Lloyd asks the question on geocaching which I was inevitably asking myself yesterday, more or less: “what’s the best GPS device to use? And can you use a standard TomTom?”

While there won’t really be a single “best” device, because it all depends on what you want and what you can afford, there are some things you may want to consider. Here’s what I’m looking out for, in rough order of importance:

PC connection: You’ll be able to enter waypoint co-ordinates by hand, but they look like this: N 39° 22.817 W 076° 43.066. That’s a lot of numbers, and if you make a typo then that could really mess up your fun. So a connection to a PC seems essential, and not all units have these. Also, those units that do offer a connection will offer serial or USB — and machines these days rarely have a serial port, I’m looking for USB only.

Robustness: From Geocacher U: “It’s not a question of whether or not you’ll drop your GPS, but of how often you’ll drop it and what you’ll drop it on.” So make sure it’s robust.

WAAS and EGNOS: A system of adding accuracy to standard GPS measurements — accuracy increases from 10-15m to 1-3m. WAAS is the US version, EGNOS the European version. According to a July 2005 press release, the “EGNOS open service will be declared available in early 2006″ — so it doesn’t look as though it’s happened yet, but it still seems to be usable now during what is presumably the test phase. For instance, the Magellan eXplorist 210 Europe claims to have “reliable accuracy to within 3 meters”, and that must require EGNOS.

Antenna: There are two kinds which you’ll find built in to a GPS unit: the basic patch antenna (small and square, and hidden inside the unit) and a more effective quadrifilar helix antenna (which is short and stubby and probably sticking out of the unit). The former is apparently perfectly good in general, but may not pick up the satellites (and hence be unable to locate you) under heavy tree cover.

Mapping: While lots of units have a plot screen, not all have maps. Plot screens display points of interest in relation to each other. Maps display other features such as roads, and they should allow you to upload new maps.

Weight: Some are heavier, some are lighter. You’ll be carrying it with you at all times, so be aware.

Battery life: Battery life can be between 15 and 28 hours for different units, with different kinds of batteries — some take AAs, some take Li-ion or Ni-Cads.

Compass: Perhaps surprisingly, GPS units will not necessarily function as a compass. They tell you where you are in the world, but they won’t all tell you which direction you’re facing, and so that means they won’t be able to point you in the right direction. Some units do contain an electronic compass, however, so will offer you this facility. But the premium you pay for an electronic compass is probably not worth it when you consider that you could get a rugged magnetic (real!) compass for less, and you’ll never find its batteries failing on you. So a built-in electronic compass is probably just a nice bonus.

Altimeter: Not all units measure your elevation, and while it’s nice to be able to say “And did you know that the top of that hill is 314.2 meters above sea level…?” it doesn’t seem to be necessary for geocaching.

Memory: Some units have more memory to store more maps and other data. Some units have replaceable memory cards. Memory capacity can vary significantly, but I’ve put this consideration low on my list simply because I’ve got no evidence that I need memory for anything beyond basic use of the unit.

With all that in mind, I’m currently looking at…

• The Magellan eXplorist 210 Europe;
• The Garmin GPS 60;
• The Garmin GPSMAP 60;
• The Magellan Sportrak — although it seems suspiciously difficult to get hold of;
• The Magellan SporTrak Pro;

And my current favourite online UK site for these is GPS Warehouse, which seems to have a good range and a pleasant feel.

Tags: gps, geocaching, shopping