Establishment of Geodetic Coordinate Systems - Geodesy: Introduction to Geodetic Datum and Geodetic Systems - page 371

5. The origin is located at Yongle township, Jingyang county, Shaanxi province but
with different geodetic origin data from the XAS80.
6. Coordinates obtained are transformed from the XAS80 after the integrated
adjustment. The precision of the coordinates is exactly the same as for the
XAS80.
7. Used as a plotting coordinate system, for maps at a scale smaller than 1:50,000,
the new and old maps splice (the break of edge-matching between the new and
old maps) together almost seamlessly.

The advantages of the new BJS54 lie in the fact that it has overcome the low
accuracy of the adjusted coordinates of the old BJS54 from the local adjustments,
and the newly drawn topographic maps based on the new BJS54 and the old
topographic maps splice together well. Generally, for maps at a scale smaller
than 1:50,000, there will be no apparent seams. However, for large-scale maps of
1:25,000 or 1:10,000, seams will arise during splicing. In terms of demand for
production and scientific development, digital products will replace the simulation
products. Hence, the new BJS54 has not been practically used in the field of analog
mapping.

7.5.4 Geocentric Coordinate System 1978

The geocentric coordinate system 1978 was obtained by transforming the BJS54
based on DX-1 coordinate transformation parameters.
DX-1 has only three translation parameters, i.e., Z 0 . The transfor-

mation parameters of DX-1 were defined and established in some relevant confer-
ences in November 1978. At that time, satellite geodetic techniques were still in
their infancy, so the geocentric coordinates could not be observed directly. DX-1
has been established by employing five methods, as identified below:

Δ X 0 , Δ Y 0 , Δ

1. Astro-gravimetric method
2. Global astro-geodetic geoid undulations
3. Difference between astro-geodetic and gravimetric geoid undulations
4. Using Doppler receivers like MX-702A to determine the transit navigation
satellite system (TRANSIT System) to establish geocentric coordinates
5. Using Doppler receivers like CMA-722B to determine the transit navigation
satellite system (TRANSIT System) to establish geocentric coordinates

The translation parameters can be obtained by any one of the above methods
alone. If different weights are assigned to these five methods, respectively, taking
the weighted mean will produce the three translation parameters of the DX-1,

Δ X 0 ,

Δ Y 0 , and Z 0 .

The three translation parameters

Δ

Z 0 denote the displacements of
the center position of the BJS54 reference ellipsoid deviating from the geocenter,
namely the three coordinate components of the center of the BJS54 in the

Δ X 0 , Δ Y 0 , and Δ