User story of the Universität Siegen - Laser scanning, Point-Cab, ArchiCAD

Point-Cab was used by the Interdisciplinary Competence Centre (Interdisziplinäres Kompetenzzentrum Altbau (InKA)) of the university of Siegen in a project that aimed at the registration of the geometry of works of a medium-sized industrial firm. The works cover an area — including buildings and other elements — of about 10,000 square meters. A great amount of laser scans were necessary because all supply pipes and disposal lines had also to be considered. Approximately 80 scans with a total size of about 7 GB were recorded with the terrestrial laser scanner FARO Photon 80.

The goal was to create a 3D model of the works in the CAD program ArchiCAD. Point-Cab was used to create top views, cross sections and longitudinal sections of the entire point cloud. This set the foundation for modeling the objects in ArchiCAD.

Point-Cab is easy to use and easily comprehensible. Users specify the areas where the point cloud is sliced to create a section view. This cross section is then output as a dimensionally accurate pixel image having an accuracy of 2 mm per pixel.
 

The idea of creating a 2D pixel image out of 3D laser scanning data, which is then used to create a 3D model, seems to be absurd, but there are many advantages to this method.

First of all, the amount of data is reduced to a level acceptable to CAD systems — an achievement that is particularly remarkable. The processing speed is reasonable and the software runs stable. The data exchange formats (png, tif, jpg) are supported by almost all CAD programs available on the market. The cross section through the point cloud is divided into several “tiles”.

That way, the user can adjust the amount of data depending on the ability of the software to process huge volumes of data. The tiles generated by Point-Cab can easily be read by all CAD programs. Each object comes with location coordinates to place it in the correct position and have it imported dimensionally accurate. Another simplification might be an integrated import plug-in in relevant CAD programs. So far, only SketchUp and Microstation are able to automatically import “tiles”. However, according to the software developer, an open Application Programming Interface (API) can be used that allows developers to integrate functionalities into 3rd-party applications.

Surely, it would be an improvement to have an option that allows users to specify multiple cross sections at once (every 2 meters in x-direction for example). When it comes to large objects, the generation of cross sections and views is time-consuming. Since every cross section generation has to be started manually, it is not possible to create cross sections virtually “overnight”.

Conclusion: The idea to generate dimensionally accurate pixel images at a sufficient level of detail from laser scanning data is brilliant and simple. Now, huge amounts of information, which are generated by laser scanners, can also be given to users that do not have “special tools” for analyzing and interpreting laser scanning data.

Tobias Hundhausen, Dr. Ing. Mathias Wirths July 2010

Photo credits: All pictures and photos: Interdisziplinäres Kompetenzzentrum Altbau (InKA) der Universität Siegen.