Handheld GPS use GPS Signal from a minimum of 3 overhead satellites to obtain a fix which is usually accurate to within 30m. Actual accuracy can be achieved down to 5m but due to US Military intervention accuracy is restricted. Popular brands include Garmin, Magellan Navigation. Prices for the devices start from around £50GBP or $100USD and range up to £400GBP or $800USD depending on features which can include barometric pressure, temperature, colour screens, NMEA 0183 outputs, Chartplotter. While GPS is mostly run off of US Military satellites(Russia has a network that is now being used worldwith with the US satellites, and Europe is throwing satellites up) the accuracy is not restricted by the military. It is restricted by the fact that satellites send time stamps and triangulating the time it takes these signals to reach the handheld receiver. Because this is measured down to nano seconds 5m is the best you'll get(until technology improves more). There are GPS systems that "cheat" by using a radio signal and satellites to give you a far more accurate reading. As close as a fraction of an inch. Most commonly used by Land Surveyors. And back to the handheld GPS you need a minimum [ - ]

Handheld GPS use GPS Signal from a minimum of 3 overhead satellites to obtain a fix which is... [ + ]