A method for monitoring performance of a navigation system onboard a vehicle is provided. The method obtains, at a vehicle electronic control unit (ECU), a triangulated vehicle location and vehicle motion data, the triangulated vehicle location obtained from the navigation system; computes an estimated vehicle location, using the triangulated vehicle location and the vehicle motion data; calculates a probability that the estimated vehicle location exists within an error bound of the triangulated vehicle location; and when the probability indicates that the estimated vehicle location does not exist within the error bound, performs a task onboard the vehicle.