Sunday, August 31, 2008

Improvised Bicycle GPS Mount

I lucked out today and found a local seller of a used Garmin eTrex Vista through at price that was too good to pass up. I've been wanting either a bike computer or a bike-mounted GPS receiver so that I could track rides, speed, distance, etc. I also used to enjoy Geocaching in the past, but had to stop when I lost my GPS receiver. (Ironic, huh? To lose one's GPS receiver)

So when I found a used GPS receiver at the same price as a bike computer, I jumped on the opportunity. I've ordered a custom Garmin bike mount, but in the meantime, I wanted to try out the eTrex on a trail ride with Roxanne.

I'm one of those people who believe that most problems can be solved through the proper application of bungee cords, duct tape, or zip ties. After eyeballing the fit by holding the eTrex up to my handlebars, I saw the obvious choice. One thick rubber band would hold the mostly flat eTrex on my mostly flat headlight. As a failsafe in case the rubber band came loose, I tied the eTrex to the handlebars with a simple lark's head knot using the lanyard.

As a bike computer, the eTrex worked very well. I was able to monitor our speed, as well as track fun data like max speed, total distance, moving time, stopped time, etc. The only anomaly happened once when the max speed jumped to 35 miles per hour for some strange reason.

I use my bike mostly for commuting and errands, and I almost never get lost, but being a technology freak, it will be fun to track ride data using the GPS receiver.


brady said...

Nicely done, Scott. I've got an eTrex vista too, but haven't mounted it to the bike yet. Did you order the mount from Garmin?

Katherine and I have done some GeoCaching in NE, IA, CO and KS with our eTrex. Lots of fun.

Have you thought of uploading the data to an online map?

Scott Redd said...

Hi Brady:

I ordered the Garmin mount from Amazon... my favorite retailer. I didn't spring for the quick shipping, however, so I might not get it for 10 days or so, but I'm patient. I can wait.

The Vista came with a serial data cable. You may recall that older, steam powered computers didn't use USB, but rather a serial RS-232 interface. Another item ordered from Amazon was a serial-to-USB cable.

I do, indeed, plan to upload track data and download routes, waypoints, etc.. I expect I'll try a Geocache or two and maybe get back out and check up on some of my old caches.

Over lunch today I went out to this USGS benchmark in the Gene Lehay Mall to calibrate my Vista's altimeter.

I had the unit sitting on my desk all afternoon and the altitude readings varied wildly; 30 feet or more. I wonder if the pressure in the building can change at all, or if the passing weather front can cause anomalous readings.