What are Ellipsoids and Datums?
Because the world is not flat, but rather an oblate spheroid, meaning it bulges at the equator and is a bit flat at the poles, it is almost impossible to accurately approximate the shape and size of the entire earth. Ellipsoids are used to provide a fairly reliable depiction of the earth’s surface for a particular area. However, one ellipsoid does not fit all. Different ellipsoids are used to represent different regions of the world. Using the wrong ellipsoid for a particular region of the world will lead to inaccuracies. Because the earth isn’t a perfect sphere, one part of the world may have a surface which is more flatter than another. Therefore, it becomes necessary to use the ellipsoid that best fits a particular region. Datums narrow things down a little more. Datums are referenced to a specific origin, and are used in combination with the most appropriate eillipsoid.
