Effective application of automated digital photogrammetry for geomorphological research

Abstract

Developments in digital photogrammetry have provided geomorphologists with an automated tool to generate digital elevation models (DEMs) at exceedingly high densities. Although such software tools are available at low cost and run on far cheaper hardware than previous generations of photogrammetric instrumentation, some expertise is still required to derive accurate data. Various recommendations are provided that should enable the inexperienced user to make effective use of digital photogrammetry. Key issues discussed include the role of photo-control, the significance of checkpoints in the object space, and the importance of camera calibration data. An overview of self-calibration methods is provided, which is valuable in situations when a non-photogrammetric camera has been used. Accurate camera modelling also affects DEM quality and this issue is examined through assessing the impact of DEM inaccuracies upon derived data used for geomorphological enquiry. Although the automated software packages are designed primarily for use with satellite imagery or vertical aerial photography, it is explained how such software can be used for both close range and oblique imagery. The procedure requires rotating the object coordinate system defined by the photo-control points and the mathematics required to achieve this is provided. The procedure is used to derive the morphology of a soil surface using oblique, close-range imagery and demonstrates the effectiveness of this particular approach. Copyright © 1999 John Wiley & Sons, Ltd.