Establishing a new gravity reference station for geophysical investigation and educational purposes: comparison with satellite gravity data in Banda Aceh city, Indonesia

The new reference point was created at the Tugu Field, which is located near the university campus. The absolute gravity value at the Tugu Field was determined by deriving it from the gravity reference point at BMKG Mata Ie, which has an absolute gravity value of 978102.87 mGal. The relative difference in gravity's value between the two points was measured using the Scintrex CG-5 gravimeter, resulting in a difference of 23.8356 mGal, which corresponds to an absolute gravity value of 978079.01 mGal. The geological data indicate that the rocks around BMKG Mata Ie are metamorphic rocks that began to form in the late Jurassic, while the strata at the Tugu Field consist of young alluvium in the Holocene epoch, which has a lower rock density. This difference in rock density is consistent with the measured difference in gravity values between the two points. To verify the absolute gravity value at the Tugu Field, it was compared with the gravity value obtained from the satellite TOPEX, which is around 978140.15 mGal, with a difference of 61.14 mGal. The new gravity reference point at the Tugu Field was established to serve as a backup in case the reference point at BMKG Mata Ie is damaged or cannot be used. The installation of the gravity reference point at the Tugu Field also aims to facilitate community researchers in performing their technical activities, such as installing and removing equipment, within a reachable vicinity. The new reference point is expected to be used for time series gravity studies and even for the 4D model of gravity study. The determination of the new gravitational point at the Tugu Field was based on ground-based gravity data and satellite data. The method used in this study involved making a gravity reference point, covering it with thick granite, and measuring the value of gravity using the Scintrex CG-5 gravimeter. The first trial of measuring the value of gravity was conducted on September 6, 2019, but the measurement was delayed due to non-technical issues. The measurement was continued at the new reference point of gravity at the Tugu Field on September 9, 2019, and at the gravity reference point at BMKG Mata Ie. The data stored on the CG-5 device was downloaded using a serial communication cable, and processing was done using Ubuntu as the system operation to run miniterm.py, a program to read the data from the device. The measurement results showed a difference in gravity values between the two points, which is consistent with the geological data. The new gravity reference point at the Tugu Field is expected to serve as a reliable reference point for geophysical investigation and educational purposes in Banda Aceh city, Indonesia. The establishment of the new gravity reference point at the Tugu Field is essential for various applications, including subsurface density modeling, which is used for exploration and sophisticated study of seismic hazard. The new reference point is also expected to be used for time series gravity studies and even for the 4D model of gravity study. The installation of the gravity reference point at the Tugu Field aims to facilitate community researchers in performing their technical activities, such as installing and removing equipment, within a reachable vicinity. The geological data indicate that the rocks around BMKG Mata Ie are metamorphic rocks that began to form in the late Jurassic, while the strata at the Tugu Field consist of young alluvium in the Holocene epoch, which has a lower rock density. This difference in rock density is consistent with the measured difference in gravity values between the two points. The new gravity reference point at the Tugu Field is expected to serve as a reliable reference point for geophysical investigation and educational purposes in Banda Aceh city, Indonesia.