Boat based mapping of geological features using 3D-Photogrammetry and hyperspectral imaging system (Case study: Greenland)

Artic environments provide a challenging ground for geological mapping and mineral exploration. Inaccessibility and harsh conditions complicate ground surveys and a dense cover of ice, vegetation, and lichens hinders supportive remote sensing surveys. Steep coastal cliffs are often the only accessible major outcrops, but are mostly not observable by air- or space-borne remote sensing data due to their off-nadir viewing angle. Former studies of those cliff sections focused on the manual interpretation of ground- or boat-based RGB images. However, detailed spectral and morphological data is missing, which is essential for common semi-automatic remote sensing data processing and interpretation of mineralogy and structures.
This contribution introduces an approach for photogrammetry and hyperspectral remote sensing of near-vertical cliff sections of geological outcrops in central west Greenland. A 3D image-based surface reconstruction technique is developed to enable a more automated outcrop evaluation. The focus lies hereby on the integration of digital photogrammetry with boat-based hyperspectral imaging to complement Digital Outcrop Models (DOM) with quantitative information about mineral variations in the outcrop. The project focuses on: 1) integration of hyperspectral images with the photogrammetry derived DOM´s, 2) geometric distortion correction of boat-based hyperspectral images, 3) extraction and mapping of geological features from close range hyperspectral images. The extreme off-nadir (nearly horizontal) scanning view and the resulting scan geometry need to be taken into account during processing. This contribution also highlights future possibilities for rapid semi-automatic interpretation of the data and advances in technology.
Our approach provides a promising workflow for off-nadir remote sensing campaigns in coastal artic environments including photogrammetry and hyperspectral imagery even in remote regions, which are only accessible by boat and can hardly be observed by classic geological mapping.