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IMPROVING THE ACCURACY OF PHOTOGRAMMETRIC ABSOLUTE ORIENTATION USING SURFACE MATCHING

∗ Corresponding author. Research was conducted into improving the accuracy of photogrammetric absolute orientation, using a least squares surface matching algorithm rather than conventional ground control points (GCPs). To ascertain the success of the developed algorithm, a comparison between the two methods was carried out. Targets were laid at a test site, and near-vertical stereopairs of small format imagery were captured using a Kodak DCS 660 camera and microlight platform, from three flying heights. Stereomodels for each height were orientated using six GCPs as control, after which DEMs were extracted using automatic routines and compared with the remaining targets. For the surface matching orientation a kinematic GPS DEM of the test area was collected, and image stereomodels recreated – this time processed only to the relative orientation stage. DEMs were again extracted but were not yet in the desired reference system, requiring development of the matching algorithm. As an alternative means of performing the orientation, GCPs were bypassed and the GPS surface was used to register the unorientated DEMs. The matched surfaces were then compared with the checkpoints, showing a higher correspondence to the checkpoints for all three flying heights. This suggests that higher orientation precisions can be achieved with DEMs than using traditional GCPs, an especially important result for small format photogrammetry where more images and more GCPs are required. Although this study focused on small format imagery of a single area, implications on the wider discipline of photogrammetry are readily apparent.