ObliqueMapper: How it Works
Absolute Orientation
Once relative orientations for each photograph have been determined, an absolute orientation can be established to relate each photograph to a real-world coordinate system such as UTM.
Two methods exist within ObliqueMapper™ to establish the absolute orientation of photographs. The first is to use ground control points (e.g. from GPS) of identifiable objects within the scene. These could be things such as utility poles, street corners, or manually placed targets.
Once at least three ground control points are provided, ObliqueMapper™ can compute the mathematical relationship between its previously determined relative orientations to the absolute (real-world) coordinate system stated by the control points.
Alternatively, the user may collect real-world coordinates of the camera when each photograph was taken (e.g. camera on a tripod with a GPS nearby). These "at-camera" locations may then be used instead of ground control points.
Although described as separate approaches, ObliqueMapper™ actually allows for both ground control points and "at-camera" locations to be incorporated into the same absolute orientation process.
