Glacier Image Velocimetry: an open-source toolbox for easy and rapid calculation of high-resolution glacier-velocity fields

Abstract. We present Glacier Image Velocimetry (GIV), an open-source and easy-to-use tool for rapidly calculating high spatial and temporal resolution glacier-velocity fields. Glaciers' velocity fields reveal their flow dynamics, stability, and thickness. Obtaining widespread glacier-velocity measurements in the field is challenging and labour intensive. Recent increases in the availability of high-resolution, short-repeat-time optical imagery improve this, as persistent irregularities on the ice surface allow us to use feature tracking – an accidental form of particle image velocimetry to obtain displacement fields, and hence, velocity over time. While these techniques have been used to calculate velocity fields for many glaciers, existing toolboxes can be expensive, complex or inflexible to use. GIV is fully parallelized, and automatically detects, filters, and extracts velocities from large datasets of images. Through this coupled toolchain and an easy-to-use GUI, GIV can rapidly analyse hundreds to thousands of image pairs on any modern laptop or desktop. We present four examples of how this model may be used: to complement a glaciology field campaign (Glaciar Perito Moreno, Argentina), calculate the velocity fields of small (Glacier d’Argentière, France) and very large (Vavilov ice cap, Russia) glaciers, and determine the ice volume present within a tropical ice cap (Volcán Chimborazo, Ecuador). Fully commented code and a standalone app for GIV are available from GitHub and Zenodo.