Global positioning in urban areas with 3-D maps

A global positioning method based on a precise 3-D drivable area map and on GPS pseudorange measurements is presented. Map and GPS measurements are represented by geometric constraints, thus turning the localization problem into a constraint satisfaction problem whose solution is the confidence domain of position. Interval analysis is employed to solve the problem by using contractions and bisections of a prior position box. If more than 3 satellites are visible, the method is robust to wrong pseudorange measurements. The system is also able to compute multiple position hypotheses in the case of ambiguities. An experimental validation using real GPS pseudorange measurements and a precise 3-D map is reported to illustrate the performance of the method with real data in an urban area, with reduced satellite visibility. Confidence domains are consistent with the truth during the whole 1 km experiment, and a 6.5 m 95% accuracy is achieved with at least two satellites in view.