Geographic coordinate systems

Wikipedia: Geographic coordinate systems

A geographic coordinate system is a coordinate system that enables every location on the Earth to be specified by a set of numbers or letters, or symbols...A common choice of coordinates is latitude, longitude and elevation.

Coordinate type X Y
Longitude and Latitude. -3.106849 51.015344
Eastings and Northings. 322454 124580

Points, lines, and polygons

Typically when dealing with geo-spatial data, this will be in the form of Points, Lines, and Polygons.

  • Points - Individual locations made up of a single coordinate set e.g. a Library.
  • Lines - Linear features made up of coordinates e.g. a Road
  • Polygons - Bounded areas (shapes) made up of coordinates e.g. a County Council.

Geocoding and reverse-geocoding

Geocoding and reverse geocoding are ways of matching address and location data with geo-coordinates.

  • Geocoding: Address -> Geo-coordinates. Example: Putting a library on a map from it's address.
  • Reverse geocoding: Geo-coordinates -> Address. Example: taking coordinates retrieved from GPS to determine current location.

GIS software

The traditional way of working with GIS data is through Desktop applications

Download and install: Quantum GIS

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