1. COORDINATE SYSTEMS IN GIS As GIS is based on geographic location you need to understand basics of Coordinate Systems: Geographic and Projected Coordinate Systems.

2. Copyright © 2014 Natural Environmental Research Council (NERC) 2 Geographic Coordinate Systems In ArcGIS: Longitude is X. Latitude is Y. http://www.geographyalltheway.com A geographic coordinate system (GCS) uses a three-dimensional spherical surface to define locations on the earth. A point is referenced by its longitude and latitude values

3. Copyright © 2014 Natural Environmental Research Council (NERC) 3 Geographic Coordinate Systems Examples: WGS 84, OSGB36, ED50 WGS 84 – basis for Global Positioning System (GPS). Geocentric, GRS 80 ellipsoid (ETRF89, ITRF) OSGB 36 – basis for Ordnance Survey maps. Airy 1830 ellipsoid. European Datum 1950 – North Sea and mainland western Europe. International 1924 ellipsoid.

4. Copyright © 2014 Natural Environmental Research Council (NERC) 4 Projected Coordinate Systems http://visual.merriam-webster.com/earth/geography/cartography/map-projections.php Projections map the spherical Earth onto a plane. Projections always: Introduce discontinuities Introduce distortions. Try peeling an orange without breaking the skin!!!

5. Copyright © 2014 Natural Environmental Research Council (NERC) 5 Projected Coordinate Systems Conformal – maintains shape Equal-area – maintains area Equidistant – maintains distance Direction – maintains some directions

6. Copyright © 2014 Natural Environmental Research Council (NERC) 6 Datum Defines the shape and orientation of an ellipsoid (mathematical representation of the earth) Identifies the reference frame in use. –May be global WGS84 ITRF series –May be local. “Astronomical fix at Hope Bay”

7. Copyright © 2014 Natural Environmental Research Council (NERC) 7 Projections recommended for mapping Antarctica 1: 1 000 000 and smaller scales Antarctic Polar Stereographic / WGS84 1: 1 000 000 to 1: 100 000 scales Lambert Conformal Conic or Polar Stereographic / WGS84 Scales larger than 1: 100 000UTM / WGS84 Note: to accurately analyse your data you need to use different projection!!!

8. Copyright © 2014 Natural Environmental Research Council (NERC) 8 Map Scale Large scale map Small scale map Map scale is the relationship between the distance on a map and the distance on the Earth