geodesias

Geodesia, or geodesy in English, is the science of measuring and understanding the Earth's geometric shape, its orientation in space, and its gravity field. It aims to determine precise positions on and above the planet, and to establish global and regional reference systems used for accurate mapping, navigation, and Earth science.

The discipline combines observation, data analysis, and mathematical modeling. Classical methods included triangulation, leveling, and gravimetry to determine coordinates and elevations. Modern geodesy relies on space-based techniques such as global navigation satellite systems (GNSS), very long baseline interferometry (VLBI), satellite laser ranging (SLR), and Doppler/dimensional tracking to measure positions, rotations, and the geoid with high accuracy. The field produces reference frames like the International Terrestrial Reference Frame (ITRF) and defines datums used in mapping, surveying, and navigation.

Key concepts in geodesy include the geoid, a model of mean sea level as an equipotential surface, and the ellipsoid, a smooth mathematical representation of the Earth's overall shape. Gravity data and geometric measurements are combined to model irregularities in the Earth's gravity field and to monitor crustal deformation, sea-level change, and variations in Earth's rotation. Geodetic products support engineering projects, cartography, satellite navigation, astronomy, and climate research.

Geodesy has ancient roots in land surveying and cartography and expanded dramatically with the advent of space geodesy in the 20th century. Ongoing work seeks to improve reference frames, strengthen connections between techniques, and track subtle geophysical processes at centimeter to millimeter scales.