geodetic

Geodetic refers to geodesy, the scientific discipline that studies the size and shape of the Earth, its orientation in space, and its gravity field, and the methods used to measure and model these properties. Geodesy provides a precise, global framework for describing locations on the Earth's surface and near space, enabling consistent positioning, navigation, and mapping.

Geodesy encompasses determining the geometric shape of the Earth (the reference ellipsoid), the physical surface known as the geoid, and temporal changes due to plate tectonics, tides, and mass distribution. It combines astronomical observations, satellite data, and terrestrial measurements to estimate coordinates, elevations, and gravity anomalies.

A geodetic datum is a coordinate reference system coupled with a model of the Earth's shape. It defines how a three-dimensional position on Earth is represented in a map or navigation system. Horizontal datums fix positions on the ellipsoid; vertical datums tie heights to the geoid or another surface. Modern practice uses widely adopted datums such as WGS 84, NAD83, and ETRS89, and it also relies on a time-dependent frame like the International Terrestrial Reference Frame (ITRF) to account for crustal motion.

Geodetic measurements are collected by networks and techniques such as Global Navigation Satellite Systems (GNSS), very long baseline interferometry (VLBI), satellite laser ranging (SLR), leveling, and triangulation, often in continuous networks to monitor deformations and gravity field variations over time.

Applications include mapping, surveying, construction, navigation, and Earth science research, as well as cadastral and engineering projects. The field continues to integrate new data sources and reference frames to support precise positioning and understanding of Earth's dynamics.