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Abstract. Unmanned aerial vehicles (UAVs) and structure from motion with multi-view stereo(SfM–MVS) photogrammetry are increasingly common tools for geoscienceapplications, but final product accuracy can be significantly diminished inthe absence of a dense and well-distributed network of ground control points(GCPs). This is problematic in inaccessible or hazardous field environments,including highly crevassed glaciers, where implementing suitable GCP networkswould be logistically difficult if not impossible. To overcome thischallenge, we present an alternative geolocation approach known asGNSS-supported aerial triangulation (GNSS-AT). Here, an on-boardcarrier-phase GNSS receiver is used to determine the location of photoacquisitions using kinematic differential carrier-phase positioning. Thecamera positions can be used as the geospatial input to the photogrammetryprocess. We describe the implementation of this method in a low-cost,custom-built UAV and apply the method in a glaciological setting at StoreGlacier in western Greenland. We validate the technique at the calving front,achieving topographic uncertainties of ±0.12  m horizontally ( ∼ 1.1 × the ground sampling distance) and ±0.14  m vertically( ∼ 1.3 × the ground sampling distance), when flying at an altitudeof ∼ 450  m above ground level. This compares favourably with previousGCP-derived uncertainties in glacial environments and allows us to apply theSfM–MVS photogrammetry at an inland study site where ice flows at2 m day −1 and stable ground control is not available. Here, we wereable to produce, without the use of GCPs, the first UAV-derived velocityfields of an ice sheet interior. Given the growing use of UAVs and SfM–MVSin glaciology and the geosciences, GNSS-AT will be of interest to thosewishing to use UAV photogrammetry to obtain high-precision measurements oftopographic change in contexts where GCP collection is logisticallyconstrained.

High-accuracy UAV photogrammetry of ice sheet dynamics with no ground control