GPS/INS Gravity Measurements in Space and on a Balloon
A comparison of using the Global Positioning System (GPS) in conjunction with a strapdown Inertial Measurement Unit (IMU) to measure the gravity vector in space and on a balloon shows the relative importance of each system element in these two different acceleration environments. With currently available instrumentation, the acceleration measurement accuracy is the deciding factor in space, while on the balloon (or other aircraft), the orientation error of the IMU platform is most critical. A simulation shows that GPS-derived accelerations in space are accurate to better than 0.1 mgal for a 30 s integration time, leading to estimates of 1° mean gravity anomalies on the Earth’s surface with an accuracy of 4–5 mgal. On a balloon, the horizontal gravity estimation error is tightly coupled to the orientation error of the platform, which can only be bounded by external attitude updates. Horizontal gravity errors of 5 mgal are achievable if the attitude is maintained to an accuracy of 1 arcsec.
KeywordsGlobal Position System Gravity Anomaly Inertial Measurement Unit Global Position System Receiver Orientation Error
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