Improving the accuracy and resolution of SINS/DGPS airborne gravimetry.

摘要

This dissertation describes improvements made to a system for airborne mapping of the gravity field of the Earth. The research is carried out using an airborne gravity system that is based on a Strapdown Inertial Navigation System (SINS) and receivers of the Global Positioning System in differential mode (DGPS). The objective of the research is to optimize the performance of the system, especially for geodesy and geophysics.; An introduction to the field of airborne gravimetry is given and the state of current research in the field is surveyed. Data from recent airborne gravity campaigns is used to provide a detailed analysis of the DGPS error budget for airborne positioning, providing a realistic evaluation of the accuracy of current kinematic carrier phase techniques. A fundamental consideration of the various processes of differentiation is given and particular differentiating filters are proposed for the determination of high precision velocity and acceleration. A detailed analysis is given in the frequency domain of the DGPS error budget for acceleration determination. This provides an understanding of the characteristics of each of the relevant error sources for spatial resolutions up to 500 m and forms the basis for a set of recommendations regarding acceleration determination for airborne gravimetry. The limitations of the SINS gravimeter that are imposed by the accelerometer biases are analyzed and quantified. A thorough analysis is provided of the dynamics experienced by survey aircraft. The high-frequency errors affecting airborne gravimetry are analyzed in detail and methods for reducing them are proposed and implemented with success.; An improvement to the performance of the system for medium-resolution applications is achieved and it is demonstrated for the first time that the SINS/DGPS system can be used for high-resolution applications. Major results include a demonstrated accuracy of 1.5 mGal for a spatial resolution of 2.0 km and an accuracy of 2.5 mGal for a resolution of 1.4 km. Improvements to processing methods have yielded slightly better performance than the LaCoste and Romberg gravimeter on a common flight. A method for removing the effect of the Phugoid motion has been proposed and implemented with success.