Coral reef monitoring by the compact airborne spectrographic imager (CASI)

Abstract

The casi has the spatial resolution of about 3 m X 3 m at the ground level and its spectral resolution is about 6 nm. The wavelength range for the measurement is from 430 to 870 nm and the number of the bands is 72 bands. An airplane carrying casi flew over Kuroshima Island, Okinawa and acquired image data of Kuroshima Island and the surrounding sea area. The flight courses were 6 courses at the altitude of 9,000 feet and 2 courses of 6,000 feet. At the same time, spectral measurements of the sea surface and several coral reefs underwater were carried out at an area of coral reefs off Kuroshima Island. The supervised and unsupervised classification were applied to the casi imageries to extract and classify the area of coral reefs off Kuroshima Island. The produced classification maps of the coral reefs were compared with the ground truth map of coral reefs made by the professional divers to evaluate the results. The results showed significant similarity of the distribution pattern of corral reefs.