This course will become read-only in the near future. Tell us at if that is a problem.


At the end of this lesson, you will be able to:
  • describe what a datum is in your own words

A Datum is the distance an ellipsoid is from the Earth's center. E.g. 'sea level' could be considered a datum (although sea leve tends to bulge with relation to the Moon's gravity).

Related Topics

  • Point of reference
  • Clarke 1866
  • NAD27
  • NAD83
  • GRS80
  • WGS84
  • Map Scale
  • representative fraction
  • 1:40,000,000 (meters) 
  • Other common scales


Task Discussion