site search by freefind

follow me


Geodesy Geodetic Reference System
"Geodesy is the science of the measurement and mapping of the earth's surface" F. R. Helmert, 1880.
"The problem of geodesy is to determine the figure and the external gravity field of the earth and of other celestial bodies as functions of time; as well as, to determine the mean earth ellipsoid from parameters observed on and exterior to the earth's surface [Torge 1991 p.2]."
Geodesy is devided into three areas [Torge 1991, p.1]:
  • global geodesy includes the determination of the shape and size of the earth, it's orientation in space, and it's external gravity field
  • geodetic surveys (national and supranational) is for the determination of the earth's surface and gravity field over a region that typically spans a country or a group of countries. The earth's curvature and gravity field must be considered.
  • plane surveying (topographic surveying, cadastral surveying, engineering surveying): the details of the earth's surface are determindes in a local level, and thus curvature and gravity effects are generally ignored.