GIS mapping data displays typically employ symbols to represent geography or physical objects. These objects can be divided into two main categories: discrete objects, which are physical characteristics like buildings or lakes, and continuous fields that are not confined to a specific area, such as elevation and precipitation levels. GIS data shows information about the presence of both discrete and continuous values utilizing one of two methods: raster data and vector mapping. The raster data method produces a digital picture that is represented in grid form.
This does not result in an exact image of the reality of the geography, but rather a general abstract of it. A common method of raster data is aerial photography. Aerial photos generate images that show discrete objects, such as housing complexes or rivers, and can be subsequently digitized to provide continuous information, such as elevation or weather patterns. The second option for displaying GIS data, vector mapping, functions using a coding system that uses geometric shapes to denote discrete values on maps. There are generally three codes utilized by vector maps: lines, points, and polygons. Lines are used to represent rivers and roads and are particularly useful in conveying their lengths.
Points are used to display static geographical information, such as buildings and wells. Polygons can be used to represent other discrete values, such as lakes or territorial boundaries, but also continuous values. The perimeter of an area affected by drought for example, could be measured by a polygon on a vector map. In addition to lines, points, and polygonal features, vector maps can be color coded to represent varying levels of elevation, precipitation, depth, etc. GIS maps present discrete and continuous information in a straightforward manner, using either raster data or vector mapping, to make it easier to comprehend. In everyday life for example, people use GIS mapping data to locate how far a grocery store is from their homes.