I was on-site with one of the Data Collectors in work and was trying to use his laptop pc (with build in GPS) to track our location. There seemed to be something wrong with the tracking because it would sometimes show us in the middle of a field or think we were on a side road when we were still on a main road. If it was trying to navigate for us, and thought we were on a side road, it would read out nonsense directions and try to get us to turn into nonexistent roads. The best (or maybe worst) was at lunchtime when the van was parked in a lay-by. The GPS thought we were flying over the town at around 300 mph!