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Precision LIDAR Data and True-Ortho Images
4.3. 3 D city models Layout of network for mobile communication, urban and environmental planning, simulation of floods, and simulation of noise distribution are some tasks, a precise 3 D city model may be used for. In case of the city of Venice, Italy (Figure 5) the building structure is extremely dense and streets and channels are very small. So, a grid width of a raster DEM must be 1 m, better 0.5 m. Therefore, Venice was scanned with a scan angle of ± 7° in order to avoid shadowing. 3D city models also allow for accurate, precise and up-to-date mapping of a road network. The LIDAR DSM, combined with complementary information (such as street names and house num-bers) in a GIS, provide an up-to-date coverage for vehicle navigation and positioning systems (see Figure 6). Of course, building blocks and road network may be vectorized to produce the conven-tional road map.  Figure 5: 1 m raster DSM of Venice, Italy © CGR, Parma, Italy  Figure 6: 1 m raster LIDAR DSM of Athens, Greece © Nama Geoinformatics, Athens, Greece Precise LIDAR DSM like that of Venice may serve as basic data for a virtual city model. The first step to come to an virtual 3D model is to convert the buildings of the LIDAR DSM to vector for-mat. ATOP is a software package especially developed for this purpose. It was applied on the DSM of the city of Parma, Italy to produce CAD conform buildings. After vectorisation the 3D building model may be draped with the true-ortho images in order to get texture on roofs and pavements (see alos Figure 7, left). Additionally taken images from ground may be put on the walls of the buildings to get a model, which looks close to reality (Figure 7, right).  Figure 7: 3 D virtual city model of Parma, Italy produced from LIDAR DSM (© CGR, Parma, Italy; Real.IT, Schwäbisch Gmünd, Germany) 5. Summary Beside small scale applications for LIDAR DEM (like topographic mapping), there is an increasing demand on precise LIDAR data for large scale applications. It could be observed that the market even asks for data of higher resolution than 1 m raster DEM. The shown examples of applications have been selected to illustrate the quality of precise LIDAR DEM. The spectrum of application for precise elevation data is much bigger as shown here and in-cludes such applications like power line mapping, precision forest management, and opens pit monitoring. During the relatively short time in which the complementary line scanner camera is operational, it turned out that more and more customers asked for both, elevation models and images. As all data is digital from the beginning, data processing is done relatively quick and highly automated - mainly quality control needs operator support. 6. References
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