The Progress of Recent Indonesia Airborne Gravity Surveys

Abstract:

The Geospatial Information Agency of Indonesia (BIG) has finished the first phase of airborne gravity data acquisition in Indonesia by conducting airborne gravity survey mission for the whole land area of Java, Bali and Nusa Tenggara, and Moluccas Island. The survey was conducted in 2019 by operating the airborne gravimeter Air-Sea II type S-130 that was installed on the single engine aircraft Cessna Grand Caravan. The flight duration itself took around 461.50 flight hours for the whole survey lines. The flight lines were separated into main and cross over line with the space length for each line around 15 km for the main line and up 100 km for the cross over line. The flight altitude used in the survey ranging from 10,000 ft to 16,000 ft depends on the terrain condition and the permission given by the authorized institution. Global Navigation Satellite System (GNSS) observations were used to determine the aircraft position using the real-time kinematic method from the GNSS receiver installed inside the aircraft. To correct the position of the aircraft we use the Continuously Operating Reference System (CORS) stations located with maximum coverage of 100 km around the survey area. The quality of airborne gravity data was evaluated by comparing the Earth Gravitational Model (EGM) 2008 data on the degrees of 2,190 with the main constraint of its RMS value. The cross over analysis was applied to assess the whole quality of airborne gravity data. The result shows the RMS of cross over analysis for the island of Java, Bali and Nusa Tenggara, and Maluku respectfully were 4.706; 4.543; and 4.543 mGal. Also, the result shows the average of cross over analysis for each island in row were 4.692; 4.579; and 4.650 mGal. In addition, the downward continuation (DWC) was calculated for each island, and it depends on the altitude of the lines.