A Methodology for Consistent Georegistration in Underwater Hyperspectral Imaging

Abstract

This article proposes a novel methodology for precise georegistration in underwater hyperspectral imaging (UHI) using a red–green–blue (RGB) camera to build a photogrammetry model that estimates the pose and a 3-D seabed model. The two main scientific contributions are: 1) the development of two methods for geometric calibration of the hyperspectral imager (HSI) with the RGB camera and 2) the development of a methodology for consistent georegistration of the pushbroom hyperspectral imagery on the seabed using the photogrammetry model and the geometrically calibrated HSI. The georegistration uses a calibrated RGB camera, fixed to the HSI, with an overlapping field of view. The RGB images are used to build a photogrammetry model. Through utilizing the geometric HSI parameters from the calibration, the hyperspectral imagery is ray cast onto the 3-D model. This methodology is exemplified for UHI from a remotely operated vehicle on a cold-water coral reef in the Trondheim Fjord, Norway. The precision is unprecedented for georegistration in UHI, demonstrated by the first-ever spatially consistent UHI mosaic to contain multiple transects.