ArcHC_3D webpage

"ArcHC_3D"

(FCT:PTDC/AUR/66476/2006) - from October 2007 to May 2011

Contributions to Architectural Heritage Conservation: Documentary Methodology based in terrestrial digital photogrammetry and 3D laserscanning

Summary

This research project arises from the need to understand the impact of the new documentary technology of 3D laser scanning and the new vectors of photogrammetric research, namely automatic and semi-automatic methods of 3D reconstruction, in the study and analysis of the architectural heritage within Conservation. It was formed a multi-disciplinary team composed of researchers from several institutions (Faculty of Architecture at the Technical University of Lisbon - FAUTL, Archaeology Unit of the University of Minho - UAUM, Office for the Application for World Heritage, University of Coimbra - UC), Institute Management of the Architectural and Archaeological Heritage - IGESPAR) and Laboratory of Architectural Photogrammetry, University of Valladolid - LFAUVA). The project methodology was strongly based on the production of documentation, using the above mentioned technologies, in the context of practical application. It is noteworthy the production of documentation underlying the Rehabilitation Project of the fa�ades of the Terreiro do Pa�o blocks in Lisbon, in which it was a survey a survey of 50000m2 of fa�ade surfaces through expedite photogrammetric processes, the production of documentation in the Conservation Project of the Arco of Rua Augusta also in Lisbon, in which we accomplished a complete survey of that architectural and sculptural structure by the use 3D laser scanning, and also the various surveys held in Tomar, in the city historic center and in the Convent of Christ. These were carried out, among other methodologies, through the implementation of automatic photogrammetric techniques.

Objectives

This research project had three main goals:
1. Create the basis for a minimum Architectural Heritage survey system based on low-cost terrestrial photogrammetry to:
- Support of three-dimensional restitution of buildings for repair or restoration interventions;
- produce plans, sections and elevations with great economy of effort.
2. Explore the possibilities of coordination between terrestrial laser scanning and photogrammetry in order to:
- Investigate the methodological implications in the analysis and diagnosis in the Architectural Conservation planning;
- Allow the acquisition and the production of basic data that enables the interventions of repair and restoration.
3. Define and propose an information system that allows the management of qualitative and geometric (2D and 3D) in order to:
- To support conservation and restoration analysis and intervention;
- Support for dissemination and study of the architectural heritage;
- To complement, with quantitative dada, other national information systems.

Main conclusions

The main conclusions of this research can be stated as follows:
- Although more and more the paradigm of 3D documentation is becoming a reality, there are more traditional methods that still are valid.
- The use of three-dimensional graphic documentation systems in the context of conservation and rehabilitation, should be made being aware of the use of complementary methods (eg GPR) and maintaining a culture and a habit of direct observation of objects.
- Although the use of three-dimensional systems results in a high amount of three-dimensional data, it is still a reality that in most cases these are used to produce 2D documentation (CAD drawings).
- However, in this production, the 3D data can facilitate the process as it is more flexible because it allows greater freedom of choice both in the features to be depicted and in amount of information to be registered.
- The three-dimensional data extend the possibilities of reuse and revisiting the same objects.
- Terrestrial laser scanning allows an extensive and reliable capture of the geometry of objects that makes it appropriate for use in documentation of complex and deformed objects.
- Terrestrial laser scanning tends to become a technology more accessible to the extent that the equipment is becoming cheaper. But it is still a technology that requires a high level of specific preparation.
- The potential of terrestrial laser scanning goes beyond simple analysis to derive the capture of the geometry of objects, as demonstrated by interpreting and processing of reflectance images.
- Like any technology, terrestrial laser scanning also presents limitations that make it unsuitable for the documentation of certain types of objects (mirrored objects, glass, polished metals) which implies the adoption of complementary techniques.
- The low-cost aerial platforms (balloon, telescopic masts, drones) are increasingly being used and present themselves as a viable alternative to classic flights.
- The low-altitude aerial photography translates into an effective tool for the analysis of urban space.
- The automated photogrammetric systems are already a reality that tends to open, increasingly, the world of photogrammetry to non-specialists. However still require high processing power. However systems are very sensitive to the texture of objects and their illumination. We believe that in a near future it can compete with laser scanning. In fact, in some domains it already competes.
- The ability to manipulate and manage information in digital 3D format is translated as an efficient tool of inquiry and analysis of objects, however complex they are, allowing the observation of multiple points of view (some physically impossible) and allow to expand the dialogue with the object. In this sense also extends the process of knowledge and information that are accepted to be necessary before, during and after the conservation process.