6326 Shades of Georeferencing BIM - Low distortion projections (LDP) for the German Railway

Abstract. Beside smart Information Management, Building Information Modeling (BIM) focuses on three-dimensional planning and model coordination. However, 3D CAD/BIM software does not conceptualize geodetic coordinates, which causes systematic deviations between geospatial surveys and 3D BIM Model. In local projects, the use of Cartesian coordinates (not curved geodetic coordinates!) is indispensable, due to the high precision demands in computational geometry. The solution is to convert geodetic coordinates into an optimized coordinate reference system. This procedure has been standardized and implemented for 6,326 traffic stations of the German Railway, minimizing systematic deviations and using the DB REF geodetic datum for consistent referencing the alignment of the railway tracks. The developed approach enables the precise use of geometric models (CAD/BIM, high quality 3D point clouds, measured surveys) less than 5ppm, facilitates conversion to other coordinate reference systems using GIS-standard tools, and allows construction projects to be directly staked out from the BIM-model.