- vector data
- raster data
- alphanumeric
- points
- lines
- polygons
Vector data is stored as a series of x,y coordinates. Each point is a pair of x,y coordinates. A line is a series of points. A polygon is a series of points that are connected to form a closed shape.
Raster data is stored as a grid of cells. It is like a matrix. Each cell has a value. The value could be a number, a category, or a color. Raster data is used to represent continuous phenomena such as elevation, temperature, or precipitation.
Alphanumeric data is stored in a table. Each row is a record. Each column is a field. A field is a single piece of information. A record is a collection of fields. A table is a collection of records.
A coordinate reference system (CRS) is a coordinate-based local, regional or global system used to locate geographical entities. A CRS is defined by a datum and a projection. A datum is a model of the earth. A projection is a method for transforming the earth's curved surface into a flat surface.
- WGS84: World Geodetic System 1984 is a global datum that is used by GPS.
- NAD83: North American Datum 1983 is a regional datum that is used by the US, Canada, and Mexico.
- NAD27: North American Datum 1927 is a regional datum that is used by the US, Canada, and Mexico.
- NAD83 (CSRS): North American Datum 1983 (Canadian Spatial Reference System) is a regional datum that is used by Canada.
- UTM: Universal Transverse Mercator is a global projection that is used by the USGS.
- State Plane: State Plane is a regional projection that is used by the USGS.
- Albers Equal Area: Albers Equal Area is a regional projection that is used by the USGS.
Note: USGS = United States Geological Survey