Color infrared film positive aerial phography was scanned at 600 d.p.i. using a Leica Planimetric scanner. Photgraphs contained 25 percent overlap, therefore, every other frame was scanned. The scanned imagery was then processed using ERDAS Imagine 8.4. Imagery was orthorectified using ERDAS/ OrthoBase. USGS digital orthophotography was used as the horizontal reference source and 30 meter digital elevation models were used as the vertical reference source. The U.S. Geological Survey camera report was used to obtain the interior and exterior orientation and other specific camera information needed in Orthobase. Ground control points and tie points were created. Nearest neighbor resampling method was employed to produce an orthorectified image.
Once orthorectified, the imagery was clipped to within approximately one mile on either side of the Yellowstone River centerline of flow using an area of interest (AOI). Images were then mosaiced using ERDAS mosaic tool. The overlap function was set for no cutlines and overlay. Image matching was not performed. Mosaiced images were compressed at a 20:1 ratio with MrSID Geospatial Encoder 1.4.