Airborne gravimetry ? A new gravimeter system and test results

Abstract

Success of airborne gravity survey mainly depends on determining the three-dimensional (3-D) position of the moving platform. Recent advances in technology, especially in Global Positioning System (GPS) have made it possible to determine the velocity and position of the moving platform with greater accuracy. Taking the advantage of these advancements in GPS technology and using a newly developed system, helicopter-borne gravity measurements were successfully carried out over the Kanto and Tokai districts of Japan. This new gravimeter system is composed of servo accelerometer sensors, stabilized platform, optical-fibre gyroscope to control the stabilized platform, GPS receivers and a data processor. The 3-D position of the helicopter at every second was accurately determined by interferometric GPS method. These GPS data were also used to compute various correction factors which are applied on the measured gravity acceleration. Real-time differential GPS positioning were also conducted using a separate receiver mounted on the helicopter. These real-time positioning data were used for controlling the optical-fibre gyroscope. The gravity acceleration data were processed and necessary corrections were applied. Numerical filtering was carried out to remove high frequency noises present in the data. The observed free-air gravity anomalies were then compared with upward continuation of the ground truth. We also made an attempt to compile airborne gravity anomaly map.