GPS attitude determination for a JPALS testbed: Integer initialization and testing

Abstract

An attitude-based search algorithm was implemented for initial ambiguity resolution and integer determination, and then tested on a three-element equilateral array with baselines of 0.5m. Running the initialization algorithm at every epoch, it was found that the search algorithm gave efficient and reliable integer solutions for a static antenna array, but was sensitive to errors in a dynamic environment in the absence of multi-epoch filtering or solution checking procedures. Incorporating knowledge of allowable array orientation into the search greatly increased execution speed and reduced spurious integer estimates. This paper reviews the fundamentals of multi-antenna GPS-based attitude determination, develops in detail a simple and efficient 3-D search algorithm, discusses tradeoffs between execution speed (search spacing), signal phase noise, and estimate reliability, and presents results from static and in-motion automotive testing. Based on these findings, the utility of integration between GPS and inertial systems for robust attitude determination cannot be overstated.