Estimation of large displacements in Viedma glacier by the implementation of optical flow

ESTEBAN LANNUTTI; TOTH CHARLES; LENZANO MARIA GABRIELA

Congreso; 37th Asian Conferemce of Remote Sensing; 2016

In this work, we assessed the feasibility of using optical flow as a possible solution to obtain accurate data at pixel level to derive ice velocities in a glacier. The study of glacier dynamics requires the detail mapping of surface velocities that vary along the glacier, following complex patterns defined by stress and strain rate distributions. In order to obtain a dense and accurate grid of ice velocities by optical flow algorithm as the result of the apparent movement pattern between objects, we carried out a test of the proposed large displacement optical flow (LDOF) method in Viedma Glacier, located at the Parque Nacional Los Glaciares, South Patagonia Icefield, Argentina. We collected a monoscopic image terrestrial sequence, time-lapse, acquired by a calibrated camera. Images were acquired every 24 hour from April 2015 until April 2016, a total of 248 days. We implemented the Correlated Image Filter (CIF) processes to avoid and minimize errors due to the important changes in lighting, shadows, clouds and snow that allowed to select a sequence of correlated image pairs. Our results show a flow field in the direction of the glacier movement with acceleration in the terminus. Then, we analyzed the errors between different images pairs, and the matches generally appear to be adequate, although some areas show random gross errors related to the presence of changes in lighting. These errors were minimized by averaging the image sequence based on seasons, which yielded good results. Finally, the use of terrestrial time-lapse data collection and the efficient LDOF solution at sub-pixel level accuracy provided a useful solution to detect large daily changes in the glacier.