GPS-based attitude determination using RLS and LAMBDA methods

This work presents a procedure for getting 3D attitude from GPS raw measurements. The method is based on differential GPS and uses four receivers; although it can be easily generalized. The disposition of the receivers is fixed in the body frame, as attached to a rigid platform that moves freely in the local navigation frame. Baseline estimation is performed through a Recursive Least Squares (RLS) algorithm using code and carrier phase measurements. This work is an extension to the work of Chang et al. (2005) to multiple roving receivers, and where the LAMBDA method has been used for integer ambiguity resolution. The dispositions of receivers are known a priori, and this information used to constrain the solution at each epoch. Finally, 3D attitude is determined from the estimated baselines using the SVD method. The performance of the proposed method is evaluated through simulation. The results show significant enhancement with respect to the original method as well as with comparison with previous work in literature.