Marine & Environmental Sciences Faculty Proceedings, Presentations, Speeches, Lectures

Reefel Carbonate Facies off Dubai, Arabian Gulf: Remote-Sensing with Ikonos Satellite Images and Ground-Truthing by Vessel-Based Video Survey

Event Name/Location

2002 Ocean Sciences Meeting

Presentation Date

2002

Document Type

Conference Proceeding

Keywords

Carbonates, Remote Sensing Technology, Arabian Gulf

Description

Satellite-based remote-sensing is a rapid and cost efficient way to obtain large-scale data of seafloor types or oganismal assemblages. Misclassifications can reduce accuracy and rigorous ground-truthing is necessary. We compared results from a vessel-based video-survey recording footage along parallel survey lines from the surface (Riegl et al., 2001, Bull. Mar. Sci. 68) and classification from an Ikonos image with 1m pixel resolution - two data-sets with 100 percent space cover. Video data were obtained in 1995/6, the Ikonos image in 2001. Facies distribution was not expected to be identical since in the five intervening years a coral mass mortality had killed most of the corals and breakdown of the skeletons had started. Also seagrass and algae beds exhibit high spatial dynamics and were not expected to be identical in the two surveys. The remotely-sensed distribution of habitats nevertheless was highly compatible with that observed by the video survey. Some differences were found in the distribution of algae and seagrass beds, but these could largely be attributed to the five-year time-lag between the surveys. The classification obtained from the satellite image suggests that the video-survey missed some areas of coral-growth. Conversely, some areas mapped as having corals in the video survey did not show in the image classification which suggests breakdown after the 1996 mass mortality. Several small coral areas surrounded by seagrass areas and dense areas of algal growth were only picked-up by the video-survey - since most dead corals were covered by algae, their pixel values on the satellite image were similar to those of algae. Also, in depths greater 10m the spectral values did not allow clear classification. Overall, for areas in less than 10m depth, the results of the satellite-remote sensing and the vessel-based video-survey compared very well. Images courtesy NASA Scientific Data Purchasing Program and F. Muller-Karger at USF.

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