Surface Geometry, Thickness Changes and Flow Fields on Creeping Mountain Permafrost: Automatic Extraction by Digital Image Analysis

Abstract

Aerial photogrammetry is an established tool for area-wide mapping and monitoring of permafrost geometry, thickness changes and surface creep. This study applies commercial software for the automatic generation of elevation models from digital imagery and presents a newly developed tool for digital measurement of surface displacements from repeated orthophotos. The accuracy and quality of automatically-derived geometry and velocity data are compared to conventionally-derived elevation and velocity data from the Muragl rock glacier in the Swiss Alps. The analysis reveals that for thickness changes and velocities digital photogrammetry provides at least the same accuracy as the reference data. Under unfavourable terrain and image conditions, such as steep slopes, shadows or snow cover, the reliability of the automatically-derived data is significantly lower than the operator-measured ones. Copyright © 2000 John Wiley & Sons, Ltd.