Abstract
The powerful 3D mapping tool at the photogrammetry laboratory of the Geological Survey of Denmark and Greenland (GEUS) is ideal for collecting high-quality 3D geological data in remote and inaccessible areas with a high degree of exposure such as Greenland (Vosgerau et al. 2010). So far this 3D mapping tool has been used to visualise and extract very precise geological data from aerial and oblique photographs. In the study reported on here, the 3D mapping tool was used to generate data for 3D geological modelling. The Skaergaard intrusion (Fig. 1) is a well-known Eocene layered gabbro. The study of the intrusion has had great importance for the understanding of magmatic petrology, magma differentiation and fractional crystallisation since the early studies by Wager & Deer (1939). It was chosen for 3D modelling because it is well studied from a petrological point of view and because the shape of the magma chamber was previously modelled in a network of 2D cross sections (Nielsen 2004). In this paper, it is modelled for the first time in 3D using a detailed 1:20 000 scale geological map (McBirney 1989), 1:27 000 scale aerial photographs from 1973, data from drill holes and geophysical data.
Highlights
The powerful 3D mapping tool at the photogrammetry laboratory of the Geological Survey of Denmark and Greenland (GEUS) is ideal for collecting high-quality 3D geological data in remote and inaccessible areas with a high degree of exposure such as Greenland (Vosgerau et al 2010)
Polylines from the aerial photographs have real 3D coordinates measured directly on the 3D stereo plotter, whereas polylines from the ArcGIS map have X-Y coordinates from the map and Z coordinates imported from the digital elevation model
This leads to additional uncertainty as elevations in the ArcGIS map and the digital elevation model are not generated from the same source and sometimes do not overlap in the entire area of interest
Summary
The powerful 3D mapping tool at the photogrammetry laboratory of the Geological Survey of Denmark and Greenland (GEUS) is ideal for collecting high-quality 3D geological data in remote and inaccessible areas with a high degree of exposure such as Greenland (Vosgerau et al 2010). This 3D mapping tool has been used to visualise and extract very precise geological data from aerial and oblique photographs. Structural readings (dip direction and dip angle) for the geological boundaries were generated from polylines using the in-house-developed software tool GEUS Planes (Fig. 2B). The boundaries from the aerial photographs are much more accurate than those of the map (Fig. 3) because they represent directly observable geological features
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