Geodetic Datum and Geodetic Control Networks - Geodesy: Introduction to Geodetic Datum and Geodetic Systems - page 100

international cooperation in 1988. Because it was originally located in an urban area
with harsh weather conditions, the observational data were modest. In 2000, the
station was moved to the suburbs and thereby the conditions for observation were
greatly improved. The CAS Yunnan Observatory began taking part in international
cooperation in 1998. Now its ranging accuracy is about 3 cm. With a telescope
aperture of 1.2 m, this system possesses strong ranging capacity and powerful laser
energy and may possibly become a lunar ranging station in the future.
The two SLR mobile stations were both developed by the China Institute of
Earthquake Science. One of them belongs to China Xi'an Research Institute of
Surveying and Mapping and the other to the Institute of Earthquake Science. These
two mobile stations are mainly used to monitor crustal movement in China.
The Chinese SLR Network was established in 1989 and was composed of the
above-mentioned stations. It is now administrated by the CAS Shanghai Observa-
tory, which is responsible for organizing and coordinating observations, unifying
observation standards, and updating technologies in a collaborative manner. Shang-
hai Observatory is the SLR regional data center and data analysis center with the
purpose of archiving domestic SLR data, making assessments of observations, and
publishing a weekly assessment report on global observations. Meanwhile, it makes
use of domestic and international SLR data to carry out research in the application
of astro-geodynamics and geodetics.

Global IVS Network

VLBI observation is a kind of multistation network observation, which requires
extensive international cooperation. To enable effective worldwide cooperation in
VLBI observations and technological development, an international VLBI organi-
zation, IVS (International VLBI Service for Geodesy and Astrometry), was
established. It serves to cooperate and organize the application of global VLBI in
astrometry and geodynamics, enhance international cooperation in VLBI observa-
tions, data processing, and technological development, and provide services. IVS
coordinates various kinds of activities in support of VLBI techniques. Its objectives
are, first, to support research and observations in geodesy, geophysics, and astrom-
etry; second, to promote studies and developments in VLBI techniques in astrom-
etry and geodesy; and third, to allow communication between groups of users of
various VLBI products and integrate VLBI techniques into the Global Earth
Observation System. In China, both the Shanghai Sheshan station and the Urumqi
Nanshan station are IVS stations. The IVS stations are distributed all over the
world, as shown in Fig. 3.22 . With regard to the different objectives of observation,
the IVS Network can be divided into the following subnets and organizations:

European VLBI Network

This was the VLBI organization initially established by European countries. Since
1994,

the Chinese VLBI stations in Shanghai and Urumqi have joined this