In engineering and drafting, a datum is a reference point, surface, or axis on an object against which measurements are made. Is the earth a sphere? No, it is a spheroid/ellipsoid.

A new conceptual data model that addresses the geometric dimensioning and tolerancing concepts of datum systems, datums, datum features, datum targets, and the relationships …

A datum is the answer to the practical problem of making an accurate map. If you wish to determine the relative location of a pair of points a few meters apart, the solution is obvious.

The first step in a typical datum conversion is to perform calculations to see if a single countywide vertical datum conversion factor can be applied to all unrevised flooding sources.

NGS will provide the tools to easily transform between the new and old datums. Read the NGS Ten-Year Plan and visit the New Datums Web page on our site to learn more.

A datum includes a set of positions that have been painstakingly surveyed, against which subsequent surveys are referenced. A datum is sometimes defined as a reference surface, …

Horizontal Datum = 1) shape and size of reference ellipsoid AND 2) location of ellipsoid center relative to center of mass of earth (geocenter).