Digital orthophoto quadrangle
A digital orthophoto quadrangle (DOQ) is aerial photography or satellite imagery that has been corrected so that its pixels are aligned with longitude and latitude lines, and have a narrowly defined region of coverage. This is a widely used format introduced by United States Geological Survey (USGS). The correction technique is called image rectification and is a large part of photogrammetry.
DOQs produced by the USGS cover an area measuring 7.5-minutes longitude by 7.5-minutes latitude (the same area covered by a USGS 1:24,000-scale topographic map, also known as a 7.5-minute quadrangle) or 3.75-minutes by 3.75-minutes. The second format is also known as a digital orthophoto quarter quadrangle (DOQQ) because each covers one quarter of a quadrangle (four 1:12,000-scale DOQQs display the same area as one 1:24,000-scale DOQ). 
- "USGS GeoData Digital Orthophoto Quadrangles" (PDF). USGS Fact Sheet 057-01. United States Geological Survey. May 2001. Archived from the original (PDF) on 2010-05-27.
- "Introduction to Photogrammetry". The Aerial Archive. Institute for Prehistory and Protohistory of the University of Vienna. Archived from the original on 2006-09-24.
- "USGS DOQ History". United States Geological Survey: Western Region. Retrieved April 24, 2012.
- "USGS 7.5-minute maps". United States Geological Survey: Eastern Geographic Science Center. Retrieved April 24, 2012.
- "DOQHEAD Toolkit". United States Geological Survey: Rocky Mountain Mapping Center. June 22, 1998. Archived from the original on 2011-10-18.