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

• Published in: Journal of Glaciology
• Main Authors: Irvine-Fynn, Tristram, Sanz-Ablanedo, Enoc, Rutter, Nick, Smith, Mark, Chandler, Jim
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: International Glaciological Society 2014
• Subjects: F800 Physical and Terrestrial Geographical and Environmental Sciences; Svalbard; glacier; Journal of Glaciology
• Online Access: https://nrl.northumbria.ac.uk/id/eprint/17686/; https://doi.org/10.3189/2014JoG14J032

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 plotscale (≤25m2) ice surface area on Midtre Lovénbreen, Svalbard. From stereo-pair images, digital surface models (DSMs) with sub-centimetre horizontal resolution and 3mm vertical precision were achieved at plot scales ≤4m2. Extraction of roughness metrics including estimates of aerodynamic roughness length (z0) 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.