Establishment of Geodetic Coordinate Systems - Geodesy: Introduction to Geodetic Datum and Geodetic Systems - page 346

center. Meanwhile, the gravity field needs to be represented using a reference
system whose origin is at the center of the Earth (see Sect. 4.1 ).
The geocentric coordinate system plays a significant role in space technology.
When artificial Earth satellites are orbiting the Earth, their orbital plane passes
through the Earth's center of mass. As a result, the coordinate system of choice for
orbital calculations is the geocentric system. Of course, tracking and observation of
the satellites will also be in the coordinate system with the origin at the Earth's
center of mass, otherwise their orbits will probably not be calculated accurately and
tracking will be adversely influenced.
Application Demands in Surveying and Mapping Engineering
In surveying and mapping engineering, the demand of the customers for surveying
and mapping products has undergone dramatic changes. People have realized that
using geocentric datum can simplify application of the integrated geographic
information (an interface switch is not needed) and can enable the geographic
information to integrate “seamlessly” in terms of category, space, and time. The
detailed interpretations are as follows:
The Demand for Integrated Application in Navigation and Construction
Layout
Currently and in the foreseeable future, maps (including spatial database) are
mostly utilized in association with the application of satellite navigation, such as
vehicle-carried navigation systems, dynamic command and management, and so
on. Using the geocentric datum as the mathematical basis for maps enables direct
orientation of the space navigation results on the map platform using technologies
like GPS. This differs from the traditional application demand whereby people are
merely concerned with finding the relative position instead of the absolute position
using maps; for instance, determining the position and orientation referenced to
isolated features or residents. Naturally, users do not have a demand for geocentric
datum. As well as the integration of various kinds of geographical information, the
geographical information of different areas and at different times referenced to the
same datum can be directly superimposed on each other, and thus an additional
interface switch can be avoided.
Similarly, in engineering construction, GPS is employed in the course of actual
measurements such as during construction layout. Hence, if the project design is
referred to the geocentric coordinate system, the transformations of coordinate
systems will be avoided.