geodésia

Geodesy is the science of measuring and representing the Earth. It focuses on determining the Earth's size, shape, orientation in space, and gravity field, as well as the precise position of points on or above its surface. Geodesy supports cartography, navigation, surveying, and Earth sciences by providing accurate reference frames and coordinates.

Geodesy distinguishes between geometric geodesy, which studies the shape and dimensions of the Earth (including the geoid, the reference surface of equal potential), and physical geodesy, which studies the Earth's gravity field and its variations. It uses both terrestrial techniques (ground-based surveying, gravimetry, leveling) and space-based methods. Modern geodesy relies on space geodesy: satellite positioning systems (GNSS such as GPS, GLONASS, Galileo, BeiDou), very-long-baseline interferometry (VLBI), satellite laser ranging (SLR), and Doppler orbitography and radiopositioning integration (DORIS). These techniques establish and maintain global reference frames, such as the geocentric terrestrial reference frame, and enable precise coordinate systems and geodetic datums.

Applications include map making, land administration, construction, navigation, and monitoring of sea level, crustal deformation, geodynamics, and Earth rotation. Data and models support climate studies, natural hazard assessment, and infrastructure planning. Challenges include accounting for plate tectonics, mass redistribution in oceans and ice, and achieving and maintaining consistent global and regional reference frames.

A brief historical note: geodesy has roots in ancient measurements of the Earth’s curvature, matured with 18th–19th century arc measurements, and advanced profoundly with space geodesy in the late 20th century.