MapMyRide vs GarminConnect

Garmin connect's elevation numbers seem to be the most accurate I've seen so far.

There have been threads about how to calculate climbing, and in those there were examples of how map my ride can usually be low, and how BT's route tracker can usually be on the high side. 

I find MapMyRide to be horribly inaccurate.  Always low.  Elevations from Garmin or from Topofusion (corrected) I find to be the most accurate.

If you go to the lower left corner of a garmin connect event you've done, you'll see a image of your device, and a button to enable or disable elevation correction.

I mapped out the bike course for my Oly this past weekend on Mapmyride and they had the elevation at 900'.  My Garmin had the course at 1600'.  I rode the course, obviously, it was no way near 900', way more.  I'll never trust mapmyrides elevation again. 

Mapmyride is horribly inaccurate.  Try this test:  Map out a 60 mile ride and note the climb.  Then map the same ride as 4-15 milers.  I tried that on my ride coming up and the 4-15 milers were less than HALF the one 60 milers.  So it's inaccurate even within itself,

Elevation is tough, but whatever program you use has to at least be consistent within itself so you can at least compare your own rides.

I use bikeroutetoaster.com. Anybody know if that site is accurate?

Garmin Connect's elevation correction is pretty accurate as long as your ride lat/long was pretty accurate.  The way it works is it uses NASA/USGS data that has known elevation points for pretty much everywhere on earth.  This is done by bouncing radar signals from a satellite down to earth and then back up again.  The exact elevations are then recorded.

While a few things can slightly tweak this (such as bridges), it's generally accepted as extremely accurate.

Ironically, I just wrote up a big thing on this on Tuesay, explaining how altitude in Garmin's work depending on your model, and how the correction works in a few different software suites.  Fwiw.

I use Delorme, mainly because it's at least completely consistent within itself so I can compare my own rides with my own rides.   Like Garmin they have accurate data points for elevation pretty much everywhere (at least in North America). 

If someone could send me a Garmin connect plot, it'd be interesting to compare it to a Delorme output.  I know that even with the same elevation points you can come up with really different numbers depending on sample distance.

Interesting Read - Thank You... thing is, I use the Garmin Edge 705, and GarminConnect still changes the elevation upon correction (not a HUGE correction compared to MapMyRide).  In your Summary, you made it sound like the 705 was just as good if not better than the "Correction" software. What are your thoughts on that?

In general, I do find the 705 Elevation pretty accurate.  However, stuff like changing weather patterns can impact it's accuracy over a longer ride - due to the changes in pressure.  The nice part is you can turn on/off the elevation correction for each activity if you want to.

One minor note for anyone who sees really wonky readings on the 500/705 - ensure the four little black holes on the back of the unit are uncovered.  If covered (such as with tape), they'll give inaccurate elevation readings.  Yes, it's also where the beeping sound comes from - but putting electrical tape over to soften the beeping sound does indeed have unwanted side effects...fwiw.