Referencing and Coordinate Systems in GIS

The fundamental requirement of Geographic Information Systems (GIS) is the use of spatially aligned map layers. If they do not, obvious errors can occur. GIS users are accustomed to working with map features on a plane surface. The map elements correspond to spatial features on the surface of earth. Map features are located using a plane coordinate system represented by x, y-coordinates, while spatial features are located using geographic coordinate system expressed by longitudes and latitudes. A map projection acts as the bridge between the two coordinate systems. Map projection converts the curved surface of the earth into a plane, yielding a map projection suitable for use with a projected coordinate system. Georeferencing is the process of connecting the internal coordinate system of a digital map or aerial photograph to a system of actual geographic coordinates on the ground. After completion of this chapter, you would be able to understand the following topics: . Map projection and their types . Coordinate system . Concept of geographic coordinate system . Concept of projected coordinate systems . Some widely used projections . Concept of georeferencing and its application in raster and vector data.