I suspect your particular problem with tracks not overlaying the roads may be more to do with the general inaccuracy of the road positions on the map as well as the somewhat imprecise positioning of the GPS device itself [3 meters/10 feet is as good as it gets and 15m/50ft is barely acceptable for vehicle guidance]. The roads shown on a City Navigator map for instance may not line up with the actual physical roads but the 'lock on road'/'snap to road' software function will show the vehicle's screen position as being on the closest likely road. This compensates for both the inaccuracy of the device itself and the 'near enough is good enough' attitude by map makers to the location of the roads on their maps. In [Only registered and activated users can see links. ] you can see the actual tracks recorded by several devices when overlaid on a satellite image. Some serious deviations are shown by some devices.