Frame Center And Corner Points
KlvInjector can calculate the following derived metadata:
- Frame Center, Tags 23 and 24
- Corner point offsets, Tags 26 to 33
- Full corner points, Tags 82 to 89
Figure: Frame-center and corner-point calculation settings.
If the camera points above the horizon, it may not be possible to calculate a valid frame center. In that case, the offset corner points also become invalid because they are defined relative to the frame center.
MISB 0601 requires special values in this case to indicate that the sensor is not pointing at the earth. Because this is common in aerial footage, KlvInjector lets you choose whether to emit or suppress frame-center and offset-corner metadata when it would not be meaningful.
Full corner points can still often be estimated if the camera is not pointing at the sky. When only partial footprint information is available, KlvInjector keeps the near corner points and estimates the far corner points from UAV altitude and horizon distance.
KlvInjector does not use terrain elevation data for this estimation, so accuracy is best on flat terrain.