What is the term for a set of control points whose geometric relationships have been established through measurement or calculation?

The term for a set of control points whose geometric relationships have been established through measurement or calculation is a geodetic datum. A geodetic datum serves as a reference frame for measuring geographic coordinates – including latitude, longitude, and elevation. It establishes the position of these points on the Earth’s surface, which is crucial for accurately mapping and interpreting geographic data.

Geodetic datums are foundational in ensuring various datasets are aligned correctly when used in mapping and GIS applications. The datum incorporates considerations such as the shape of the Earth, local variations in the gravitational field, and other factors that influence how distances and angles are measured on the surface.

In contrast, a horizontal datum specifically refers to the framework used to define the horizontal positions (latitude and longitude) of points on the Earth’s surface, while a vertical datum is used to define elevations or depths. Map projection, on the other hand, involves transforming the three-dimensional surface of the Earth into a two-dimensional representation, which may utilize a datum but is a separate concept related to how geographic information is visually represented on maps. This distinction highlights the comprehensive nature of a geodetic datum in providing a consistent framework for spatial data across various applications.