What is an Orthophoto?
An orthophoto is an aerial photograph planimetrically corrected. Orthophotographs have the positive attributes of a photograph such as detail and timely coverage, and the positive attributes of a map, including uniform scale and true geometry. This enables orthophotographs to be used in their primary role as a backdrop on which map features can be overlaid. Orthophotos are now created by scanning aerial photographs and converting them into a Raster image file format. A digital terrain model is added as a means of collecting ground points to indicate the changes in elevation. When control points are identified on the aerial photos, stereo models are developed and geometric distortions are estimated. The image is rectified and geo-referenced using mathematical models of photogrammetry to remove tilt, terrain, atmospheric and other digital image distortions.
