BASIS POINT NETWORK GRAVITY BMKG

Gravity data necessary for correction of the barometer, spring scales, lab force and pressure, and for the purposes of exploration geophysics. For said purposes, the basic point of gravity is needed as a reference point pengukurani / binding of price measurement gravity.
In general, the gravity measurements carried out in a short time cover (short-time closures), therefore the necessary distribution network for distributing basic point of gravity is more evenly distributed in Indonesia. This will assist and facilitate the user in taking the point of gravity data base as a reference measurement / binding of the closest, so it take more concise and efficient.

From experience in the field during this much gravity data users who have difficulty in finding the gravity reference point that was made by the Directorate of Geology. Many of the basic points made in the first gravity Airport terminal for easy access to transport, because of the development area of the airport, the basic point is largely lost.
Climatology Meteorology and Geophysics Agency in the medium term, plans to make the basic point of gravity in Indonesia who originally started the implementation phase with a network of gravity base point in several locations in Sumatra and Java.
Basic point made at the gravity pillar of gravity at the station Geophysics, Meteorology and Climatology. At some locations there are no pillars, the measurement location was chosen in place that are considered strategic and permanent, all the basic point of gravity created a description and photo that will enable users to find the location of point gravity data base. Data from the basic point of gravity include the value of gravity, coordinates and elevation.
Classification based on the gravity base point order derivative of the national gravity base point exists, for measurements with the first derivative of the parent base is called the gravity base order 1 (one), while the derivative measurements of order 1 is called the gravity base order (2) and so on.

The main point of gravity made in Jakarta, Lembang, Medan and Surabaya where cultivated in the implementation of the measurement period covers less than one day. The choice of location for the placement of the gravity base point BMKG prioritized at Station Geophysics, Meteorology, Climatology and Meteorology and Geophysics Institute office on the pillars that have been made, or at other locations that are considered strategic considerations include:

Site selection is also considering means of transportation, so it will be easy in measuring gravity data, in addition to ease of permissions problem. Implementation of the basic point gravity measurements carried out using a minimum of two tools in every tripnya, all the tools used in the measurement must first be calibrated to the base-base calibration of the gravity and gravity gets the recommendation of the National Committee both before and after they finish used in the measurement.
Gravimeter equipment used is composed of geodetic type:

For the determination of the coordinates used NAVPRO Magellan GPS 5000 and GPS Garmin 60CSx, elevation data from measurements using microaltimeter Pauline MDM.5 and Suunto.

4. DATA REDUCTION
As a reference point basis point gravity measurements, gravity measurements starting from the base BMKG Headquarters Jl.Angkasa I No.2 Kemayoran Jakarta (PIER BMG.0), with prices BMG.0 = 978 149.68 mgal and also from Base Absolut Directorate of Geology of Bandung with DG.0 price = 977 976 701 mgal. Then proceed to the basic point of gravity which is planned for later closed at the same gravity base again. The price difference measurement data processing start and end at the base of reference would be eliminated by the earth tide correction (Earth Tide Correction) and with drift correction (drift).

BMKG has built a network of gravity base point in Indonesia, which began in 2003. The addition of the gravity base point location (Gravity Base Station) is uniformly very helpful and important in order to refine the gravity Basis Point Network in Indonesia. Publication of the gravity point is expected to help as one of information for the purposes of exploration geophysics and so forth.