For the Garmin bike computer geeks

Earlier this week I clipped my bars on a sapling on the side of the trail and lost my computer. I went back to that section of trail (thinking it was the only place where I had made contact with anything during the ride) and searched carefully, but could not find it. Luckily, another rider that came along five hours later saw it lying off to the side of the trail, and snagged it. From the experience I learned three things:

(1) Use a lanyard
(2) There is a little-known setting that allows you to put your contact info in the startup screen on your Garmin: https://www.dcrainmaker.com/2013/08/display-number-garmin.html
(3) Over the course of five hours sitting statically on the ground, my Garmin slowly and very consistently gained elevation at the rate of 15 feet per hour. Most of you may not care, but I found it interesting that the computer gained 75 feet just sitting in the dirt... and it may help to explain why there is often a discrepancy between elevation numbers when several people are biking together and they all end up with slightly different elevation numbers.

Makes me want to put several bike computers out on my back deck, turn them on, and after six hours see if any of them show location creep.

 

That's cool, thanks for posting. I can confirm it works for Garmin Oregon 600. Should work with any unit you can plug into a computer and access the file system via windows explorer.

As to the stats changing while unit is stationary, these units only have so much accuracy. Can't recall what the current number is, but lets say its accurate to within 10 ft. As it tracks multiple satellites, some of which move in/out of range, it shouldn't be surprising the unit registers different locations over time. It seems odd if it only added elevation, as I would expect there to be elevation loss too. Pull up the GPS track for that 5 hour period, it'll probably look like a bird's nest on a map. I see this every time I stop for longer periods but leave the unit on. I see it as well if I turn it on before I start riding. It'll show 50 or even 100ft on the odometer despite sitting on my bumper.

Differences between units can arise for a bunch of reasons... which satellites and how many satellites it connects to, the accurate to __ errors mentioned above, settings (how often it pings satellites), what it uses for altimeter (barometric or other), etc

 

Yeah, the location (lat/long) looked like a bird's nest, but the elevation was a relatively straight line increase over time. That's the point I was trying to make - there is (at least on that unit for that ride) a bias creep in elevation. I don't go on too many six hour rides, but it would suggest (all things equal) that after a six hour ride I should deduct 90 feet from my elevation stats. Based on my rides in CNF, which typically were in the 1000 foot to 1200 foot per hour rate, it is only a 1.0 - 1.5% error.

 

I don’t use a Garmin anymore, but the intro screen on my 510 used to say “Pedal A$$hole”.

Address and phone number might have been better...

 

Keep in mind it's barometric. If you lost it in the morning, and it sat throughout the day as temps warmed (and air pressure dropped with increase in temp) then it makes perfect sense that altitude was gained.

I gained 300 feet sitting still at Crystal Lake once. In about 20 minutes. It warmed up fast.

 

You use the word geek in your title......90ft. in 6 hours, that's relatively nothing, unless you gain 2oo ft in 6 hrs. Personally I don't concern myself with super accurate elevation. I know when people compare elevation after a ride they've done together you may see +/- 100-400ft. Eh, no big deal to me.

 

Mark beat me to the barometric explanation. Once you uploaded it, you can have the elevation corrected.

 

Crystal Lake is a great place to "gain 300 feet sitting still". I've gotten at least that high there before, too.