An iterative method for the accurate determination of airborne gravity horizontal components using strapdown inertial navigation system/global navigation satellite system

Abstract

In strapdown inertial navigation system and global navigation satellite system-based airborne gravimetry, there is a circular problem between the navigation solution and the gravity vector estimation. On one hand, the gravity vector estimation depends on the navigation solution. On the other hand, the navigation solution requires a predetermined gravity model. The normal gravity, which differs from the actual gravity by an amount known as the gravity disturbance, is commonly used for the navigation solution, and this will result in errors of gravimetry. We reviewed this problem and found that an iterative method can be effective if there were no gyroscope biases in the inertial navigation system measurements. Iteratively, the differences between the estimated gravity vector and actual gravity vector can converge to constant values in this specific condition. If we know the gravity values at the endpoints of each survey line, these constant values can be compensated for by matching these endpoints. After such compensations, the repeatability of the estimated horizontal gravity components can be improved significantly. An application to real airborne data was performed to test the validity of the new method. The results yielded an internal accuracy in the horizontal component of approximately 3 mGal with a spatial resolution of 4.8 km.