测量基础（Measurement basis）.doc

测量基础（Measurement basis） Geodetic datum is the basis of national geodetic coordinate system and calculate the national geodetic control network in the geodetic coordinates. It includes parameter measurement of the earth group and a group of initial data, which mainly includes the establishment of geodetic parameters as large Four constant earth ellipsoid coordinate system on the basis of the earths equatorial radius of ellipsoid, geocentric gravitational constant GM, J2 (with harmonic coefficients derived flattening of ellipsoid and the earth rotation angle of W F), and to determine the coordinates of the earth Geodetic control network system and the length of the benchmark light speed in vacuum C; and a set of initial data refers to the national geodetic control network starting point (as the origin of the earth) earth longitude, latitude, and elevation of the earth to earth to neighbor direction angle. The geoid is an irregular closed surface formed by the extension of the surface of the stationary sea surface to the continent. It is the equipotential surface of gravity, that is, when the object moves along the surface, gravity does not do work (as water does not flow on this surface). large The geoid is an important physical reference surface for describing the shape of the earth, and also the starting point of the elevation system. The geoid is determined by determining the distance between it and the reference ellipsoid - the geoid gap (for quasi terrestrial water) The quasi plane is called elevation anomaly. The parameters and concepts of geoid and elevation are ubiquitous in the objective world and play an important role in the national economic construction. The geoid is the geodetic benchmark First, to determine the geoid is an important project in the national basic surveying and mapping. It combines geometric geodesy with physical geodesy, enabling people to determine the geometric positions of space while achieving elevation and elevation Spherical gravit