> There is no real disadvantage to dead reckoning as long as the system is always powered up.
With dead reckoning the error accumulates over time. Because GPS provides absolute positioning it does not have that problem.
With dead reckoning the error accumulates over time. Because GPS provides absolute positioning it does not have that problem.
A simple Particle Filter conditioned on "90% chance the car is on a road or other drivable space" will robustly get rid of any error accumulation, leaving you a position estimate that may even typically be more accurate than GPS.