Abstract
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.
Highlights
Data acquisition methods on earth observation and monitoring applications, have seen great technological advancements in recent years, such as the introduction of airborne and terrestrial LiDAR (Light Detection and Ranging) and a wide variety of satellite sensors with varying geometric resolutions that can be combined with other techniques of data acquisition to substantially improve the quality of the observations (Paul et al, 2009)
In order to better understand the velocity field at the lower end of the glacier, ice velocities were obtained by means of the vector field flow based upon 354 photographs obtained from a fixed camera installed near Viedma glacier ice front
We have applied dense optical flow field methods to estimate with high precision glacier movement
Summary
Data acquisition methods on earth observation and monitoring applications, have seen great technological advancements in recent years, such as the introduction of airborne and terrestrial LiDAR (Light Detection and Ranging) and a wide variety of satellite sensors with varying geometric resolutions that can be combined with other techniques of data acquisition to substantially improve the quality of the observations (Paul et al, 2009). Glacier changes have been surveyed with a variety of methods since the mid-nineteenth century. The optical images have been the most important types of imagery to monitor the glaciers because they provided different spatial resolutions for mapping glacier changes/dynamics, even at present. Aerial and terrestrial photogrammetry has become a widely used technique to map rough and complex glacier topographies. Time-lapse imagery provides high temporal frequency and high spatial resolution over a long period of time, it may be applied in reduced areas
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