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.
Center
for Remote Sensing and Mapping Science