The Garmin eTrex series consists of decent, full featured handheld GPS units. The cheaper monochrome eTrex models have a basic RS-232 serial interface, and the color eTrex models sport USB connectivity.
In this article I'll talk about my experience with connecting both USB and serial port versions of the eTrex series to my Mac and to my Linux-based PC.
I personally use the Garmin Vista HCx GPS now, but the other Garmins in the eTrex series, including the inexpensive but well specified Garmin eTrex Venture should work the same way.
Dealing with the eTrex Series with USB:
Most of the eTrex units with a color screen have a USB port on the back. Happily, this USB port uses a common USB connector, so it is easy to physically connect a USB eTrex to a Mac or a PC running Linux.
I have found two pieces of software perfect for use with a USB eTrex, without the need for special drivers: GPSBabel+ and Google Earth.
The Mac version of the freeware program "GPSBabel+" can natively read and write waypoint, track, and route data directly from the eTrex. I simply connect my GPS to my Mac via the standard USB cable. Once connected, I start up GPSBabel+.
GPSBabel+ can then be used to easily import and export waypoint and track data from the GPS. Simply choose "Use GPS receiver for input" or "output", choose "Convert", and then select the "Garmin USB" port. No special drivers or software beyond GPSBabel+ required.
Google Earth can communicate with the eTrex in real time, plotting your location on the fancy Google Earth map. In addition, like GPSBabel+, Google Earth can download routes, tracks, and waypoints from the eTrex and plot them on the Google Earth map.
I have had good luck with Linux too. I'm running Fedora Core with the latest updates, and find that it too can communicate with the USB eTrex series without issue. No kernel recompiles were required. Yay! I simply plug the thing into a USB port and then execute this command:
gpspoint -p /dev/ttyUSB0 -da -dt -dr -dw > gpsdata.gpd
With this command, all of the routes, tracks and waypoints are sucked down from the Garmin into a text file. From there, I can convert the file into any form I wish. I particularly like the open-source program Viking.
non-USB eTrex GPS on my Mac or Linux
I found that I could easily hook up the dirt cheap eTrex models, like the Garmin eTrex H and the other eTrex models that sport a serial interface.
My classic eTrex Legend is such a device. It's a nice GPS, but modern Macs and most modern PCs don't include near-obsolete serial ports. Happily, there is a simple and inexpensive solution - an eTrex serial cable with a reasonably good, low-cost USB to Serial Adapter.
[Note: updated on 8-Feb-2010 with more recent information]