We should remember the earth is not a simple sphere, if it was, we need one datum "= One calculation system to find a point on earth", earth is more ellipsoid, but not exactly. Earth is an astronomic geoid without a regular shape, so we may have many ways to calculate coordination of a point in this irregular 3D object, with many opinions and concepts, each one is a datum.

ICSM's Fundamentals of Mapping page on Datums 1 – The Basics can be visited for more information.

We should remember the earth is not a simple sphere, if it was, we need one datum "= One calculation system to find a point on earth", earth is more ellipsoid, but not exactly. Earth is an astronomic geoid without a regular shape, so we may have many ways to calculate coordination of a point in this irregular 3D object, with many opinions and concepts, each one is a datum.

ICSM's Fundamentals of Mapping page on Datums 1 – The Basics can be visited for more information.

We should remember the earth is not a simple sphere, if it was, we need one datum "= One calculation system to find a point on earth", earth is more ellipsoid, but not exactly. Earth is an astronomic geoid without a regular shape, so we may have many ways to calculate coordination of a point in this irregular 3D object, with many opinions and concepts, each one is a datum. please visit http://www.icsm.gov.au/mapping/datums1.html Regards

We should remember the earth is not a simple sphere, if it was, we need one datum "= One calculation system to find a point on earth", earth is more ellipsoid, but not exactly. Earth is an astronomic geoid without a regular shape, so we may have many ways to calculate coordination of a point in this irregular 3D object, with many opinions and concepts, each one is a datum.

ICSM's Fundamentals of Mapping page on Datums 1 – The Basics can be visited for more information.