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Measuring glacier surface roughness using plot-scale, close-range digital photogrammetry

By Tristam D.L. Irvine-Fynn, Enoc Sanz-Ablanedo, Nick Rutter, Mark W. Smith and Jim H. Chandler

Abstract

Glacier roughness at sub-metre scales is an important control on the ice surface energy balance and has implications for scattering energy measured by remote-sensing instruments. Ice surface roughness is dynamic as a consequence of spatial and temporal variation in ablation. To date, studies relying on singular and/or spatially discrete two-dimensional profiles to describe ice surface roughness have failed to resolve common patterns or causes of variation in glacier surface morphology. Here we demonstrate the potential of close-range digital photogrammetry as a rapid and cost-effective method to retrieve three-dimensional data detailing plot-scale supraglacial topography. The photogrammetric approach here employed a calibrated, consumer-grade 5 Mpix digital camera repeatedly imaging a plot-scale (≤25 m2) ice surface area on Midtre Lovénbreen, Svalbard. From stereo-pair images, digital surface models (DSMs) with sub-centimetre horizontal resolution and 3 mm vertical precision were achieved at plot scales ≤4 m2. Extraction of roughness metrics including estimates of aerodynamic roughness length (z 0) was readily achievable, and temporal variations in the glacier surface topography were captured. Close-range photogrammetry, with appropriate camera calibration and image acquisition geometry, is shown to be a robust method to record sub-centimetre variations in ablating ice topography. While the DSM plot area may be limited through use of stereo-pair images and issues of obliquity, emerging photogrammetric packages are likely to overcome such limitations

Topics: Applied glaciology, Energy balance, Glaciological instruments and methods, Snow/ice surface processes, Surface melt
Publisher: © International Glaciological Society
Year: 2014
DOI identifier: 10.3189/2014JoG14J032
OAI identifier: oai:dspace.lboro.ac.uk:2134/16546
Journal:

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