My sincere thanks to my supervisor, Adriaan van Niekerk, for his valuable technical input and guidance and for all the patient encouragement. Jan Vlok was instrumental in this research, and he is gratefully acknowledged for his vision, support and remarkable field expertise. Special thanks to Julie Verhulp, Raoul Duesimi and Aslam Parker of Chief Directorate: National Geospatial Information, for their generous provision of aerial imagery and related support. The Centre for Geographical Analysis, especially Garth Stephenson, Theo Pauw and Jascha Muller, graciously assisted with data, computing and software resources. Ilze Boonzaaier beautified some of the maps and Helene van Niekerk assisted with editing. Camera calibration software was kindly provided by Adrian Roos of Intergraph SA. Bernhard Jacobs of GeoSpace International assisted with valuable calibration discussions and data. Andrew Knipe, of the Gamtoos Irrigation Board, helped with funding administration. Finally, to Mireille van Reenen, for your moral support and great companythank you.

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