I have recently (August 2007) replaced my Garmnin etrex Legend GPS receiver with a Garmin etrex Vista HCx. GPS means Global Positioning System, a network of 24 satellites that broadcast signals that permit computing the position of the receiver to within 100 meters in theory and between 5 and 10 meters in practice. The H in HCx is critical: it means that the device has the newer SirfStar chipset, which is much faster finding a fix, and finds a fix even in difficult situations where the non-H version gives up after half an hour. Don't buy the old model, it's very frustrating in comparison to the HCx! mounted Garmin GPS, 9.8k
GPS receivers got a lot better. With my old Garmin 38 I spent half the time fantasizing that a piece of paper with the words "Poor GPS coverage" written on it would make a very cost-effective replacement for the receiver - lightweight, no batteries, with most of the functionality. The Garmin Vista HCx is the current generation which is far more reliable. After turning the receiver on, it finds an initial fix in less than a minute, and then it's quite good at staying syncronized. Trees, buildings, and other obstacles don't block satellite reception as easily as the older non-HCx versions.
The etrex also stores maps; I have the Europe city street maps loaded in mine and I love it. Very expensive though, and installation is infuriatingly braindead. You must create an account on the Garmin web site, type in all sorts of private information (of course I typed in garbage, including a bogus email address), and numerous poorly identified serial numbers and bonus codes. And you must have Windows, if you have a Mac or Linux, like I do, you lose.
Once installed, the software is quite good. It can also do turn-by-turn routing: you enter an address or click a location on the map, and the device gets you there. Before and at intersections it tells you where to go. It can be set on bicycle mode, but that doesn't work too well - it avoids freeways, but I live in the old Berlin downtown with its many one-ways, blocked roads, and mandatory turns, almost all of which don't apply to cyclists, but the Garmin map doesn't know that and suggests fantastically complicated detours. Now I know how car drivers must feel here...
Garmin GPS receivers allow keeping a track log, basically painting a line on the map for the route taken. That requires that it's turned on all day; I use about one NiMH battery charge per day. In 2002 I recorded an entire tour with 500-meter accuracy, and in 2004 a 1600-km tour with 1.5 and 0.5 km accuracy. I use the handlebar mounting bracket. Really nice. That was with an older Garmnin Legend; the Vista HCx can store tracks on a flash card and should have a much higher capacity. I didn't try it yet.
Once again, mapping GPS receivers are great, but DO NOT buy one that doesn't have the SirfStar chipset!
See also an article on "Taking A good picture"
