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) used to
describe the Earth ellipsoid in both theoretical studies and practical applications.
3. The Krassowski Ellipsoid is adopted in geodetic surveying and computation,
whereas in gravity data processing, the formula for normal gravity derived by
Helmert in 1901-1909 is adopted:
gravitational constant GM, and angular velocity of the Earth rotation
ˉ
:
005302 sin
2
000007 sin
2
2
ʳ
0
ﾼ
978030 1
þ
0
:
ˆ
0
:
ˆ
Hence, we cannot incorporate the two geometric parameters a and f of the
Krassowski Ellipsoid with the physical parameters
ʳ
e
ﾼ
978030 mGal, and
0.005302 of Helmert's formula for normal gravity, used as the unified
parameters for both geometric and physical geodesy.
4. The reference ellipsoid surface corresponding to BJS54 has a systematic slope
from west to east relative to the geoid in China. In eastern regions the height
anomaly can reach +65 m, and the nationwide average is 29 m (cf. Fig.
7.8
).
5. It has ill-defined orientation. The pointing direction of the minor axis of the
ellipsoid is neither the universally adopted CIO nor the polar origin JYD
1968.0
in
China. The plane of the initial geodetic meridian is not parallel to the Greenwich
Mean Astronomical Meridian defined by the BIH. This is inconvenient and can
cause errors in coordinate transformations.
6. Compared to the Xi'an Coordinate System 1980 in China, BJS54 has carried out
a local rather than an integrated adjustment. The former, on the other hand, uses
integrated adjustments and thus boasts higher accuracy than BJS54. The results
of geodetic points provided stepwise by local adjustments will inevitably lead to
some contradictions or unjustified situations.
7. The coordinate system is not established by China alone, and the geodetic origin
is not in Beijing. So the “Beijing coordinate system” is more superficial than
real, which may easily cause misperceptions. Its definition is neither simple nor
clear enough.
We should certainly note that these problems arose for historical reasons
which, for a country just starting to establish an astro-geodetic network, was
very hard to avoid.
ʲ ﾼ
7.5.2 China's National Geodetic Coordinate System 1980
(Xi'an Coordinate System 1980)
Long before the early 1960s, when the national astro-geodetic survey began to take
shape, experts and scholars had started to embark on research by making use of the
astro-geodetic survey data to calculate the ellipsoid parameters that better approx-
imate the geoid in China. This attempt to tackle the deficiencies and problems of
BJS54 reaped some early results.
In April 1978, the “Symposium of National Astro-Geodetic Network Integrated
Adjustment” was held in Xi'an, China. Experts and scholars devoted a full
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