Combined Methodologies for the Survey and Documentation of Historical Buildings: the Castle of Scalea (CS, Italy)

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Article Combined Methodologies for the Survey and Documentation of Historical Buildings: The Castle of Scalea (CS, Italy)

1, 2, , Eugenio Donato † and Dario Giuﬀrida * † 1 Dipartimento di Civiltà Antiche e Moderne, Università degli Studi di Messina, SS. Annunziata, 98168 Messina, Italy 2 Institute for Chemical and Physical processes, National Research Council (IPCF-CNR), Viale F. Stagno d’Alcontres 37, 98158 Messina, Italy * Correspondence: dario.giuﬀ[email protected] These authors contributed equally to this work. † Received: 28 June 2019; Accepted: 8 August 2019; Published: 9 August 2019

Abstract: In the last few years, new technologies have become indispensable tools for specialists in the field of cultural heritage for the analysis, reconstruction and interpretation of data but also for promotion of artefacts or buildings sometimes inaccessible or in a bad state of conservation. The discipline of geomatics offer many opportunities and solutions for integrated digital surveys and the documentation of heritage (point-based methods, image-based photogrammetry and their combination): These data can be processed in order to derive metric information and share them using databases or GIS (geographic information system) tools. This paper is focused on the description of combined survey methodologies adopted for the geometric and architectural documentation of the site and surviving structures of the Castel of Scalea (Cosenza, Italy). It is a typical context where traditional survey procedures do not fully succeed or require a longer amount of time and great effort if a high level of accuracy is requested: For this reason, aerial close-range digital photogrammetry enhanced by the GNSS (global navigation satellite system), and total station positioning systems have been used at various levels of detail for the production of a detailed 3D model and 2D thematic maps with an excellent level of in the positioning of the structures and in the architectural drawing. Thanks to the collected dataset, it was possible to better identify the building units (CF), to digitize the limits of the masonry stratigraphic units (USM), and to draw up a first constructive diachronic sequence hypothesis on which to base chronology. Moreover, some particular masonry techniques have been sampled and compared at the regional level with the aim to better dating of constructive expedients. It was finally demonstrated how the use of integrated methodologies allows us to obtain a complete and detailed documentation including information regarding not only architectural and geometrical features but also archaeological and historical elements, building materials and decay evidences—all useful as support of the interpretation of data.

Keywords: archaeology of architecture; Encastellation; digital photogrammetry; survey; 3D model; geometric documentation; diagnostic study; thematic maps; cultural heritage

1. Introduction The current study is part a wider research project concerning the Encastellation phenomenon and the settlement on Mediterranean feudal areas, started in the end of the 90s by the Chair of Medieval Archaeology of the University of Florence [1] and continuing to date with several papers by E. Donato [2–4]: One of the topics of this research was the retracing the steps of the Encastellation process of the Tyrrhenian coastal area of Calabria between the Norman period and XIX century. In the

Heritage 2019, 2, 2384–2397; doi:10.3390/heritage2030146 www.mdpi.com/journal/heritage Heritage 2019, 2 2385 Heritage 2019, 2 2385 thesub-regional sub-regional zone zone between between Capo Capo Scalea Scalea (northern (northern border) border) and and the the Savuto Savuto riverriver (southern border), border), these studies have identified identified 14 castles (Figure 1 1a),a), oneone forfor thethe mainmain centrecentre andand severalseveral isolatedisolated towerstowers located alongalong thethe stagesstages of of a a north–south north–south coastal coastal route route dating dating back back to to the the Trajan Trajan age age (in (in particular particular to the to thejunction junction with with the transverse the transverse route route towards towards the hinterland) the hinterland) or in proximity or in proximity of harbours. of harbours. It is, however, It is, plausiblehowever, plausible that the system that the also system included also included other important other important fortresses fortresses mentioned mentioned by the by sources the sources (such (suchas the as Castrum the Castrum Fellae, Fellae, Cetraro Cetraro and Fuscaldo), and Fuscaldo), whose whose remains remains have nothave been not stillbeen identified still identified on field. on field.In many In casesmany thecases available the available documentation documentation allowed allowed us to follow us to the follow salient the phases salient of thephases settlement of the settlementhistory of thishistory fortress, of this starting fortress, from starting the conquest from the ofconquest the Tyrrhenian of the Tyrrhenian Calabria byCalabria Normans by Normans until the untildefeat the of thedefeat last of Bourbon the last resistances Bourbon resistances against the French,against inthe 1806, French, when in all1806, the castles,when all quashed the castles, their quashedfunction, their suffered function, definitive suffered abandonment definitive andabandonment spoliation and processes. spoliation processes. Our research fits fits into this chronological range and aims to add a piece to a complex historical mosaic, such as the Encastellation of of Southern It Italy,aly, which represents not only a solution for the organization and management of the territory but also for the protection andand controlcontrol ofof thethe viability.viability. The site of Scalea (Figure 11b,c),b,c), perhapsperhaps fortifiedfortified beforebefore thethe arrivalarrival ofof thethe NormansNormans [[5]5] and conquered in 1057 by Roger de Hauteville as the first first stage stage of of the the unification unification process process of Southern Southern Italy Italy to the Kingdom ofof Sicily,Sicily, is is an an integral integral part part of of the the described described defensive defensive network: network: Its Its strategic strategic function function is islinked linked to to the the presence, presence, in in ancient ancient times, times, of of an an important important seaport seaport mentioned mentioned by by Idrisi Idrisi and and illustrated illustrated on onseveral several portulan portulan charts; charts; it is it also is also linked linked by theby the possibility possibility to control to control a section a section of the of roadthe road viability viability (via (viaCapua-Regium) Capua-Regium) towards towards theactual the actual Basilicata Basilicata [6]. [6].

Figure 1. (a) The medievalmedieval defensedefense system system of of the the Tyrrhenian Tyrrhenian coast coast of of Calabria Calabria between between the the Norman Norman (XI (XIcentury) century) and theand Viceroyalty the Viceroyalty (XIX centuty) (XIX centuty) (b) The Tyrrhenian(b) The Tyrrhenian coastal area coastal of Cosenza. area of (c )Cosenza. Topographic (c) Topographicmap of the area map of of Scalea. the area (Images of Scalea. processed (Images by processed authors). by authors).

It is necessary to premise that this paper, withoutwithout any pretence of completeness, is conﬁguredconfigured as a synthesis of the methodologicalmethodological processes used for analysis and integration of data collected through different diﬀerent approaches on castles. In In fact, fact, on onlyly few few data relating to some parts of buildings have been reported by way of example, waiting for an overall and exhaustive edition of the historical, stratigraphic, and chronological data of which the two authors are already taking care.

Heritage 2019, 2 2386 have been reported by way of example, waiting for an overall and exhaustive edition of the historical, Heritage 2019, 2 2386 Heritagestratigraphic, 2019, 2 and chronological data of which the two authors are already taking care. 2386 The Site and the Evidences The Site and the Evidences The site rises on the top of a limestone dolomite slightly levelled artificially, which, with its The site rises on the top of a limestone dolomite slightly levelled artificially, artiﬁcially, which, with its elevation (80 m above sea level), dominates the village and the surrounding valleys (Figure 2). elevation (80 m above sea level), dominates the village and the surrounding valleysvalleys (Figure(Figure2 2).).

Figure 2. The ruins of the castle on the top of the hill (view from N-E). Figure 2. TheThe ruins ruins of of the castle on the top of the hill (view from N-E). The structures of the castle are characterized by an irregular plan, adapted to the morphology of The structures of the castle are characterized by an irregular plan, adapted to the morphology of the hill (Figure 3), with walls built upon the edges of the high ridges, especially along the western the hill (Figure(Figure3 ),3), with with walls walls built built upon upon the the edges edge ofs theof the high high ridges, ridges, especially especially along along the westernthe western and and southern sides. andsouthern southern sides. sides.

Figure 3. AerialAerial view view of of the the hillfort from S-W. Figure 3. Aerial view of the hillfort from S-W. Only a part of thethe originaloriginal complexcomplex isis preservedpreserved today:today: The currently visible perimeter of Only a part of the original complex is preserved today: The currently visible perimeter of2 fortificationsfortiﬁcations surround, surround, in in fact, fact, exclusively exclusively the the southern southern half half of ofthe the hill hill (an (an area area of about of about 1400 1400 m2), m but), fortifications surround, in fact, exclusively the southern half of the hill (an area of about 1400 m2), but itbut is itconceivable is conceivable that, that,in ancient in ancient times,times, the castle the castlewould wouldextend extendto the north, to the following north, following its natural its it is conceivable that, in ancient times, the castle would extend to the north, following its natural boundaries.natural boundaries. boundaries. The height of the the preserved preserved walls walls is is imposing imposing and, and, on on elevation, elevation, it itis is possible possible to to read read that that it itis isa The height of the preserved walls is imposing and, on elevation, it is possible to read that it is a complexa complex stratification stratiﬁcation attesting attesting the the succession succession of of th thee various various construction construction phases phases (Figure 4 4).). AfterAfter thethe complex stratification attesting the succession of the various construction phases (Figure 4). After the Norman first installation, confirmed by historical sources, the structures were subjected to multiple Norman first installation, confirmed by historical sources, the structures were subjected to multiple interventions of a destructive and reconstructive nature which have sometimes altered the general interventions of a destructive and reconstructive nature which have sometimes altered the general layout of the complex up to the eighteenth century; what instead seems to have remained unchanged, layout of the complex up to the eighteenth century; what instead seems to have remained unchanged,

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Norman first installation, confirmed by historical sources, the structures were subjected to multiple interventions of a destructive and reconstructive nature which have sometimes altered the general Heritage 2019, 2 2387 layout of the complex up to the eighteenth century; what instead seems to have remained unchanged, judging by the historicalhistorical archive documentation,documentation, is the strategicstrategic andand defensivedefensive function,function, an elementelement that sets it apart from allall otherother complexescomplexes that,that, duringduring post-medievalpost-medieval times,times, lostlost theirtheir defensivedefensive role.role. Among its ruins, in 1908 (few years after the finalfinal abandonment), a large water basin was built connected to the firstfirst Scalea aqueduct. A legend tells that the castle castle is is connected connected with with an an underground underground passage to the ancient TorreTorre Talao,Talao, whichwhich standsstands on on an an imposing imposing rock. rock.

Figure 4. Example of a well-preserv well-preserveded multi-stratification multi-stratiﬁcation on external elevation.

2. Materials and Methods DiDifferentfferent survey methodologies were adopted in order to respond to didifferentfferent study needs and according to various levels of detaildetail (Table(Table1 1))[ 7[7].]. An accurate analysis of the geo-morphology of the site, the evidences, the elevations stratigraphy and the construction techniques was Tablecarried 1. Surveyout by methods.integrating direct explorations to close-range photogrammetryType and of remote Survey survey inspections, Goals all with the aim to identify Methods structures and to date, for the first time, the chronological phases of occupation and abandonment of the site. Creation of a base-map UAV The 3D architecturalTopographic surveys were performedGeoreferencing using two methodologies: Image-based and point- D-GPS based modelling. The former, based onPositioning computer ofvi structuresion algorithms combined with photogrammetric procedures, was useful to obtain a photorealistic 3D model of the castleTotal and stationto generate a new digital Creation of elevation orthoimages 2D base-map of theArchitectural site with contour lines; the UAV (unmanned aerialPhotogrammetry vehicle) system also helped in Drawing of single layer (USM) documentation of some structures (such as external elevation) not entirelyDirect measurements accessible because of their locations. Differential GPS (with WGS-84/UTM32N coordinate system) was used to geo-reference the photogrammetricAn accurate analysis block and of theto precisely geo-morphology position of the the evidence. site, the evidences, A total station the elevations (TST) was stratigraphy helpful to andcollect the points construction for a techniquessmaller scale was survey carried of out diagnostic by integrating walls directand explorationsto document to architectural close-range photogrammetrystratigraphic layers. and Auxiliary remote surveymanual inspections, sketches and all eidotypes with the aimwere to also identify collected. structures and to date, for the first time, the chronological phases of occupation and abandonment of the site. The 3D architectural surveys were performedTable 1. Survey using twomethods. methodologies: Image-based and point-based modelling. TheType former, of Survey based on computer vision Goals algorithms combined with photogrammetric Methods procedures, was useful to obtain a photorealistic 3DCreation model of thea base-map castle and to generate a new digital 2D base-map of UAV Topographic Georeferencing D-GPS Positioning of structure Total station Creation of elevation orthoimages Architectural Photogrammetry Drawing of single layer (USM) Direct measurements

Heritage 2019, 2 2388 the site with contour lines; the UAV (unmanned aerial vehicle) system also helped in documentation of some structures (such as external elevation) not entirely accessible because of their locations. Differential GPS (with WGS-84/UTM32N coordinate system) was used to geo-reference the photogrammetric block and to precisely position the evidence. A total station (TST) was helpful to collect points for a smaller scale survey of diagnostic walls and to document architectural stratigraphic layers. Auxiliary manual Heritagesketches 2019 and, 2 eidotypes were also collected. 2388 The achieved results were merged into a GIS (geographic information system) environment and processedThe achieved for the purpose results ofwere obtaining merged thematic into a GIS maps, (geographic while all theinformation elevation system) drawings environment were performed and processedin a CAD environment.for the purpose of obtaining thematic maps, while all the elevation drawings were performedThis approach, in a CAD whichenvironment. could be defined as “global” [8] due to its interdisciplinary nature, in fact makesThis use approach, of the historical-archaeological which could be defined traditional as “global” tools [8] ofdue research to its interdisciplinary (bibliographic research, nature, in study fact makesof written use sources,of the historical-archaeological stratigraphic analysis oftraditional elevations, tools periodization, of research (bibliographic study of historical research, buildings), study ofadding written the sources, most innovative stratigraphic technologies analysis of useful elevations, for the periodization, surveying, management, study of historical and interpretation buildings), addingof data. the most innovative technologies useful for the surveying, management, and interpretation of data. 2.1. Site Surface Survey: Detection of Above-Ground Structures and Units of Building (CF) 2.1. Site Surface Survey: Detection of Above-Ground Structures and Units of Building (CF). A surface survey of the whole hillfort helped to gather information about all kind of activities on theA surface site, identify survey and of the locate whole the hillfort above-ground helped to structures gather information and their features,about all kind and betterof activities plan theon theinterventions. site, identify The and analysis locate the of theabove-ground surviving structures structures of and the their castle features, was conducted and better through plan the the interventions.following steps: The analysis of the surviving structures of the castle was conducted through the following steps: 1. 1.TheThe detection, detection, cataloguing cataloguing and and mapping mapping of of unit unit of of buildings buildings (Table (Table2). 2). 2. 2.Masonry Masonry stratigraphic stratigraphic analysis analysis and and the the drawing drawing of of diagnostic diagnostic elevations. elevations. 3. 3.The The construction construction of of a chronologicala chronological sequence sequence starting starting from from architectural architectural stratification stratification process process of of thethe castle castle from from the the 11th 11th to the to the 15th. 15th. In total, 11 building units (CF) were detected and mapped (Figure 5). Some of these were already In total, 11 building units (CF) were detected and mapped (Figure5). Some of these were already known, while others were integrated through field survey and drone flights (e.g., CF 11). known, while others were integrated through field survey and drone flights (e.g., CF 11).

Figure 5. 2.5D view of the structure on topographic map (processed by authors). Figure 5. 2.5D view of the structure on topographic map (processed by authors).

Table 2. List of recognized topographic building units (CF).

Id Function Description Quadrangular keep (9.30 × 7.90 m) located at the highest point of the hill. The northern and western walls are still preserved for a maximum height of about 8.5 and 9 m, respectively. The tower was articulated on different CF Central tower levels: in the first level there was a cistern covered by a barrel vault, as 1 (donjon) shown by the layer of hydraulic plaster still visible in the walls; it is possible that, in the first phase, the first level housed a silo. There are two windows, one north in bricks and one in the east. On the south side, the

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Table 2. List of recognized topographic building units (CF).

Id Function Description Quadrangular keep (9.30 7.90 m) located at the highest point of the hill. The × northern and western walls are still preserved for a maximum height of about 8.5 and 9 m, respectively. The tower was articulated on different levels: in the first level there was a cistern covered by a barrel vault, as shown by the layer CF 1 Central tower (donjon) of hydraulic plaster still visible in the walls; it is possible that, in the first phase, the first level housed a silo. There are two windows, one north in bricks and one in the east. On the south side, the tower binds to a wall with N–S course, which could be part of a first contemporary wall. The perimeter masonry, visible for a length of 24 m, has a double row of CF 2 North-west subcircular bastion embrasures along the internal elevation which were accessed by a wooden walkway (the holes for the supports in the masonry remain). Two adjacent rooms, with a N–S rectangular plan. The eastern room is accessible from E through a more recent scale system than the original walls, which are linked to the tower. The western room was accessible from the CF 3 Central rooms south, where there is a small embrasure in squared lava stone blocks. In the internal façade of the west wall, four putlog holes are visible, probably related to the support of a barrel vault roof and an opening: Its walls are slightly off axis compared to CF1. Sub-circular bastion, located on the southern edge of the castle, with the function of containing an artificial embankment. The drone survey along its CF 4 South sub-circular bastion inaccessible external facade highlighted the various constructive interventions not attributable, at the moment, to any chronological phase. Its construction incorporated CF11. Wall preserved for a length of about 15 m. It is characterized by a system of embrasures organized on two levels; the highest one is formed in the infill of CF 5 Eastern curtain wall the oldest battlements; outside the wall is protected by a talus added at a later date. Quadrangular tower characterized in the upper part by a first rectangular nucleus (4.30 x 5.30 m) to which a quadrangular talus was later added, bringing the overall dimensions to approximately 6.30 x 7.30 m. It had to be CF 6 North-east tower characterized by different levels. On the southern side, a machicolation is still visible, an element of defense of one of the accesses to the village that was located in that point. The tower has an articulated and complex constructive stratigraphy. Building equipped with talus, which continues the path of the CF5 wall towards N-N/E, but compared to this, it is more advanced than ca. 3 m. It is characterized by an interesting sequence of construction phases, but the CF 7 Portion of Eastern curtain wall presence of plaster does not allow for the stratigraphic analysis of the entire façade. The reconstruction of the battlements, which took place three times, is visible in the external perspective. System of access, probably related to the last phases of life of the complex, CF 8 Southern access system characterized by the presence of a small arched opening, set directly on the rock bench. North–south curtain, with irregular path. It follows the morphology of the plateau, connecting the western and southern bastions. At the level of the ground, only the crests are visible, while the view of its external facade is CF 9 Western curtain wall visible only from the outside and has been analysed by drone flight. To the south, there are the remains of an arch whose function is not at this time well defined. Curtain wall (approximately 22 m long), preserved for a maximum height of 9 m. In the upper part, rectangular embrasures are visible. Covered at times by large patches of plaster (USM 5), the general external facade, on which the CF 10 North-eastern curtain wall operations of survey and stratigraphic reading were concentrated, is characterised by a complex stratification that testifies to the numerous building phases that have alternated over the centuries. Three construction macro-phases have been identified. Building unit protruding about 1.90 m from the outer limit of CF 4 bastion; along the south-east facade there is a trace of a square curtain tower, relating CF 11 Southern tower to an earlier phase, which was probably incorporated by the construction of the bastion. Heritage 2019, 2 2390

Heritage 2019, 2 tower, relating to an earlier phase, which was probably incorporated by 2390 the construction of the bastion.

2.2. Topographic SurveySurvey ofof thethe HillfortHillfort As a preliminary task for the study of the castle,castle, a topographic survey was carried on the whole hill (an area of about 6000 square metres), with the aim of obtaining a geo-referenced and metrically correct digitaldigital modelmodel toto bebe used as a working base and from which to generate DEM (Digital Elevation Model), contour lines, sections, and 2D orthophotos. For this step, close-range aero-photogrammetric acquisition technologies were combined with GNSSGNSS (global(global navigationnavigation satellitesatellite system)system) positioningpositioning systems according to an approach already successfullysuccessfully tested by authors during other works [9,10]. [9,10]. Respectively, wewe used used a a Phantom Phantom DJI DJI 4 pro4 pro drone drone (equipped (equipped with with a 12 a mega 12 mega pixel pixel camera camera sensor, sensor, FOV (fieldFOV (field of view) of view) 94◦ 20–35 94° 20–35 mm formatmm format equivalent) equivalent) and aand Topcon a Topcon GR-3 GR-3 GNSS GNSS receiver, receiver, equipped equipped with awith base a andbase a and mobile a mobile rover rover antenna antenna set in set the in maximum the maximum configuration configuration for the for reception the reception of GPS of GPS and GLONASSand GLONASS (GLObal (GLObal NAvigation NAvigation Satellite Satellite System) System) satellites satellites [11]. [11]. A firstfirst flightflight waswas made made keeping keeping the the camera camera in in nadiral nadiral position position at aat height a height of 35 of m 35 and m takingand taking care tocare keep to keep an overlap an overlap and sidelapand sidelap between between the frames the frames of 75%. of 75%. Maintaining Maintaining this distance this distance from from the area, the thearea, area the was area covered was covered with 130with images 130 images (Figure (Figure6). Finally, 6). Finally, a network a network of ground of ground control control points (GCP)points was(GCP) planned was planned and measured and measured by differential by differential GPS (in GPSReal (in Time Real Kinematic Time Kinematicmode) for mode) the correction for the correction and the referencingand the referencing of acquisition. of acquisition.

Figure 6. In blue the positions of cameras during the ﬂight.flight.

2.3. Architectural Survey: Wall Elevations The structuresstructures have have been been documented documented combining combining oblique oblique and zenithal and zenithal images manuallyimages manually acquired accordingacquired according to a non-stereoscopic to a non-stereoscopic scheme [12 scheme], approximately [12], approximately 5 m off the 5 evidence.m off the evidence. This method made it it possible possible to to obtain, obtain, in in a ashort short time time (if (if compared compared to to other other techniques), techniques), a acomplete complete and and detailed detailed photographic photographic coverage (because(because itit was was performed performed with with low-altitude low-altitude flights) flights) of allof theall the structures structures and and to visually to visually reach reach parts ofparts the of buildings the buildings that, due that, to theirdue positions,to their positions, were partially were inaccessiblepartially inaccessible (e.g., CF11, (e.g., the CF11, external the elevationsexternal elevations of CF2 and of CF4CF2 towers,and CF4 and towers, the CF9 and wall). the CF9 wall). For each diagnosticdiagnostic elevation, measurements vi viaa a laser total station (Mod. Topcon GPT 1004) werewere alsoalso performedperformed in orderorder toto acquireacquire thethe necessarynecessary datadata forfor thethe creationcreation ofof drawingdrawing basedbased onon ortho-photo, on whichwhich toto representrepresent thethe resultsresults ofof stratigraphicstratigraphic analysisanalysis (Figures(Figures7 –7–9).9). Any other information regarding masonry techniques andand materials was finallyfinally noted in specificspecific tabstabs andand sketches:sketches: During the stratigraphic analysis phases, a sampling of masonry techniques andand aa mapping ofof thethe distributiondistribution ofof bricksbricks waswas alsoalso performedperformed (Figure(Figure7 7).). These vast array kinds of data were elaboratedelaborated and integrated into the architectural drawings, developing thematicthematic maps maps that that recorded recorded and representedand represented the current the preservationcurrent preservation state of the state monument of the andmonument concerning and majorconcerning construction major construction phases, building phases, materials building and materials decay. and decay.

Heritage 2019, 2 2391 Heritage 2019,, 2 2391

FigureFigure 7.7. Thematic map:map: Distribution ofof bricksbricks andand plasterplaster ofof CF6CF6 elevation.elevation. TheThe numbersnumbers indicateindicate thethe Figurearchitecturalarchitectural 7. Thematic stratigraphicstratigraphic map: Distribution layerlayer (USM).(USM). of bricks and plaster of CF6 elevation. The numbers indicate the architectural stratigraphic layer (USM).

FigureFigure 8.8. CF7:CF7: Orthoimage-basedOrthoimage-based drawingdrawing andand stratigraphicstratigraphic analysis.analysis. Some Examples: TheFigure Documentation 8. CF7: Orthoimage-based of CF1 drawing and stratigraphic analysis. 2.3.1. Some Examples: The documentation of CF1 2.3.1.On Some CF1, Examples: the stratigraphic The documentation analysis of wasCF1 focused on the best preserved western and northern On CF1, the stratigraphic analysis was focused on the best preserved western and northern elevations, from which an interesting stratiﬁcation emerged (see Figures9 and 10): It is interesting to elevations,On CF1, from the which stratigraphic an interesting analysis stratification was focus edemerged on the (see best Figures preserved 9 and western 10): It is and interesting northern to observe the edge between the two walls (USM 1) characterized by a masonry in well squared blocks of elevations,observe the from edge which between an interesting the two walls stratification (USM 1) ch emergedaracterized (see byFigures a masonry 9 and in10): well It is squared interesting blocks to lava stone and calcarenite set in parallel courses and laid in alternate rows of stretchers and headers. observeof lava thestone edge and between calcarenite the two set wallsin parallel (USM courses1) characterized and laid by in a alternate masonry rowsin well of squared stretchers blocks and These corner blocks seem to be in phase with curtain wall portions (USM 10) consisting of a masonry ofheaders. lava stone These and corner calcarenite blocks seem set in to parallelbe in phase courses with andcurtain laid wall in alternateportions (USMrows of10) stretchers consisting and of a made of split or rough-hewn stones, installed on courses that tend to be horizontal and parallel, where headers.masonry These made corner of split blocks or rough-hewn seem to be instones, phase insta withlled curtain on courses wall portions that tend (USM to 10)be horizontalconsisting ofand a the horizontal courses are placed at intervals of about 40 cm. Numerous wedges consisting of stone masonryparallel, wheremade ofthe split horizontal or rough-hewn courses stones,are placed insta atlled intervals on courses of about that 40tend cm. to Numerousbe horizontal wedges and chips and rare bricks can be seen at the joints of the blocks. This type of masonry, made by volcanic parallel,consisting where of stone the chipshorizontal and rare courses bricks are can placed be seen at at intervals the joints of of about the blocks. 40 cm. This Numerous type of masonry, wedges stone blocks, can be found also in the S/E angle and in the N/E one. consistingmade by volcanic of stone stonechips blocks,and rare can bricks be found can be al soseen in atthe the S/E joints angle of and the inblocks. the N/E This one. type of masonry, The other type of masonry visible on USM 11 seems to belong to a diﬀerent phase: It is characterized made by volcanic stone blocks, can be found also in the S/E angle and in the N/E one. by split stones installed on courses that tend to be horizontal and parallel; the horizontal courses are in

Heritage 2019, 2 2392 Heritage 2019, 2 2392 The other type of masonry visible on USM 11 seems to belong to a different phase: It is The other type of masonry visible on USM 11 seems to belong to a different phase: It is characterized by split stones installed on courses that tend to be horizontal and parallel; the Heritagecharacterized2019, 2 by split stones installed on courses that tend to be horizontal and parallel; 2392the horizontal courses are in this case placed at intervals of about 35 cm and marked by rows of bricks horizontal courses are in this case placed at intervals of about 35 cm and marked by rows of bricks and chips of stones, also present between the joints. This masonry is visible along the entire surface and chips of stones, also present between the joints. This masonry is visible along the entire surface ofthis the case two placed elevations at intervals (USM 4). of aboutAnother 35 interesting cm and marked feature by is rows the presence of bricks of and another chips ofirregular stones, type also of the two elevations (USM 4). Another interesting feature is the presence of another irregular type ofpresent masonry between (USM the 3), joints. recognised This masonry in the upper is visible part along of the the elevations entire surface and of perhaps the two attributable elevations (USM to a of masonry (USM 3), recognised in the upper part of the elevations and perhaps attributable to a reconstruction4). Another interesting of the upper feature part. is the presence of another irregular type of masonry (USM 3), recognised inreconstruction the upper part of ofthe the upper elevations part. and perhaps attributable to a reconstruction of the upper part.

Figure 9. Western and northern elevation of CF1: Example of a CAD (Computer-Aided Drafting) Figure 9.9. Western and northern elevationelevation of CF1:CF1: Example of a CAD (Computer-Aided Drafting) drawing and sampling of masonry techniques. drawing and sampling of masonrymasonry techniques.techniques.

Figure 10. Thematic map: Distribution of bricks and plaster of CF1 elevation. The numbers indicate the USM. Heritage 2019, 2 2393

2.4. Data Processing and Post-Processing One of the advantages of the image-based survey is linked to the possibility of exploiting the algorithms of structure from the motion (SfM) range imaging technique, which is able to reconstruct the surface and volume of a given object in the three dimensions through the automatic collimation of common points between adjacent frames. The following processing steps were performed in Agisoft® Photoscan software [13]:

(1) Preliminary calibration of the camera using Lens, an Agisoft® plug-in [14], in order to reduce the Heritageerror 2019,generated 2 by the optical distortion during processing. 2393 (2) Alignment of camera and creation of tie points (sparse cloud) between the frames: High quality Figure 10. Thematic map: Distribution of bricks and plaster of CF1 elevation. The numbers indicate and pair pre-selection was set; the process was based on reference (i.e., the position given by the USM. drone GPS). (3)2.4. DataCreation Processing of dense and cloudPost-Processing was (Figure 11a) (setting medium quality and deep filtering on moderate). (4) Creation of the three-dimensional model (mesh) starting from the point cloud (Figure 11b). (5) OneThe generationof the advantages of the texture of the enabling image-based adaptive survey orthophoto is linked parameter: to the possibility This parameter of exploiting caused the algorithmshorizontal of structure and vertical from surfaces the motion to be (SfM) treated range separately imaging (the technique, first were which texturized is able by to orthographic reconstruct the surfaceprojection, and volume while the of latter, a given like object the elevation, in the three were dimensions textured starting through from the automatic oblique images. collimation of common points between adjacent frames. The following processing steps were performed in (6) The semi-automatic classification of dense cloud points in order to exclude the elevations given Agisoft® Photoscan software [13]: by non-ground points from the calculation of the digital elevation model (DTM). (7)(1) PreliminarySubsequently, calibration a DTM was of th produced.e camera using Lens, an Agisoft® plug-in [14], in order to reduce the (8) errorVector generated contour linesby the were optical generated distortion with during 1 m of processing. equidistance and exported to a shp file. (9)(2) AlignmentA complete of GEOti cameraff orthophotoand creation (reference of tie points system (sparse WGS-83 cloud)/UTM between 33N) the was frames: finally High generated, quality andwhich pair was pre-selection useful for was updating set; the the process planimetry was base of thed on structures. reference (i.e., the position given by drone GPS). (3) Finally, Creation aofnew dense up-to-date cloud was building(Figure 11a) plan (setting (see medium Figures4 quality and 12 and) was deep digitized filtering on on moderate). the new cartographic(4) Creationbase-map. of the three-dimensional model (mesh) starting from the point cloud (Figure 11b).

(a) (b)

Figure 11. ((aa)) Dense Dense cloud cloud model: model: View View from from the the east. east. (b) ( b3D) 3D textured textured mesh mesh model: model: View View from from the thesouth-west. south-west.

2.5.(5) Database The generation and GIS of Management the texture enabling adaptive orthophoto parameter: This parameter caused the Forhorizontal each building and vertical unit, surfaces a digital to databe treated sheet separately was generated (the first to record were texturized all the alphanumeric by orthographic and spatialprojection, and information while the usinglatter, MySQLlike the ®elevation,, a free andwere open textured source starting relational from oblique database images. management system,(6) The suitable semi-automatic for desktop classification and web-based of dense applications. cloud points The in order database to exclude was connected the elevations to Qgis given (GPL by software,non-ground version points 3.6.3) andfrom implemented the calculation with of the architectural digital elevation and building model (DTM). materials data, geometric documentation(7) Subsequently, (vector a DTM drawings) was produced. and other types of information with the aim to create a dynamic ‘integrated(8) Vector archive.’ contour lines were generated with 1 m of equidistance and exported to a shp file. (9) A complete GEOtiff orthophoto (reference system WGS-83/UTM 33N) was finally generated, which was useful for updating the planimetry of the structures. Finally, a new up-to-date building plan (see Figures 4 and 12) was digitized on the new cartographic base-map.

2.5. Database and GIS Management For each building unit, a digital data sheet was generated to record all the alphanumeric and spatial and information using MySQL®, a free and open source relational database management system, suitable for desktop and web-based applications. The database was connected to Qgis (GPL software, version 3.6.3) and implemented with architectural and building materials data, geometric documentation (vector drawings) and other types of information with the aim to create a dynamic ‘integrated archive.’

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3.3. Results Results and and Discussion Discussion 3.1. Documentation Data 3.1. Documentation Data TheThe deployment deployment of combined combined close-range close-range aero-photogrammetry, aero-photogrammetry, combined combined to traditional to traditional point- point-basedbased methods methods (total (total station station and andDifferential Differential GPS GPSpositioning positioning technologies) technologies) proved proved to be toessential be essential to toget, in in a a short short time, time, all all the the necessary necessary tools tools for for supporting supporting our ouranalysis analysis and anddata dataintegration integration [15,16]. [15 In,16 ]. In particular: (1)(1) A A high-resolution high-resolution photographicphotographic coverage of of th thee whole whole site site (made (made of of overlapping overlapping stereoscopic stereoscopic pairs)pairs) usable usable as as a a tooltool forfor monitoring the the state state of of conservation. conservation. (2)(2) A A basic basic cartography cartography of of the the geo-referredgeo-referred and ortho-rectified ortho-rectified site site to to be be used used as as the the basis basis of ofa GIS a GIS for for thethe study study of of thethe wholewhole area: area: This This is isavailable available in 2D in 2Dversions versions (as a (as plan a planin GeoTIFF in GeoTIFF format) format) or in a or inscalable a scalable 3D model 3D model in suitable in suitable formats formats to be included to be included in other inanalyses, other analyses, developments developments and creation and creationplatforms platforms for the promotion for the promotion of multimedia of multimedia products. products. (3)(3) A A database database of of scalable scalable digital digital (CAD)(CAD) drawings of of the the diagnostic diagnostic elevations, elevations, useful useful both both as asa basis a basis forfor our our stratigraphic stratigraphic surveysurvey and for for any any digital digital reconstruction reconstruction / restoration./restoration. (4) A detailed 3D model (dense cloud and triangulated irregular network ) for metric measurements (4) A detailed 3D model (dense cloud and triangulated irregular network ) for metric measurements and for the realization of multimedia products (education and virtual visit). and for the realization of multimedia products (education and virtual visit). The advantage of the drone survey lies not only in the ever-increasing economic affordability of The advantage of the drone survey lies not only in the ever-increasing economic affordability of high-performing equipment and in the semi-automated sfm processing but, above all, in the quality high-performing equipment and in the semi-automated sfm processing but, above all, in the quality of of the photorealistic restitution, comparable metrically and geometrically to those obtained by thescanning photorealistic systems restitution, methods [17] comparable that are much metrically more and expensive geometrically and complex to those in obtainedthe data processing by scanning systemsphase. methods [17] that are much more expensive and complex in the data processing phase. InIn relation relation to to our our objectives, objectives, we we cancan concludeconclude that these these methods methods have have proven proven to to be be appropriate appropriate forfor a a better better understandingunderstanding of of the the castle, castle, having having allowed allowed us to usupdate to update the plan the of the plan complex of the (Figure complex (Figure5) to grasp5) to grasp some someunknown unknown construction construction problems problems and confirm and confirmothers already others known: already From known: the geo- From themorphological geo-morphological analysis analysis of the site of (as the we site can (as see we on can the see DTM, on theFigure DTM, 12), Figure it is possible, 12), it isfor possible, example, for example,to assume to assumethe presence the presence of structures of structures even in the even northern in the half northern of the halfhill, ofwhich the hill,is free which of evidence is free of evidencetoday. today.

Figure 12. 2.5D rendering of structure on the digital elevation model (DTM), contour line base-map, and Google satellite images.

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3.2. Archaeological Data The study did not succeed in the detection of pre-Norman/Byzantine phases, highlighted in other fortified centres such as San Michele sull’Abatemarco, Pietramala, Amantea, Savuto and Aiello. It is not clear if it is to be interpreted as a document of a Norman foundation of the site, to a lack of research, or to the failure to preserve the structures: Only future and more in-depth investigations (excavation or geo-physical prospection) will be able to verify the presence of previous phases. In the regard of the preserved structures, we must point out the extreme situation of abandonment and degradation of the complex, which has not always allowed us to safely carry out works. The analysis of the construction sequence of the buildings based on the stratigraphic relationships allowed us to elaborate a first unpublished chronology of the main phases of the complex based on a regional comparison of the construction techniques. In total, four main construction phases were distinguished (Figure 13): Even if the stratification is much more complex and suggests a greater number of phases, only certain data have been reported in theHeritage current 2019, 2 conditions, postponing further distinctions to future insights. 2396

Figure 13. Schematic chronological map.

4. ConclusionsThe oldest recognizedand Future building Developments nucleus belongs to the Norman quadrangular tower (donjon) built in direct contact with the natural rocky bank, which is linked to the remains of a ﬁrst curtain wall that The multidisciplinary methodological process described in this paper has proven to be suitable surrounded the higher plateau: It is possible to attribute its construction to the earliest stages of the to achieve the initial goals: The 3D and 2D geometric and graphic documentation provided conquest by Roger de Hauteville, who, in accordance with the sources, chose to use the site as a base information regarding building techniques and materials used in the exterior façades and helped in for raids in the territory. With the exception of the imported volcanic stone inserts, the stone material identifying all the construction phases of the castle. This kind of combined documentation, based was extracted from the calcareous conformation on which the site stands. both on traditional and innovative instrumental surveys, represents (as well-demonstrated) a valid In the Swabian phase (early XIII century) the castle was enlarged according to new planimetric tool supporting the interpretation and analysis of historical buildings. models and construction techniques: Walls were built with battlements (CF 7), fortiﬁed by quadrangular On the other hand, even if the precision on the measurements obtained is not enough for the towers (only the CF 6 tower has been preserved). architectural monitoring of structures (this was not our goal), it is enough for creating an exhaustive, The model introduced is the “castle-fortress,” characterized by a quadrangular plan and projecting representative 3D model of the monumental complex which is useful for the fruition and diffusion towers whose origins date back to the type of the Roman castrum or to examples of eastern of the knowledge of heritage. For this purpose, the active contribution of these technologies is clear, military architecture. since the graphic documentation is an essential moment of investigation. Between the XIII and XIV centuries (Angevin period), works were carried out to restructure and In conclusion, all these products obtained represent a fundamental tool of specialised knowledge reinforce the structures: The raising of the curtains (on the elevation of CF 7, the Swabian phase was in the archaeological field, supporting stratigraphic, monitoring and diagnosis for conservation or followed by a raising of the curtain with reconstruction of the battlements), the reconstruction of the future restoration activities. Nevertheless, they are already saved in a format suitable for embedding battlements, and the addition of talus (CF 6) have been recognized. in GIS and H-BIM (Heritage Building Information Modeling) environments, where they can be managed and implemented with further research.

Funding: This research received no external funding.

Conflicts of Interest: The authors declare no conflict of interest.

References

1. Vannini, G. ’Progetto Strategico d’Ateneo’ Finanziato dall’Università di Firenze (Concorso1999): La Società Feudale Mediterranea. In Profili Archeologici. Apogeo e Declino, Alle Origini Dell’europa Moderna 2000–2003. 2. Donato, E. L’incastellamento Medievale nell’alto Tirreno Calabrese (XII-XIV sec.). Prime Indagini e Prospettive di Ricerca. In III Congresso Nazionale di Archeologia Medievale, castello di Salerno, Complesso di Santa Sofia. Salerno, 2–5 Ottobre 2003; pp. 435–442. 3. Donato, E. Il Contributo Dell’archeologia Degli Elevati Alla Conoscenza Dell’incastellamento Medievale in Calabria Tra L’età Normanna E Quella Sveva: Un Caso Di Studio. In “Archeologia Medievale” XXXI; Firenze, Italy, 2004; pp. 497–526.

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To a fourth post-medieval macro-phase (VXI century) belong the two large sub-circular bastions on the east and north sides (CF 2 and 4), which are characterized by a more irregular masonry, Taking into account the data coming from the most recent research on the region, we can conclude that the settlement-architectural developments of the Scalea castle ﬁt fully into the general framework: Building typologies and settlement dynamics were widely compared at the regional and extra-regional levels (Basilicata). However, it is necessary to specify that the general data of the sites embedded in Calabria are anything but deﬁnitive.

4. Conclusions and Future Developments The multidisciplinary methodological process described in this paper has proven to be suitable to achieve the initial goals: The 3D and 2D geometric and graphic documentation provided information regarding building techniques and materials used in the exterior façades and helped in identifying all the construction phases of the castle. This kind of combined documentation, based both on traditional and innovative instrumental surveys, represents (as well-demonstrated) a valid tool supporting the interpretation and analysis of historical buildings. On the other hand, even if the precision on the measurements obtained is not enough for the architectural monitoring of structures (this was not our goal), it is enough for creating an exhaustive, representative 3D model of the monumental complex which is useful for the fruition and diﬀusion of the knowledge of heritage. For this purpose, the active contribution of these technologies is clear, since the graphic documentation is an essential moment of investigation. In conclusion, all these products obtained represent a fundamental tool of specialised knowledge in the archaeological ﬁeld, supporting stratigraphic, monitoring and diagnosis for conservation or future restoration activities. Nevertheless, they are already saved in a format suitable for embedding in GIS and H-BIM (Heritage Building Information Modeling) environments, where they can be managed and implemented with further research.

Author Contributions: Conceptualization, E.D.; data curation, D.G.; investigation, D.G.; methodology, E.D.; project administration, E.D.; supervision, E.D.; visualization, D.G.; writing—original draft, D.G.; writing—review & editing, E.D. and D.G. Funding: This research received no external funding. Conﬂicts of Interest: The authors declare no conﬂict of interest.

References

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