Handheld GPS use GPS Signal from at least three overhead satellites to obtain a fix which is usually accurate to within 30m. Actual accuracy can be achieved right down to 5m but due to US Military intervention accuracy is restricted. 

Costs for the devices start from around $100.00 and range up to  $800.00 depending on features that can include barometric pressure, temperature, color screens, NMEA 0183 outputs. 

While GPS is mostly run off of US Military sattelites(Russia features a network that is now being used worldwith with the US sattelites, plus Europe is throwing sattelites up) the accuracy is not restricted by the military. It is restricted by the incontrovertible fact that satellites send time stamps plus triangulating the time it takes the signals to reach the hand-held receiver. Because of the undeniable fact that this is often measured right down to nano seconds 5m is the best you’ll get(untill technology improves more). There are discount handheld GPS systems that “cheat” by employing a radio signal plus sattelites to present you a far more accurate reading. As close as a fraction of an inch. The majority of commonly employed by Land Surveyors. Plus back to the hand-held GPS you want at least 4 satelites to receive any kind of accurate position, 1 for x cordinate, 1 for y, and one for z with the extra being as a check of sorts. The additional satelites you’ve got and the longer you retain your handheld on a fixed position the more correct it’ll be. 

There are  lots of handheld GPS Receivers out available, it’s beginning to become awfully difficult to get the wood from the threes.  The majority of of the receivers are of similar specification, but a few can be quite different in value, therefore we’ve tried to bring together the most well-liked handheld GPS Receivers plus compare the complete manufacturer specifications.