The Global Positioning System relies on the signals transmitted by military satellites. Precision of 30 meters in actual use is standard. Easy to use but you need also reliable maps and a compass as backup system. We use the Garmin and Magellan ranges since a long time and are quite satisfied.
If you buy any GPS make sure it has an data output line. All of the expensive ones have this line and some cheap ones also. This output was not used much except from professionals but this is about to change. Graphical map digitizing tablets will come out in the next few months at afordable prices and those need this connection.

The handheld GPS model best suited to the average enthusiast is surely the new GARMIN III. (Some older units still on the market so take care of what you buy). It's display not only shows your position but has a built-in world map. This is very helpful but does not replace a paper map. It also features an removable antenna so you can mount it outside the car for better reception in difficult conditions. Completely self-contained, works independantly from car systems on 4 AA-batteries but can be connected to 12 Volts with accessory car adapter.
We can now get the new GARMIN III for 21.500.- Flux (1.050.-DM, 590.-US-$, 878.-Can-$ ). Further discounts have already be announced so you better ask us before ordering. Accessories are fixed mount external antenna, 12-Volt car adapter (strongly recommended), data connection cable for PC's. For shorter trips or as a backup system we recommend the MAGELLAN 2000. This handheld unit features the same precision than the GARMIN III but without some special features as the built-in map or the detachable antenna. This good unit will soon be replaced by a new and cheaper model but this one without data output. Features: Waterproof, scratch proof display, shock resistant, 12-channel tracking, lightweight, 4 different navigational screens, backlight display, 24 hours working on the 4 AA-batteries.
It's strong point is the price: 8.500.- Flux (420.- DM, 233 US-$, 347 Can-$). We recommend that every vehicle in the group has at least an Magellan 2000 or equivalent when travelling through remote areas. As it's not more expensive than a good compass this is a cheap insurance.
12-Volt connecting/data cable and mounting kit available separately Disadvantages of the GPS: As the signals are transmitted from military satellites and civil use is allowed but not guaranteed, they are susceptible to be switched off in case of an crisis without warning. This happened to a friend's group out in southern Lybia some time ago when the signals were suddenly switched off for 48 hours. Although this is very rare you should be prepared. Navigating on GPS also needs good maps and some knowledge on how to use them as well a minimal skill in locating the GPS coordinates on those maps. Navigation in heavily wooded terrain is also reduced although surprisingly good in most cases. Also they have quite an appetite for batteries. Usually you get 24 hours of continuous use when running on built-in batteries. Not a lot but enough if you have to walk as you will switch it on only every half an hour or so. By this the batteries will last more than 2 weeks. For every GPS bought we will give an instruction hour to get you started.