The Raster GIS

Abstract

Current GISs differ according to the way they organize reality through the data model. Each model tends to fit certain types of data and applications better than others. The data model chosen for a particular project or application is also influenced by the software available, the training of the key individuals, and historical precedent. There are two major choices of data models: Raster & Vector. This presentation focuses on the Raster model. The Raster model divides the entire study area into a regular grid of cells in specific sequence. The conventional sequence is row by row from the top left corner. Each cell contains a single value. The model Is space-filling since every location in the study area corresponds to a cell in the raster. One set of cells and associated values is a layer. There may be many layers in a database (Examples: soil type, elevation, land use, land cover). The model tells what occurs everywhere - at each place in the area.