Hawaii Land Cover C-Cap

U.S. NOAA

The Hawaii project focused on developing baseline data for the main eight Hawaiian Islands . Although lack of usable historical imagery prevented a quantitative change analysis, numerous change processes were evident and detailed by analysts. These changes were of two types: changes in agricultural practices, and urban human development processes, particularly in the form of resorts and hotels being built along the coasts. Project focus centered on the eight main Hawaiian Islands including Niihau, Kauai, Oahu, Molokai, Lanai, Maui, Kahoolawe, and Hawaii. Landsat 7 Enhanced Thematic Mapper (ETM) imagery was used. Land cover change requires two dates of imagery to make a comparative assessment. Due to the lack of historical data from Landsat Thematic Mapper 4 and 5, it was not possible to perform a change analysis. Imagery was ordered from the EROS Data Center (EDC), georeferenced in Albers equal area projection. Hawaii is characterized by almost constant cloud cover. To minimize cloud cover, multiple image dates and scenes were used to map each island. In some cases, no clear imagery was available for portions of the land surface. To get a clear picture of Hawaiian land cover it was necessary to combine multiple pieces of cloud-free images to form a cloud-reduced image mosaic. A band ratio technique was used to identify clouds and cloud shadow areas and mask them out of the imagery. After removing these clouds, cloud-free pieces of overlapping images were reinserted into these holes, forming a cloud-reduced mosaic. Even though multiple images and scenes were used to piece together a cloud-free mosaic, the final cloud-reduced imagery is still characterized by 10 to 15 percent cloud cover.