These distortions of scale within an image can be removed
through orthorectification. During orthorectification, digital
scans of aerial photos are subjected to algorithms that
eliminate each source of spatial distortion. The result is a
georeferenced digital mosaic of several photographs with uniform
scale throughout the mosaic. Features near land are generally
georeferenced with greater accuracy while the accuracy of
features away from land is generally not as good. Where no land
is in the original photographic frame only kinematic GPS
locations and image tie points were used to georeference the
images. After an orthorectified mosaic is created,
photointerpreters can accurately and reliably delineate
boundaries of features in the imagery as they appear on the
computer monitor using a software interface such as the Habitat
Digitizer. Prints and diapositives were created from the
original negatives. Diapositivies were then scanned at a
resolution of 500 dpi using a photogrammetric quality scanner,
yielding on