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Benthic Habitat Mapping
Raster Data
The raster data model represents map features as cells in a grid matrix. The matrix is organized by continuous, evenly spaced rows and columns. Each cell is coded with an attribute that represents a data parameter (for example, the predominant type of sediment, the average bottom depth, the sea surface temperature) that appears within the cell. The size of the cells in the grid matrix determines the level of detail of the map features. Raster data sets are described primarily by the dimensions, or resolution, of the individual cells or pixels (for example, 1 square meter or 5 square meters). Cell resolution of raster data is an important consideration in benthic habitat mapping applications because the dimensions of the cell determine the representational precision of mapped features. For example, side-scan sonar imagery with a resolution of less than one square foot is considered "high resolution" data because it can distinguish small features such as sand waves. However, if the resolution of the imagery were to be increased to five square feet, small features like sand waves might no longer be visible. Raster data are acquired from both airborne (aircraft and satellite) and water-based remote sensing platforms for benthic habitat mapping. Aerial photographs, satellite imagery, side-scan sonar records, and underwater video are examples of data collected in raster form. The section on Spatial Analysis describes how raster data are used to examine and display benthic habitats. |
