Remote geological mapping using 3D photogrammetry: an example from Karrat, West Greenland

The geology of the Paleoproterozoic Karrat Group in West Greenland (71°–74°50´N) was investigated during the field seasons 2015–2017, using a combination of digital photogrammetry and traditional field work in a collaboration between the Geological Survey of Denmark and Greenland and the Ministry of Minerals Resources of Greenland. The area is characterised by steep alpine terrain with more than 2000 m of relief that in many places is completely inaccessible, which makes field work extremely difficult. Therefore 3D mapping using digital photogrammetry is an invaluable tool in the investigation of the region. Early geological investigations of the area involved the first use of photogrammetry in Greenland (Henderson & Pulvertaft 1987). This contribution serves as an example of the present-day use of photogrammetry in geological interpretation, following the workflow outlined in Sørensen & Dueholm (2018). During the last three years, more than 50 000 stereo images have been collected using handheld, calibrated digital cameras while conducting field work in the area (Rosa et al. 2016, 2017, 2018). The images, which cover large parts of the steep cliff sections in which the geology is superbly exposed, are essential to the ongoing revision of the geological map sheets covering the area. Here we present a small subset of the data from the island of Karrat (Fig. 1), showcasing the potential of 3D geological mapping in Greenland as well as presenting new insights into the geology of the Karrat Group.