One last item to consider is camera calibration. To produce accurate photogrammetric measurements PhotoModeler needs to know the precise parameters of the camera that took the photos (focal length, lens distortion, etc.).
PhotoModeler has a method for doing indoor or ground-based camera calibration (see Calibrating a Camera) but this is often inappropriate for UAV cameras because of the distances involved. Instead, PMU has the ability to Auto-calibrate the camera while all the photos are being processed (see Processing SmartMatch Settings). The auto-calibration step does slow down processing though so we suggest that once you have one or two successful projects processed with your UAV and its camera, that you save that camera in the Camera Library, and use it for subsequent projects by loading the camera during the wizard setup steps and skipping Auto-calibration.
For certain scenarios, auto-calibration requires external information to produce a good result. The bad result can be seen as a big curve in the model in the 3D view. These projects are sometimes called ‘umbrella’ or ‘soccer ball’ projects because that is what they look like. Good quality GPS data, consistency in the vertical control, or a good spread of ground control, used during auto-calibration, usually solves this problem.
Once a good calibration has been achieved, the camera parameters can be saved in the Camera Library so future projects do not need to perform calibration and the need for camera station control or ground control is reduced.