Attitude determination with GPS: experimental results

A method for real-time attitude determination of a very short baseline based on triple-difference phase measurements has been evaluated experimentally using two commercial off-the-shelf GPS (global positioning system) C/A code receivers delivering integrated Doppler measurements. The algorithm is robust with respect to phase cycle slips and does not require the usual integer ambiguity of the measurements to be solved. Preliminary results show that absolute attitude determination requires a calibration of the baseline and that the relative attitude accuracy is of the order of 0.1 degrees or 2 mrads for the case of a 2-m-long baseline. Accuracy in the determination of the attitude of a baseline using the GPS signals depends mainly on the receiver noise level, the baseline length, and the geometry of the GPS satellite constellation. The range of accuracies that have been measured points towards the feasibility of a real implementation of an integrated attitude sensor based on GPS signals