Geoscience Reference
In-Depth Information
Table 3.5 Overview of international gravity datums
Time of initial
measurements
Time of
application
Precision
(
10
5
m/s
2
)
Name
Vienna Gravity System
1884
1900-1908
10
Potsdam Gravity System
1898-1904
1909-1971
3
International Gravity Standardization
Net 1971
1950-1970
1971-1983
0.1
International Absolute Gravity Base
Station Network
Established since
1983
-
0.01
3.4.2 Basic Gravimetric Networks in China
In the late nineteenth century, foreigners conducted gravity measurements by
means of a resilient pendulum in Shanghai and the southwest of China. In the
1930s, gravity measurement was carried out also using a resilient pendulum by the
Physics Research Institute, Beiping Research Academy. Thereafter, Shanghai
Petroleum Bureau determined several gravity points by means of a gravimeter in
the vicinity of Shanghai. Up until the founding of P.R. China, the number of gravity
points determined was only about 200, with accuracy of 5
10
5
m/s
2
to
10
5
m/s
2
. These points were distributed in very limited areas, and no basic
gravimetric networks were established then. After the founding of P.R. China, three
generations of basic gravimetric networks were established in succession, i.e.,
China Gravity Basic Network 1957, China Gravity Basic Network 1985, and the
National Basic Gravity Network 2000 as the third-generation gravity network in
China.
10
China Gravity Basic Network 1957
During 1956 and 1957, in order to meet the needs of height anomalies and vertical
deflections in data processing of the national astro-geodetic control network, China
and the former Soviet Union jointly established the first-generation basic gravity
network in China. No absolute gravity measurement was conducted then. Gravity
values of the reference stations were measured by aerial survey from Moscow via
Irkutsk, Almaty, and Chita base stations. Nine relative gravimeters were tied to the
Beijing Airport in the west suburb for observation. Prior to this, the airborne gravity
surveying group of the former Soviet Union had been conducting tie point obser-
vations between Potsdam and Moscow. The gravity station at Beijing Airport in the
west suburb is the first gravity origin in China. It belongs to the Potsdam Gravity
System, with an accuracy of
10
5
m/s
2
relative to the Potsdam interna-
tional gravity datum. Meanwhile, 21 gravimetric basic points and 82 first-order
gravity stations were established throughout China. The accuracy of tie point
observations at the gravimetric basic points was
0.51
10
5
m/s
2
, and the
0.15
10
5
m/s
2
. After adjustment of
accuracy of the first-order station was
0.25
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