Geodesy is a surveying and mapping activity to determine the position, earth shape, gravity field and their changes with time and space for establishing and maintaining surveying and mapping datum and surveying and mapping system.
Geodesy Belongs to space Geographic Information Science Is the description of object information, specifically 3W (what, where, when). Geodesy is the science of describing object space information in a broad sense. - Chinese name
- Geodesy
- Foreign name
- geodetic surveying
- Phonetic transcription
- dà dì cè liáng
(1) For Topographic mapping And large-scale engineering survey to provide basic plane and elevation control; (2) For space science and National defense construction Provide accurate point coordinates, distance azimuth And the earth's gravity field; (3) To study the shape and size of the earth crustal movement and earthquake prediction And so on. For solving Geodesy Disciplinary issues and the establishment of a horizontal and Vertical control network The precise measurement carried out. The shape, size and gravity field of the earth should be taken into account when surveying. It is to establish countries and regions Geodetic control network The basic means of Topographic survey And other basic work of engineering survey, and provide data for studying and measuring the shape and size of the earth, spatial target coordinates and orientation, and crustal deformation. his Horizontal control network , triangulation Trilateral measurement 、 Corner measurement 、 Precision traverse and Space geodesy Establish and coordinate with astrometry and gravimetry, usually reduce the observation results to Ellipsoid of the earth On, calculate the Geodetic coordinates , finally passed Map projection Convert to Plane rectangular coordinate , as the basic control of the plane; Vertical control network , generally established by leveling to measure the Normal high , as the basic control of elevation. The ways to describe the spatial information of objects are the various methods mentioned in the first part, but in practical applications, 3S4D is the most commonly used or familiar. 3S：GPS、RS、GIS； 4D ：DOM、DEM、DLG、DRG。 
