A digital orthophoto is a georeferenced image prepared from a perspective photograph, or other remotely-sensed data in which the displacement within the image due to sensor orientation and terrain relief has been removed. Orthophotos combine the image characteristics of a photograph with the geometric qualities of a map. They serve a variety of purposes, from interim maps to field Standards for Digital Orthophotos references for earth science investigations and analysis. The Tongass National Forest digital orthophoto quarter quads (DOQQs) were produced from airborne panchromatic film-based imagery collected in 1996 and 1998 between mid-July and early-August. The nominal scale for the acquistion of photography for the 1.8-meter Tongass National Forest digital orthophoto quarterquads was 1:40,000. This image-based data set of digital orthophoto quarter quadrangles can be considered as baseline geographic and planimetric reference for the Tongass National Forest and southeast Alaska.The Tongass National Forest quarter quadrangle boundary footprints were defined by the United States Geological Survey (USGS). There are 794 DOQQs, each is approximately 49MB filesize in geotiff format without compression. Glacier Bay National Park coverage is not included with this data set.
