3D Photogrammetry Tutorial about Orthorectification

As per 3D aerial photogrammetry mapping, you have to line up the 3D aerial images with the geolocations exactly. This involves, not just lining up the corners of a photo, but also correcting to account for lens distortions. The process is called orthorectification.

More precisely Orthorectification is a processing step in which aerial photos are adjusted to correct distortions due to topographic relief, lens distortion, and camera tilt

These geometrical corrections should mean that the scale of the photograph is uniform, such that the photo is equivalent to a map. Unlike an uncorrected 3d aerial photograph, an orthophotograph can be used to measure true distances, angles and areas. As such it can used to derive a map
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