The datum

It is often assumed that the world is a sphere. In fact it is more nearly an ‘oblate ellipsoid of revolution’. Although the flattening of the ellipse for the earth is negligible on small-scale maps, it does need to be included in calculations for accurate maps at a scale of 1:1,000,000 or greater. It can also be significant for some 1:5,000,000 scale maps, for example of the United States, affecting plotted shapes by up to 0.7%.

Datums are the systems that attempt to describe the size and shape of the Earth. Hundreds of different datums have been devised and are in use. Referencing coordinates to the wrong datum can result in positional errors of hundreds of meters. Different nations and mapping agencies base their coordinate systems on different datums, so care needs to be taken when using data from different sources.

MapLink Pro Studio stores information about a wide range of Datums, including information about accurately transforming data from one Datum to another. Providing the user inputs the datum used for their data, and selects the datum required for their output map, MapLink Pro Studio will automatically manage the transformation accurately and efficiently. The user may over-ride MapLink Pro Studio's transformation method with their own selection if they wish.