Geodesy
Introduction
The term geodesy, from the Greek γη ("land") and δαιζω ("to divide"), was initially used by Aristotle (384-322 BC), and can mean both "geographical divisions of the land" and also the act of "dividing land", for example, between owners.
Geodesy is, at the same time, one of the Earth sciences and engineering. It deals with the survey and representation of the shape and surface of the Earth, global and partial, with its natural and artificial forms.
Geodesy is also used in mathematics for measurement and calculation on curved surfaces. Methods similar to those used on the curved surface of the Earth are used.
The goal of geodesy
Contenido
La geodesia suministra, con sus teorías y los resultados de sus mediciones y cálculos, la referencia geométrica para las demás geociencias como también para la geomática, los sistemas de información geográfica, el catastro, la planificación, la ingeniería, la construcción, el urbanismo, la navegación aérea, marítima y terrestre, entre otros, e incluso para aplicaciones militares y programas espaciales.
La geodesia superior") o geodesia teórica, dividida entre la geodesia física y la geodesia matemática"), trata de determinar y representar la figura de la Tierra en términos globales; la geodesia inferior, también llamada geodesia práctica o topografía, levanta y representa partes menores de la Tierra donde la superficie puede considerarse plana. Para este fin podemos considerar algunas ciencias auxiliares, como es el caso de la cartografía, de la fotogrametría, del cálculo de compensación") y de la teoría de errores de observación, cada una con diversas subáreas.
Además de las disciplinas de la geodesia científica, existe una serie de disciplinas técnicas que tratan problemas de la organización, administración pública o aplicación de mediciones geodésicas como, por ejemplo, la cartografía sistemática, el catastro inmobiliario, el saneamiento rural"), las mediciones de ingeniería y el geoprocesamiento.
Theoretical geodesy
The observation and description of the gravity field and its temporal variation is considered the problem of greatest interest in theoretical geodesy. The direction of the force of gravity at a point is produced by the rotation of the Earth and the Earth's mass, as well as the mass of the Sun, the Moon and the other planets, and the same as the direction of the vertical (or plumb line) at some point. The direction of the gravity field and the vertical direction are not identical. Any surface perpendicular to this direction is called an equipotential surface. One of these equipotential surfaces (the geoid) is that surface that is closest to the mean sea level. The problem of determining the terrestrial figure is solved for a given moment if the gravity field is known within a spatial coordinate system. This gravity field also suffers alterations caused by the rotation of the Earth and also by the movements of the planets (tides). Like sea tides, the earth's crust also, due to the same forces, undergoes elastic deformations: . For a hypothesis-free geoid determination, first of all gravimetric measurements are needed, in addition to astronomical measurements, triangulations, geometric and trigonometric levelings and satellite observations.