Coplanar tiepoints in a georef direct linear
You may have a problem with coplanar tiepoints when you use a georeference direct linear and during screen digitizing you notice a shift between the location of the segments or points which you were digitizing and the location where these digitized segments and points are appearing in the photo on the screen.
In a georef direct linear, at least 2 tiepoints should clearly deviate in Z-direction from a (tilted) plane that can be fit by means of a least squares approximation through the active tiepoints.
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