If you're in the continental United States (or Canada), and have a GPS receiver that can handle the WAAS adjustment signal (http://en.wikipedia.org/wiki/Wide_Ar

If you're in the continental United States (or Canada), and have a GPS receiver that can handle the WAAS adjustment signal (http://en.wikipedia.org/wiki/Wide_Area_Augmentation_System http://en.wikipedia.org/wiki/Wide_Area_Augmentation_System), you can get a much more accurate signal as quickly as a regular GPS signal.