outside the CTR and also counts an extension of private land east of the plot which allows the UAV to take off and land in total security. The capture flights were done both inside and outside the building. Inside, the flight was done in A mode, with the indispensable skill of the pilot to fly with precision between the accumulated elements and manually take the photos to be used in the 3D photogrammetric survey (Figure8b). Outside, the flights were done in P mode with GPS, which allowed automated flights with pre-set photogram captures to be programmed, executed with precision in a very short time. Sustainability 2020, 12, 6068 12 of 29 Sustainability 2020, 12, x 12 of 29

(a) (b) (c)

Figure 8. ((aa)) 1st 1st capture capture phase, phase, total total station; station; ( (bb)) Indoor Indoor capture capture with with UAV; UAV; ( c) Outdoor capture with photographic camera (Source: Authors).

The possibility possibility of using using the the 3D 3D laser laser scanner scanner was was studied, studied, producing producing a scanning plan ove overr a a plan plan of the complex complex.. The The building’s building’s characteristics characteristics greatly greatly hindered hindered the the work, work, and and it it was considered that an incomplete job would would be be obtained obtained at at high high financial financial cost cost,, making making it it an an operation operation unsustainable unsustainable for for private property property.. Its effective effective use was thereforetherefore ruledruled out.out. 2.3.2. San Telmo, a Convent Converted into a Public Museum in the City’s Historic Centre 2.3.2. San Telmo, a Convent Converted into a Public Museum in the City’s Historic Centre The example selected for this analysis is the Museum of San Telmo, a 16th-century religious The example selected for this analysis is the Museum of San Telmo, a 16th-century religious monastery converted into a museum and situated in the historic centre of San Sebastián [58]. monastery converted into a museum and situated in the historic centre of San Sebastián [58]. The The building’s most important values consist of features built in sandstone exposed to continuous wear building’s most important values consist of features built in sandstone exposed to continuous wear caused by the saline environment. It is a building that experiences a major flow of people due to its use caused by the saline environment. It is a building that experiences a major flow of people due to its as a museum. It nevertheless has an effective management plan and presents a perfect state. It might use as a museum. It nevertheless has an effective management plan and presents a perfect state. It be said that it is not at risk of either real estate pressure or lack of maintenance, though it is not immune might be said that it is not at risk of either real estate pressure or lack of maintenance, though it is not from suffering a fortuitous and unexpected fatal incident. Indeed, the building’s cloister suffered immune from suffering a fortuitous and unexpected fatal incident. Indeed, the building’s cloister some damage in the citywide fire of 1813 and part of the original ashlar vaults have been replaced suffered some damage in the citywide fire of 1813 and part of the original ashlar vaults have been by plaster replicas suspended from a concrete framework. That intervention is not in line with the replaced by plaster replicas suspended from a concrete framework. That intervention is not in line principles of the ICOMOS charter for analysis, conservation and restoration of architectural heritage with the principles of the ICOMOS charter for analysis, conservation and restoration of architectural structures [59]. According to the recommendations of that charter, to preserve such elements in the heritage structures [59]. According to the recommendations of that charter, to preserve such elements future, there is an obvious need for effective collection and processing of data in order to determine in the future, there is an obvious need for effective collection and processing of data in order to an integral action plan, analysing the problem of the structural elements in stone [60]. Additionally, determine an integral action plan, analysing the problem of the structural elements in stone [60]. the need to understand the structure’s evolution from its original to its current state is indicated, with Additionally, the need to understand the structure’s evolution from its original to its current state is the indispensable compilation of a detailed record of the asset. Furthermore, the International Scientific indicated, with the indispensable compilation of a detailed record of the asset. Furthermore, the Committee on Risk Preparedness (ICORP) emphasises “the growing capacity of science and technology International Scientific Committee on Risk Preparedness (ICORP) emphasises “the growing capacity to enable the conservation and rehabilitation of cultural heritage” [61]. It is therefore necessary to of science and technology to enable the conservation and rehabilitation of cultural heritage” [61]. It make an inventory of heritage assets before possible disasters, as ICORP stipulates. is therefore necessary to make an inventory of heritage assets before possible disasters, as ICORP The building was originally a 16th-century monastery in which the cloister and the church stand stipulates. out (Figure9a). The large and narrow plot is squeezed between a street and a hillside with very The building was originally a 16th-century monastery in which the cloister and the church stand steep slopes. The typology, therefore, had to adapt and presents singularities such as, for example, out (Figure 9a). The large and narrow plot is squeezed between a street and a hillside with very steep the rhomboidal form of the floor plan. The proportions of the church space or the latticework of the slopes. The typology, therefore, had to adapt and presents singularities such as, for example, the cloister’s ground floor date to the Renaissance, while the latter’s vaults and the construction solutions rhomboidal form of the floor plan. The proportions of the church space or the latticework of the in general still pertain to the Gothic. In the 19th century, it was declared a national monument and cloister’s ground floor date to the Renaissance, while the latter’s vaults and the construction solutions placed under state protection. In 1928, the Provincial Monuments Commission made the decision in general still pertain to the Gothic. In the 19th century, it was declared a national monument and to restore the complex and turn it into a museum. In 2004, an expansion project was developed, placed under state protection. In 1928, the Provincial Monuments Commission made the decision to and in 2011, the new Museum of Society and Citizenship opened (Figures9b and 10). It is, therefore, restore the complex and turn it into a museum. In 2004, an expansion project was developed, and in a renovated building, much visited, which counts planning and sufficient financial backing to be 2011, the new Museum of Society and Citizenship opened (Figures 9b and 10). It is, therefore, a renovated building, much visited, which counts planning and sufficient financial backing to be managed and maintained by part of the public administration. It is also one of the city’s oldest Sustainability 2020, 12, 6068 13 of 29

SustainabilitySustainability 20 202020, , 1122, , xx 1313 ofof 2929 managed and maintained by part of the public administration. It is also one of the city’s oldest entirely preserved buildings. Apart from the obvious differences, we stand before a case similar to that of entirelyentirely preservedpreserved buildingsbuildings.. ApartApart fromfrom thethe obviousobvious differencesdifferences,, wewe standstand beforebefore aa casecase similarsimilar toto Notre Dame, as San Telmo is not immune from suffering a fortuitous accident like what happened in thatthat of of Notre Notre Dame, Dame, as as San San Telmo Telmo is is not not immuneimmune fromfrom suffering suffering a a fortuitous fortuitous accident accident like like what what the 1813 fire. Even after the recent expansion, it does not have a complete and accurate textured 3D happenedhappened inin thethe 18131813 fire.fire. EvenEven afterafter thethe recentrecent expansion,expansion, itit doesdoes notnot havehave aa completecomplete andand accurateaccurate model that could safeguard the heritage site against an unexpected disaster. texturedtextured 3D3D modelmodel thatthat couldcould ssafeguafeguardard thethe heritageheritage sitesite againstagainst anan unexpectedunexpected disadisaster.ster.

((aa)) ((bb))

FigureFigure 9. 9. ((aa)) Location Location mapmap inin 1728;1728; (( bb)) Map Map of of the the reform reform of of the the convent convent in in 2011 2011 (Source: (Source: SanSan TelmoTelmo MuseumMuseum ( (STM)).(STMSTM))).).

AlthoughAlthough therethere there areare are financialfinancial financial meansmeans means forfor for itsits its preventivepreventive preventive maintenance,maintenance, maintenance, iinn early inearly early 2019,2019, 2019, whenwhen when thethe 3D the3D digitaldigital3D digital survey survey survey wa wasswas conductedconducted conducted,,, the the the public public public ownership ownership ownership was was was not not not awar awar awareee ofof of the the the need need need to to to record record record a a comprehensivecomprehensive model model of of the the entire entire recently recently renovated renovated building, building, whereby whereby the the work work only only covered covered parts parts ofof thethe propertyproperty that that were were de deemeddeemedemed of of greate greatergreaterr interest. interest.

FigureFigure 10.10. GroundGround floorfloor ofof thethe 20112011 ReformReform projectproject (Source:(Source: SanSan TelmoTelmo MuseumMuseum ((STMSTM))).). Figure 10. Ground floor of the 2011 Reform project (Source: San Telmo Museum (STM)). TheThe cloistercloister areaarea waswas basicallybasically capturedcaptured withwith precision,precision, althoughalthough toto placeplace itit inin contextcontext,, transitiontransition elementselements werewere collected.collected. DuringDuring thethe firstfirst stage,stage, singulasingularr elementselements ofof thethe cloistercloister suchsuch asas thethe archesarches oror vaultsvaults were were also also captured, captured, and and during during thethe secondsecond stage stage,, thethe external external surroundings surroundings were were also also captured,captured, includingincluding nearbynearby buildingsbuildings andand MountMount UrgullUrgull ((FigureFigure 11)11).. Sustainability 2020, 12, 6068 14 of 29

The cloister area was basically captured with precision, although to place it in context, transition elements were collected. During the first stage, singular elements of the cloister such as the arches or vaults were also captured, and during the second stage, the external surroundings were also captured, includingSustainability nearby 2020, 12 buildings, x and Mount Urgull (Figure 11). 14 of 29

FigureFigure 11. 11.Model Model of of the the building building renovated renovated by by Nieto Nieto and and Sobejano Sobejano in in 2011, 2011, exposed exposed in in the the Museum Museum (Source:(Source: Authors). Authors). Bearing in mind that the museum is under controlled airspace in a historic centre, strict Bearing in mind that the museum is under controlled airspace in a historic centre, strict authorisations are required. This aspect, along with the fact that it abuts the southeast face of authorisations are required. This aspect, along with the fact that it abuts the southeast face of the hill, the hill, where, in addition, the GPS signal is weak, led to the exterior UAV flight being ruled out. where, in addition, the GPS signal is weak, led to the exterior UAV flight being ruled out. They were They were only used in manual mode for the building’s interior, to obtain detailed photos of inaccessible only used in manual mode for the building’s interior, to obtain detailed photos of inaccessible areas areas of the cloister’s arches and vaults, and to make a continuous detailed video flight of the ground of the cloister’s arches and vaults, and to make a continuous detailed video flight of the ground floor floor gallery of the cloister. The massive point capture was therefore achieved mainly with a 3D laser gallery of the cloister. The massive point capture was therefore achieved mainly with a 3D laser scanner. For that purpose, three devices of the Leica Geosystems brand were tried, with different scanner. For that purpose, three devices of the Leica Geosystems brand were tried, with different characteristics that are more or less suitable depending on the singularities of each proposed objective. characteristics that are more or less suitable depending on the singularities of each proposed In the first stage, to capture part of the building, the RTC360 and the BLK360 (F11a) were used objective. (Figure 12a). Recently introduced on the market, they stand out for three features: they are extremely In the first stage, to capture part of the building, the RTC360 and the BLK360 (F11a) were used light, there is no need to waste time on levelling, and they capture 360 spherical images in HDR (Figure 12a). Recently introduced on the market, they stand out for three◦ features: they are extremely in a short time, generating a cloud of colour points. They can also be linked to the Cyclone FIELD light, there is no need to waste time on levelling, and they capture 360° spherical images in HDR in a 360 application using a tablet or mobile phone to keep recording and relating scans as the work is short time, generating a cloud of colour points. They can also be linked to the Cyclone FIELD 360 carried out in the building. The RTC360 has a recording range of up to 130 m, which can entirely cover application using a tablet or mobile phone to keep recording and relating scans as the work is carried this building. Its measurement rate reaches 2 million points/second, which can be completed in two out in the building. The RTC360 has a recording range of up to 130 metres, which can entirely cover minutes. It is especially interesting from the efficiency standpoint, because it counts VIS technology, this building. Its measurement rate reaches 2 million points/second, which can be completed in two enabling it to record automatically and without targets the device’s movement from one scanning point minutes. It is especially interesting from the efficiency standpoint, because it counts VIS technology, to another, so that the partial point clouds are recorded in a spatial location related to the other scans, enabling it to record automatically and without targets the device’s movement from one scanning thereby facilitating the office work. The building’s scanning plan was made taking this device’s features point to another, so that the partial point clouds are recorded in a spatial location related to the other into account. The work started with an exterior scan in the square east of the building, from which the scans, thereby facilitating the office work. The building’s scanning plan was made taking this device’s museum is accessed. A total of 19 scans were completed, focusing, above all, on capturing the cloister features into account. The work started with an exterior scan in the square east of the building, from in detail. The BLK360 has a recording range of 60 m, collecting 360,000 points/second. Although this which the museum is accessed. A total of 19 scans were completed, focusing, above all, on capturing device is cheaper to rent than others, more time would have to be spent, because it requires more the cloister in detail. The BLK360 has a recording range of 60 m, collecting 360,000 points/second. scans and more in-office processing time than the other scanners used. Actually, its use would not be Although this device is cheaper to rent than others, more time would have to be spent, because it needed if the RTC360 is available, though it does have a couple of singular features that make it very requires more scans and more in‐office processing time than the other scanners used. Actually, its interesting. It has a 360 thermal camera that is very useful with respect to sustainability and energy use would not be needed◦ if the RTC360 is available, though it does have a couple of singular features efficiency for work associated to maintenance or facility management, and it is very small and only that make it very interesting. It has a 360° thermal camera that is very useful with respect to sustainability and energy efficiency for work associated to maintenance or facility management, and it is very small and only weighs 1 kg, so it could be easily raised by hand to capture hidden points at heights of over 2 m in the area of the vaults. In the second stage, the ScanStation P40 was used, with a range of up to 270 m and a scan speed of 1 million points/second. In this case, its use was of interest to capture the external surroundings of the museum, including nearby buildings and the hill the building abuts (Figure 11). This P40 scanner is older than the ones mentioned above, though it does have some interesting advantages for other Sustainability 2020, 12, x 15 of 29 which the museum is accessed. A total of 19 scans were completed, focusing, above all, on capturing the cloister in detail. The BLK360 has a recording range of 60 m, collecting 360,000 points/second. Although this device is cheaper to rent than others, more time would have to be spent, because it requires more scans and more in-office processing time than the other scanners used. Actually, its use would not be needed if the RTC360 is available, though it does have a couple of singular features thatSustainability make it2020 very, 12 , 6068interesting. It has a 360° thermal camera that is very useful with respect15 of 29 to sustainability and energy efficiency for work associated to maintenance or facility management, and it is very small and only weighs 1 kg, so it could be easily raised by hand to capture hidden points at weighs 1 kg, so it could be easily raised by hand to capture hidden points at heights of over 2 m in the heightsarea of of the over vaults. 2 m in the area of the vaults. In Inthe the second second stage, stage, the the ScanStation ScanStation P40 P40 was was used, withwith aa rangerange of of up up to to 270 270 m m and and a scana scan speed speed of of1 million 1 million points/ pointssecond/second.. In In this this case, case, its its use use was was of interest toto capturecapture the the external external surroundings surroundings of of thethe museum, museum, including including nearby nearby buildings buildings and and the hill the buildingbuilding abuts abuts (Figure (Figure 11 11).). This This P40 P40 scanner scanner is olderis older than than the the ones ones mentioned mentioned above, above, though though it does havehave somesome interesting interesting advantages advantages for for other other kindskinds of ofwork; work; it italso also has has disadvantages disadvantages that that can can slow down thisthis specificspecific survey. survey. On On the the one one hand, hand, eacheach scan scan point point must must be be levelled levelled with with a a great great deal deal of precision, although,although, in in interiors, interiors this, this process process can can be befacili facilitatedtated using using a wheeled a wheeled base base (Figure (Figure 12b) 12b).. On On the the other other hand, hand, the the scanner scanner weighs weighs more more than than 12 kg,12 and kg, to and move to moveit from it one from scan one point scan to point another to another,, it is recommendable it is recommendable to take to it takeoff the ito tripod.ff the tripod. Finally, theFinally, 360° image the 360 capture◦ image option capture is not option as efficient is not as as e ffiincient the other as in thetwo other models. two If models. the intention If the intentionis to obtain a colouredis to obtain point a coloured cloud, an point external cloud, digital an external camera digital perfectly camera calibrated perfectly in calibrated height is inused height (Figure is used 12c). It was(Figure therefore 12c). It waspossible therefore to capture possible the to capturehill and the surrounding hill and surrounding buildings buildings using few using scans few in scans a black in - anda- black-and-whitewhite cloud to optimise cloud to optimiseworking workingtimes. times.

(a) (b) (c)

FigureFigure 12. 12. (a)( BLK360a) BLK360 and and RTC360 RTC360 scanners scanners used used in inthe the first first phase; phase; (b ()b P40) P40 scanner scanner used used indoors; indoors; (c) P40(c ) scanner P40 scanner used used outdoors, outdoors, with with head head disassembled disassembled so so a a 360° 360◦ imageimage can be be taken taken with with external external camera.camera. (Source: (Source: Authors). Authors).

AlthoughAlthough the the public public administration administration does does not not see see the the need need to toobtain obtain an an accurate accurate 3D 3D model, model, the the work carried out, besides producing a textured 3D model, enabled the research to address two work carried out, besides producing a textured 3D model, enabled the research to address two aspects of interest for this building: the obtaining of a BIM model for sustainable management and aspects of interest for this building: the obtaining of a BIM model for sustainable management and maintenance of the museum, and the possibility of building replicas of stone elements by means of maintenance of the museum, and the possibility of building replicas of stone elements by means of advanced manufacturing. advanced manufacturing. 3. Results 3. Results 3.1. Salt Valley of Añana 3.1. SaltData Valley collection of Añana by means of UAV-assisted close-range photogrammetry, organised using flight controlData andcollection planning by software,means of enables UAV-assisted a digital close terrain-range model photogrammetry, to be obtained for organised the entire Saltusing Valley flight controlcomplex, and using,planning for thatsoftware, purpose, enables less thana digital 48 actual terrain flight model hours. to be This obtained implies for a very the substantialentire Salt Valley cost reduction compared to those using data collection by means of static photogrammetry techniques and TLS, which require instrumental stationing (Table4). Sustainability 2020, 12, x 16 of 29

complex, using, for that purpose, less than 48 actual flight hours. This implies a very substantial cost reduction compared to those using data collection by means of static photogrammetry techniques and TLS, which require instrumental stationing (Table 4). Given the size of the intervention area, the programming of flight missions enables more efficient Sustainability 2020, 12, 6068 16 of 29 management of the photo-taking process. This allows, with the necessary periodicity, repetition of the photo shoot, reproducing the flight itinerary and altitude, alignment, position and number of shotsGiven. The methodology the size of the is intervention thus adjusted area, to thethe programmingUNESCO Managing of flight Cultural missions World enables Heritage more guidelines efficient managementfor the monitoring of the phase, photo-taking as it is process.a systematic This methodology allows, with thethat necessary minimises periodicity, the subjectivity repetition of the of data the photocollection shoot, process, reproducing allowing the repetition flight itinerary and comparison and altitude, in time alignment, [11]. position and number of shots. The methodology is thus adjusted to the UNESCO Managing Cultural World Heritage guidelines for the monitoring phase, asTable it is a4. systematicSummary of methodology UAV photogrammetry that minimises capture data the. subjectivity of the data collection process, allowing repetition and comparison in time [11]. Flight Ground Sample Nadir Shot Oblique Shot Frontal Lateral Flight Sectors Batteries Photos Height Distance GSD (−90°) (−45°) Overlap Overlap Time Table 4. Summary of UAV photogrammetry capture data. Sector type 20 m 0.5 cm/pixel 1 4 75% 75% 55 min 4 sets 700 0.5 ha Ground Nadir Oblique Flight Frontal Lateral Flight Sectors Sample Shot Shot Batteries Photos Set of sectors Height Overlap Overlap Time 2420 20 m Distance0.5 cm/pixel GSD ( 4490 ◦) ( 17645◦ ) 75% 75% 176 sets 30,800 22 ha − − min Sector type 20 m 0.5 cm/pixel 1 4 75% 75% 55 min 4 sets 700 0.5 ha Set of sectors This procedure20 m does 0.5 cmnot/pixel offer a 44 sufficiently 176 precise 75% geometric 75% description 2420 min 176 of setsvery 30,800 slender features22 ha, such as the structural supports at the edges of the salt production platforms, and it evidently does not enable capture of the set of structural elements hidden under those platforms. ThisThe procedure use of a hand does not scanner offer awith suffi SLAMciently precisetechnology geometric enables description completion of very of the slender digital features, model suchobtained as the using structural UAV- supportsassisted close at the-range edges photogrammetry, of the salt production facilitating platforms, the andrecording it evidently of geometry does not of enablelimited capture or hidden of the access. set of structural It was thus elements possible hidden to describe under those the geometry platforms. of the hidden wooden structuresThe use (po ofles a hand, beams scanner and joists with) SLAM (Figure technology 13). The linkage enables of completion different itiner of thearies digital allowed model an obtained area of using0.125 UAV-assisted ha, including close-range those hidden photogrammetry, spaces, to be recorded facilitating in the eight recording minutes of (Figuresgeometry 14 of and limited 15). orA hiddenscanning access. estimate It was for thus the possibleentire Salt to Valley describe complex the geometry was made, of the computing hidden wooden a total structures of 28 h of (poles, actual beamsscanning and (Table joists) 5). (Figure 13). The linkage of different itineraries allowed an area of 0.125 ha, including those hidden spaces, to be recorded in eight minutes (Figures 14 and 15). A scanning estimate for the entire Salt Valley complexTable 5. wasSummary made, of computing BLK2GO dynamic a total 3D of 28laser h ofscanner actual capture scanning data (Table. 5).

Itineraries Total Length of Link Absolute Sectors Table 5. Summary of BLK2GO dynamic 3D laser scannerTime capture Spent data. Travelled Itinerary Overlap Average Error Sector type Itineraries Total Length of Link Absolute Average Sectors 4 120 m 60% Time8 Spentmin 7 mm 0.125 ha Travelled Itinerary Overlap Error SectorSet of typesectors0.125 ha 421,120 120 m m 60%1408 8 min min 7 mm Set of sectors 22 ha704 704(estimate) (estimate) 21,120 m (estimate) 60%60% 1408 min (estimate) 20 mmmm (estimate) (estimate) 22 ha (estimate) (estimate)

FigureFigure 13.13. PointPoint cloud cloud of of aa platform, platform, with with thethe lower lower wooden wooden structure structure sectioned sectioned to to three three heights heights (Source:(Source: Authors).Authors). Sustainability 2020, 12, 6068 17 of 29

Sustainability 2020, 12, x 17 of 29

Figure 14. 360° panoramic view of the interior of the salt pans detail photo of the exterior (right), Figure 14. 360360°◦ panoramicpanoramic view view of of the the interior interior of of the the salt salt pans detail photo of the exterior (right), location and cone of adjustable view on the ground, all all in the free application JetStream Viewer (Source: Authors).

Figure 15. 360° panoramic view of the exterior of the salt pans, with the option of obtaining Figure 15. 15. 360360◦ °panoramic panoramic view view of the of exterior the exterior of the of salt the pans, salt with pans, the optionwith the of obtaining option of coordinates obtaining coordinatesand distances, and in distances, JetStream in Viewer JetStream (Source: Viewer Authors). (Source: Authors).

3.2. Heritage Heritage B Builtuilt of W Woodood

The C Churchhurch of San AndrAndrésés de Ibarrangelua Given the size of the selected example and considering that most churches that comprise this heritage group group are are much much smaller, smaller, the method the method and procedure and procedure used can used be extrapolated can be extrapolated in its application in its applicationto any of the to churches any of the in churches the group. in the group. A three-dimensionalthree-dimensional digital digital model model was was obtained obtained in thein the form form of a of textured a textured three-dimensional three-dimensional mesh meshexportable exportable in FBX, in OBJ, FBX, STL, OBJ, PLY STL, and PLY PTS and formats PTS format (Figures (Figure16a,b). The16a, exportb). The via export PTS via format PTS enabled format enabledthe generation the generation of point clouds of point linkable clouds using linkable ReCap PRO using (Autodesk) ReCap PRO software (Autodesk) with educational software licence with educational licence in RCP format (Figure 16c). This format enables export of the model to the REVIT (Autodesk) software with educational licence, as a step prior to generating a BIM model. The heritage Sustainability 2020, 12, 6068 18 of 29 inSustainability RCP format 2020 (Figure, 12, x 16c). This format enables export of the model to the REVIT (Autodesk) software18 of 29 withSustainability educational 2020, 1 licence,2, x as a step prior to generating a BIM model. The heritage asset’s documentation18 of 29 isasset thus’s enableddocumentation through is di thusfferent enabled operating through environments different operating for management environments of the 2Dfor andmanagement 3D graphic of asset’s documentation is thus enabled through different operating environments for management of information.the 2D and 3D This graphic information information. can be sharedThis information thanks to the can free be collaborativeshared thanks Autodesk to the free Viewer, collaborativ withoute Autodethe 2Ds kand Viewer, 3D graphic without information. the need toThis install information any kind can of besoftware. shared thanks to the free collaborative theAutode needs tok Viewer, install any without kind the of software. need to install any kind of software.

(a(a) ) ((bb)) (c) (c)

FigureFigureFigure 16. 16.16. ( a(a) )(Geometric aGeometric) Geometric triangulartriangular triangular mesh;mesh; mesh; ( (bb)) Textured ( Texturedb) Textured mesh; mesh; mesh; (c ()c Point) (Pointc) Point clou cloud cloud (Source:d (Source: (Source: Authors). Authors). Authors).

ByBy exporting exporting in in OBJOBJ format,formatformat, the textured textured digital digital model model was was implemented implemented in inthe the repository repository of 3D of 3D SketchfabSketchfab objects, objects, whichwhich by by means of of WebGLWebGL technology technology enables enables orbiting orbiting around around the the model model in real in in real real-- - time, using any common browser and mobile device (Figure 17). Bearing in mind that this resource time,time, usingusing anyany commoncommon browser and mobilemobile devicedevice (Figure(Figure 1717).). Bearing in mind that this resourceresource enables the embedding of complementary information in the model, in the form of URL links, text, enables the embedding of complementary information in the model, in the form of URL links, text, image and video, the model was complemented with detailed photos, obtained by UAV, of some of imageimage and video, video, the the model model was was comple complementedmented with with detailed detailed photos photos,, obtained obtained by by UAV UAV,, of ofsome some of the most significant polychrome work (Figure 17). Using a practically automated process of the ofthe the most most significant significant polychrome polychrome work work (Figure (Figure 17). 17). Using Using a ap practicallyractically automat automateded process process of the application,application, the the model model waswas configuredconfigured so so it it could could be be viewed viewed in in virtual virtual reality reality format, format, thus thus enabling enabling application,immersive experimentationthe model was configured by means of so a VRit could viewer be (Figure viewed 18). in virtual reality format, thus enabling immersiveimmersive experimentationexperimentation byby meansmeans ofof aa VRVR viewerviewer (Figure(Figure 1818).).

Figure 17. Textured 3D model with added information, on the free Sketchfab platform (Source: Authors).

Figure 17. TexturedTextured 3D model with added information, on the free Sketchfab platform (Source: Authors).Authors). Sustainability 2020, 12, 6068 19 of 29 Sustainability 2020, 12, x 19 of 29 Sustainability 2020, 12, x 19 of 29

FigureFigureFigure 18.18. 18.Immersive ImmersiveImmersive VRVRVR experience.experience.experience. (Source: (Source:(Source: Authors). Authors).Authors).

TheTheThe modelmodel model waswas was subsequentlysubsequently subsequently transformed transformedtransformed intointo aa PDF3D PDF3D document, document,document, recognised recognisedrecognised as as asa universally aa universallyuniversally accessible international standard (ISO 32000). To do so, the OBJ file was exported to Adobe accessibleaccessible international international standard standard (ISO (ISO 32000). 32000). To do To so, do the so, OBJ the file OBJwas exported file was to exported Adobe Photoshop, to Adobe Photoshop, creating, in a new file, a 3D overlay based on that file, adding the textures to the creating,Photoshop, in a newcreating file,, ain 3D a overlay new file based, a on3D thatoverlay file, adding based the on textures that file, to theaddin workspace.g the textures Next, the to 3Dthe workspace. Next, the 3D overlay was exported to U3D format so that a PDF3D could be generated overlayworkspace. was exportedNext, the to 3D U3D overlay format was so thatexported a PDF3D to U3D could format be generated so that from a PDF3D it (Figure could 19 ).be The generated PDF3D from it (Figure 19). The PDF3D configuration process makes it possible to create cover images or configurationfrom it (Figure process 19). The makes PDF3D it possible configuration to create process cover imagesmakes it or possible predetermined to create orthogonal cover image views,s or predetermined orthogonal views, and also to produce animations (movement, rotation), generating andpredetermined also to produce orthogonal animations views, (movement, and also to rotation),produce animations generating (movement, a dynamic sequence. rotation), generating The result a dynamic sequence. The result is an interactive document that facilitates navigation and access to is an interactive document that facilitates navigation and access to the 3D model, as well as to a dynamicthe 3D model, sequence. as well The as toresult complementary is an interactive information. document that facilitates navigation and access to complementarythe 3D model, as information. well as to complementary information.

(a) (b)

Figure 19. (a) 3D model(a) in universal PDF3D format; (b) 3D model in Photoshop(b) 3D (Source: Authors).

FigureFigure 19.19. ((a)) 3D model inin universaluniversal PDF3DPDF3D format;format; ((bb)) 3D3D modelmodel inin PhotoshopPhotoshop 3D3D (Source:(Source: Authors).Authors). The model in FBX, STL and OBJ formats is also accessible from the interactive 3D viewer of Microsoft Windows 10, making it possible to orbit around it, and providing augmented reality (AR) TheThe modelmodel in in FBX, FBX, STL STL and and OBJ OBJ formats format is alsos is accessible also accessible from the from interactive the interactive 3D viewer 3D of vi Microsoftewer of experiences. WindowsMicrosoft 10,Windows making 10, it possible making to it orbitpossible around to orbit it, and around providing it, and augmented providing reality augmented (AR) experiences. reality (AR) experiences. 3.3.3.3. Heritage Heritage Constrained Constrained in in the the Urban Urban FabricFabric 3.3. HeritageAlthoughAlthough Constrained this this case case studyin study the hasU hasrban a a number numberFabric ofof commoncommon elements, elements, public public or or private private ownership ownership with with more or less resources to maintain the heritage asset results in an uneven state of conservation that more or less resources to maintain the heritage asset results in an uneven state of conservation that affectsAlthough the capture this case techniques study hasand athe number results of obtained. common elements, public or private ownership with amoreffects or the less capture resources techniques to maintain and the the results heritage obtained. asset results in an uneven state of conservation that affects3.3.1. theIndustrial capture H techniqueseritage: NCO and Case the results obtained. 3.3.1. Industrial Heritage: NCO Case Given that the work objectives centred on preservation of the heritage element, beginning with 3.3.1Given. Industrial that theHeritage: work objectives NCO Case centred on preservation of the heritage element, beginning with repair and restoration of the building, the capture result is reflected in two important aspects. On the repair and restoration of the building, the capture result is reflected in two important aspects. On the oneGiven hand, thata BIM the model work that objectives allows the centred restoration on preservation to be undertaken of the w heritageithout losing element, its heritage beginning values with; one hand, a BIM model that allows the restoration to be undertaken without losing its heritage values; repairon the and other, restoration a textured of exterior the building, 3D model, the capturefrom which result elevations is reflected can bein extractedtwo important at scale aspects. with metric On the on the other, a textured exterior 3D model, from which elevations can be extracted at scale with metric onequality hand, (FA1) a BIM, where model the that pathologies allows the and restoration deformations to be undertakenare observed w inithout detail. losing its heritage values; quality (FA1), where the pathologies and deformations are observed in detail. on the other,To produce a textured the BIM exterior model, 3D four model, elements from whichresulting elevations from the can work be extractedcarried out at werescale used:with metricthe To produce the BIM model, four elements resulting from the work carried out were used: the 1941 quality1941 project (FA1), drawingswhere the; the pathologies points gathered and deformations by means of traditionaare observedl topographical in detail. techniques (Figure project drawings; the points gathered by means of traditional topographical techniques (Figure 20); 20)To; the produce point cloud the generatedBIM model, by fourthe UAV elements in interiors, resulting to complete from the and work corroborate carried out the wereinterior used: data the the point cloud generated by the UAV in interiors, to complete and corroborate the interior data (pillars, 1941 project drawings; the points gathered by means of traditional topographical techniques (Figure 20); the point cloud generated by the UAV in interiors, to complete and corroborate the interior data Sustainability 2020, 12, 6068 20 of 29 Sustainability 2020, 12, x 20 of 29 Sustainability 2020, 12, x 20 of 29 (pfurnaces,illars, furnaces stairways,, stairways, etc.); and etcthe.) data; and obtained the data from obtained the exterior from UAV the exterior flight, which UAV complemented flight, which complementedthe(p work.illars, furnaces the ,work. stairways, etc.); and the data obtained from the exterior UAV flight, which complemented the work.

FigureFigure 20. 20. PointsPoints Points on on on the the the ground ground ground floor floorfloor collected collected with topographic techniques techniques (Source: (Source: Auth Auth Authors).ors).ors).

AsAs previously previously previously commented, commented,commented, use use use of of ofthe the the 3D 3D 3Dlaslaserer laser scanner scanner waswas ruledruled was out ruledout for for outvarious various for reasons. various reasons. In reasons. Inthis this case,Incase, this because case,because because the the building building the building has has abundant abundant has abundant stored stored material,material, stored material, a scanningscanning a scanning plan plan was was plancalculated calculated was calculated for for an an area area for of the ground floor where two of the four furnaces are found and one of the building’s two chimneys ofan the area ground of the floor ground where floor two where of the two four of furnaces the four are furnaces found are and found one of and the onebuilding’s of the building’stwo chimneys two (Figure 21). It was possible to verify that to accurately capture the interior in 3D, in this zone that (Fchimneysigure 21). (Figure It was 21 possible). It was to possibleverify that to verifyto accurately that to accuratelycapture the capture interior the in interior3D, in this in 3D,zone in that this encompasses about a quarter of the ground floor’s total surface area, more than 50 scans are needed. encompasseszone that encompasses about a quarter about aof quarter the ground of the floor’s ground total floor’s surface total area, surface more area, than more 50 scans than are 50 scans needed. are Of them, 18 cannot be carried out because there is accumulated material—this accounted for 36% of Ofneeded. them, Of18 them,cannot 18 be cannot carried be out carried because out becausethere is ac therecumulated is accumulated material material—this—this accounted accounted for 36% forof the options to rule out. Given that the building has three floors, a roof and an exterior space the36% options of the options to rule to out rule. Given out. Given that thethat building the building has has three three floors, floors, a roofa roof and and an an exterior exterior space comprising two small constructions, more than 1000 scans could have been necessary; with such a comprising two small constructions, more than 1000 scans could have been necessary; with such a high comprisinghigh percentage two small of impossible constructions, scans ,more this would than 1000have scansresulted could in an have incomplete been necessary work. Fu; rthermore,with such a percentage of impossible scans, this would have resulted in an incomplete work. Furthermore, weeks highweeks percentage of effort of would impossible have been scans needed, this wouldto capture have and resulted edit the in clouds, an incomplete entailing awork. very highFurthermore, cost. It of effort would have been needed to capture and edit the clouds, entailing a very high cost. It is not, weeksis not of, efforttherefore would, a sustainable have been optionneeded for to capture the building’s and edit private the clouds, ownershi entailingp. However, a very thehigh points cost. It therefore, a sustainable option for the building’s private ownership. However, the points collected is notcollected, therefore with ,traditional a sustainable topographical option for devi theces building’s did enable private collection ownershi of the pointsp. However, indispensable the points for collectedwithcompleting traditional with thetraditional topographical BIM model, topographical devicesusing, for did devi example, enableces did collection in enable the entire ofcollection the ground points of floor, indispensablethe points only 12 indispensable topographical for completing for completingthestations BIM model, which the BIM using,were model, able for example,to using,captur e for in96 the points example, entire in five ground in thedays entire floor,of fieldwor only ground 12k and topographical floor, a half only-day 12 of stationstopographical office work which stationswere(Figure able which 20). to capture were able 96 points to captur in fivee 96 days points of fieldworkin five days and of a fieldwor half-dayk ofand offi ace half work-day (Figure of office 20 ).work (Figure 20).

FigureFigure 21. 21.Partial Partial ground ground floor floor scanningscanning plan.plan. All All necessary, necessary, possible possible (green) (green) and and impossible impossible (red) (red) scanscan points. points. Figure 21. Partial ground floor scanning plan. All necessary, possible (green) and impossible (red) scan points. Sustainability 2020, 12, x 21 of 29

SustainabilitySustainability 20202020, ,1122,, x 6068 2121 of of 29 29 The collection of topographical data was compared to the point cloud obtained by the UAV inside.The Itcollection was not possibleof topographical to complete data that was cloud compared in the entire to the factory, point cloud as the obtained building bydoes the not UAV have inside.suitableThe It was collectionlighting not possible in of all topographical areas to complete (Figure data that22a). was cloud The compared coordinatesin the toentire the pointoffactory, the cloud point as the obtained clouds building with by thedoes respect UAV not inside. haveto the suitableItprecision was not lighting possibleof the intopog toall complete areasraphical (Figure thatpoints cloud 22a). show inThe thedifferences coordinates entire factory, of centimetres,of asthe the point building whichclouds does, although with not respect have they suitable toare the not precisionlightingvalid for inof other allthe areas topogwork, (Figureraphical are nevertheless 22 a).points The show coordinates acceptable differences of for the generatingof point centimetres, clouds an initial with which respect model, although toin theBIM they precision that are allows not of validthecon topographical servationfor other ofwork, the points building are shownevertheless through differences reacceptablenovation of centimetres, .for The generating exterior which, UAV althoughan initial capture theymodel was are morein not BIM validprecise, that for allows thanks other conwork,toservation GPS. are It nevertheless also of the enabled building acceptable details through to for be re generating novationobtained. Theregarding an initialexterior modelpathologies UAV in cap BIMture that that was cannot allows more be conservationprecise, accessed thanks with of tothevideo GPS. building andIt also photos through enabled (Figure renovation. details 22b). to All Thebe this obtained exterior resulted UAVregarding in a capturetextured pathologies was 3D moreexterior that precise, model, cannot thanks with be accessed toa GSD GPS. (ground Itwith also videoenabledsample and details distance)photos to (Figure be or obtained maximum 22b). All regarding thispixel resulted s pathologiesize of in 2.75 a textured that mm, cannot whence 3D exterior be accessedit was model, possible with with video a to GSD generat and (ground photose the sample(Figureorthophotos 22 distance)b). All to scalethis or resulted maximum(Figure in23). apixel textured From s izethese 3D of exterior textured 2.75 mm, model, mesh whence withexterior a it GSD wasmodels (ground possible, details sample to can generat distance)be obtainede the or orthophotosmaximumabout the pixel deformationsto scale size of(Figure 2.75 that mm, 23). willwhence From be these useful it was textured possible for determining mesh to generate exterior the the models re orthophotosnovation, details project to can scale be with (Figure obtained greate 23). r aboutFromprecis thesetheion deformations(Figure textured 24). mesh that exterior will models, be useful details for determining can be obtained the about renovation the deformations project with that greate will ber precisusefulion for (Figure determining 24). the renovation project with greater precision (Figure 24).

(a) (b)

Figure 22. Captures(a) by UAV: (a) Partial textured mesh of the entrance to(b )the ovens on the ground floor; (b) Detail photography of the pathologies of the chimneys (Source: Authors). FigureFigure 22. 22. CapturesCaptures by UAV:UAV:( a(a)) Partial Partial textured textured mesh mesh of of the the entrance entrance to theto the ovens ovens on the on groundthe ground floor; floor;(b) Detail (b) Detail photography photography of the of pathologies the pathologies of the of chimneys the chimneys (Source: (Source: Authors). Authors).

(a) (a)

(b) FigureFigure 23. 23.( a(a)) North North elevation elevation textured textured with with metric metric(b) quality quality from from the the NCO NCO factory; factory; ( b(b)) South South elevation elevation texturedtextured with with metric metric quality quality from from the the NCO NCO factory factory (Source: (Source: Authors). Authors). Figure 23. (a) North elevation textured with metric quality from the NCO factory; (b) South elevation textured with metric quality from the NCO factory (Source: Authors). Sustainability 2020, 12, 6068 22 of 29 Sustainability 2020, 12, x 22 of 29

(a) (b)

Figure 24. 24. ((aa)) Detail Detail photography photography of theof the pathologies pathologies in façades in façades and carpentry; and carpentry; (b) 3D model(b) 3D of model textured of texturmeshed and mesh geometric and geometric triangular triangular mesh with mesh pathologies with pathologies (Source: Authors).(Source: Authors).

All this previous documentation was used to generate a current current-state-state BIM model with the Revit software of Autodesk (Figure 25).25). The The model’s model’s developme developmentnt level level was was LOD LOD 200, 200, which will will later later evolve to LOD 300 300 in the the p planlan and and LOD LOD 400 400 to to begin begin the the re renovation;novation; it it will will culminate culminate with an an as as-built-built LOD 500 model when the work is finished.finished. The The work work was was done done with a central architecture model linkedlinked to to the the structural structural model model and and to theto the cloud cloud model model generated generated by the by UAV. the ToUAV. determine To determine the families the familiesto model, to the model, existing the existing project documentation project documentation was used was as a used basis, as along a basis, with along the informationwith the information gathered gatheredduring visits during to the visits building. to the Basically, building. the following Basically, families the following were generated: families walls were (façades, generated: chimneys walls (façades,and partitions), chimneys doors, and windowspartitions), and doors, railing. windows The roof, and floorsrailing and. The stairways roof, floors are and built stairways of concrete, are builtwhereby of concrete, they were whereby directly they modelled were directly in the associated modelled structuralin the associated model. structural Once the model. model wasOnce built, the modelthe Pointsense was built, surface the Pointsense analysis tool surface for Revit analysis enables tool generationfor Revit enables of a 3D gener inspectionation of map a 3D and inspection analysis mapof di ffanderences analysis between of differences the 3D model between generated the 3D model with the generated UAV, and with the the BIM UAV model, and prepared the BIM formodel the preparedrenovation, for which the re doesnovation not, reflect which the does pathologies. not reflect the pathologies.

Figure 25. BIM model. 3D models, textured elevations, and first floor corresponding to the levels Figure 25. BIMBIM model. 3D 3D models, models, textured textured elevations, elevations, and and first first f floorloor corresponding corresponding to to the levels (Source: Authors). (Source: Authors). Authors).

Sustainability 2020, 12, 6068 23 of 29 Sustainability 2020, 12, x 23 of 29

3.3.3.2.3.2. The The M Museumuseum DifferentDifferent results were obtained from the research conducted.conducted. On the one hand, after the editing work with Leica Cyclone software software,, the point cloud cloudss resulting f fromrom the two scanning phase phasess were generated. The The colour colour cloud cloud generated generated with with the the BLK360 BLK360 and RTC360 was edited in Autodesk Recap and a ann .e57 file file was generated containing 360° 360◦ imagesimages of of the the building building and and detailed detailed photos photos of of singular singular featuresfeatures,, confi configuringguring an an important important document document for for the the building building’s’s documentary documentary record. record. Although Although the buildingthe building was wasrenovated renovated in 2011, in 2011, it must it mustnot be not forgot be forgottenten that the that museum the museum is a public is a publicbuilding building which whichwill have will to have take tointo take account into account the European the European public contracting public contracting directive directive (2014/24/EU), (2014 /which24/EU), requires which workrequires on ren workovating on renovating public heritage public to heritagebe tendered to bebased tendered on electronic based onbuilding electronic design building tools. Spanish design legislationtools. Spanish already legislation mandates already that such mandates work that be developed such work using be developed BIM technology. using BIM It is technology. therefore indispensableIt is therefore indispensable to possess a complete to possess BIM a complete model to BIM enable model efficient to enable manag efficientement management and predictive and predictivemaintenance maintenance of the building. of the Although building., for Although, the time for being the, time the ownership being, the ownershipdoes not deem does it not necessary, deem it thenecessary, HBIM model the HBIM is being model modelled is being and modelled it can andcontain it can all contain the historical all the historicalinformation information about the aboutbuilding the inbuilding its different in its di phases,fferent phases, includi includingng all repairs all repairs and andrenovation renovation work. work. The The cloister cloister has has begun begun to to be modelled, using using,, as a reference reference,, the colour point cloud produced. For the HBIM HBIM mo model,del, the Autodesk Autodesk Revit software is also being used, starting from a central architecture model (Figure 2626).). TheThe colour point cloud cloud has has been been linked linked to this to thismodel, model, along along with a with structural a structural model; an model; MEP model an MEP will model eventually will eventuallybe linked, enablingbe linked, the enabling capture ofthe characteristics capture of characteristics of the installations of the restoredinstallations in the restored last project, in the with last a project,view to with sustainable a view maintenance.to sustainable maintenance.

Figure 26. HBIM (historical building information model modelling)ling) model in Revit (Source: Authors).

On the otherother hand,hand, complementing complementing the the work work with with the the photos photos obtained obtained using using the the digital digital camera camera and andthe UAV,the UAV, a photogrammetric a photogrammetric rendering rendering of solely of solely the cloister the cloister was accomplished was accomplished (Figure (Figure 27). The 27). Gothic The Gothicvaults and vaults the and arches the of arches the cloister of the can cloister be considered can be considered the building’s the building iconic features,’s iconic and features although, and althoughthey are in they a very are goodin a very state good today, state it istoday, important it is important to have a to very have precise a very record precise of record them soof theythem can so theybe preserved can be preserved over time. ove Ther time. south The wing south of thewing cloister of the did cloister not preservedid not preserve its original its vaultsoriginal due vaults to a duefire (Figure to a fire 28 a). (Figure For that 28a). purpose, For that the purpose, acquisition the ofacquisition precise replicas of precise of such replicas singular of such elements singular is of elementsspecial interest. is of special The result interest. obtained The result from theobtained cloister from is summed the cloister up in is two summed products. up in First, two an products. accurate First,textured an accurate 3D digital textured model, 3D which digital enabled model, museum which exhibitionenabled museum on free platformsexhibition suchon free as Sketchfab,platforms withsuch accessas Sketchfab, via virtual with reality access possible via virtual Second, reality a file possible was prepared Second, for a file advanced was prepared manufacturing for advanced of the manufacturingvault and arch by of means the vault of 3D andprinters arch (Figure by means 28b) [62 of ]. 3D Various printers scale (Figure prototypes 28b) were [62] printed,. Various and scale the prototypes were printed, and the acquisition of real-size replicas printed in 3D are being studied, SustainabilitySustainability 20202020,, 1212,, 6068x 2424 of 2929 Sustainability 2020, 12, x 24 of 29 using a combination of limestone and ash, a system that is already being used to create prototypes usingacquisitionfor the a reconstructioncombination of real-size of of replicas limestone Notre printedDame and [63] ash, in 3D. a aresystem being that studied, is already using being a combination used to create of limestone prototypes and forash, the a system reconstruction that is already of Notre being Dame used [63] to. create prototypes for the reconstruction of Notre Dame [63].

(a) (b) (a) (b) Figure 27. (a) Textured 3D partial model in Sketchfab; (b) Vault point cloud (Source: Authors). FigureFigure 27. ( 27.a) Textured(a) Textured 3D 3Dpartial partial model model in Sketchfab; in Sketchfab; (b) (Vaultb) Vault point point cloud cloud (Source: (Source: Authors). Authors).

(a) (b) (a) (b) FigureFigure 28.28. (a) Cloister of the San Telmo Museum.Museum. Vaults inin sandstonesandstone (left);(left); vaults replacedreplaced inin plasterplaster Figureinin thethe south south28. (a ) wingwing Cloister (right);(right); of the ((bb ))San PrototypePrototype Telmo Museum. mademade byby 3D3DVaults printerprinter in sandstone (Source:(Source: Authors).Authors). (left); vaults replaced in plaster in the south wing (right); (b) Prototype made by 3D printer (Source: Authors). 4.4. Discussion 4. Discussion TheThe startingstarting hypothesishypothesis focusedfocused onon thethe possibilitypossibility ofof obtainingobtaining fastfast andand accurateaccurate digitisationdigitisation ofof heritageheritageThe instartingin multiplemultiple hypothesis cases cases and and focused in in a sustainablea sustainable on the possibility manner. manner. After of After obtaining analysing analysing fast the and the results, accurateresults, it can it digitisation becan stated be stated that of heritagethisthat isthis financially inis financiallymultiple possible, cases possible, and without in without a investingsustainable investing much mann muc time.er.h time.After analysing the results, it can be stated that thisHowever,However, is financially itit isis alsoalso possible, clearclear thatthat without toto achieveachieve investing thisthis aim, aimmuc, therehthere time. isis notnot justjust oneone singlesingle methodologymethodology asas thethe onlyonlyHowever, option.option. Each it is heritagealso clear site that has to specific,specifachieveic, this unique aim ,characteristics there is not just that one require single specificspecificmethodology studystudy as ofof the the onlymostmost option. appropriateappropriate Each solution,solution,heritage depending sitedepending has specif on on theic, the unique objective objective characteristics of of the the work. work. Onethat One ofrequire of the the first firstspecific aspects aspects study to to assess ofassess the is mosttheis the extent appropriate extent of protectionof protection solution, and dependingand risk presentedrisk presented on the by theobjective by heritage the heritage of site.the work. Another site. OneAnother important of the important first aspect aspects isaspec the to t degreeassess is the isofdegree the accessibility, extent of accessibility, of protection both inside both and andinside risk outside, and presented outside, to all by pointsto theall pointsheritage of the of site thesite. to site Another be to digitised, be digitised, important conditioned cond aspecitionedt byis the by degreemarket-availablethe market of accessibility,-available devices devices both and inside and techniques andtechniques outside, for pointfor to allpoint captures. points captures. of Finally,the siteFinally, theto be technical thedigitised, technical di condfficulty difficultyitioned of each by of thecaptureeach market capture method-available method must devices bemust assessed, be and assessed, correspondingtechniques corresponding for topoint the to financialcaptures. the financial capabilities Finally, capabilities the of technical those of inthose chargedifficulty in charge of theof eachrespectiveof the capture respective management method management must and be protection. assessed, and protection corresponding Considering. Considering the to characteristics the the financial characteristics capabilities of the case of studies,theof those case it studies,in has charge been it ofverifiedhas the been respective that verified the bestmanagement that option the best always optionand protection involves always ainvolves. methodConsidering a combining method the characteristics combining capture techniques. capture of the techniques case If, in studies, addition,. If, init hastheaddition, been limited verified the economic limited that economic the capacity best option capacity of those always of responsible those involves responsible for a method protecting for protectingcombining the property the capture property is techniques introduced is intro.duced If, as in a addition,as a conditioner, the limited although economic the options capacity are of reduced those responsible, there may for be protecting alternatives the that property allow such is intro a captureduced asin aa conditioner, sustainable manneralthough with the optionsscant resou are reducedrces and, inthere a short may time. be alternatives that allow such a capture in a sustainable manner with scant resources and in a short time. Sustainability 2020, 12, 6068 25 of 29 conditioner, although the options are reduced, there may be alternatives that allow such a capture in a sustainable manner with scant resources and in a short time. Regarding capture techniques, it can be stated that there are two cutting-edge technologies, close-range photogrammetry and TLS (terrestrial laser scanner), which mark a major step forward in digital element recording. Both enable data acquisition by massive point capture technology, and when combined, can cover all the cases. However, the proliferation in recent years of automated planning and control applications for photography operations using UAVs, along with the novel appearance of dynamic TLS capture, has resulted in further expansion of the heritage documentation phase panorama. Automation simplifies the process by reducing data collection times, besides allowing a more extensive work range and enabling more efficient management of the capture process. Moreover, it is a systematic methodology that minimises the subjectivity of the data collection process, allowing repetition and comparison over time, and is adjusted, among others, to the UNESCO Managing Cultural World Heritage guidelines for the monitoring phase. TLS is, in principle, a more precise option, since it enables capturing a large amount of information with millimetric precision. It also has an advantage over photogrammetry—the possibility of obtaining 360◦ panoramic images which, together with the point cloud, enable precise reading of coordinates and measurement of distances directly from the digital model, thereby facilitating detailed in-office study and reducing fieldwork. However, there are many TLS models, and not all of them permit the most efficient workflow, as they require instrumental stationing and precise levelling in many cases. The appearance of dynamic TLS-capture makes it possible to optimise these processes, although it is a novel option that involves more exhaustive research. It can be stated that the combination of automated photogrammetry and TLS enables fast and accurate capture in all the cases. Furthermore, in unique cases of heritage sites such as the Salt Valley of Añana, automated photogrammetry assisted by UAV and dynamic TLS makes it possible to substantially reduce working time. As shown, the capture in 28 h of 22 ha with very high geometric complexity enables a 3D digital model with information to be obtained in less than two days. In comparison, an Autocad 3D model was previously developed over three years of work. Automated photogrammetry using a UAV allows points to be captured in areas where TLS is unable to complete the work (building roofs, interior areas inaccessible due to stockpiled material or wooden structures in poor condition, outdoor areas with limited access, etc.). However, UAVs, which are cheaper than TLS, require qualification with a professional pilot’s licence and their use is conditioned in numerous areas, such as those under airport control and urban centres, where permits must be applied for, well in advance. In cases where the heritage element requires carrying out a renovation or efficient management and maintenance to contain intense use or activity, the documentation generated by means of photogrammetry and TLS can be used to create a BIM model that will allow the activity to evolve while cutting costs in a sustainable manner. For this to happen, initial financial support and a good management plan are necessary. The BIM model will have to meet that plan’s requirements and allow predictive maintenance of the respective heritage. Financial investment, in this type of model for heritage conservation, is still a pending subject. As those responsible for heritage sites become generally aware of this technology’s potential, the specific determination of models for each case will generate a wide field of investigation. The different techniques for creating the digital model start with capturing and defining the points of the real model. Traditional techniques capture discrete points while modern techniques massively capture millions of points. Point-processing software like Autodesk Recap, nowadays allows collection of data from different techniques such as laser scanning or automated photogrammetry. All the models generated in the research were edited with Recap, combining data from the different capture techniques. The file generated in Recap can be exported to many types of 3D modelling software, such as the one for our models, built using the BIM software Revit from Autodesk. Sustainability 2020, 12, 6068 26 of 29

In cases where the entity responsible for the heritage site does not have financial resources, digital camera photogrammetry is the most affordable option with an acceptable degree of precision. Point clouds, geometric triangular mesh models and textured meshes are obtainable when all points can be easily accessed from a large and well-lit space, thereby enabling preservation of the heritage element. Universal open-access platforms and software can make the digitised heritage fit for museum purposes and further exploration using virtual and augmented reality. The possibility of integrating these digital models in Virtual Reality media improves access to the heritage asset, so it can overcome the spatial complexity of certain environments and the respective access restrictions or effect on the public. At the same time, there are new possibilities for interaction with the site and knowledge about it, promoting dissemination and understanding of its values. Some of these models were configured on the Sketchfab platform for viewing in VR, as a prior step toward broader investigation into how these new Immersive Reality techniques are applied; this could, for example, help ease the restrictions on access to wooden churches in the Basque Country, leading to greater recognition of their heritage value. It can be said that every heritage element is exposed to some unforeseeable or inevitable risk. The social and political contexts of historical heritage assets significantly influence their proper management and preservation. The involvement of governments and those responsible for overseeing heritage, depending on available financial resources, can either reduce or increase the risk of destruction. Since cultural heritage is constantly endangered [61], one of the fundamental steps to ensure its protection should be the respective digitisation. Market-available digitisation tools and technologies have improved remarkably in recent years, enabling fast compilation of an accurate and affordable record of heritage assets. It is therefore essential for heritage managers and governments to encourage this process. In the event of a disaster, digitisation will enable the historical legacy to be restored in accordance with accepted conservation practices [61]. Such a record will also enhance understanding of the heritage and contribute toward better management and awareness thereof. The results of the conducted research indicate that the preservation of heritage monuments and sites in diverse situations and risks is certainly possible. The time to intervene is now.

Author Contributions: Conceptualization, I.L. and M.S.; methodology, I.L. and J.J.P.; software, J.J.P.; validation, I.L., J.J.P. and M.S.; formal analysis, M.S.; investigation, I.L., M.S. and J.P; data curation, J.J.P.; writing—original draft preparation, I.L and J.J.P.; writing—review and editing, M.S.; supervision, I.L. All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. Acknowledgments: The authors would like to thank the Department of Architecture of the UPV/EHU for the support in this article; to Ana Azpiri as head of the work team for the preservation of NCO; to the Valle Salado de Añana Foundation, the Ibarrangelua City Council and the San Telmo Museum for facilitating access to the facilities. Conflicts of Interest: The authors declare no conflict of interest.

References

1. Myriah, J.A. 3D Printing of the Proximal Right Femur: It’s Implications in the Field of Forensic Anthropology and Bioarchaeology. Master’s Thesis, University of Montana, Missoula, MT, USA, 2019. 2. Vannucci, P.; Masi, F.; Stefanou, I. A nonlinear approach to the wind strength of Gothic Cathedrals: The case of Notre Dame of Paris. Eng. Struct. 2019, 183, 860–873. [CrossRef] 3. Maira, R. La estereotomía de las claves en el gótico primitivo europeo: Diferentes diseños geométricos y soluciones constructivas. EGA Expresión Gráfica Arquitectónica 2020, 22, 152–159. [CrossRef] 4. Tenschert, R. Cathedral Notre Dame in Paris—The inscription of the south transepts façade: Medieval relict or 19th century recreation? In Proceedings of the 27th CIPA International Symposium Documenting the Past for a Better Future, Ávila, Spain, 1–5 September 2019. 5. Tallon, A. Divining Proportions in the Information Age. Archit. Hist. 2014, 2, 1–14. 6. United Nations. The World’s Cities in 2016 Data Booklet; Economic and Social Affair: New York, NY, USA, 2016. 7. Cohen, B. Urbanization in developing countries: Current trends, future projections, and key challenges for sustainability. Technol. Soc. 2006, 28, 63–80. [CrossRef] Sustainability 2020, 12, 6068 27 of 29

8. Araoz, G.F. Preserving heritage places under a new paradigm. J. Cult. Herit. Manag. Sustain. Dev. 2011, 1, 55–60. [CrossRef] 9. Meyer, É.; Grussenmeyer, P.; Perrin, J.-P.; Durand, A.; Drap, P. A web information system for the management and the dissemination of Cultural Heritage data. J. Cult. Heritage 2007, 8, 396–411. [CrossRef] 10. Carter, B.; Grimwade, G. Balancing use and preservation in cultural heritage management. Int. J. Herit. Stud. 1997, 3, 45–53. [CrossRef] 11. Makuvaza, S.; Chiwaura, H. African States Parties, Support, Constraints, Challenges and Opportunities for Managing Cultural World Heritage Sites in Africa. In Springer Briefs in Archaeology; Springer: New York, NY, USA, 2014; pp. 45–53. [CrossRef] 12. ICOMOS. The ICOMOS Charter for the Interpretation and Presentation of Cultural Heritage Sites. International Committee on Interpretation and Presentation of Cultural Heritage Sites. 2008. Available online: http://icip.icomos.org/ENG/groups_charter.html (accessed on 18 June 2020). 13. Tobiasz, A.; Markiewicz, J.; Łapi´nski,S.; Nikel, J.; Kot, P.; Muradov, M. Review of Methods for Documentation, Management, and Sustainability of Cultural Heritage. Case Study: Museum of King Jan III’s Palace at Wilanów. Sustainability 2019, 11, 7046. [CrossRef] 14. Young, C.; Chadburn, A.; Bedu, I. Stonehenge. In World Heritage Site Management Plan; English Heritage: London, UK, 2009. 15. Logothetis, S.; Delinasiou, A.; Stylianidis, E. Building Information Modelling for Cultural Heritage: A review. ISPRS Ann. Photogramm. Remote. Sens. Spat. Inf. Sci. 2015, 5, 177–183. [CrossRef] 16. Agustín-Hernández, L.; Quintilla, M. Virtual Reconstruction in Bim Technology and Digital Inventories Of Heritage. ISPRS Int. Arch. Photogramm. Remote. Sens. Spat. Inf. Sci. 2019, XLII-2/W15, 25–31. [CrossRef] 17. Bruno, N.; Roncella, R. A Restoration Oriented HBIM System for Cultural Heritage Documentation: The Case Study of Parma Cathedral. ISPRS Int. Arch. Photogramm. Remote. Sens. Spat. Inf. Sci. 2018, XLII-2, 171–178. [CrossRef] 18. Santana, M.; Lerma, J.L.; Heine, E.; Van Genechten, B. Theory and Practice on Terrestrial Laser Scanning: Training Material Based on Practical Applications, 4th ed.; Universidad Politecnica De Valencia Editorial: Valencia, Spain, 2008; pp. 1–241. 19. Grussenmeyer, P.; Alby, E.; Landes, T.; Koehl, M.; Guillemin, S.; Hullo, J.F.; Assali, P.; Smigiel, E. Recording Approach of Heritage Sites Based on Merging Point Clouds from High Resolution Photogrammetry and Terrestrial Laser Scanning. ISPRS Int. Arch. Photogramm. Remote. Sens. Spat. Inf. Sci. 2012, XXXIX-B5, 553–558. [CrossRef] 20. Luhmann, T.; Robson, S.; Kyle, S.; Boehm, J. Close-Range Photogrammetry and 3D Imaging; Walter De Gruyter: Boston, MA, USA, 2013; Volume 81. 21. Mancini, F.; Dubbini, M.; Gattelli, M.; Stecchi, F.; Fabbri, S.; Gabbianelli, G. Using Unmanned Aerial Vehicles (UAV) for High-Resolution Reconstruction of Topography: The Structure from Motion Approach on Coastal Environments. Remote. Sens. 2013, 5, 6880–6898. [CrossRef] 22. Plata, A. Génesis de una villa medieval. Arqueología, Paisaje y Arquitectura del valle salado de Añana (Álava); Servicio Central de Publicaciones del Gobierno Vasco: Vitoria-Gasteiz, Spain, 2008. 23. Plata, A. El Valle Salado. Askegi 2013, 7, 68–85. 24. Plata, A. Arqueología de las salinas. El método de estudio de un paisaje cultural construido. Kobie 2009, XXVIII, 255–266. 25. Sun, Z.; Cao, Y. Data processing workflows from low-cost digital survey to various applications: Three case studies of Chinese historic architecture. ISPRS Int. Arch. Photogramm. Remote. Sens. Spat. Inf. Sci. 2015, 5, 409–416. [CrossRef] 26. Gaiani, M.; Remondino, F.; Apollonio, F.I.; Ballabeni, A. An Advanced Pre-Processing Pipeline to Improve Automated Photogrammetric Reconstructions of Architectural Scenes. Remote. Sens. 2016, 8, 178. [CrossRef] 27. Sun, Z.; Zhang, Y. Using Drones and 3D Modeling to Survey Tibetan Architectural Heritage: A Case Study with the Multi-Door Stupa. Sustainability 2018, 10, 2259. [CrossRef] 28. Carvajal-Ramirez, F.; Vega, F.A.; Carricondo, P.J.M. Effects of image orientation and ground control points distribution on unmanned aerial vehicle photogrammetry projects on a road cut slope. J. Appl. Remote Sens. 2016, 10, 34004. [CrossRef] Sustainability 2020, 12, 6068 28 of 29

29. Vega, F.A.; Carvajal-Ramirez, F.; Martínez-Carricondo, P. Assessment of photogrammetric mapping accuracy based on variation ground control points number using unmanned aerial vehicle. Measurement 2017, 98, 221–227. [CrossRef] 30. Barba, S.; Barbarella, M.; Di Benedetto, A.; Fiani, M.; Limongiello, M. Quality Assessment of UAV Photogrammetric Archaeological Survey. ISPRS Int. Arch. Photogramm. Remote. Sens. Spat. Inf. Sci. 2019, XLII-2/W9, 93–100. [CrossRef] 31. Lehtola, V.V.; Kaartinen, H.; Nüchter, A.; Kaijaluoto, R.; Kukko, A.; Litkey, P.; Honkavaara, E.; Rosnell, T.; Vaaja, M.; Virtanen, J.-P.; et al. Comparison of the Selected State-Of-The-Art 3D Indoor Scanning and Point Cloud Generation Methods. Remote Sens. 2017, 9, 796. [CrossRef] 32. Zlot, R.; Bosse, M. Efficient Large-scale Three-dimensional Mobile Mapping for Underground Mines. J. Field Robot. 2014, 31, 758–779. [CrossRef] 33. Chang, H.J.; Lee, C.S.G.; Lu, Y.-H.; Hu, Y.C. P-SLAM: Simultaneous Localization and Mapping with Environmental-Structure Prediction. IEEE Trans. Robot. 2007, 23, 281–293. [CrossRef] 34. ICOMOS. Principles for the Conservation of Wooden Built Heritage. International Wood Committee. 2007. Available online: https://www.icomoswood.org/doctrines/publications (accessed on 23 June 2020). 35. Santana, A. Ars Lignea. Zurezko Elizak Euskal Herrian: Las Iglesias de Madera en el País Vasco; Electa: Madrid Spain, 1996. 36. Santana, A. Baserria; Serie Bertan 4; Diputación Foral de Gipuzkoa: Donostia, Spain, 1993. 37. Baeschlin, A. La Arquitectura del Caserío Vasco; Editorial Canosa: Barcelona, Spain, 1930. 38. Duvert, M. Etude d’une famille de charpentiers en Basse-Navarre. Bulletin du Musée Basque 1989, 123, 1. 39. Lavedan, P. Por Connaitre les Monuments de France; Arthaud: Paris, France, 1971. 40. Santana, A.; Larrañaga, J.A.; Loinaz, J.L.; Zulueta, A. La arquitectura del caserío de Euskal Herria: Historia y Tipología; Servicio Central de Publicaciones del Gobierno Vasco: Vitoria-Gasteiz, Spain, 2001. 41. Marín, J.A. Semejante Pariente Mayor, Parentesco, Solar, Comunidad y Linaje en la Institución de un Pariente Mayor en Guipúzcoa; Universidad de Deusto: Bilbao, Spain, 1997. 42. Lema, J.A.; Fernández de Larrea, J.A.; García, E.; Munita, J.A. Los Señores de la Guerra y de la Tierra: Nuevos Textos para el Estudio de los Parientes Mayores Guipuzcoanos (1265–1548); Diputación Foral de Gipuzkoa, Departamento de Cultura, Euskera, Juventud y Deportes: Donostia-San Sebastián, Spain, 2000. 43. Lema, J.A.; Fernández de Larrea, J.A.; García, E.; Larrañaga, M.A.; Munita, J.A. El Triunfo de las Élites Urbanas Guipuzcoanas: Nuevos Textos para el Estudio de las Villas y de la Provincia: Siglos XII–XVI; Diputación Foral de Gipuzkoa, Departamento de Cultura, Euskera, Juventud y Deportes: Donostia-San Sebastián, Spain, 2003. 44. Ibañez, A.; Mauleon, J. Arquitectura Rural en Madera en el Siglo XVI en el Área de Tolosaldea: Los Caserío-Lagar de Etxeberri (Gaztelu) y Etxenagusia (Eldua); Zainak. Cuadernos de Antropología-Etnografía no. 17; Sociedad de Estudio Vascos: Donostia-San Sebastián, Spain, 1998. 45. Susperregi, J.; Telleria, I.; Urteaga, M.; Jansma, E. The Basque farmhouses of Zelaa and Maiz Goena: New dendrochronology-based findings about the evolution of the built heritage in the northern Iberian Peninsula. J. Archaeol. Sci. Rep. 2017, 11, 695–708. [CrossRef] 46. Santana, A. Igartubeiti, un Caserío Guipuzcoano: Investigación, Restauración, Difusión; Diputación Foral de Gipuzkoa; Departamento de Cultura, Euskera, Juventud y Deportes: Donostia-San Sebastián, Spain, 2003. 47. Pérez-Agote, A. Cambio Religioso en España: Los Avatares de la Secularización; Centro de Investigaciones Sociológicas: Madrid, Spain, 2012. 48. Viollet-le-Duc, E. Dictionnaire Raisonnée de l’Architecture Française du XI au XVI Siécle; Morel, A.: Paris, France, 1854–1868. 49. De Reu, J.; Plets, G.; Verhoeven, G.; De Smedt, P.; Bats, M.; Cherretté, B.; De Maeyer, W.; Deconynck, J.; Herremans, D.; Laloo, P.; et al. Towards a three-dimensional cost-effective registration of the archaeological heritage. J. Archaeol. Sci. 2013, 40, 1108–1121. [CrossRef] 50. Cazorla, M.P.; Fiel, M.V.; Sanjuán, L.M.; Felip, F. Representaciones Virtuales y Otros Recursos Técnicos en la Accesibilidad al Patrimonio Cultural. EGA Revista de Expresión Gráfica Arquitectónica 2011, 16, 164–173. [CrossRef] 51. Boutsi, A.-M.; Ioannidis, C.; Soile, S. An Integrated Approach to 3D Web Visualization of Cultural Heritage Heterogeneous Datasets. Remote Sens. 2019, 11, 2508. [CrossRef] 52. AVPIOP. Puente Vizcaya. Available online: https://avpiop.com/es/patrimonio/puente_vizcaya/6 (accessed on 23 June 2020). Sustainability 2020, 12, 6068 29 of 29

53. TICCIH. Puente Vizcaya. Available online: http://www.100patrimonioindustrial.com/Ficha.aspx?id=107 (accessed on 25 June 2020). 54. Herreras, B. Los Paisajes de la Industrialización de Gipuzkoa t Álava. In Patrimonio Industrial en el País Vasco; Servicio Central de Publicaciones del Gobierno Vasco: Donostia-San Sebastián, Spain, 2012; Volume 1, pp. 69–96. 55. Aja, G.; Altuna, N.; Apraiz, A.; Cárcamo, J.; Hernández, A.; Herreras, B.; Ibáñez, M.; Juaristi, J.; Martínez, A.; Martínez, M.A.; et al. Patrimonio Industrial en el País Vasco, 1st ed.; Servicio Central de Publicaciones del Gobierno Vasco: Donostia-San Sebastián, Spain, 2012. 56. ICOMOS. Carta de Nizhny Tagil Sobre Patrimonio Industrial. Available online: https://www.icomos.org/ 18thapril/2006/nizhny-tagil-charter-sp.pdf (accessed on 25 June 2020). 57. Azpiri, A.; Etxepare, L.; Garcia, L.; García, F.; Sánchez, D. La Arquitectura de Luis Tolosa, 1st ed.; Autoridad Portuaria de Pasaia, COAVN, Editorial Nerea: San Sebastián, Spain, 2012; pp. 186–188. 58. Soto, S. San Telmo, hacia un nuevo museo. Rev. Subdirección Gen. Museos Estatales 2009–2010, 5–6, 198–207. 59. ISCARSAH. Carta ICOMOS—Principios para el Análisis, Conservación y Restauración de las Estructuras del Patrimonio Arquitectónico. 2003. Available online: https://iscarsah.org/documents/ (accessed on 19 June 2020). 60. López, A.L. Cabecera cuadrada renacentista con bóveda pseudo-esférica cruzada en la iglesia Santiago de Orihuela (Alicante). EGA Expresión Gráfica Arquitectónica 2015, 25, 148–157. [CrossRef] 61. ICORP. Statement by ICOMOS-ICORP and Yildiz Technical University of Istanbul from the International Symposium on Cultural Heritage Protection in Times of Risk: Challenges and Opportunities, 15–17 November 2012 at Yildiz Technical University, Istanbul, Turkey. Available online: http://icorp.icomos.org/wp-content/ uploads/2017/05/ICORP-Istanbul-Statement-2012.pdf (accessed on 22 June 2020). 62. Wabi´nski,J.; Mo´scicka,A. Natural Heritage Reconstruction Using Full-Color 3D Printing: A Case Study of the Valley of Five Polish Ponds. Sustainability 2019, 11, 5907. [CrossRef] 63. Rebuilding Notre Dame: A Phoenix Rising from the Ashes. Available online: https://medium.com/@eric_ geboers/rebuiling-notre-dame-a-phoenix-rising-from-the-ashes-f087bf89f5ed (accessed on 21 June 2020).

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