What are the classifications of engineering measurement control network?

Classical measurement control network is broadly divided into three categories: plane control network, elevation control network and gravity control network.

According to certain technical requirements by a number of measurement control points, used to obtain the point of plane coordinates or elevation of the network. Measurement control network should be a national first-class level as the starting data, using fixed data leveling and 1985 national elevation benchmark.

Plane control network is a certain form of graphics to the earth control points constitute a mesh, the determination of the coordinates of the mesh points, or through the determination of the angle, side length and azimuth in the network, the coordinates of the projected mesh points.

To carry out these ground geodesy, a (reference) coordinate system must be selected in advance, and all the data measured in the geodetic control network will be calculated to the reference coordinate system, data processing, and calculate the coordinates of the control points.

In order to measure the needs of the map, the measurement control network also needs to be projected onto the plane, that is, the geodetic coordinates of the network points are transformed into the corresponding projected plane coordinates.