Development of a GPS Multi-Antenna System for Attitude Determination PhD Thesis

A GPS multi-antenna system consisting of multiple off-the-shelf GPS sensors has been successfully developed and extensively tested in operational marine environments. The advantages to use such a system are the flexibility in the selection of GPS sensors, the cost-effectiveness of the system with the emerging low-cost high performance GPS products and the increased productivity of equipment which can be assembled into a multi-antenna system or dissembled for other positioning purposes. The underlying methodologies to integrate multiple GPS sensors into an attitude determination system are presented. Specifically, the observation model and its error sources are analyzed. A direct computation method and a least squares procedure for attitude estimation are given. On-the-fly carrier phase ambiguity resolution methods are investigated with emphasis on the use of baseline constraints, a priori attitude information from other low-cost attitude sensors, and special antenna configurations. A specialized post-processing software package for attitude estimation using raw GPS multi-antenna measurements has been developed. A marine test has shown that the proposed multi-antenna system and processing software give consistent results with those from a commercial dedicated attitude system. When a wide antenna spacing was used on a 52metre long surveying vessel with a four GPS sensor attitude system, an accuracy better than 0.06 degrees at an output rate of 10 Hz for the estimated ship attitude parameters has been achieved, when the ship attitude reference was provided by a high accuracy INS. Such a performance of multiple GPS sensor attitude systems demonstrates an alternative means to provide accurate, cost-effective and reliable attitude information for hydrographic surveys and other applications.