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In this study, we assessed the feasibility of using optical flow, in particular, large displacement optical flow (LDOF) method as a possible solution to obtain surface movement data to derive ice flow velocities in a glacier. Tests were carried out at the Viedma Glacier, located at the South Patagonia Icefield, Argentina, where terrestrial monoscopic image sequences were acquired by a calibrated camera from April 2014 until April 2016. As for preprocessing, the Correlated Analysis method was implemented to avoid and minimize errors due to the measurable changes in lighting, shadows, clouds, and snow. The results show a flow field with a maximum surface velocity value of 3.5 m/d. The errors were minimized by averaging the image sequence results based on seasons, in which the Total Error Reconstruction yielded fairly good mean accuracy (0.36 m/d). In summary, it was demonstrated that LDOF can provide accurate and robust solution to detect daily changes in the glacier surface. [ABSTRACT FROM AUTHOR]

In this work, we assessed the feasibility of using optical flow to obtain the motion estimation of a glacier. In general, former investigations used to detect glacier changes involve solutions that require repeated observations which are many times based on extensive field work. Taking into account glaciers are usually located in geographically complex and hard to access areas, deploying time-lapse imaging sensors, optical flow may provide an efficient solution at good spatial and temporal resolution to describe mass motion. 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 South Patagonia Icefield, Argentina. We collected monoscopic terrestrial time-lapse imagery, acquired by a calibrated camera at every 24 hour from April 2014 until April 2015. A filter based on temporal correlation and RGB color discretization between the images was applied to minimize errors related to changes in lighting, shadows, clouds and snow. This selection allowed discarding images that do not follow a sequence of similarity. Our results show a flow field in the direction of the glacier movement with acceleration in the terminus. We analyzed the errors between image pairs, and the matching generally appears to be adequate, although some areas show random gross errors related to the presence of changes in lighting. The proposed technique allowed the determination of glacier motion during one year, providing accurate and reliable motion data for subsequent analysis. [ABSTRACT FROM AUTHOR]