When using the signal from the Global Positioning System for precise estimation of the heading of a vehicle, the main challenge is finding the integer ambiguities that the carrier phase measurements contain. Using the known distance between the antennas, this process may return improved results, which
can be even further enhanced if careful selection of observable data, the measurement from each satellite, is applied. This paper presents a study of the overall influence of the number of used observables in the precision and stability of the heading estimation solution. The presented conclusions provide clear guidance on how to elect which observables are the most beneficial to the solution.