The Geodetic Research Group is an interdisciplinary group of scientists because it uses measurements on the Earth’s surface from spacecraft to study the shape and size of the Earth, its planets and satellites, and its changes; determine the exact position and velocity of points or objects on the surface of the earth or orbit the earth and planets in a particular reference system; as well as applying that knowledge to various scientific and engineering applications using mathematics, physics, astronomy, and computer science. Based on the current definition of Geodesy given by IAG, the main field of geodetic study is divided into 3 parts: positioning, gravity field determination, and temporal variation of gravity position and field, where the spatial domain is earth and other space objects. Each field of study mentioned above has a very wide spectrum, from theoretical to practical, from the earth to other space objects, and also includes land, sea, air, and also spaceGeodesy is identical with positioning. Position (a point) can be expressed either qualitatively or quantitatively. When viewed quantitatively the position of a point is expressed with coordinates, either in space one, two, three, or four dimensions (1D, 2D, 3D, 4D).

To ensure consistency and standardization, there needs to be a system in declaring the coordinates. This system is called the coordinate reference system, or briefly called the coordinate system, and its realization is generally called the coordinate reference frame. The position of the point on the surface of the earth is generally set 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 Earth’s mass (geocentric coordinate system), or at any point on the surface of the earth (topocentric coordinate system). Meanwhile, the position of points in space (satellite positions, and space objects) is usually set in a celestial coordinate system/ Innertial system (CIS: Conventional Inertial System). Surveys for the positioning of a network on the surface of the earth, can be done terrestrially or extra-terestris. In a survey with terrestrial methods, the positioning of points is done by observing the target or object located on the surface of the earth. Meanwhile, in an extra-terrestrial positioning survey, the positioning of the points is made by observing or measuring the objects of the sky or objects in space, such as stars, moons, and quarsars, as well as man-made objects i.e. satellite.

**DETERMINATION OF EARTH GRAVITY ZONE**

One of the objectives of geodesy science is to determine the shape and size of the earth including determining the gravity of the earth in the dimensions of space and time. The shape of the earth is approximated through several models such as ellipsoid which is the ideal form with the assumption that the density of the earth is homogeneous. Meanwhile, the real fact, the heterogeneous density of the earth’s mass in the presence of mountains, oceans, hollows, terrain, etc. will make the ellipsoid turn into a Geoid. Geoid has an important role in various things such as for the purposes of geodesy applications, oceanography, and geophysics. Examples for the geodesy field are the use of GPS technology in orthometric high determination for various practical uses such as engineering, surveying, and mapping requires meticulous geometric information. In principle geoid (geopotential model) can be derived from gravity data as the main data whose distribution covers the entire surface of the earth. The accuracy of a geopotential model is determined primarily by the quality of gravity data, but is also determined by the mathematical formulation used when deriving the model. The gravity data can be obtained from terrestrial measurements using the gravimeter, from the air by the water borne gravimetry technique, and derived from satellite data (satellite geometric systems such as altimetry satellites and dynamic system satellites such as GRACE and GOCCE, as well as through interpolation for the region – areas with no gravity data.

**MONITORING OF EARTH DYNAMICS SYSTEM**

In the past, people thought the earth was static. Along with the development of science and technology, the paradigm of the static earth turned into a dynamic earth, which is indeed in real terms that the earth is a dynamic system. The dynamics of the earth movement have a very wide spectrum, from the scale of the galaxy to the scale of local movement in the earth’s crust. Earth moves together our galaxy relative to other galaxies. The earth rotates with our solar system in our galaxy. Earth orbits around the sun with other planets. The earth rotates against its rotational axis, and the earth’s crust is also moving (relatively very slowly) relative to one another. As a result of the movement of the earth’s crust appears mountains, volcanoes, and mountains, and resulted in volcanic eruptions, earthquakes, landslides, and other natural disasters. One of the domains of geodesy is the monitoring of earth systems, in this case addressed as for defining coordinate systems, and dynamics of coordinate systems. In addition, the role and geodesy in monitoring the dynamics of the earth system that contribute to the monitoring of the potential and mitigation of natural disasters such as volcanic activity, earthquakes, landslides, land subsidence, and others.

**Members:**

- Dr. Ir. Wedyanto Kuntjoro, M.Sc.
**(Head)** - Ir. Bambang Subekti, M.T.
- Ir. Kosasih Prijatna, M.Sc.
- Prof. Dr. Ir. Hasanuddin Z. Abidin, M.Sc.
- Dr. Ir. Agustinus Bambang Setyadji, M.T.
- Ir. Mipi Ananta Kusuma
- Dr. Ir. Dina Aggraeni Sarsito, M.T.
- Dr. Irwan Meilano, S.T., M.Sc.
- Dr.Techn. Dudy Darmawan Wijaya, S.T., M.Sc.
- Heri Andreas, S.T., M.T.
- Drs. Zamzam Akhmad Jamaludin T., M.Si.
- Irwan Gumilar, S.T., M.Si.
- Dr. Ir. Vera Sadarviana, M.T.