DOQQ maps, Digital Orthographic Quarter-Quads, are aerial photographs that have the geometric qualities of a map. It is georeferenced and orthorectified, which means it defines its existence in physical space and the image has been geometrically corrected so that the scale is uniform throughout.
This is done because when taking photographs at high altitudes some distortions will naturally occur. The edges of the photo the top of the "object" is not aligned with its base because of the Earths curvature and objects at higher elevations are shown in more detail because they are closer to the imaging equipment. The map above is a DOQQ of Lake Travis, Texas where a study is being conducted to review the changing of the floodplain. From the photographic map it is possible to overlay data onto the map to show floodplains which could aid in emergency management scenarios.
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