Proposal N°: SEP-210139712 (Id:636984)

DELIVERABLE 4.2

Building Template Modeller

Revision: 01 Due date: 31/09/2016 (M16) Actual submission date: 9/12/2016 Lead contractor: DIETRICH’S

Dissemination level

PU Public, to be freely disseminated, e.g. via the project website X

IN Internal, to be used by the project group

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 636984.

Published in the framework of:

BERTIM – Building Energy Renovation through Timber Prefabricated Modules BERTIM website: www.BERTIM.eu

Deliverable administration and summary:

Nº & Name: 10 – Building Template Modeller Status: First final version Due M16 Date 31/09/2016 DIETRICH’S (Yvon Sebesi, Uwe Emmer, Peter Philipps), FCBA (Zaratiana Author(s): Mandrara), POBI (Hervé Coperet), TECHNALIA (Asier Mediavilla Intxausti) Editor: Yvon Sebesi (DIETRICH’S) Comments:

Document history:

Version Date Author(s) Description 01 10.11.2016 Yvon Sebesi Version 1 – Summary and Draft First advanced French version 02 01.12.2016 Yvon Sebesi except Chapter 3 and end of 4 First complete version 03 05.12.2016 Yvon Sebesi French/English for internal review 04 08.12.2016 Yvon Sebesi Final version Revision 01

Disclaimer:

The project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 636984.

The content of this report does not reflect the official opinion of the European Union. Responsibility for the information and views expressed in the therein lies entirely with the author(s).

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Table of content

1. Executive summary ...... 7 2. Introduction ...... 8 2.1 3D Acquisition, part of the BERTIM holistic process with RenoBIM ...... 8 2.2 High accuracy for prefabrication ...... 9 2.3 Unusual high accuracy for surveying ...... 10 2.4 Devices and technologies: preliminary enquiry ...... 11 2.4.1 Cameras or Camcorders, drones or lifts ...... 11 2.4.2 Total stations ...... 12 2.4.3 3D laser scanners ...... 13 3. Total stations process ...... 14 3.1 Building survey tests ...... 14 3.1.1 Device / Process 1: Leica TCRP 1205, for data export ...... 14 3.1.2 Device / Process 2: Leica 3D Disto and tablet, for data export ...... 15 3.1.3 Device / Process 3: Leica 3D Disto and PC, with DIETRICH’S CAD system ..... 16 3.1.4 Surveying strategy 1: Five points on each opening and scanned lines ...... 16 3.1.5 Surveying strategy 2: Alternative for openings...... 18 3.2 Import in CAD Systems ...... 18 3.3 Analyses before 3D modelling ...... 19 3.4 Evaluation of the 3 devices / processes and 2 strategies used ...... 22 3.4.1 Devices ...... 22 3.4.2 Processes ...... 22 3.4.3 Survey strategies ...... 22 4. 3D Laser Scan Process ...... 25 4.1 Overview of workflow and deliverables ...... 25 4.2 Finalizing contract and settling up contractor support measures...... 27 4.2.1 Setting targets and deadlines ...... 27 4.2.2 From invitation to tender, through appraisal to final contract ...... 28 4.2.3 Contractor support measures and quality plan ...... 31 4.3 Devices and software used by provider and other parties...... 32 4.4 Survey of the building to obtain point clouds ...... 33 4.4.1 Strategy, logistics and climatic conditions ...... 33 4.4.1 Surveying practice ...... 36

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4.4.1 Geo-referencing ...... 37 4.5 Registration and point cloud processing ...... 38 4.5.1 Registration of the point clouds ...... 39 4.5.2 Reducing and cleaning the point cloud ...... 40 4.5.3 Exploitation of first deliverables by other parties ...... 41 4.6 3D Modelling ...... 42 4.6.1 Import of a georeferenced point cloud in Revit ...... 42 4.6.2 Modelling strategy ...... 44 4.6.3 Preparations before 3D modelling ...... 45 4.6.4 Walls process ...... 46 4.6.5 Windows process ...... 49 4.6.6 Floors process ...... 54 4.6.7 Other 3D objects ...... 54 4.6.8 Use of advanced deliverables by other parties ...... 55 4.7 Next stages with IFC files ...... 55 5. Conclusions ...... 58 5.1 At a first stage in energy renovation of the POBI demo-building ...... 58 5.2 Comparison of total station and 3D laser scanner processes ...... 59 6. References ...... 61

Acronyms

BIM : It can be used to denote the process of producing and managing the digital information of the building process (Building Information Modelling) as well as the digital model itself (Building Information Model) CAD : Computer Aided Design DWG : proprietary file format from AutoCAD DXF : Drawing eXchange Format, a common format for exchanging geometry between CAD tools IFC : Industry Foundation Classes, format developed for open BIM LOD : Level of Development (used to define BIM models development)

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List of figures

Figure 1 BERTIM process with RenoBIM tool ...... 8 Figure 2 Demo building to be renovated by POBI at La Charité sur Loire (France) ...... 9 Figure 3 Example of operating clearance ...... 10 Figure 4 Scanning outside wall for Bentley ContextCapture ...... 11 Figure 5 Circling round a building at different heights for Bentley ContextCapture ...... 12 Figure 6 Three total stations working simultaneously in the courtyard of the demo building ... 14 Figure 7 Points localisation on an old plan ...... 14 Figure 8 Sketch on fixed points and measure on Leica interface ...... 15 Figure 9 North angle of demo building for survey test with 3 total stations ...... 16 Figure 10 Lines scanned and points fixed for each opening on facade ...... 17 Figure 11 Lines scanned and points fixed for each opening on Leica interface ...... 17 Figure 12 Tool rectangle, alternative for openings ...... 18 Figure 13 Import tests in Revit on left and in DIETRICH’S system on right ...... 19 Figure 14 2D analyses in DIETRICH’S CAD system before 3D modeling ...... 19 Figure 13 New recommanded points around openings ...... 23 Figure 16 Procurement and production processes for building acquisition with laser scanner 25 Figure 17 Flattened 360° panoramic photo, with door on both sides...... 26 Figure 18 Tools used by provider and other parties to produce or use data and 3D model ..... 32 Figure 19 Location of all the stations in and outside of the building ...... 34 Figure 20 Openings not scanned from inside the building ...... 35 Figure 21 First-floor windows of SW facing wall on 360° photo ...... 35 Figure 22 First-floor windows of SW facing wall in point cloud ...... 36 Figure 23 Targets as checkerboard fixed on walls ...... 37 Figure 24 Sphere target visible on all faces ...... 37 Figure 25 Targets seen from several stations to assembly points cloud ...... 37 Figure 26 Setting topo points for geo-location ...... 38 Figure 27 Target above a geolocalisation point ...... 38 Figure 28 Two extracts of Trimble Realworks report: accuracy of the target coordinates ...... 39 Figure 29 Total point cloud, radius more than 100 m ...... 40 Figure 30 Areas to reduce the point cloud: building, sun masks and working zone ...... 40 Figure 31 Navigation in Trimble Scan explorer from one position point to another ...... 41 Figure 32 Measurements and mark-up in Trimble Scan explorer ...... 42 Figure 33 Revit message for points with coordinates up to 30.000 ...... 42 Figure 34 Decision to delete the first three figures for X and Y Topo points ...... 43 Figure 35 Topography point in Revit defines a +0 for the building ...... 43 Figure 36 Point cloud imported in Revit ...... 44 Figure 37 Creation on the point cloud of storey level references ...... 45 Figure 38 Point cloud in Revit cut on a storey between 2 heights ...... 45 Figure 39 Most usual architectural objects families in Revit ...... 46 Figure 40 Properties definition of a 3D object Wall ...... 47 Figure 41 Horiz.view during 3D wall creation on a line added to the points cloud ...... 48 Figure 42 Vertical view of a 3D wall modelled in storey N0 and points cloud ...... 48 Figure 43 3D wall and not adjusted 3D Opening modelled on the point cloud ...... 49

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Figure 44 Visibility domain of 2 vertical work cuts fixed on horiz.cut ...... 50 Figure 45 Thickness of the point cloud and wrong perpendicular on a lintel ...... 50 Figure 46 Adjustment of a 3D Opening in a 3D wall on reference lines ...... 51 Figure 47 3D walls, openings and floors on points cloud on SW facade ...... 51 Figure 48 Details of an existing window, shutters closed ...... 52 Figure 49 Opening families on facade NE ...... 53 Figure 50 Windows families and dimensions ...... 53

List of tables

Table 1 Example of tolerances for concrete or masonry works (French regulations) ...... 11 Table 2 Results and comparison of B and H dimensions of openings through 3 processes .... 21 Table 3 Basic analysis of initial bids by 3D scan service-providers ...... 29 Table 4 Planned settings of scanner TRIMBLE TX5 (each station)...... 29 Table 5 Real settings of scanner Faro Focus 3D for indoor positions ...... 33 Table 6 Real settings of scanner Faro Focus 3D for outdoor positions ...... 33 Table 7 Comparison of total station and 3D laser scanner processes ...... 60

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1. Executive summary

This deliverable is part of the Building Energy Renovation through Timber Prefabricated Modules (BERTIM) project. The purpose of this public deliverable is to serve as guidelines for 3D acquisition of the building template prior to renovation with BERTIM modules. So it should be of particular interest to firms insulating the outside walls of buildings undergoing renovation, as well as those specializing in surveying existing buildings and producing digital models.

The introduction explains the context for this study, which is also the first part of a demonstration on a building due to be renovated by POBI Industrie, as part of the BERTIM project. It highlights the very specific requirements with regard to accuracy for the process of surveying and modelling an existing structure, in preparation for fitting prefabricated modules. It also explains the need to integrate in the model the data necessary for physical and energy analysis projected as part of the BERTIM process, concluding with a presentation of the various devices and associated software tools currently available for surveying an existing building.

Chapter 3 describes the methods used for a partial survey using three total stations, then compares and discusses the results obtained. It concludes with the definition of a better method for surveying with such devices the buildings to be renovated with prefabricated modules.

Chapter 4, which is the longest section of the study, looks in detail at the entire survey process with a 3D scanner and subsequent digital modelling. Analysis of this process starts with the invitation to tender addressed to two specialist service providers and follows it through to delivery of a 3D model of the building, with drawings and an Industry Foundation Classes (IFC) data model to continue design work. A specific method is proposed in response to the particular requirements regarding accuracy posed by a survey paving the way for prefabricated modules.

The conclusion compares the two tools and acquisition methods in the specific context of fitting prefabricated modules to the outside walls of a building undergoing renovation.

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2. Introduction

2.1 3D Acquisition, part of the BERTIM holistic process with RenoBIM As BERTIM project concerns renovation, before any design of the modules by the manufacturers, the architect will need a 3D model to obtain the geometry of the existing building to be clad by the modules, in order to define the dimensions of the modules and manage all the aesthetic aspects of the renovation job. As this mainly concerns energy renovation, the 3D template will not only concern geometrical aspects. It must also allow energy analysis with specialist software and simulation of return on investment. In line with the BERTIM process, these stages of the design phase (after the feasibility phase and before the manufacturing phase) will be produced with RenoBIM software through a BIM process described in deliverables 2.4 and 4.1. Then this software will be developed in the course of Tasks 4.2 through to 4.5. Interoperability of the results with the software being used will be validated in Task 4.6.

Figure 1 BERTIM process with RenoBIM tool

During Task 4.1 it was decided that the ideal scenario was to obtain an initial contract from the building owner at an early stage of the process, survey the building (3D scan) and provide the various parties with a 3D model of the building. This preliminary stage is defined as the start of the design phase, after completing the feasibility phase. Thus, this 3D acquisition is provided much earlier than current situations, to obtain benefits from this 3D model of the building for all the design process.

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As we want to avoid creating it twice along this holistic BERTIM process, the goal now more clearly defined of this guideline, is also to provide this early 3D template of the building, fulfilling in so far as possible the requirements of all possible players during the entire BERTIM process: architect, engineers, prime contractor, manufacturers and onsite fitters.

In early 2016, POBI Industrie announced plans to change the sequence of the virtual demonstration planned for the initial BERTIM project, turning it into a real-life demonstration on a building undergoing renovation. The building is in La Charité sur Loire, France, where POBI production plant is located. This renovation project seemed an ideal basis for the work planned under task 4.2 and for drawing up these guidelines. However it proved difficult to synchronize planning of this renovation work with producing task 4.2, which explains the delay in completing the present deliverable.

Figure 2 Demo building to be renovated by POBI at La Charité sur Loire (France)

At the time of writing, it is worth noting that the commitment on the part of the local council, which owns the building due to be refurbished, did not yet give rise to an initial written contract for a survey of the building. Taking a more conventional route the council is going to commission its appointed architect to carry out the initial part of the study.

2.2 High accuracy for prefabrication As the BERTIM timber modules will be prefabricated, the singularity of BERTIM 3D acquisition of the building is the high accuracy required. We must emphasize this point because the high level of accurancy required, represents a big difference with all kinds of 3D acquisition for any conventional renovation process, starting with an architectural project, then design work by contractors (perhaps using BIM processes), and finally the main part of renovation work carried out onsite with many (too many considering the non-quality costs entailed) adaptations to the real building.

In the special case of our prefabrication, the clear goal is of course to install the modules and carry out inside finishes, especially around windows, without any onsite alterations to the prefabricated modules or cutting existing concrete walls.

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At this early stage, it is difficult to set a target accuracy for the survey of the building, but when questioned on this issue, POBI (one of the BERTIM-project manufacturers) said it should be close to 5mm, if possible less, in order to define the dimensions of modules, windows and doors. It is also important to note that although an industrial manufacturing process reduces the variation between the dimensions defined in a CAD model and the real object produced, it never achieves absolute precision. For example, in a Quality Plan, POBI defines tolerances for dimensions and the location of a window frame in a timber prefabricated module, as being defined in their CAD system (i.e. data input into machines) and checked at the end of the production line. This plan also strictly defines many other tolerances check output. The two sources of tolerances, from surveying (TS) and fabrication (TF), must be aggregated. Construction rules, such as operating clearances (OC), will be required to manage them in all situations.

Figure 3 Example of operating clearance

This detailed horizontal cross-section of a window illustrates one of the most important cases to be solved by these construction rules and operating clearances, with OC = TS+TF.

2.3 Unusual high accuracy for surveying In a conventional renovation job tolerances for dimensions are directly linked to tolerances for masonry work. In France these tolerances are given in NF DTU 20.1 “Ouvrages en Maçonnerie de Petits Eléments – Parois et Murs” for masonry with small components and NF DTU 21 “Exécution des Ouvrages en Béton” for concrete work. A few examples are cited in the table below. Of course these tolerances will vary in other EU countries but not a great deal, because they relate directly to these technologies and it seems really difficult to set much higher requirements. These tolerances explain how all companies become accustomed to onsite adaptation. They also explain why the accuracy requirement for surveying buildings is currently not as high as that required for prefabricated modules.

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Reference Definition Tolerance NF DTU 21 Distance between two storeys ± 20 mm NF DTU 21 Distance L between two concrete beams Highest value between ± 20 mm or L/600 NF DTU 20.1 Planimetry on a 10 m line 2 cm NF DTU 20.1 Planimetry under a 2 m rule, depending maxi 0.5 cm of materials and execution type to maxi 1.5 cm NF DTU 21 Planimetry under a 2 m rule for walls, maxi 0.5 cm depending of execution type to maxi 1.5 cm

Table 1 Example of tolerances for concrete or masonry works (French regulations)

It is also interesting to note that these tolerances, mentioned here in the context of renovation, are mainly defined for new buildings. Thus, this BERTIM document, created for renovation work will be also relevant to any case of prefabrication with timber modules, including new buildings. In the latter case it is increasingly frequent on big construction sites to carry out a 3D scan to check the building ‘as built’ and assess the differences with the theoretical 3D model provided by the design team.

With regard to the special accuracy requirement of less than 5 mm, set by POBI, our preliminary inquiries, before work started on these guidelines, sought to establish which technologies and devices were suitable.

2.4 Devices and technologies: preliminary enquiry

2.4.1 Cameras or Camcorders, drones or lifts Photogrammetry is an emergent technology currently used to survey landscapes or cities for planning projects, industrial sites and also buildings. Its great advantage is the low cost of the devices as basic cameras (even smartphones) or camcorders can be used for the first stage of the 3D acquisition process.

Bentley proposes ContextCapture, a software for processing this data set created by overlapping photographs. ContextCapture automatically provides a point cloud and then creates a 3D textured triangle-mesh model. Bentley also provides useful guidelines for photo acquisition (Bentley, 2016), from which we have extracted a few illustrations of the process.

Figure 4 Scanning outside wall for Bentley ContextCapture

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From each position you need to take several photos to capture each part of the building at least three times, while limiting the angle between photos to 15°.

Figure 5 Circling round a building at different heights for Bentley ContextCapture

To be sure of capturing the whole building without any shadows, you need to take photos from the ground but also at several elevations. So the cameras or camcorders are used with lifts to elevate the user, or with drones. In the latter case, several cameras are required to obtain several pictures from each shooting position.

These emergent technologies are very attractive but it soon became clear that this kind of device could not deliver the target accuracy. Distributors announced 1cm as the maximum accuracy, failing to meet the prefabrication requirement. We consequently did not explore this solution any further for BERTIM applications. Of course new, improved photogrammetry solutions may be available in the near future.

2.4.2 Total stations A total station, also known as a tacheometer, is a theodolite that measures vertical and horizontal angles, combined with an electronic device for measuring distances. The device emits a laser beam. This beam is reflected back from any surfaces it encounters enabling the range to be measured. Reflecting prisms are also used, enabling the operator to work alone. Total stations are the modern equivalent of instruments which have been used for many years by surveyors. However they are also increasingly used by building contractors, large and small, for surveying and for positioning structures.

”For jobs involving simple geometries and readily accessible work sites, 3D imaging systems may not be the best choice.” (GSA, 2009).This claim, made seven years ago, is now a little outdated considering how information technology has evolved. But it still holds true for one of the main players in this market, manufacturing and selling total stations and 3D scanners as well as associated technologies.

In fact, companies now working on insulating outside walls still seem to prefer conventional theodolites to obtain the data they need, both for onsite construction and for manufacturing and installing prefabricated modules. There are probably two main reasons for this choice:

° The cost of a total station (€6,000 to €12,000) is substantially lower than for a 3D scanner (circa €40,000); it is also possible to hire them. ° Only limited additional know-how needed to operate such conventional equipment.

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° As the issue for such a process is to define clearly a methodology for surveying the building, they often prefer doing it themselves to test, assess and validate a process that suits their production requirements.

At present POBI only manufactures prefabricated modules for new buildings, using their own CAD systems and machinery. So work with a total station was a new departure. But parent company AST was able to supply the device and corresponding skills. Initially acquisition with a total station seemed to be a cost-effective solution.

The AST surveyor had never used this device for such applications, so the challenge was to define the best methodology to obtain an optimal set of points, prior to building a 3D model of the existing building. It is important here to note that for most of the survey, the operator acquires each point needed to build the model, one after another. A few devices also offer an automated process to obtain many points on a same line to check the flatness of a surface.

POBI uses DIETRICH’S software as its manufacturing CAD, so the best first solution to be explored was to enter the data from the total station (points and possibly lines) directly into this CAD system and use common objects, such as walls, windows and floors, to produce the model.

2.4.3 3D laser scanners A 3D laser scanner is a terrestrial or aerial device which automatically scans the surrounding space with a laser beam in order to capture the coordinates of tens of millions of points defining a point cloud. The point cloud may be recorded in shades of grey or in colour. A terrestrial 3D scanner on a tripod scans vertically through about 300° and rotates horizontally on its vertical axis to acquire a point cloud over 360°. This technology is known as Laser Detection and Ranging (Ladar). The various types of device vary regarding the maximum range for accurate acquisition. In addition to point-cloud capture a 3D laser scanner is fitted with a digital camera, which takes still photographs.

Much as for photogrammetry, in order to capture a scene the scanner must be moved to different positions to acquire point clouds which are subsequently registered in a single coordinate frame to reconstitute the whole scene. Depending on the type of work the settings on the scanner may be adjusted to vary the resolution, which determines how many million points a cloud comprises and its quality (noise cancelling) by reprocessing data during acquisition. These two parameters affect accuracy, often expressed as the distance in millimetres between two points scanned at a range of 10 metres, and as acquisition speed which ranges from 25.10 3 to 10 6 points per second. This determines how long a scan at any given position will take, ranging from less than a minute to over an hour.

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3. Total stations process

3.1 Building survey tests The BERTIM demo project undertaken by POBI Industrie created an opportunity for a real-life trial. In July 2016 a partial survey was carried out of the building due for renovation in La Charité sur Loire, France. POBI’s parent company AST employs a full-time surveyor, who uses a Leica total station for topographic surveys. The resulting possibility of creating a 3D model of the building using in-house resources seemed worth pursuing. As DIETRICH’S had not had an opportunity to check the output from this particular instrument – primarily designed for surveying building topography – the firm offered to take part in the trial survey operation, using its own Leica 3D Disto total station. The Leica sales representative for this type of equipment was also invited, taking part with a second, identical device. So the trial survey was carried out simultaneously on three total stations.

Figure 6 Three total stations working simultaneously in the courtyard of the demo building

Three different procedures of the same series of points previously defined could be surveyed simultaneously thanks to the three different stations available on site.

3.1.1 Device / Process 1: Leica TCRP 1205, for data export The surveyor used his topography Leica TCRP 1205 total station and reported points targeted with an optical sight in a classic method. They were named and numbered when recorded and manually marked on an existing map of the building as shown on the below chart.

Figure 7 Points localisation on an old plan

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This method that seems archaic today, appeared to be efficient, as it allowed him to finish the survey first in 60 mn, ahead, in this “contest” of the second position by 40 mn. We of course noted that the Geometer uses his station daily which constituted a significant asset.

3.1.2 Device / Process 2: Leica 3D Disto and tablet, for data export

The Leica 3D DISTO total station used by the representative of Leica Geosystems is a quite specific total station: equipped with a motor and a video camera, it can be piloted with a Leica or Windows pad or even a PC and the target associated to a laser point projected on the facade can be managed directly from this device either connected via a Wlan (Wifi network) or via a USB cable. For an increased mobility of the operator, the Wlan connection will be preferred to the USB one. Less precise than the surveyor total station and rather used for indoor works, it is nevertheless recommended by Leica for this kind of works of surveying facade data in the limit of a 15 meters distance to respect the precision required by the BERTIM process. It has been used here connected to a Windows pad which allows to pilot the station with targeted points on a “video” display and the control of the recorded points thanks to lines on a “diagram” display. This “diagram” display also allows to add or remove lines between points and therefore get measures or surfaces data. The video camera allows to capture images of the reported objects that can also help documenting the project. The registration of different sequences of recorded points in successive files can ease the use of the data lately by the operator of the CAD system they will be imported in.

Figure 8 Sketch on fixed points and measure on Leica interface

After recording all points according to the first defined method (see below) in 100 min, the Leica Geosystems representative suggested a second method and did a few more records according to it.

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3.1.3 Device / Process 3: Leica 3D Disto and PC, with DIETRICH’S CAD system

This very same Leica 3D DISTO station was used by DIETRICH’S team, but this time connecting it to a PC using the pad interface. During the 1 st and 2 nd process, the created points and lines were saved in files of different forms to be then imported in CAD software. In this 3 rd protocol, the recorded points were directly reported one by one in DIETRICH’S software. This latter approach is much slower as only a little over half of the defined points could be reported in 100 min. A large part of this slowness can be attributed to the operator lack of experience as well as the unfamiliar process of direct reporting into the CAD, but this approach is definitely slower even if we consider it allows to save time by skipping the import step.

3.1.4 Surveying strategy 1: Five points on each opening and scanned lines This test was performed on one single location of each total station. The relocation of the stations and the link between the different positions is made according to the standard method of topography by a system of reference points. The digital 3D model to be created can also be geo-referenced. The location of the station requires to refer to several points with known coordinates. If they are missing on the construction site, they can be implemented thanks to a GPS solution. This study performed later with the laser scanner, has not been reported here with the total stations.

The strategy, defined before the present people started the survey (POBI, AST, DIETRICH’S, FCBA, LEICA Geosystems), consisted in recording enough points to define the North angle of the below building with 4 windows on the NE facade and 3 windows on the NW one.

Figure 9 North angle of demo building for survey test with 3 total stations

On each record, a point located on the platform of the front door allows to define the +0 level of the building. On the picture below, we can see horizontal lines at the concrete floor levels (position where the modules will be fixed in the future) and vertical lines, on which points are distributed at regular spaces. Thanks to these points, the map of the facade will be designed in the CAD and the planimetry gaps will be identified. Positioning two vertical lines at 0.10 m from the North edge will allow to better define this edge than recording points on the edge itself. With the motorized 3D DISTO, this function called “scan” can be automated.

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Each window is then defined by 5 points targeted by the operator: 1. at mid-height from the opening, outside edge of the left reveal 2. at mid-height from the opening, inside of the left reveal (against the window) 3. at mid-height from the opening, outside edge of the right reveal 4. in the middle of the outside edge of the lintel 5. at the crossing of the window sill and the outside edge of the reveal, right or left of the opening

Figure 10 Lines scanned and points fixed for each opening on facade

On the 3D DISTO pad, once the recording program is completed, it then takes the shape of the below image on which the red lines represent the scanned lines at regular spaces and the black lines represent the 5 points recorded on each opening (linked in the order of the survey).

Figure 11 Lines scanned and points fixed for each opening on Leica interface

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3.1.5 Surveying strategy 2: Alternative for openings This other strategy is based on using the tool “Rectangle”, one of the sketch up tools suggested by the Leica Geosystems pad or PC interface.

Figure 12 Tool rectangle, alternative for openings

To save time, the proposal is made of recording only two points in the diagonal of each opening and to place a rectangle on these two points. Two additional points are then recorded on the front of the window sill to be able to get the measure of the sill jutting out of the wall, which is a necessary information for POBI.

3.2 Import in CAD Systems The total stations allow recording simultaneously all registered data in different file formats compatible with most CAD:

° Text files in format .txt and/or .csv in which the coordinates xyz of each of the points, the name of these points and possibly the lines linking these points and measures are recorded. ° DXF-3D files in which this same information is already organized in a standard exchange format to be directly usable in a 3D CAD ° DXF-2D files in which these data are re-processed to provide plane views of the projected points with possible addition of complementary information of plans (measure between points or level of points, legends, cartridges...) ° Dwg files in which the DXF-3D and DXF-2D data can be grouped in a single file under the “Objects” and “Layouts” tabs in the native AutoCAD format. ° These various import formats have been tested to our satisfaction in the different Revit, AutoCAD and DIETRICH’S CAD system formats.

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Figure 13 Import tests in Revit on left and in DIETRICH’S system on right

3.3 Analyses before 3D modelling The creation of a 3D model wasn’t continued beyond the preliminary steps because the decision was taken a little after these partial results with total stations became available, to do a complete survey of the building with a laser scanner. These first steps allowed the analyses that enabled the new strategy described in 3.4.

Operating in the DIETRICH’S CAD system is much easier with a 2D file projected on a 3D facade in order to get the information of the below picture. The openings have been sketched again with a “Line” tool before they were 3D modelled with a “Window” tool.

Figure 14 2D analyses in DIETRICH’S CAD system before 3D modeling

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The too large number of points conducted to decrease the size of measures and levels (in light blue). Well organized in layers, these data, not very useful here, can also be hidden which is not possible for the points, all located in the same layer. This first observation leads to suggest to create two files or several layers to be able to screen the points (see 3.4.3).

Point #21 marked in red is an erratic point. Keeping the horizontal measure at the level of point #23 would make this opening too wide from standard. Why? It is quite easy when we target a precise point on the edge of a window reveal to be so close to the side that the station records a point on the window itself and no longer on the facade. The addition of point #20 allows here to sketch the opening which is not possible on the left side. This lack of information leads towards recommending to record at least two points per segment (see 3.4.3). Such irregular points were found in the files corresponding to the three processes and this problem does not seem to be related to the operator professionalism and could be reduced by increased experience and attention to this well identified risk.

Point #19 corresponding to the recorded point 1 (chart 10, p.16) is almost here confounded with a second point which corresponds to the recorded point 2 on this same chart. Two far from the façade plane, it is not numbered and only a 3D measure allows here to differentiate these two points. Recording two points stackable on a 2D view is not recommended.

Sketching each segment of the opening with a single point imposes here vertical and horizontal lines which is probably not accurate enough for the BERTIM prefabrication process. Recording each segment with 2 or 3 points will allow to get polygons in which the CAD operator will be able to sketch up rectangles (see 3.4.3). To this point, it is interesting to compare and refer also to 4.6.5 which addresses this same issue of openings modelling on a cloud of points coming from a 3D scan.

Comparing the measures of the existing openings allow then to set the minimum measures that will be the basis of the standard window measures for their integration into the modules: see measures in blue in the table on the following page.

With specific kinds of outside cladding of the modules (panels fixed with recessed facing joints), windows have to be perfectly re-aligned vertically and/or horizontally. An additional preparatory work will consist in sketching these vertical and horizontal lines to set other minimum values to take into account this additional constraint of re-alignment.

This comparison between the windows can also be made in between the results of the 3 processes to evaluate the accuracy of the measures provided. The table on the following page provides results for:

° survey of the 4 openings of the NE facade according to all three processes ° survey of the 3 openings of the NW facade according to processes 1 and 2 only

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NE1 NE2 NE3 NE4 NO2 NO3 NO4 Maxi Maxi Dif. Difference corrected process 1 1568 1570 1577 1588 1592 1601 1594 33 33 process 2 1577 1578 1570 1593 1578 1583 1578 23 23 process 3 1570 1581 1545 1619 49 11 Fidelity 9 11 32 31 14 18 16 Fidel. corrected 9 11 7 5 14 18 16

B measure NE1 NE2 NE3 NE4 NO2 NO3 NO4 Maxi Maxi Dif. Difference corrected process 1 1407 1408 1405 1403 1480 1482 1433 79 30 process 2 1418 1423 1401 1411 1429 1426 1409 28 28 process 3 1415 1412 1404 1426 22 11 Fidelity 11 15 4 15 51 56 24 Fidel. corrected 11 15 4 8 x x x

Table 2 Results and comparison of B and H dimensions of openings through 3 processes

This table compares 36 values measured from the records imported in DIETRICH’S CAD system. Firstly, the 3 minimum values of the B and H measures (in blue in the table) are very close one to another. The difference between the minimum and maximum values are in between 23 and 33 mm for the 2 processes whose records refer to all 7 openings.

Secondly, 7 of these values (close to 20% of them) have been qualified erratic and should therefore be eliminated from the analysis. Other reasons add to the ones presented in the previous page. The significant differences between records tend to consider errors in manipulating stations. The competitive emulation combined to the 3 simultaneous recordings may have generated a bit of a hurry. The heat wave, difficult to stand for the operators, also tends to influence the air flow and may also have been an additional factor. This confirms in any case the absolute necessity to be able to confirm each point by at least a second one and potentially a third one.

Fidelity which is impacted as much by the targeting of the operator as by the precision of the total station itself, can be given for only 11 comparisons. The extreme values of 18 and 16 mm for NW3 and NW4 heights, can possibly be explained by the fact that one of the two operators positioned point #5 (chart 10 p.16) on the left and the other operator on the right of the window. We can therefore keep the value of 15 mm and note that it is well superior to the precision goal for survey that we foresaw at the beginning of our thoughts about prefabrication. One more time, this surprising value can only lead to increase the number of recorded points to secure results.

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3.4 Evaluation of the 3 devices / processes and 2 strategies used

3.4.1 Devices The total station for topography used by the surveyor was nicely available in the POBI group but it is oversized compared to the use it has been made of it here, in regards to the small distance for such a survey of facades. The price of total stations depends on the quality of their optical lenses which is the first precision factor.

On the other hand, the 3D DISTO complete station will be limited when measuring higher buildings than the ones of the tests done here and will impose that stations be located at a maximum distance of 10 meters. The accuracy of the targeted point can also be limited by the video camera resolution when shooting at a certain distance or in specific lightening conditions. When possible, the operator will be able to overrule this by getting closer and controlling the laser red light.

In building construction, the more often used Leica range is the Builder range, more basic stations, non-motorized, but most of the time more accurate. The latest versions of these Builder stations can also be connected to pads which makes them more attractive for the possibility of documenting the survey with drawings, easing their use after introducing data in CAD systems.

3.4.2 Processes The first two processes produced several files that could be imported in a CAD software. The third total station worked to directly input the points in DIETRICH’S CAD system. Unluckily, the recording performed at La-Charité-sur-Loire was made on a heat wave day and everyone present has been well informed of this specific. Decreasing on site recording time and spending more time in the office for post treatment seems to be the current strategy of professionals. This ordinary practice for a professional surveyor has also been chosen by a Project Manager of the company SYBOIS (DIETRICH'S customer questioned on this topic) while recording data with a HILTI total station for a significant renovation project using prefabricated timber modules. If this strategy could be adopted with success for recording a small number of points, it should not be selected for such a long survey.

3.4.3 Survey strategies

3.4.3.1 Openings The first suggested strategy was made of surveying 5 points by opening (chart 10). The opening angles are rarely recommended because the connecting point between the 3 planes is often inaccurate as anticipated when defining the middle of the segments. But this number of 5 points often appeared too low when analysing results as too many points (20%) showed evident erratic positions. It is finally recommended to record each segment by at least two points, close to the angles, approximately 50 mm. In case a point would be missing, this missing point could be replaced by a point vertically below or horizontally from the first one, which would be of course not very accurate but maybe enough if the missing points are not too many. Recording 3 points per segment can also be an alternative. Even the CAD system user

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has to manage additional problems caused by the non-alignment of these 3 points, it is a good method to better secure the survey.

The second strategy suggested to create openings, always rectangular by the two points of the diagonal. Evidently, this simple approach seems now too far from the reality of openings, to be selected in a perspective of prefabrication.

Point #5 is used to measure the height of the window but it can only be seen on one side, the other one being always masked by the prominent window sill. The proposal of the second strategy to record two points on the front of the window sill answers POBI’ need to get the measure of the sill jutting out from the wall. Surveying two points of the higher edge of this window sill allows to get, not only this information but also the height searched with point #5. The window sill is slightly inclined so the height difference between point #5 and these new points is a quite standard measure which only requires to survey a few more points #5 for post-treatment. Surveying systematically 2 or 3 points on this prominent window sill is also recommended to address the same risk of a point on the window rather than on the window sill.

Point #2 which is used to define the width of the reveal, from the facade to the window plan, is certainly not useful for each opening because this measure, which does not much vary, is not essential for POBI prefabrication: the inside connection of the future window which is part of the prefabricated module to be fixed on the existing walls, will be most probably done on site. This point was anyway not always recordable as it was often masked by the folded shutters for all apartments with open shutters.

Considering all these remarks, the best surveying strategy for the windows seems to be the suggested below image with 4 edges recorded by 2 (or 3) points each (in red), and 2 recorded points on a few windows only (in blue). The regular order of the record of the points linked by lines is also important to ease the work in CAD systems.

Figure 15 New recommanded points around openings

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3.4.3.2 Walls This chapter is written after realizing a complete survey with a 3D laser scanner. Even if these two technics are very different, this approach of the most pertinent strategy for a total station benefit from the conclusions with the complete scan : it is very important, right from the beginning, to define the direction selected for each wall with two points as far apart as possible. Choosing the most pertinent points for this direction is explained further down in 4.6.4. These series of two points for each wall are added to the point defined for the +0 level of the project, to the reference points of the successive positions of the station and to all the points defining the openings.

In case it becomes necessary to control the façade planimetry, it seems useful to set all other surveyed points on horizontal and vertical lines in a second file (or if possible in a second layer) in order to facilitate their use in a CAD system later. Since this recording test was performed, the issue of deliverable 3.1 revealed that all these other points, considering the fixing method of the modules on the walls, will most probably not be useful to POBI.

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4. 3D Laser Scan Process

4.1 Overview of workflow and deliverables As 3D laser scanners are expensive devices, which few construction companies could amortize simply on the basis of their own needs, specialist service providers have recently appeared to survey buildings, followed by 3D modelling with BIM software using point clouds from the survey.

Seizing the opportunity presented by a real-life test, in the form of a BERTIM demo-project carried out by POBI, drafting of the present guidelines drew on the survey of a building in La Charité sur Loire, France, awaiting renovation. Acting on behalf of POBI, DIETRICH’S took charge of the tender, consulting two service providers. Contrary to the ideal scenario originally projected by D4.1, POBI has not yet received specific instructions in this matter. However, considering that the local council had made a sufficient commitment to the project, the firm decided to go ahead and commission the surveying services.

Figure 16 Procurement and production processes for building acquisition with laser scanner

The diagram above describes the workflow for surveying a building. It separates two processes: an initial procurement process, to contract the work to a service provider (A); then production of a geo-located survey (B1), from which all the required deliverables will be extracted (B2 to B4), all covered by a quality-control plan (B0).

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A geo-located survey of a building is carried out using a 3D scanner, equipped with a GPS antenna, at several positions, or with two separate devices. This is the onsite data acquisition phase. Onsite acquisition of point clouds is automated and quick. The operator only needs to place the scanner at each position and select the right targets to achieve registration. The time required is directly related to the number of scanning positions. For example, the forecast time for surveying the building at La Charité sur Loire, which entailed specific requirements regarding accuracy due to prefabrication, varied depending on the quotes from half a day to a full day.

The initial result of a survey is a series of point clouds, which are then merged, or registered, to form a single point cloud. This data set is checked to validate registration and filtered to remove surplus data. Nowadays registering these point clouds in advanced dedicated software such as Faro-Scene, Leica-Cyclone, Trimble-RealWorks or Autodesk-Recap360, is a highly automated process. Only checking and possible corrections demand some operator input. Geo-location, based on several survey points, enables the building to be fitted into a system of XYZ coordinates, fixing longitude, latitude and elevation as well as orientation in relation to the north. This geo-located point cloud is supplemented by a series of 360° panoramic photos, providing additional data as well as the point cloud provided by the 3D laser scan carried out at each position. Each geo-located cloud point and its set of 360° photos constitute the first deliverables.

Figure 17 Flattened 360° panoramic photo, with door on both sides

A very accurate point cloud may resemble a photograph, but unlike the pixels in a photo all the points it contains are located by XYZ coordinates. It can already be used to make measurements for use in the early phases of design. But it is still only an intermediate result, the first stage of modelling with CAD software. CAD modelling will enable the point cloud to be imported and used as a geometrical basis for constructing three-dimensional objects. The modelling process, carried out by an increasing range of 3D CAD tools which import point clouds, may in some cases be supplemented by modelling aids such as Faro/Kubit- PointSense, Leica-CloudWorx or Trimble-EdgeWise-Scene. The modelling process is the most important part of the whole building-acquisition operation.

Another way of using a point cloud is to make a textured triangle-mesh model to obtain the surfaces. This automated operation is mainly used for land surveys. However in the case of BERTIM modules it may be used to check the flatness of existing outside walls and consequently the margin for adjusting anchoring systems to achieve a completely flat surface.

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The 3D volumetric model produced by a CAD software tool will then serve as the basis for other secondary deliverables, such as 2D drawings (storeys, outside walls, cross sections, benchmarks, etc.), lists and quantities (net floor area, surface area of façades, number of windows in each category, etc.) in keeping with more usual procedures.

An IFC file (the OpenBIM format) will be exported from the initial CAD tool used to model the existing building. Imported by other software tools this file will be used in the subsequent stages of the BERTIM workflow under Work Package 4:

° Decision on the renovation brief and preliminary design work using RenoBIM ° Energy audit using Energy+ ° Detailed design work for manufacturing, using the manufacturers’ CAD tools

Producing the 3D model is certainly the most important phase, both in terms of the time required (five to ten longer than the time it takes to capture data) and the skills involved, because the final quality of the resulting model and its usefulness depends on the modelling method used by the CAD operator. The skills needed to build a model on the basis of point clouds are very different from those used in conventional CAD work. This was a key factor in the decision to use the services of a specialist company rather than start from scratch ourselves. Our input focused on the specific requirements of a BERTIM project and how best to adapt the usual methods to suit the BERTIM project, in partnership with a service provider well versed in acquisition and modelling.

The deliverables associated with this 3D model are then produced using the CAD tool, in keeping with the usual processes familiar to end-users, which require no particular comment on our part.

4.2 Finalizing contract and settling up contractor support measures This topic concerns the whole procurement process with a company specializing in 3D scan services, as well as quality management during the production phase. It has already been very well described in several documents, such as “Client-Guide-to-3D-Scanning-and-Data- Capture” (UK BIM Task Group, 2013), which proved very helpful.

Some features of these guidelines relate to the specific conditions in the United Kingdom, but otherwise it provides detailed information on a wide range of topics with regard to tendering and contracting with specialist service providers. However, it applies to fields which are not directly related to the specific issues raised by the BERTIM project.

In the following, we describe the details and adaptation of the proposed methodology in line with BERTIM’s specific needs.

4.2.1 Setting targets and deadlines As stated above the BERTIM demo project, carried out by POBI Industrie on a building in La Charité sur Loire, France, requiring renovation, provides a very concrete basis for investigation. Acting on behalf of POBI, DIETRICH’S asked two service providers to tender.

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Once the local council of La Charité sur Loire was sufficiently committed to the building renovation project, DIETRICH’S commissioned the relevant surverying services.

There are always difficulties involved in procuring a product or service when hampered by the specific problems of inadequate experience. Regarding the particular 3D scanning and modelling services with which we are concerned, potential buyers are still relatively inexperienced. Moreover in many cases the service providers have only recently started trading and the work demanded of them often involves prototyping and experimentation.

So, during preliminary contacts with the two service providers, we emphasized the specific nature of our demands. The survey needed to be much more accurate than usual, notably for the outside walls and above all for window geometry. Surveying would focus mainly on the building envelope; the inside was only of any use for a very general definition of the structure (interior walls and slab floors). It was also necessary to assess the flatness of outside walls.

Initial contact was made in July 2016. Then a file was sent, containing photographs and any available drawings, as well as details of the services, including various options, for which a quote was required. The first option related to the addition of interior partitions. The aim here was to assess the additional cost, over and above the baseline service covering just the outside walls, and the possible merits of a more comprehensive brief which might be useful to the architect. The second option related to the possibility of carrying out a second survey, focusing on the slab under the roof. This survey would be carried out once the existing roof had been dismantled, as part of an as yet unscheduled initial work phase.

We should point out that, at this early stage, the local council in La Charité sur Loire had not yet drafted a final schedule of works. One of the options still on the table was to build an additional flat in the roof space, resting on the slab. To pursue this idea it would be necessary – once the existing roof resting on this slab had been dismantled – to make an accurate survey of the slab, allowing the proper positioning of new 3D modules located in the roof space. Given the possible need of a second survey, it was obviously important to choose the right moment to carry out surveying work. Meanwhile some renovation work could start, with an initial dismantling phase. As regards the BERTIM project, this concerned the roof but also the metal shutters on windows. The shutters, no longer of any use, concealed part of the masonry reveals. In the case of other projects, this preparatory work may involve partial demolition, for instance to remove balconies which may form too great a thermal bridge, or demolishing curtain walls to reveal the supporting structure, or indeed removing equipment on outside walls such as air-conditioning appliances. Carrying out a second survey entails additional costs, but we opted to stick to BERTIM’s initial objective of delivering, at the outset, a model of use to the architect and POBI. We accordingly decided to carry out a survey before any work started on the building. The two service providers filed preliminary quotes at the end of July 2016.

4.2.2 From invitation to tender, through appraisal to final contract Preliminary, broad-brush examination of the two quotes immediately highlighted these points:

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Initial bid Provider 1 Provider 2 Nb of pages 1 17 Support measures - Quality plan no yes Price r atio for basic service 100 265

Table 3 Basic analysis of initial bids by 3D scan service-providers

A service well presented by a well organized company does not necessarily yield the best quality final service. So we continued our talks with the two firms. Some of the differences between the quotes, and the exchanges they prompted, enabled us to gain a better technical grasp of the services on offer.

Our talks on the preliminary quotes focused on the following points:

° Acquisition of a point cloud in colour or shades of grey: ultimately we settled on shades of grey, which costs less because less (roughly half as much) time is spent at each scanning position. In addition colour did not seem particularly useful to the project. ° Number of scanning positions for survey: one bid explicitly quoted 10 positions with a unit price; the other did not give any details on this point, but set a goal ‘of achieving an exhaustive 3D survey of the existing building’. ° Scanner settings:

Points acquired Distance (mm) Noise cancelling Colour Scanning per rotation between points (scale of 1 to 8) time (million points) at 10 m (min : s)

28 7.670 3 NON 03 : 17

Table 4 Planned settings of scanner TRIMBLE TX5 (each station)

This answer was provided by the second service provider, responding to a question on the accuracy we wanted to achieve and its possible relation to survey resolution. We relied on their experience of survey work, having no first-hand experience of using this type of device, nor yet the resulting point clouds. A higher resolution (number of points acquired) or quality (noise cancelling) reduces the distance between points at a range of 10 metres. This may mean fewer positions are needed but with longer scanning time. The correlation between the settings and the distance between points at a range of 10 metres or scanning time is not linear. At the highest setting the scanning time for this device is 1 hour and 50 minutes. On the basis of past experience, the service provider strikes a balance between these parameters to achieve a level of quality suited to the project’s requirements, coupled with cost-effective overall surveying time. Furthermore the aim that each part of the outside walls should be surveyed from at least two positions, often more, opens the way for much denser point clouds than the value stated above, which corresponds to a single cloud obtained from one position.

° Level of Development (LOD) specification: the first quote offered an LOD value of 200, the second one 300 (without non-graphic information). The Level of Development (LOD) is a reference that enables practitioners in the AEC Industry to specify and articulate with a

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high degree of clarity the content and reliability of Building Information Models at various stages in the design and construction process. LOD is sometimes interpreted as Level of Detail rather than Level of Development . Level of Detail is essentially how much detail is included in the model element. Level of Development is the degree to which the element’s geometry and attached information has been thought through – the degree to which project team members may rely on the information when using the model. Thus, this LOD is a specification of the 3D model, starting from the initial concepts in the architect’s sketches, at LOD 100, up to LOD 400 construction models with details of the materials, cuts and all the assembly connections on carpentry work or geometrical details and steel-work for concrete structures. The various LODs are described in detail in the Level of Development Specification (BIMForum, 2016). It is perhaps worth noting that BIMForum is the American chapter of buildingSMART International, an organization which promotes use of BIM through the work of 18 national or language-based chapters (at time of writing). So this definition of the LODs in 3D building information modelling coincides exactly with the contracting and building methods of architecture, engineering and construction industry (AEC) in English-speaking countries. It may at times be well less suited to countries which diverge from these methods. In France, for instance, a key factor in the organization of the building industry is the Loi sur la Maîtrise d’Ouvrage Public (or Loi MOP). Bim/Maquette Numérique: Contenu et Niveaux de Développement, a set of guidelines published by Le Moniteur and distributed by MediaConstruct, buildingSMART France (SYNTEC- INGENIERIE, 2014) proposes, as an alternative to LOD, the Niveau de Développement concept, ranging from ND1 to ND6, the aim being to achieve a better fit with the various development phases specified by French legislation. The (second) quote, offering LOD 300, specified ‘without non-graphic information’. This refers to the dimensional, physical and regulatory properties usually associated with smart objects in a digital model, the properties of the materials or components of an object, such as a wall, floor, roof or window, not available to a service provider building a model on the basis of a point cloud. Such supplementary data, which contribute to the power of a BIM process, may nevertheless be added subsequently. We finally opted for the LOD 300 solution, without non-graphic information, but in what followed we were not really able to determine whether it provided a sufficiently high resolution to which we could refer in the event of a dispute with the supplier. The examples provided to illustrate the selected mode of modelling and accompany the level of definition ultimately proved more useful than the definition itself: - Dimensions: height, width and depth will be true to the real state of finite elements. - Shape: the shape of the element will be true to its real state; generic elements made up of several elements will be represented as a single element, e.g. for a wall of concrete blocks with rendering, the wall will be represented as a single elements, not with the concrete block and rendering elements . - Position: elements will be positioned in relation to one another as they are located in the building. - Texture: the final texture of objects will be smooth, their colour approximating to the actual colour.

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° Checking the flatness of outside walls: two approaches were proposed. The first one consisted of analysis carried out by the point-cloud processing software to colour facades depending on their distance from a baseline plane, highlighting surfaces above this plane in shades of blue, below this plane in shades of red. This report was only available as a PDF file. The second solution was to make a textured triangle-mesh model representing the walls. The triangular lines and surfaces approximating the geometry of the walls can then be exported to CAD software. ° Geo-location: our lack of experience of this type of job led us to suppose that this service would be included. Our talks to clarify the initial quotes made us realise that this was not the case. So this additional service was included in the second quote prior to signature of the contract. This added a series of survey nails. First they were geo-located using a global positioning system, as part of the Lambert 93 reference system, in order to comply with France’s NGF guidelines on elevation (one of the systems used by French surveyors). Then they were pinpointed using the 3D scanner with a known target for elevation.

The additional information obtained from the two tendering contractors confirmed our preliminary analysis and the final contract was signed with: SARL IM-PACT 10 rue Condorcet 63000 Clermont-Ferrand.

4.2.3 Contractor support measures and quality plan Though not very formal, the contractor support measures proved effective. They initially involved talks which led to a specific methodology suited to the high level of accuracy required for the project. With regard to surveying, our talks finalizing the contract led to a higher number of indoor scan positions (see 4.4.1). As for modelling, after a half-day session presenting the methods commonly used, it was decided to adopt a specific method for this project (see 4.6.4 to 4.6.7). Regarding the definition of style rules for 2D drawings, also mentioned in the contract, no particular requirements emerged and Im-pact applied standard rules. As for the study of the flatness of outside walls, for which no method was clearly established, it was agreed to carry out tests on an outside wall using the two methods specified in the contract, in order to determine which one would be used for the whole project. The primary deliverables were made available very promptly (see 4.5.3). Then all the way through the modelling phase, as stipulated in the contract, a Dropbox account was used to publish advanced deliverables (see 4.6.8). Various documents explaining how to access these deliverables (primary and advanced) and how to install the corresponding tools accompanied these deliveries. Im-pact operated an efficient hotline, enabling regular exchanges between the service provider and DIETRICH’S regarding minor corrections to the model. Furthermore Im-pact supplied a quality report on: ° Scanner settings (see 4.4.1); ° Windows that could not be surveyed from the inside (see 4.4.1); ° Definition of GPS points and their processing for Revit (see 4.6.1); ° Method adopted for modelling walls and windows (see 4.6.4 to 4.6.7).

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4.3 Devices and software used by provider and other parties The following diagram defines the tools used throughout the process: in the upper part by Im- pact; in the lower part by the end-users, currently DIETRICH’S and POBI, and in the future the architect, their engineering team or the project owner.

The contract provided for use of a Trimble Tx5 laser scanner, but the device which was actually used was a Faro Focus 3D laser scanner, with largely similar characteristics, combined with a Leica GS08 GPS for geo-location. This data was supplied by Im-pact in its report on the survey of the building site.

Figure 18 Tools used by provider and other parties to produce or use data and 3D model

The point cloud was assembled, or registered, and processed using Trimble RealWorks software which also uses 360° photos. These photos were delivered to end-users via Trimble Scan Explorer a free extension to the Microsoft Edge / Internet Explorer browser. A link to a (3.5Mo) download file, containing data and access to the interface made it easy for POBI and DIETRICH’S to share it. These aspects have been well documented. A solution was soon found to an initial obstacle, for the file had to be unlocked before being unzipped.

Another link enabled us to download the (2GB) point cloud file in the standard E57 format, which all point-cloud processing software packages can import. DIETRICH’S worked on it using Autodesk Revit 2017, but the architect using Graphisoft Archicad, version 19, was also able to import it. A third link connected to another (1.6GB) file in RCS format. This is Autodesk format to save a point cloud imported in Revit.

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The service provider produced the model of the existing building using Autodesk Revit 2017, using the imported point cloud. Modelling lasted about two weeks and the model under construction was constantly available for DIETRICH’S to check and comment on. For this collaborative work the service provider set up a specific Dropbox account. We were thus able to access the latest version of the model at all times, which was very helpful. It should be noted that the point cloud is never saved with the 3D model, to avoid producing too big a file that is difficult to handle. The point cloud is reloaded into the 3D model at each new step in the modelling process.

Revit produced the 2D drawings stipulated in the contract for the four storeys, four outside walls and three sections, all dynamically linked to the 3D model. They were exported in DWG format and printed as PDF files. The two versions of the drawings were delivered to the same Dropbox account. DWG is the native Autodesk Autocad format and can be imported by almost all 2D or 3D CAD softwares.

While the 3D model was being produced, DIETRICH’S was able to use the Revit file to produce various IFC (the OpenBIM format) files and make one or two comments, taken into account by Im-pact. The IFC format will be used subsequently to import a model into RenoBIM, the software associated with the BERTIM process.

4.4 Survey of the building to obtain point clouds

4.4.1 Strategy, logistics and climatic conditions The number of positions was not explicitly defined by the contract, which set a performance target rather than the means for achieving the result. The requirements (clearly specified during the discussion phase) concerning the quality of the survey of windows led Im-pact to implement a position inside the building, before each open window. Sixty-nine positions were implemented, including 56 indoors and 13 outdoors, according to the below settings of the scanner.

Points acquired Distance (mm) Noise cancelling Colour Scannin per rotation between points (scale of 1 to 8) g time (million points) at 10 m (min : s)

28 7.670 3 No 03 : 17

Table 5 Real settings of scanner Faro Focus 3D for indoor positions

Points acquired Distance (mm) Noise cancelling Colour Scannin per rotation between points (scale of 1 to 8) g time (million points) at 10 m (min : s)

44 6.138 4 No 08 : 09

Table 6 Real settings of scanner Faro Focus 3D for outdoor positions

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Figure 19 Location of all the stations in and outside of the building

For good accuracy on the outside wall survey, the 13 outside positions were arranged so that there were about four positions per outside wall: three of them from 7 to 15 metres and a last one at about 2 metres for better accuracy on ground-floor details. Only the SE outside wall, which would have required access to the neighbouring property, was surveyed from only two positions.

This survey approach of one indoor position per window had not been raised during the finalization of the contract. During discussions with DIETRICH’S, the indoor surveys were initially supposed to be limited to a few positions in the stairwell, in order to accurately survey the floor levels, and in the housing units for the installation of partitions. This strategy revealed several unforeseen onsite difficulties: some of the occupied housing units could not be entered during the two half-days spent onsite. The image below, which is an excerpt from the survey’s quality-control report submitted by Im-pact, shows the openings concerned on the ground and first floor.

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Figure 20 Openings not scanned from inside the building

This partial lack of information has consequences on the resolution accuracy for the door and the five windows on the ground floor and the two first-floor windows. However, the two images below are reassuring. On the first image, the two windows of the SW outside wall are localized on the photo. On the second, which is a screen shot of the point cloud in Recap360, we note that, while the density of the points is lower than on the windows of the upper storeys, it remains accurate, given the large number of surveys carried out on the outside walls. It is likely, however, that the accuracy of the details on the first-floor window sill is less good: firstly it only appears on the sole position corresponding to the photo, far enough away (about 20 metres) not to be completely shadowed by the terrace of the shop. In addition, as the survey was only carried out from the outside and from the ground, it is only to expected that the window set into the wall should be concealed by the masonry support.

Figure 21 First-floor windows of SW facing wall on 360° photo

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Figure 22 First-floor windows of SW facing wall in point cloud

These potential risks concerning the future quality of the 3D model clearly demonstrate the need for very good logistical preparation for the survey, in the event that access to occupied housing units is required. This is likely to be frequently the case for BERTIM projects. Possible confirmation of a problem of accuracy could in this case require an additional survey, which would incur further costs, mainly because of the extra travel required.

During talks with Im-pact on this survey report, DIETRICH’S proposed another methodology, inspired by the Bentley ContextCapture proposal: a survey from a scissor lift. This technique would help considerably reduce the shadowed areas and thus the lack of data that necessarily appear at the bottom of windows when outside surveys are all conducted from ground level. This technique has never been used by Im-pact, but the suggestion seems to be an interesting possibility to be considered for low buildings which can be circled from the ground. The additional cost of renting these lifts could be offset by a reduction in the overall number of positions, and above all by simplified management of access to housing units.

It should also be noted that acquisition using a laser scanner is impossible under certain climatic conditions. Indeed, it cannot be carried out with rain, snow or fog: the device must not be exposed to water; the survey itself is disturbed by bad weather. During the survey of this building, rain on the first half-day delayed the 13 outside scans, which were all done on the second day, between positions 44 and 56.

4.4.1 Surveying practice As previously explained in detail, surveying with a laser scanner consists in scanning several successive positions, whose point clouds are later registered to form a single data set. This operation requires at least three clearly identified points from two scans, to be used for registration. These points are obtained by setting up targets that are then automatically recognized by the registration software. There are two types of targets: checkerboard targets to paste on flat surfaces, and spheres that can be recognized from any direction. Spheres are used more frequently for outdoor work.

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Figure 23 Targets as checkerboard fixed on walls

Figure 24 Sphere target visible on all faces

Figure 25 Targets seen from several stations to assembly points cloud

The operator must ensure that these groups of at least three targets are clearly visible from one position to the other, as in the flattened 360° photo above. This photo is directly associated with each of the positions and also determines the spread of the point cloud.

4.4.1 Geo-referencing In theory geo-referencing requires three points. However, in Im-pact's experience three is sometimes not enough. This is why it chose to reference six points. These appear in the image below, spread out around the building.

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Figure 26 Setting topo points for geo-location

Some next-generation laser scanners include GPS. As this was not the case of the FARO Focus 130 model used, these survey points – which are traditionally marked on the ground, as in topography work – were first geo-located using the Leica GPS GS08. Then they were integrated in the point cloud using targets set on a tripod, positioned precisely at 1.50 m above the point, as shown in the image below.

Figure 27 Target above a geolocalisation point

As for the registration targets, these geo-location targets must be visible from several positions to be sure of an accurate result.

4.5 Registration and point cloud processing Im-pact uses the Trimble Realworks interface, but equivalent ones are used by other major manufacturers – Faro Scene and Leica Cyclone to name the best known. Two stages are

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clearly defined in the menu of Trimble Realworks, to manage the point clouds obtained from the survey of the building: the first, 'Registration’, registers point clouds; the second, ‘Office Survey’, concerns processing of the registered cloud.

4.5.1 Registration of the point clouds Trimble Realworks is now ready to register, almost automatically, the point clouds obtained from the 69 stations. The operator must nevertheless check the quality of registration. A common error is for the software to identify false registration targets. On this building, the two- tone flooring tiles laid with a checkerboard pattern generated several dozen additional false targets in some surveys. The operator had to identify and manually delete these because they were unnecessary and an impediment.

The operator has several complementary methods available for these verifications. One of them is to perform visual checks in the overall registered point cloud. Two point clouds that may be poorly registered due to too much inaccuracy in the superimposition of targets will show duplicated or irregular objects that can be identified fairly easily. The second method is to analyze the reports provided by Trimble Realworks. Two excerpts from these reports are provided on the next page. The first locates each of the objects identified as a target (here, 415 and 417) and associates them with numbers of targets identified in the various clouds obtained from each position. It clarifies its position using the selected X, Y, Z coordinates, with a mean distance. It then displays the distances measured in each of the partial clouds where the target has been identified. The second report shows each partial point cloud (here, P_042) and defines all the targets identified in this cloud, with a new mean distance for all the targets.

Figure 28 Two extracts of Trimble Realworks report: accuracy of the target coordinates

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From these various verifications, the operator can make manual corrections to obtain the best registration of all the partial point clouds.

4.5.2 Reducing and cleaning the point cloud The image below shows the entire registered point cloud, with the building at its centre. Given the range of the FARO Focus 130 laser scanner, this cloud has a radius of more than 100 metres for all parts, without any masque. The cloud obtained represents a very heavy file, most of which is unnecessary. The operator can therefore make cuts to reduce its useful area.

Figure 29 Total point cloud, radius more than 100 m

Depending on the case, we can limit the cloud to the just the building or, as in this case with the area outlined in blue, also retain a view of its immediate surroundings, including all sun masks creating shadow on the building for energy analyses. This can also help the company installing the BERTIM modules in onsite facility and supply management.

Figure 30 Areas to reduce the point cloud: building, sun masks and working zone

The second operation frequently carried out in a cloud is to remove extraneous objects, or noise. This may include people, including the operator, or vehicles that appear in the scanned scene, or they may be furnishings or objects considered as needless. For this project at an occupied site, many objects of no real use were scanned. However they were not an impediment to subsequent modelling work. Further, the cloud will not be used by other parties who would require objects to be cleaned. So no provision was made for this time-consuming task in the contract. The point cloud was used unprocessed and with household objects.

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4.5.3 Exploitation of first deliverables by other parties As we have already explained the point cloud and 360° panoramic photos were the first results made available to other parties.

The direct use of the point cloud in CAD software (Revit 2012 and later, Archicad 19 and later, etc.) is really only of interest for the stages developed later, regarding the modelling of 3D objects or surface meshing from the cloud. To directly obtain information from a point cloud, many viewing applications are offered as freeware or shareware by 3D laser scanner suppliers, as well as by leading developers of CAD software for the building industries. Examples are Faro's Scene LT, Leica’s Truview + Cyclone Publisher and Autodesk’s Recap360. None of these tools require advanced skills, and they can be used by non-expert users to view, measure and mark up … after a little training. However it is not the purpose of this document to provide a tutorial on these applications, for which extensive documentation already exists.

The Trimble RealWorks interface that Im-pact used to manage the point cloud is not the tool made available to other parties; however, a downloadable freeware version does exist. Im- pact has proposed the Trimble Scan explorer, which reads only the 360° panoramic photos associated with all the positions of the project. The information provided by these photos is much more readable than the point cloud. Further, this interface, which can be used without any special training, may be of interest to many users concerned by the project, including the project owner. For this reason, it may be useful here to present a few of the features available in this browser.

Browsing each of the 360° panoramic photos is very intuitive. Views can be rotated by holding the left mouse button down, and zooming is done using the scroll wheel of the mouse. Navigation between the different panoramic views, which are explorable in 360° around the position, is done by double clicking on one of the 69 flattened 360° thumbnail views corresponding to the positions. These thumbnails appear in the left margin of the interface presented in the image below. It can also be done by double clicking on any position marked in the panoramic 3D view by a yellow triangle.

Figure 31 Navigation in Trimble Scan explorer from one position point to another

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This interface, like those that process point clouds, can be used for measuring. The points of these 360° panoramic views are not simple pixels, since they all have coordinates, like in a point cloud. It can therefore obtain the three spatial (XYZ) coordinates of any of these points. It is also possible to measure between two points. Test results indicate that the tool for measuring distances does not work very well, but that the vertical and horizontal measurements are relevant and useful. They are displayed directly on the screen.

Figure 32 Measurements and mark-up in Trimble Scan explorer

In conclusion, this tool allows for different types of mark-up for project documentation, directly on the images. These notes can be saved.

4.6 3D Modelling

4.6.1 Import of a georeferenced point cloud in Revit When it imports a geo-located point cloud Revit 2017 displays an error message (see below) relating to possible problems importing more than 30,000 point coordinates.

Figure 33 Revit message for points with coordinates up to 30.000

The altitude in metres Z cannot reach this value, but the longitude and latitude values in the Lambert 93 system are 0.7 to the power 106 and 6.7 to the power 106, way beyond this limit. Im-pact’s first suggestion to get round this issue was to reduce the latitude values by a factor of 1,000, but after talking to the firm’s surveyor it emerged that it would be much more reliable to delete the first three figures to the left of the longitude and latitude values.

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Figure 34 Decision to delete the first three figures for X and Y Topo points

The following table, supplied with the survey report, indicates which figures were deleted. Please bear in mind that this correction should be treated with caution when transferring data from the model to heat analysis software. The operation makes no difference to the orientation of the building in relation to the north. But it is definitely no longer located in La Charité sur Loire! Similarly, before adding another point cloud for the roof of the building or any other building in the locality, the X and Y values would have to be truncated in the same way.

It is worth noting that the six topographic points in the point cloud must not be confused with the two points subsequently attached to the Revit model:

° The topographic point set by the Im-pact operator in the entrance to the building to define, in the conventional manner, an elevation zero for the project. This topographic point can be seen in the picture below, with truncated latitude (N/S) and longitude (E/W) coordinates, and the NGF true elevation coordinate; ° The Revit base point, which has the same X and Y coordinates in the project but is set to elevation zero, is consequently located on the same vertical axis.

Figure 35 Topography point in Revit defines a +0 for the building

Surveying the site and point-cloud processing under Realworks was completed quickly, taking up about one day’s work, not including travel. In contrast it took at least five days’ work on the point cloud, using Revit, to obtain a 3D volumetric model as clear as the picture above. It was now ready for the subsequent stages of the BERTIM project, for use by other software tools, imported as an OpenBIM IFC file. The image is an indication of how the point cloud appears in Revit when first imported.

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Figure 36 Point cloud imported in Revit

The point-free zones correspond to areas that were not scanned: the inaccessible neighbouring plot to the south-east; the south-east adjoining wall below the terrace of the adjoining building to the north of the stairwell, the roofspace and roof.

4.6.2 Modelling strategy The aim of modelling is to produce a model. As for a model used in mathematics, its 3D equivalent is merely an approximate description of reality. What is immediately apparent for a new building is even more obvious when renovating an existing building, surveyed in situ than modelled on the basis of a point cloud. Several examples may illustrate this point. In a model of a building of this sort, constructed by Revit, the wall objects are parallelepipeds, vertical rectangles geometrically defined by their thickness, height (floor to floor), length and direction between two points. This simplification reflects an economic constraint (the cost of producing a 3D model) and the need for ready exploitation of the model. In the real world a wall is never a perfect, vertical parallelepiped:

° Its two main surfaces are not perfectly flat, nor is its thickness constant; ° Its two main surfaces are not perfectly flat, nor does it form a perfectly straight line between two points, lengthwise; ° Its two main surfaces are not perfectly flat, nor does it form a perfectly vertical line, heightwise.

So modelling is always a matter of producing a deliberate approximation. On the one hand the procedures deployed must ensure that the 3D model can actually be used; were it too true to real life this might be difficuilt. On the other hand, as we pointed out in the introduction, the goal of prefabricating modules on the basis of this model of an existing buiding substantially increases requirements for accuracy, compared with the production of models which merely serve for architectural design. So special procedures were worked out jointly, between Im- pact, DIETRICH’S and POBI, in attempt to achieve the best compromise, specific to BERTIM projects, guaranteeing both operability and accuracy.

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4.6.3 Preparations before 3D modelling The first step in the Revit workflow consists in preparing a structure with several floors, enabling us:

° To obtain elevation sections for work in the point cloud; ° To define a structure for classifying the 3D objects created subsequently, this same structure also appearing in the IFC file produced once the model is complete.

To obtain the floor structure, reference lines are superimposed on a working section of the upper floors in the point cloud. The reference lines are then defined as the elevation of the floors in Revit. In view of the poor flatness of the slabs, the elevation of the floors as defined here is subject to a tolerance of plus or minus 10 mm.

Figure 37 Creation on the point cloud of storey level references

Figure 38 Point cloud in Revit cut on a storey between 2 heights

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Once it has been defined this floor structure appears in Revit’s lefthand margin. The View Range property of floors enables the operator to obtain horizontal sections between elevations H1 and H2) that are both relevant and easy to select in the context of the project, as in the picture below. To boost the contrast, the point cloud can be coloured, as shown here.

4.6.4 Walls process To facilitate subsequent steps in modelling prefabricated BERTIM modules, it was decided to start by defining that the outside walls of the existing building must form a vertical plane parallel to the plane occupied by the future prefabricated modules. The verticality of the future module plane is an absolute constraint to enable ease of assembly at the corners. In a conventional model the walls are divided up by the floors of the projected building. Accordingly they are superimposed, from bottom to top, without any offset attempting to represent possible divergence from the vertical observed during the survey of the outside walls.

To position the vertical plane, it is consequently necessary to define the horizontal direction of each outside wall in relation to two points. The BERTIM modules built by POBI will be horizontal modules (width greater than height). They will be installed, starting with the bottom module and working upwards, resting on a base section anchored to the foot of the existing wall. It might therefore have made more sense to define the direction of the wall in a plane close to the building’s elevation base. However, given that there are generally a large number of openings in a ground floor, with the possible addition of shop fronts, it often represents an exception in relation to the upper floor. So we decided to use the bottom of the first floor as our baseline. To reveal the thickness of walls under Revit, this baseline section was located just above the slab, between 0.10 m and 0.20 m above the elevation of the first floor. In the model this section corresponds to the top, rather than the bottom, of the first BERTIM modules to be fitted to the walls. All the walls of the existing building are positioned in relation to this section. Each wall is positioned in terms of its outer surface, by defining its direction on the section in the point cloud by the two points observed as jutting the furthest out from the building (bumps on the outside wall).

Figure 39 Most usual architectural objects families in Revit

The walls – much as the doors, windows, floors and roofs – belong to the families of objects most commonly used under Revit (and all other architectural design softwares).The dialogue shown below is used to change, duplicate or rename a ‘basic wall’ object, by defining the many properties associated with it. In the present dialogue only the thickness values have been changed, as measured on the point cloud, without specifying the sorts of inside insulation (not known): 300 mm for the outside walls of the upper floors; 315 mm for the wall

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base of the groundfloor, with a few exceptions on the groundfloor for walls that are apparently not insulated.

Any inside insulation there may be is integrated in the total thickness of the wall. It would probably be helpful to define the make-up of the wall on the inside, for the architect and for heat analysis planned under RenoBIM. It will be necessary to probe the walls onsite and then, if necessary, change the outside wall objects modelled as being 300 mm thick and solid concrete. It is currently difficult to foresee such probing work, which might be destructive, given that the dwellings are still occupied. The masonry cladding on the north-west wall, wrapped round onto the south-west wall, has also been modelled, as in real life, with a wall added to the concrete wall.

Figure 40 Properties definition of a 3D object Wall

Analog windows are used in Revit for all types of object. The new generation of 3D CAD tools for BIM (to which Revit belongs) may be described as modelling tools associated with a database, for managing all the properties attached to built volumes. We may thus consider a BIM (or digital) model to be a 3D model enhanced with a large number of properties.

Once the object and its properties have been defined, we may start 3D modelling. The picture below shows a wall being modelled. It is in the process of being positioned in a plan view along a baseline (clearly visible in the opening) through the point cloud (coloured red here), using the method described above.

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Figure 41 Horiz.view during 3D wall creation on a line added to the points cloud

The picture below represents subsequent viewing of the wall on a vertical section, showing it on the elevation zero floor being modelled.

Figure 42 Vertical view of a 3D wall modelled in storey N0 and points cloud

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4.6.5 Windows process

4.6.5.1 Modelling The outside walls are of similar thickness but, even when the openings in the masonry house identical windows, each opening has specific dimensions. As before, the task of defining these openings differs from the process of modelling a new building. It involves fitting them as closely as possible to the real-life conditions of the point cloud. The screen dump below shows preliminary positioning of a window, prior to fitting its dimensions to the surface of this opening, visible here as a whole in the point cloud.

Figure 43 3D wall and not adjusted 3D Opening modelled on the point cloud

The first strategy we considered, which involved transposition from the trial survey carried out with the total stations, consisted in modelling non-rectangular windows precisely defined by the four corners of the opening. We soon dropped this approach. Instead we opted to model the widest, highest rectangular opening that would fit in the opening in the point cloud. This approach, which is more accurate, takes into account any points that may jut out into the opening, between each of the four corners, taken in pairs. Moreover these ‘salient’ points are not only defined on the external plan of the outside wall, but over the whole visible thickness of the reveals, up to the existing window. It is thus possible to make allowance for any faulty squaring of the rendered reveals.

To achieve this goal the operator creates working sections to restrict the field of visibility of the point cloud. A CAD tool defines a section by two planes which delimit – on the screen or a 2D drawing – a reduced view of the whole project. A ‘section’ differs from a ‘slice’ in the sense that the latter refers to a field of visibility of a project defined on a single plane. A slice is a particular section. You may choose to subsequently make the objects in front of the section more or less transparent, in order to conceal, or not, elements located behind these objects. It is thus possible to obtain realist-looking slices. In a point cloud, by definition transparent, the

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problem does not arise: all the points selected in a section will be visible and superimposed, regardless of their position in the depth of the section.

The horizontal section of the picture below, defining a vertical section, limited by two (vertical) planes located between the side reveals, and a second vertical section, limited by two (vertical) planes, the first one in front of the outside wall, the second one in front of the existing window, enables us to delimit a field of visibility in the cloud (coloured red here) for the purpose cited above.

Figure 44 Visibility domain of 2 vertical work cuts fixed on horiz.cut

Work on the first of these vertical sections, as we can see in the picture below, will make it possible to view all the points corresponding here to the lintel over the opening (and then the sill), across the full breadth of this section of the opening and in the full depth of the lintel, from the outside wall to the window. Doing this makes it easy to see the squaring defect on the rendered lintel or measure the disparity between the highest and lowest points in the cloud (not coloured here), a disparity measured as 10 mm on the outside wall.

Figure 45 Thickness of the point cloud and wrong perpendicular on a lintel

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With the second vertical section of the picture below – which may also be defined as a view of the outside wall – it becomes possible to spot the points in the limited point cloud that jut out furthest towards the inside of the opening, then to plot, passing through these salient points four (horizontal and vertical) reference lines, to which the opening may now be fitted.

Figure 46 Adjustment of a 3D Opening in a 3D wall on reference lines

To make it easier to understand the picture above does not show the point cloud. The figure below shows the result obtained for part of the south-west outside wall with the point cloud.

Figure 47 3D walls, openings and floors on points cloud on SW facade

In this figure, components associated with the existing window can also be seen in the point cloud: the masonry sill jutting out, the shutters folded back against the reveals, the metal guard

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rail, the half-open windows. The shutters might have been an obstacle for a clear picture of the masonry reveals. But as all the windows were also scanned from the outside, and almost all of them had the shutters closed, as in the picture below, the resolution on the reveals is acceptable.

Figure 48 Details of an existing window, shutters closed

The existing window will be removed, prior to replacement, unless it is decided to keep the existing window and its shutters, behind a new window. This approach is most unusual in France. The same applies to the metal guard rail which would get in the way of the prefabricated modules. The salient sills will be hidden by POBI’s BERTIM modules. Only the measurement of how far they jut out is of any use in the subsequent process, in order precisely to define the position of the rear plane of the modules. This aspect will be addressed below when we analyse the flatness of outside walls. In its quote Im-pact defined a level of detail (LOD) of 300. This justified the rather particular method for modelling all the windows. But ultimately all these objects were rejected as useless and were not modelled in 3D. If a need arises later, the data is present in the point clouds and the 360° panoramic photos.

4.6.5.2 Families and dimensions for manufacture With this method of modelling, each opening has quite specific dimensions. These dimensions appear on the outside wall drawings delivered with the 3D model. However, these openings will have to be grouped into families in order to manufacture windows of identical dimensions.

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Figure 49 Opening families on facade NE

These families have been created in Revit, which will make it possible to produce lists in Excel to define the window-manufacturing dimensions for each family, based on the smallest of the two dimensions. As with the trial carried out using total stations, these dimensions make no allowance for any constraints associated with realigning windows (see 3.3 p20)

Figure 50 Windows families and dimensions

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On the main series F1, the height dimensions vary between 1545 and 1568 mm, or a 23 mm variation, and width dimensions between 1382 and 1423 mm, or a 41 mm variation. POBI and DIETRICH’S have noted that these minimums, lowered further by the survey and manufacturing tolerances as seen in Chapter 2.2, could have the final effect of reducing the glass surface of the windows too much. Verifications could therefore be carried out on the values in the point cloud that are too different from the mean scores. If the industrial strategy advocates standardization, an alternative strategy could also be to manage more than one family of manufacturing. This point will be more thoroughly considered in the next stages of Task 6.4, which is associated with the POBI demo building.

4.6.6 Floors process The floors of the storeys and loggias of the south-west outside wall allow for a complete architectural model. They also help define the areas where the BERTIM modules will be attached. Their upper side is positioned in relation to the elevation zero of each floor, as specified in Chapter 4.6.3. As in the case of the walls, only the fact that they are concrete and their total thickness are known; details on the layers of ceiling insulation are not specified and will require additional surveying, if deemed necessary. The only exception is the slab forming the roof of the shops on the ground floor, for which two layers could be distinguished: the supporting slab and the damp-proofing.

The floor of the loft (under the existing roof), is positioned (contrary to all the others) by its only known side, the underside. Its actual thickness cannot be guaranteed. In the event that the architectural project selected includes the creation of new housing-unit surfaces or a mechanical room on this roof floor using BERTIM 3D modules, extra surveys will be necessary to validate the thickness of the slab and its mechanical capacity for supporting additional weight, and to evaluate its layout for the installation of the 3D modules.

4.6.7 Other 3D objects For the next steps of the BERTIM process, Walls, Openings and Floors were able to meet the needs of the manufacturer (POBI), which commissioned Im-pact to do the corresponding survey and modelling work. However, to provide the architect with a fuller model, it was agreed to add the following 3D objects as well:

° Shutters and landings in the stairwell; ° Concrete posts on the unglazed openings of the drying rooms (NE wall); ° Natural ventilation openings (NE wall); ° Projecting concrete window frames of the stairwell (SW outside wall).

On the other hand, some of the elements that had not been dismantled according to plan remain very visible on the panoramic 360° photos as well as in the point cloud:

° Windows, doors or shop windows; ° Railings of windows and loggias; ° Shutters; ° Canopies over the two entrance doors;

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° All the elements attached to the outside walls: rainwater drainpipes, lighting, mailboxes, utility cabinet.

4.6.8 Use of advanced deliverables by other parties

4.6.8.1 Revit 3D model All the way through the modelling phase the Revit model was made available to DIETRICH’S and POBI via a specific Dropbox account, enabling discussion on the progress of work. As the key points of the procedure had been decided well upstream there was little need for comment, mainly in the form of email. The BCF format specified in the contract for entering comments directly in the model was not used on this relatively small project. Having a Revit license was useful, but it does not seem absolutely essential for a client commissioning a survey and modelling service of this sort. The model can be delivered in IFC format, and possible comments on the model can be produced on the final version, after the model is imported into the software used by the client.

4.6.8.2 Project drawings As provided for by the contract, the drawings of the storeys, outside walls and three sections were also made available and updated in the Dropbox folder in DWG and PDF formats. While owning a Revit license provided the advantage of being able to consult these drawings directly in Revit, once again, this does not seem absolutely necessary for the client, as the DWG and PDF formats are two truly universal standards.

4.6.8.3 Lists : These lists will appear in Revit as ‘Schedules’. They make it possible to obtain – in spreadsheet form – the floor space of living areas, the surface area of the outside walls, and the dimensions of the openings registered in each family. These can then be edited in Excel.

4.6.8.4 Analysis of outside walls flatness Tests on the methods described in the contract (colour mapping or mesh size) were carried out; their initial results are not very satisfactory. As this D4.2 report must be finalized, these results will be part of the deliverables associated with the result of the POBI demonstration process for Task 6.4.

4.7 Next stages with IFC files The IFC format is the OpenBIM file format specification promoted by the international association buildingSmart, which seeks to facilitate maximum interoperability of all construction industry software. This format has been developed since 1997, and in 2016 the version most used by software publishers is still IFC2x3, released in 2006. However, the most enriched version of this format is IFC4, completed and recognized as meeting ISO Norm 16739 in March 2013. There are 653 usable classes in IFC2x3, and now 766 classes in IFC4.

4.7.1.1 IFC files structure checked with viewers To ensure the compliance of a 3D model, it is very useful and very common to use viewers. These viewers make it possible to analyze whether unexpected results – obtained after import into a software B of an IFC file produced by export of a software A – come from the

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methodology used for modelling and organizing the digital model in software A, from the IFC export procedure from this software A, or from the IFC import procedure in the software B. Many such viewers exist, but for this usage we can recommend two, both of which can be downloaded for free:

° DIETRICH’S uses FZK (KIT Karlsruhe Institute of Technology - Instit. for Applied Computer Science (IAI), 2016) which has two very interesting advantages: - It is tolerant when files with errors are opened, and then it documents the errors found on the IFC file reviewed. - it proposes consultation of all the details of the properties associated with the objects. ° Im-pact uses BIMVision (Datacomp Sp. z o.o., 2016) whose main advantage is the very high user-friendliness of its interface in comparison with many other viewers in much broader circulation. ° For this project, the first unexpected result was not the model but the viewer itself. The use of a geo-referenced Revit project with a base point at elevation zero and a geo- referenced point at the actual NGF elevation is a quite particular case that concerns only survey projects for renovation. It highlighted a defect in the management of FZK display (linked to the distance of the building from the base point), which made it difficult to use. It is for this reason that DIETRICH’S used BIMVision, a viewer with less developed features but that nonetheless was quite useful and that users could become familiar with quickly.

Here, we can give an example of a correction of a minor problem that was not clearly visible when the model was viewed in Revit. To best manage the base of the groundfloor wall, the thickness of which is different from the standard walls resting on it, the Im-pact operator created two groundfloors in Revit. Subsequently, when modelling a little hastily, some of the standard groundfloor walls were assigned to the ‘groundfloor wall base ’, thereby making an incomplete storey appear. This filter by storey is a very accessible feature in the DIETRICH’S system, which allowed for detection of the error. This error was quickly confirmed by the viewer and sent to Im-pact for correction.

4.7.1.2 Using IFC files with other software The specific objectives of each software programme called on to operate the IFC format and the specific structures associated with these objectives can lead to the need for adaptations to the digital model. This validation of interoperability will be the subject of upcoming Task 4.6.

An initial illustration is given with the need to reread the IFC file in the Energy + software for the purpose of heat analysis and energy consumption assessment. This example was already mentioned in Chapter 4.2.3 of Deliverable 4.1 and will therefore be developed in detail later.

A second illustration concerns manufacturers ’ software and among them the DIETRICH’S CAD system used by POBI. The IFC file produced here is just the first step in the RenoBIM software, and the work of Task 4.6 will concern the use, in manufacturers ’ software, of the IFC file produced as an output of RenoBIM. However, a few comments can already be made regarding this first file imported into DIETRICH’S.

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The walls as well as the openings and floors used in the Revit model are among the most common families of 3D objects in all architecture software. They are also among the most common classes of objects in the IFC files (the C for Classes): IfcWallStandardCase or IfcWall, IfcOpeningElement, IfcSlab. IfcColumn and IfcBeam are also among the classes most frequently used by architecture or structure software. In static analysis software it is essential to clearly differentiate the walls (plates), beams and columns (bars), which have quite distinct mechanical behaviour. In the DIETRICH’S system, the wooden columns and masonry columns are not modelled with the same tools or encoded with the same structures. To appear on the drawings of a storey, the masonry columns are represented with the ‘Wall ’ tool. Initially, the Im-pact operator had conventionally used Revit's ‘column ’ tool for two uses: to represent the columns appearing in the openings of the drying rooms of the NE outside wall, and to represent two masonry pillars thicker than the walls appearing in the ground-floor structure. In this second case, DIETRICH’S requested that these pillars be defined as ‘walls’, so that they would appear immediately with the entire masonry structure in its CAD system.

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5. Conclusions

The conclusion to this report focuses on the relevance of the work carried out for the energy renovation of a building at La Charité sur Loire, but also on a comparison of the two techniques for capturing the building that we have investigated her a.

5.1 At a first stage in energy renovation of the POBI demo-building The deadlines for the deliverables associated with a research project such as BERTIM are linked to mandatory milestones. The present report concludes Task 4.2, but is also the first part of Task 6.4, which concerns POBI’s demonstration on a real building of the entire BERTIM renovation process.

This particular BERTIM survey is very different from the surveys often carried out now in preparation for renovation work. Instead of preparing onsite work it paves the way for a design process which will be used all the way through the project, leading up to the manufacture and installation of prefabricated modules. For this reason particular attention has been paid, throughout the process, to the unusually high level of accuracy required for the survey and subsequent 3D model for manufacturing. Care has also been taken to ensure that this model fully meets the requirements of subsequent heat and energy analysis..

To fulfil the 3D-laser-scan strategy defined here we had to survey from many positions inside the building, in order to obtain the full accuracy needed for the openings, but otherwise modelling of the building’s interior was very limited. This is because BERTIM projects concern renovation of the outside envelope of buildings, the goal being to save energy and enhance the outside appearance. Such projects do not necessarily involve interior refurbishment. So, inside the building, we only need to:

° Capture the elevation and thickness of floors; ° Capture load-bearing walls, for any static structural analysis; ° Define unheated indoor spaces, such as stairwells, for heat analysis.

Had we deployed a different surveying strategy, using an elevated work platform, we would only have needed five interior scanning positions. In the case of a survey of the whole of the outside of the building using a total station, the relevant data could have been captured with measuring tapes or laser measuring sensors.

At the time of concluding this report, POBI has received the 3D deliverables, drawings, 360° panoramic photos and IFC file, but work has not started on them. The architect has not yet been officially commissioned by the local council, nor have they received the above deliverables. So it is too soon to expect any feedback on the 3D model delivered by Im-pact. The model will continue to be used throughout Task 6.4, which covers the design, manufacture and installation of the modules. The reader should look forward to our conclusions on the quality and completeness of the above data in the report on Task 6.4.

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5.2 Comparison of total station and 3D laser scanner processes Our comparison of the two processes did not cover the full range of operations, for the simple reason that the survey with the total stations and subsequent modelling exercise only constituted a partial trial. The lead author of the present study started the experiment with the assumption that a total-station process would be more straightforward for small and medium- sized enterprises. We supposed that the tools and methods were more accessible and would afford smaller organizations greater freedom of action. The trial did not wholly invalidate these assumptions, but it did show that the laser-scanning process can deliver data that is much more accurate and, above all, far more complete over the whole of the building.

This accuracy is particularly important with regard to the survey of openings, which is one of the really sensitive points on which this study has focused. The strategy for the survey with a total station (redefined here after tests), consists of defining the opening by eight points whereas the scanner makes it possible to survey all the points of the opening, not only in the plane of the facade but also In 3D over the width of the reveals and lintel, from the facade to the window. This makes possible to identify wrong perpendicular on reveals and lintels. This situation is frequent with buildings such as this demonstration building, for which the masonry does not seem to be full made of concrete but of coated concrete blocks.

Use of the point cloud and 360° panoramic photos, initially restricted to essential aspects related to the manufacture and installation of prefabricated modules, can if necessary be enlarged to cater for other needs such as the organization of onsite storage, or lifting machinery for the fitting and renovation of heating and ventilation equipment, plumbing and such.

The 3D-laser-scanning survey, subcontracted to a specialist firm, may seem more expensive than an equivalent total-station survey carried out in-house, but in the last analysis the overall cost is much the same. Summing up, the following table compares these two processes, described in detail in chapters 3 and 4 of the present report.

Total station 3D laser scanner Primary Points, lines and point references, ° Points cloud in e57 or any other Deliverables eventually measures, in DWG, usual formats. 2DDXF, 3DDXF or txt, csv ° Panoramic photos 360 on each formats. position of the scanner. Advanced No link with the device : Depends No link with the device : Depends Deliverables only on the CAD software used for only on the CAD software used for modelling. modelling. Wheather No rain, no snow, no fog. No rain, no snow, no fog. conditions for Not too high temperatures to avoid Not too sunny to avoid too much survey accuracy trouble with air agitation? noise on reflecting surfaces. Operator for ° Internal or external Company specialized in surveying survey professional surveyor and 3D modelling on points cloud is ° Operator (producing both really recommended for the whole surveying and 3D modelling) process, with a clear methodology hired by the manufacturer. defined with the manufacturer.

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Total station 3D laser scan ner Methodology to How many points to be fixed to How to obtain enough points all be define before check eventual erratic or forgotten around openings (enough positions survey points. inside or outside the building). Accuracy of ° Device used (optical or camera ° Optimized settings of the device. survey resolution quality). ° Care about the position of ° Excessive heat? targets to obtain a good registration of the points cloud. Reliability of Requires constant attention of the The scanning is full automatic. surveying operator when shooting points. Exhaustiveness The survey is limited to points ° Points cloud deliver an exhaustiv of survey fixed one by one. information ° Additional information is obtained from the panoramic photos 360. Time for survey Not finalized for the whole Time has been 1 day on site for 56 (based on building, but time depends mainly internal positions and 13 external demo-building) on the operator : positions. But using a mobile ° produced by a professional elevating work platform could reduce surveyor, the time could be 1 this time, with less positions and less day. wasted time about dwellings ° produced by another operator accessibility. practicing occasionally, this time could be 2 days. Accuracy and Limited number of points give a Points cloud requires specific reliability of limited but clear information to be knowledge and methods to be well modelling used by a CAD software user. exploited. 3D modelling Possible for a CAD software user. Not recommended, at least for first internely experiences : service to be realised by the points cloud provider Time for 3D Not finalized but can be estimated Around 5 days for a professional modelling between 3 to 5 days (for a 3D operator. (based on model less complete than those demo-building) produced on a points cloud).

Table 7 Comparison of total station and 3D laser scanner processes

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6. References

Bentley. (2016). ContextCapture / Guide for photo acquisition.

BIMForum. (2016, 08 25). LOD-Specification-2016_08-25. Retrieved from http://bimforum.org/: http://bimforum.org/wp-content/uploads/2016/08/LOD-Specification-2016_08- 25.compressed.pdf

Datacomp Sp. z o.o. (2016). BIMVision. Cracow, Poland.

GSA, (. (2009). Building information Modeling Guide Series: 03 - GSA BIM Guide for 3D Imaging . Retrieved from http://www.gsa.gov/bim

KIT Karlsruhe Institute of Technology - Instit. for Applied Computer Science (IAI). (2016). FZK Viewer. Karlsruhe , Germany.

SYNTEC-INGENIERIE. (2014, 12). BIM/Maquette numérique : contenu et niveaux de développement. Retrieved from Moniteur.fr.

UK BIM Task Group. (2013, July). Client-Guide-to-3D-Scanning-and-Data-Capture . Retrieved from http://www.bimtaskgroup.org: http://www.bimtaskgroup.org/wp- content/uploads/2013/07/Client-Guide-to-3D-Scanning-and-Data-Capture.pdf

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