Softcopy photogrammetric techniques for mapping mountainous terrain : Great Smoky Mountains National Park
Jordan, Thomas Robert
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Softcopy photogrammetric techniques were adapted for use in the establishment of a seamless digital geographic information system (GIS) database and vegetation maps for Great Smoky Mountains National Park in the southern Appalachian Mountains – an area of approximately 2000 square kilometres. This difficult mapping project presented a number of challenging problems resulting from extreme terrain relief, the near-continuous canopy cover and the lack of roads and cultural features that precluded the use of conventional methods for identifying and measuring the coordinates of ground control points (GCPs). Issues addressed included generation of ground control using analytical aerotriangulation and differential rectification of vegetation overlays to correct for displacements caused by relief in aerial photographs.|As part of a cooperative agreement between the Center for Remote Sensing and Mapping Science, The University of Georgia, and the National Park Service, softcopy photogrammetric procedures were employed with approximately 1000 large-scale color-infrared aerial photographs corresponding to 17 U.S. Geological Survey (USGS) 1:24,000-scale topographic quadrangles in the Park. Ground control points identified on USGS Digital Orthophoto Quarter Quadrangles with elevations extracted from USGS Digital Elevation Models were employed with analytical aerotriangulation methods to compute the X, Y, Z ground coordinates of over 4300 GCPs and pass points - enough to permit differential rectification of the aerial photographs and associated overlays. The RMSEXY error at 1195 GCPs used in the aerotriangulation adjustment was r 12.6 m.|The photo coordinates of the GCPs were mathematically registered to photo interpretation overlays using fiducial marks and employed to orthorectify the overlays. The vegetation polygons on the raster overlays were then converted to vector format and transferred to the GIS database where they were edited, edge-matched with adjacent overlays and assigned attributes according to the vegetation classification system.