LIDAR-Aided True Orthophoto and DBM Generation System

Abstract

Orthophotos have been utilized as basic components in various GIS applications due to the uniform scale and the absence of relief displancement. Differential rectification has been traditionally used for orthophoto generation. For large scale imagery over urban areas, differential rectification produces severe artifacts in the form of double mapped areas at object space locations with abrubt changes in slopes. Such artifacts are removed through true orthophoto generation methodologies, which are based on the identification of occluded portions of the object space in the involved imagery. Basically, true orthophotos should have correct positional information and corresponding gray values. There are two requirements for achieving these characteristics of true orthophotos: there must be no false visibilities/occlusions, and the building boundaries must not be wavy. To satisfy the first requirement, a new method for occlusion detection and true orthophoto generation is introduced in this paper. The second requirement, which is for non-wavy building boundaries, can be fulfilled by generating and utilizing a DBM in the true orthophoto generation procedure. A new segmentation algorithm based on a neighborhood definition, which considers the physical shapes of the involved surfaces, is introduced to obtain planar patches of which mainly man-made structures consist. The implementation of DBM generation methodology using segmented planar patches is complicated and requires in-depth investigation; hence the research in the generation of DBM and in the refinement of true orthophotos is still in progress. This paper suggests a new system that achieves accurate true orthophotos without introducing any external DBM information. The feasibility and performance of the suggested techniques are verified through experimental results with real data.