I bought my magellan 315 on a whim from Maplin Electronics, who also sell some of the support stuff. I had read Ranulph Fiennes accounts of using one. I do a bit of foreign travel to hotels and the like, and thought it would be a good way of always finding my way back. I found the machine took some time to get used to, but once learned became intuitive. Does it work - definitely yes, but sometimes the information is not helpful. It is good for calibrating the speedo in your car, as it will record not only direction of travel, but also speed, and possibly ETA. I also got mine to work in an airplane, and it was fascinating watching the inbuilt map move, showing movement over countries.It also confirmed the height of the aircraft, its speed, and again, ETA. It eats batteries, and especially nicads. I have bought the lead for a car which is great. I once got stranded and had to call the AA. It was on a country road, and I was able to give them my exact position, not only in latitude and longitude, but also the OS grid reference. The AA phone man said "is that anywhere near junction 14 of the M1." They were unable to interpret or use the information. Its great having the information, but make sure that is worth having. fun value - great.
Having bought a GPS for trekking purposes about a year ago, having had the magellan brand recommended from a friend in the Military, the model I bought, the GPS Blazer12 has now been replaced by an upgraded version. I paid just over 100 pounds for mine and it has been worth every penny. With a multitude of different map datums and grid reference systems, it is nearly impossible to get lost with one!. However, a note of caution DO NOT USE IT ON ITS OWN WHEN OUT IN THE COUNTRYSIDE/MOUNTAINS as, if it fails and no back-up is provided you're gonna be up s**t-creek! Always use it as a secondary piece of kit to the map and compass. The blazer12 is an excellent starter GPS (I'm now looking to trade mine for a more thorough system) but as a first GPS it was excellent value for money. If you walk a lot it is well worth the money, as it gives that little extra bit of accuracy. Combined with an accurate altimeter in the mountains makes it impossible to get lost. The new model, Magellan GPS310, is even better as it can be linked to a computer laptop for greater variety, as pre-loaded waypoints or points of interest can be uploaded to the GPS. Also, with the selective availability now removed (a certain degree of error installed by the US Government who run the 24 or so sattelites) so they are accurate to within a few metres, a mate and I tested mine versus his and one was 5 metres out from the other!
The GPS (Global Positioning System) is maintained via 27 or so satellites provided by the US Government. With a suitable reciever, you can (within say 50metres) find your position anywhere on the Planet. The Magellan GPS 315 is a 12 channel parallel receiver, which can communicate with up to 12 "birds" at any given time. There are a choice of "read-out" screens giving information such as speed, altitude, co-ordinates etc. Other screens offer a "plot" of your path, so you can eventually re-trace that path just by reading the screen. Most usefull of all are the user waypoints. These allow you to "mark" a specific location and assign a name to that point (waypoint). You can then navigate back to that position or use it as a reference at any time. Getting used to all the information made available by this device seems daunting at first, but plenty of research and newgroup reading pays off too quickly make sense of it all. The downside of GPS devices in general is that they eat batteries at an alarming rate and do not work if the sky is obstructed by buildings/trees etc. I found that once I had a better understanding of this unit, it became more and more valuable and trusted. A good buy for hikers and gadget freaks alike.
As far as James Bond style gadgets go GPS has got to be the best available to non 00 agents. GPS, like most technology, has come down in price dramatically as more companies produce them. Basically they tell you where you are and how to get to here you want to go. The system uses satellites to triangulate your position. The satellites are owned and operated by the US Department of Defence and until recently they held a few tricks up their sleeve. For them GPS is a military system, so they wanted to stop other users getting the most accurate reading. They added a code to the satellites signal and they only gave the code to their very best friends. The code is known as Selective Availability (SA) and can result in your position being as much as 250m out, and the altitude it gives is virtually useless. GPS has taken on such a commercial importance for navigation, surveying etc. that private companies were considering sending up their own satellites. If this happened the US DOD would lose the ability to control the system. So they have decided to turn off SA, until the next war. Good news for those that use it privately as positions will now be very accurate.
Short name: Magellan GPS 315