At this moment many architects involved in conservation still work in the traditional way. They use hand-measured (tapes, plumb-bobs, levels...) or instrument based (theodolite, total station, photogrammetry) survey methods. This information is usually transferred to 2D paper drawings: plans, sections and facades. The main drawback of this approach is that all information is distributed in different types of documents (2D drawings, texts, photographs...). This makes it often very difficult for policy makers, engineers or others persons involved in one particular phase of the process, to get a complete and unambiguous overview of the available information. In addition, it is very difficult to use this material for exchange with other architects or researchers (for comparative studies...) or for distribution to the public (publications in periodicals, tourist information...).
As many architects are shifting towards computer-aided design for new buildings, they also try to apply these programs to renovation or conservation projects. However, the number of tools available to accomplish the task of 'getting the existing building in the CAD program' is limited, and mainly directed to 'translate' traditional methods to CAD (automatic import of full station co-ordinates, error-adjustment of triangulation...). Based on a limited number of actually measured points, 2D plans and sections or a 3D model can be constructed. This typically results in a very 'simplified' representation of the building, which is absolutely not in line with the high requirements for conservation purposes.
The technology presented in these notes can be very useful in this context. We have an ongoing project with architects that aims at developing a technology that enables an operator to build up an accurate three dimensional model - without too much repetitive work - starting from photos of the objects. For a number of reasons, such as the need for absolute coordinates, the choice was made to also measure reference points using a theodolyte. This allows to simplify a number of calibration issues. In Figure 9.23 an example is shown. A more detailed description of this project can be found in .