Garmin noob elevation question
 

I just purchased a Gamin Edge 510 and took my first real ride this morning. It was one of my normal weekday morning rides along the coast that starts and ends at my house. My question is how is that the elevation chart is different at the end of the ride? I would think that if you could take the chart and fold in over itself at the midway point that the elevation would match since I rode out and back along the exact same course. I started at 31 feet (which seems off as well) and ended up at 2-3 feet or so. There are some parts of the course that shows below sea level.

http://i1230.photobucket.com/albums/...2B5C2C3993.png

You can get different charts depending which software you use. I think they interpret the data different using formulas. I live in Houston which is basically flat but still manage to ascend and descend several hundred feet on a 30 mile ride. Upload your ride in several programs to see how each calculates the metrics. I use SportsTrack, Ridewithgps.com, Garmin Connect and Strava.

See here: https://support.garmin.com/support/s...00000000000%7D


Did you calibrate at the beginning and did the temperature change? It's also subject to changes in air pressure of weather changes. I'm not sure what you saw is outside normal accuracy expectations but others with more experience may be able to provide better guidance.

Elevation is hard for GPSs to calculate as it requires a satellite near the horizon to be decently accurate. Honestly your 46ft elevation "change" is pretty "good" in my book.

Alternatively, some programs/computers use elevation maps during run processing (after you're done) to "calculate" the elevation. (Basically it plots your ride/run on an elevation map and just gets the elevation data from that.)

EDIT: Didn't realize the 510 had a barometer. Cool! My advice doesn't directly apply to it, but it does to devices that use GPS to find elevation.

Did the weather improve somewhat during or after your ride? Elevation generally going down means air pressure generally going up, implying fair weather and clear skies.

"The barometric altimeter is not temperature compensated. Temperature changes in the measuring device will affect the barometric pressure sensor and altimeter readings."

That's pretty lame. I believe my Suunto watch is temperature compensated.

Yeah that is sort of odd not to have temperature compensation. It's on other Garmin devices. Maybe the 510 being near the bottom of the Edge 510/810/1000 pile has something to do with it?

Weird (and crappy).

Why do these units have thermometers then? It's not because you need it while riding...

Temp changed a few degrees. From Saturday and Sunday morning rides I'm seeing the same thing. Started at around 7:30 AM and the start elevation is higher than the finish at the same place. Not sure if this is connected but on Saturday while riding up the coast into some decent headwinds I noticed elevation would drop further below sea level as the wind increased. Could be unrelated, not sure, still figuring this thing out. Glad I got it though, nice to come home from a 50 mile ride with my phone still at 100%

The wind was probably connected to the elevation being wrong. Wind = air rushing from a high pressure zone to a low to equalize the pressure. Higher pressure also = lower altitude. And yours were head winds, coming at you from the high.

If you use the GC website you can turn elevation corrections on and usually get a more accurate chart and total.