Which datum is centered on the Earth and based on control point fits?

The correct answer is NAD83, which stands for the North American Datum of 1983. This geodetic datum is indeed centered on the Earth and is defined by a set of control points across North America. NAD83 was developed to provide a more accurate representation of the Earth's shape by using a three-dimensional ellipsoidal model. It is based on the concept of fitting a mathematical surface (the ellipsoid) to the Earth's surface through the use of geodetic control points, which enhances position accuracy for mapping and GIS applications.

The reason why this is significant for GIS professionals is that NAD83 supports more precise location measurements and better integration of spatial data. This datum is widely used in modern GPS technology and mapping applications as it aligns closely with the global positioning system, allowing for more reliable data interpretation and analysis in geographic information systems.

Other datums, like NAD27 and NAD92, may not be centered on the Earth in the same way or may be based on less accurate fitting methods when compared to NAD83. WGS84 is a global datum that also serves many of the same purposes as NAD83. Therefore, while WGS84 is frequently used internationally and shares some characteristics with NAD83, NAD83’s specific fitting to the North American