Establishing large area Geodetic control Network
A geodetic control network (also geodetic network, reference network, control point network, or control network) is a network, often of triangles, which are measured exactly by techniques of terrestrial surveying or by satellite geodesy.
A geodetic control network consists of stable, identifiable points with published datum values derived from observations that tie the points together.
Classically, a control is divided into horizontal (X-Y) and vertical (Z) controls (components of the control), however with the advent of satellite navigation systems, GPS in particular, this division is becoming obsolete.
The higher-order (high precision, usually millimeter-to-decimeter on a scale of continents) control points are normally defined in both space and time using global or space techniques, and are used for “lower-order” points to be tied into. The lower-order control points are normally used for engineering, construction and navigation. The scientific discipline that deals with the establishing of coordinates of points in a high-order control network is called geodesy, and the technical discipline that does the same for points in a low-order control network is called surveying.