Early procedures and algorithms for digital orthophoto generation in the National Digital Orthophoto Program (NDOP) were based on historic US Geological Survey mapping operations, such as field control,aerotriangulation, the quarter-quadrangle-centering, 1:40,000 aerial photographs, and 2.5D digital elevation models, some of which have not been updated in decades. Additionally, the Standard for Digital Orthophoto formulated by the NDOP has not considered the requirements of large-scale urban orthophoto generation. This collaborative project with USGS is intended to provide the technical base (algorithms, procedures, etc.) and experience needed for urban large-scale digital orthophoto creation for the near future national large-scale urban digital orthophoto deployment and the revision of the Standards for National Large-scale City Digital Orthophoto in the National Digital Orthophoto Program (NDOP). The project will build on an earlier small NSF grant which explored true orthophoto generation using existing algorithms and procedures. In that effort, the problems of the existing algorithms, and investigated potential techniques for solving them were identified. Phase II, (this project) will conduct a systematic, end-to-end scientific investigation, including: o How to plan urban photogrammetric flying missions to minimize the impact of occlusion, o How to effectively represent buildings (i.e., digital building model-DBM) for the detection of the occluded and shadow areas when generating urban orthophotos, o How to automatically (NOT manually) compensate for the occluded and shadowed areas from conjugate areas in adjacent .slave. orthophotos, o How to automatically (NOT manually) choose the .best. imagery and optimal seam lines when refilling the occluded areas, o How to automatically compensate for the missed wall information/data in true orthophoto, and o How to best deploy these technical improvements within the National Digital Orthophoto Standard initiative.
The broad impacts from this project are expected to include:
(1) Develoopment of revised National Standards for Digital Orthophoto specifications to ensure that large-scale urban orthophoto products under the National Mapping Program (NMP) reflect current mapping and data policies and are accurate and consistent in style and content. (2) All levels of government who will be users of large-scale urban digital true orthophotos. Recent advances in GIS technology have facilitated the integration of digital orthophotos, with an increasing variety of other geospatial data, into myriad applications. Traditional users of USGS orthophotos, like federal land and resource management agencies, will be principal users. (3) Advances in true orthophoto generation that will be transferred to American industry to contribute to the competitiveness of these companies in the global GIS marketplace. ESRI Inc. joins this Phase II as a collaboratork and will be in a position to make direct use of project results. (4) The developed procedures and algorithms, and the firsthand research results will be directly and immediately fed into photogrammetry and GIS courses at Old Dominion University and other academic institutions. The created experimental data sets,including original images, orthorectified images, DEM, urban spatial data, 3D urban model, etc., will be directly used in laboratory classes of photogrammetry and GIS.
