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

Published version
Peer-reviewed

Type

Article

Change log

Authors

Christoffersen, Poul  ORCID logo  https://orcid.org/0000-0003-2643-8724
Snooke, Neal 

Abstract

jats:pAbstract. Unmanned Aerial Vehicles (UAVs) and Structure from Motion with Multi-View Stereo (SfM-MVS) photogrammetry are increasingly common tools for geoscience applications, but final product accuracy can be significantly diminished in the 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 networks would be logistically difficult if not impossible. To overcome this challenge, we present an alternative geolocation approach known as GNSS-supported aerial triangulation (GNSS-AT). Here, an on-board carrier-phase GNSS receiver is used to determine the location of photo acquisitions using kinematic differential carrier-phase positioning. The camera positions can be used as the geospatial input to the photogrammetry process. We describe the implementation of this method in a low-cost, custom-built UAV, and apply the method in a glaciological setting at Store Glacier in West Greenland. We validate the technique at the calving front, achieving topographic uncertainties of ±0.07 m horizontally and ±0.14 m vertically when flying at an altitude of ~ 450 m a.s.l. This compares favourably with previous GCP-derived uncertainties in glacial environments, and allowed us to apply the SfM-MVS photogrammetry at an inland study site where ice flows at 2 m day−1 and where stable ground control is not available. Here, we were able to produce, without the use of GCPs, the first UAV-derived velocity fields of an ice sheet interior. Given the growing use of UAVs and SfM-MVS in glaciology and the geosciences, GNSS-AT will be of interest to those wishing to use UAV photogrammetry to obtain high-precision measurements of topographic change in contexts where GCP collection is logistically constrained. </jats:p>

Description

Keywords

37 Earth Sciences, 4013 Geomatic Engineering, 3709 Physical Geography and Environmental Geoscience, 40 Engineering

Journal Title

The Cryosphere Discussions

Conference Name

Journal ISSN

1994-0432
1994-0440

Volume Title

Publisher

Copernicus GmbH
Sponsorship
European Commission Horizon 2020 (H2020) ERC (3276207)
NERC (NE/L002507/1)
NERC (1795514)