During the digitizing process, image stretches and manipulation of image contrast, brightness and color balance were performed in the ArcView Image Analysis Extension to enhance features in the processed imagery. Additional collateral information, including previously completed habitat maps, NOS nautical charts, and other descriptive references dealing with benthic and coastal habitats of Salt River National Historic Park and Ecological Preserve was used to assist with image interpretation.
A first draft map was completed and features in the imagery where uncertainties existed, due to confusing or difficult to interpret signatures, were identified for future ground validation effort. An ArcView GIS point theme was generated with points positioned on the features of uncertain habitat type or along transects through gradients between habitat types. The GIS points were converted to GPS waypoints, and were visited for on the ground habitat validation.
Benthic habitat characterization was conducted at each site by snorkeling, free diving, or via observations from the surface where water depth and clarity permitted. Mangrove habitat characterization was conducted by driving, kayaking or hiking to points and visually identifying mangrove type and cover. GPS data was collected at each location, and site ID, depth, habitat type, and the method used to make the assessment were recorded. The ground validation data was incorporated into the second draft of each map.