Efficient Integration of Aerial and Terrestrial Laser Data for Virtual City Modeling Using Lasermaps

One of the first steps during evaluation of terrestrial LIDAR measurement is the co-registration of the data sets, which are collected from different stations and their transformation to a suitable reference coordinate system. As it is demonstrated within the paper, this can be achieved automatically, if low-cost components are used for direct georeferencing parallel to LIDAR measurement. By these means the position and orientation of the laser scanner can be determined. Further refinement is feasible, if the terrestrial scans are aligned to a DEM from airborne LIDAR or existing 3D building models. Frequently, terrestrial lasers scanning (TLS) is used to collect building facades at a large amount of geometric detail. For this type of application, the integration of existing 3D building models from airborne data collection as complimentary data source is especially suitable for the modeling step. Due to viewpoint restrictions of airborne data collection, the amount of detail, which is available for the building facades, is very limited. Thus, after alignment, the terrestrial scans are ideally suited to refine these models. However, as it is demonstrated in the second part of the paper, the large effort required for explicit modeling can be avoided if so-called LASERMAPs are extracted from TLS and mapped against the coarse 3D building model.