Geodetic Datum and Geodetic Control Networks - Geodesy: Introduction to Geodetic Datum and Geodetic Systems - page 81

Fig. 3.9 Traverse network

Overview of China's Astro-Geodetic Network

The first-order triangulation chain together with the second-order network in China
is called the astro-geodetic network, which started to be built in 1951 and was
completed in 1971. The entire length of the first-order triangulation chain is roughly
80,000 km, including over 400 chain segments that have formed more than
100 chain loops and a total of over 5,000 first-order triangulation points (trig
points); cf. Fig. 3.10 . The overall adjustment of the astro-geodetic network was
completed in 1982. Such an astro-geodetic network consists of the first-order
triangulation chain, second-order network, some third-order network, as well as
traverses. There are nearly 50,000 control points, 467 initial sides, and 916 initial
azimuths. Approximately 300,000 error equations and more than 150,000 normal
equations are formed. The adjustment shows that the mean square error of the point
farthest away from the geodetic origin is 0.8 m and mostly the relative accuracy

of adjacent points is less than 1/200,000.

3.1.5 Establishment of a Horizontal Control Network

Establishment of the horizontal control network includes technical design, recon-
naissance for site selection, erection of survey marks, monument setting, distance