The shape of the Earth referred to in the context of geospatial data is defined as what?

The shape of the Earth in geospatial data is defined as an ellipsoid. An ellipsoid is a mathematically defined surface that closely approximates the shape of the Earth. It is used because the Earth is not a perfect sphere; rather, it is slightly flattened at the poles and bulges at the equator due to its rotation.

Using an ellipsoid allows for more accurate calculations and representations of geographic features and coordinates. In geospatial sciences, the ellipsoid serves as a fundamental basis for modeling positions on the Earth's surface, which is essential for mapping, navigation, and various geographic information systems (GIS).

While a datum provides a reference frame for measuring locations on the Earth's surface based on an ellipsoid, it is the ellipsoid's shape that describes the Earth's geometric representation itself. A GIS, on the other hand, refers to the system used to analyze and visualize geospatial data, and a tactical system typically refers to a framework or tools used in military operational contexts.