Establishment of Geodetic Coordinate Systems - Geodesy: Introduction to Geodetic Datum and Geodetic Systems - page 378

system of CGCS2000. The geodetic points for which a combined adjustment
cannot be carried out should be corrected to CGCS2000 by precise coordinate
transformations.
2. We obtain precisely the transformation parameters from BJS54, XAS80, and
urban independent coordinate systems to CGCS2000 and compile corresponding
coordinate transformation software dedicated to public use. The accuracy indi-
cators of the coordinate transformation can be sorted into the following three
categories: for low-precision transformation in common navigation applications,
the mean square error of each coordinate component is in the range of 5-10 m;
for medium precision transformation as a 3D coordinate similarity transforma-
tion, the mean square error of each coordinate component is in the range of 0.5-
5 m; for high-precision transformation in sheet lines of topographic maps and
coordinate grid transformations, the mean square error of each coordinate
component should not exceed 0.5 m.
3. The printed paper topographic maps in the old coordinate system can be
corrected to the CGCS2000 by replotting the neat lines and grid lines. Compu-
tation shows that, while changing the coordinate system for the maps at scales
larger than 1:1,000,000, the changing value in the geographical location of the
points on the maps will exceed the mapping accuracy, and the maps should be
replotted. However, when the distance and azimuth shift between any pair of
points on a map at any scale are within the mapping accuracy, the changes can be
neglected. Hence, for the correction of existing paper maps, all that needs to be
done is to translate the sheet lines and the square grids of each map.
4. For digital topographic maps, we transform the coordinates of all the map layers
and map elements using software, followed by cutting and clipping over again.
5. The gravity anomaly that is referenced to other ellipsoids can be transformed to
the gravity anomaly referred to the CGCS2000 ellipsoid using software based on
the normal gravity formula. Likewise, the height anomalies and deflections of
the vertical that are referenced to other ellipsoids can also be converted to that
referred to CGCS2000.
It is perfectly viable to ensure a smooth transition from the old to the new
coordinate system through a well-conceived plan and well-arranged implemen-
tation by using the existing technologies available in China. The CGCS2000 was
put into effect on July 1st, 2008 in China. With regards to the transformation and
connection between CGCS2000 and the existing national geodetic coordinate
systems (referring to BJS54 and XAS80), the transition period is regulated to
take 8-10 years according to the correlative provisions.
Review and Study Questions
1. Draw a geometric figure to explain the concept of Euler angles.
2. By referring to the “double-parallel conditions” (i.e., the minor axis of the
ellipsoid is parallel to the Earth's rotation axis, and the planes of the initial