Uncoupled GPS Road Constrained Positioning based on Constrained Kalman Filtering

Car navigation systems take advantage of the synergies between the Global Positioning System (GPS) and digital road maps. For this kind of applications the digital road maps can provide a priori information to improve the positioning accuracy. This paper presents a method for the estimation of the user’s position, based on GPS positioning estimates, constrained to a road map. A low-cost GPS receiver was assumed as being the source of the positioning information. The techniques used in the proposed estimator were developed taking in consideration that the platforms where typically they would be implemented are characterized by having reduced computational capabilities. The algorithm’s positioning accuracy was characterized based on real data from a low-cost GPS receiver installed in a car. Different scenarios were used in the field trials in order to evaluate the impact of the satellite constellation visibility and geometry in the algorithm’s performance