Optical flow applied to time-lapse seriesto estímate glacier motion in the southern of Patagonia Icefield

TOTH, C; LANNUTTI, E; LENZANO L; LENZANO, M. G.; RIBERA ANDRES

PRAGA

Simposio; XXIII ISPRS CONGRESS; 2016

ISPRS

In this work, we assessed the feasibility of using optical flow to obtain the motion estimation of a glacier. In general, formerinvestigations used to detect glacier changes involve solutions that require repeated observations which are many times based onextensive field work. Taking into account glaciers are usually located in geographically complex and hard to access areas, deployingtime-lapse imaging sensors, optical flow may provide an efficient solution at good spatial and temporal resolution to describe massmotion. Several studies in computer vision and image processing community have used this method to detect large displacements.Therefore, we carried out a test of the proposed Large Displacement Optical Flow method at the Viedma Glacier, located at SouthPatagonia Icefield, Argentina. We collected monoscopic terrestrial time-lapse imagery, acquired by a calibrated camera at every 24hour from April 2014 until April 2015. A filter based on temporal correlation and RGB color discretization between the images wasapplied to minimize errors related to changes in lighting, shadows, clouds and snow. This selection allowed discarding images thatdo not follow a sequence of similarity. Our results show a flow field in the direction of the glacier movement with acceleration in theterminus. We analyzed the errors between image pairs, and the matching generally appears to be adequate, although some areas showrandom gross errors related to the presence of changes in lighting. The proposed technique allowed the determination of glaciermotion during one year, providing accurate and reliable motion data for subsequent analysis.