Evaluation of structure-from-motion for analysis of small-scale glacier dynamics

Abstract

Measurement of the geometry of marine-terminating glaciers is challenging due to the lack of stable ground areas in close proximity to the glacier. This precludes the use of fixed measuring devices and restricts the placement of ground control points. We propose a measurement procedure for marine-terminating glaciers using structure-from-motion including proper survey planning, control point design and model alignment. As a case study, we surveyed Hans Glacier, Hornsund fjord, South Spitsbergen. We demonstrate that our method is indeed effective for documentation of small-scale glacier dynamics, show the importance of appropriate alignment strategies for models with poorly distributed control points and compare two SfM tools (Agisoft Metashape and Bentley ContextCapture) concluding that ContextCapture offers around 17% lower error, 25% faster processing and better reconstruction of fine details and shadowed concavities.