Strapdown INS/DGPS airborne gravimetry tests in the Gulf of Mexico

Combining data from a Strapdown Inertial Navigation System and a Differential Global Positioning System (SINS/DGPS) has shown great promise in estimating gravity on moving platforms. Previous studies on a ground-vehicle system obtained 1–3 mGal precision with 2 km spatial resolution. High-accuracy Inertial Measurement Units (IMU) and cm-level positioning solutions are very important in obtaining mGal-level gravity disturbance estimates. However, these ideal configurations are not always available or achievable. Because the noise level in the SINS/DGPS gravimetric system generally decreases with an increase of speed and altitude of the platform, the stringent constraints on the IMU and GPS may be relieved in the airborne scenario. This paper presents an investigation of one navigation-grade and one tactical-grade IMU for the possibility of low-cost INS/GPS airborne gravimetry. We use the data collected during the Gravity-Lidar Study of 2006 (GLS06), which contains aerogravity, GPS, and INS along the northern coastline of the Gulf of Mexico. The gravity disturbance estimates from the navigation-grade IMU show 0.5–3.2 mGal precision compared with the onboard gravimeter’s measurements and better than 3 mGal precision compared with the upward continued surface control data. Due to relatively large (240 s) smoothing window, the results have about 34 km along-track resolution. But the gravity estimates from the tactical-grade IMU have much poorer precisions. Nonetheless, useful contributions from the tactical-grade IMU could be extracted for longer wavelengths.