Geodetic Datum and Geodetic Control Networks - Geodesy: Introduction to Geodetic Datum and Geodetic Systems - page 72

Fig. 3.2 Geodetic origin
mark of China's classical
geodetic control network.
Source: SBSM

3.1.2 Methods of Establishing a Horizontal Control Network

Traversing

A series of geodetic control points P 1 , P 2 , P 3 ... , each intervisible with its adjacent

points, are chosen to form a system of broken lines called a traverse, as shown in
Fig. 3.3 . The distances between nearby traverse points and the angles at all traverse
points are measured and reduced to a plane. Assume D 12 , D 23 ,

are the lengths of

...

the traverse lines in the plane, and β i is the horizontal angle at each traverse point;

knowing the plane coordinates (x 1 , y 1 ) of point P 1 and the grid bearing (grid
azimuth) T 10 of P 1 P 0 , the grid bearing of each traverse leg can be obtained starting
from T 10 , namely:

T 12 ¼ T 10 þ β 1 ,

180 T 23 ¼ T 12 þ þ β 2 :

...

According to these bearings and lengths of the traverse lines, the coordinates of
other traverse points can be obtained from the coordinates of point P 1 :

x 2 ¼ x 1 þ D 12 cos T 12 ,

P 2 :

y 2 ¼ y 1 þ D 12 sin T 12 :

P 3 : x 3 ¼ x 2 þ D 23 cos T 23 ,

y 3 ¼ y 2 þ D 23 sin T 23 :

This is the fundamental principle of establishing the horizontal control network
by traversing.