DOQQ map

A DOQQ map or digital orthophoto quarter quadrangle is a map in which is used to measure true distance because it has been geometrically corrected. This is a type of aerial photograph that is done in black and white. Unlike other aerial photographs which have not been orthorectified the scale in a DOQQ is uniform even though it has the same amount of distortion as other aerial photographs. This is a DOQQ of the Lake Travis flood plain.

Link: http://www.utexas.edu/depts/grg/hudson/grg360g/EGIS/final_project/spring04_projects/web_justin_reynolds/Lake%20Travis.htm