Geodesy Research Group is a science discipline for using the measurements on the surface of the Earth from aircraft and spacecraft to learn about the shape and size of the Earth, planets and satellites, as well as changes to them; accurately determining the position and speed of the points or objects on the Earth’s surface or the ones orbiting the Earth and planets in a particular reference system; and apply the knowledge to a variety of scientific and engineering applications using mathematics, physics, astronomy and computer science. According to the latest definition of Geodesy given by IAG, the major fields of study in Geodesy are divided into 3 parts: positioning, determining the field of gravity, and the temporal variation of positioning and gravity field, where Earth along with other celestial objects as the spatial domains. Each field of study has a very wide spectrum, from theoretical to practical, from the earth to the other celestial bodies, including the land, sea, air, and space forces.
Geodetic science would certainly be identical with positioning, and vice versa. The position (point) could be expressed both qualitatively and quantitatively. Viewing position quantitatively, the point is expressed by the coordinates, whether it is one, two, three, or four dimensional (1D, 2D, 3D, 4D).
To ensure consistency and standardization, there needs to be a system in stating the coordinates. This system is called the reference coordinate system, or briefly referred to as the coordinate system, and the realization is usually called a frame of reference coordinates. Point positions on the Earth’s surface are generally defined in a terrestrial coordinate system (CTS: Conventional Terrestrial System). The zero point of this terrestrial coordinate system can be located at the center of the mass of the Earth (geocentric coordinate system), and at one point on the Earth’s surface (topocentric coordinate system). Meanwhile, the positions of the point in space (satellite positioning and heavenly bodies) are usually set in a celestial or inertia coordinate system (CIS: Conventional Inertial System). Survey for positioning of a network on the Earth’s surface could be done in either terrestrial or extra-terrestrial ways. In a survey by the method of terrestrial, positioning the points is performed by observing the target or object located on the surface of the Earth. Meanwhile, the survey by the method of extra-terrestrial, positioning the points is performed by observing or measuring the celestial objects or objects in the sky, such as stars, the moon, quarsar, and also objects or man-made objects in satellite forms.
