graphic map features

graphic map features

(Data West Research Agency definition: see GIS glossary.) Map graphic features or elements can be classified as points, lines, areas, or "raster." In GIS, these features are grouped together to form more complex objects such as "networks" of streams or roads, three-dimensional terrain "surface," and multi-polygon regions. The first four of these feature types are:

1) Points - GIS map "points" have no length or area but simply define the coordinate location of the feature (survey monuments, wells, mountain peaks, building permits, and traffic incidents are represented as points in a GIS database).

2) Lines - Lines have a linear extent in the GIS database but no area. (Road centerlines, stream centerlines, sewer lines, and utility mains are represented as lines in a GIS database.)

3) Areas - Areas, normally called "polygons" or "regions," are defined by a set of enclosing perimeter lines and are two-dimensional (property parcels, census tracts, and soils are represented as areas in a GIS database).

4) Raster Data - "Raster" or "grid-based" format areas and other map features as cells of a grid matrix; the fineness of the grid or the size of the cells in the grid matrix determines how accurately original map features are represented (scanned images of documents and satellite imagery are examples of raster data).