Real-time attitude determination system based on GPS and aided by low-cost inertial sensors

13th IAIN world congress and exhibition. Stockholm, Sweden, October 27-29, 2009.

 María Campo-Cossío, Alberto Puras, Raúl Arnau, Daniel Bolado

 Abstract:

This paper explores a low-cost GNSS attitude determination solution based on L1 GPS receivers with the aiding of MEMS gyroscopes. The proposed approach resolves integer ambiguity on-the-fly using single frequency carrier phase measurements overcoming the problems of reliability, availability and performance present in high dynamic environments in common low-cost GNSS attitude determination systems.

For high-precision GPS-based attitude determination reliable integer ambiguity resolution (IAR) has been a critical issue, being performance and computational efficiency of the ambiguity search process its main concern. Single-epoch approaches have shown low success rates when carrier phase observations are affected by multipath, residual atmospheric effects or unfavourable satellite geometry, etc. On the other hand, works in LEO (Low Earth Orbit) satellite applications, where the effect of the aforementioned errors is reduced, have shown the advantages of this approach.

In the proposed solution not only a fast IAR method is evaluated, but also a high frequency angular rate data integration procedure is considered. To fit with the fast integer ambiguity resolution requirement, a search space reduction from 3D to 2D is accomplished by a one-epoch algorithm based on a Gram-Schmidt orthogonalization. The subsequent Attitude Estimation is performed by means of Davenport’s q-method. In addition, improvements in reliability, availability and performance in high dynamic conditions are achieved by fusing angular rate data in an ad-hoc Extended Kalman Filter.

In order to evaluate the performance of the proposed navigation system suitable for real-time high dynamic applications, several tests and simulations have been accomplished. Detailed analysis of the viability of the method is presented.