How accurate a GPS receiver can provide?
The greater the number of satellites you GPS can “see”, the more accurate it will determine your position. The number of satellites that your GPS is able to acquire depends on the time of day and your location. Thunderstorms, tall buildings, and dense overhangs can block the signals from the satellites. Also keep in mind, that due to military restrictions , GPS receivers for recreational or commercial purposes are only accurate to within approximately 2-10 meters.