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- to study the gravity field of the Earth, the shape and the size of
the Earth, the geodynamic phenomenon such as polar motion, earth
tides, crustal motions such as plate movements and continental drifts;
- to determine space coordinate system according to time and

specifying rotational ellipsoid parameters;
- to establish a set of points which has space positions on the
physical Earth and a set of points at a national level with known space

coordinates;
- to determine geometry of the physical Earth in detail;
- to transfer new geometries designed in the projects of the
engineering of the structures to the physical Earth;

- to monitor the geometry changes at the Earth crust.

Classification of geodesy

According to the scope of the geospace studied, geodesy can be
classified into:

Ellipsoidal geodesy studies the body of the Earth as a whole,
determines the shape of the Earth and its external gravity field, and
establishes the geodetic reference system.
Geodetic control survey measures the coordinates and heights of

a sufficient number of surface points within one or several countries in
an appropriately chosen reference system and establishes a unified
national geodetic network to meet the needs of topographic mapping

and engineering construction.
Marine geodesy establishes a geodetic control network on the
Earth’s surface covered by oceans to realize positioning on the sea
surface and underwater and to measure the marine gravity field, sea

surface topography and marine geoid.
Engineering geodesy determines the details on the Earth’s
surface regionally in a small area and usually refers to the horizontal

plane for measurements gravity field and attraction of the Sun, the
Moon and planets.
Physical geodesy studies geophysical and geodynamic properties

of the Earth and includes the Earth’s gravity.
Geometric geodesy adopts geometric control network onto the
regular reference ellipsoid as the basis for calculating the geometric

position of the surface points.

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