The idea relates to ArcPAD whilst using layers with GPS on. When one is driving with ArcPAD's GPS on, the position symbol moves across the screen until it reaches the edge of the screen. When the symbol reaches the edge of the screen the layers need to refresh with the symbol centred in the middle of the screen. The idea is to make it so that the layers refresh before, not when, the GPS symbol reaches the edge of the screen. This would be particularly good for devices that have difficulty in generating layers in a small amount of time.