On a ride today I recorded 4423ft on a Garmin 800 & my wife recorded 3099ft on a Garmin 200 over the same route.
Mine was at the correct height above sea level when we set off.

Why the big difference & how do we make them the same?

Garmin 800 uses a barometric altimeter. Garmin 200 uses the GPS signal to calculate it.

On garmin connect there is an option to enable altitude correction.

Also depends on the frequency of recording points.
ie if you only record one point every 10 seconds, it will miss out some of the small ups and downs. And over the course of a ride, this can add up to a big difference. I don’t think you can adjust the recording interval on the Edge 200, it always uses ‘smart’ recording.

Zigzag has it- the 800 is by far the most reliable for altitude due to the internal barometer.

GPS only elevation is notorious for being wrong.

Also you won’t be able to enable elevation correction on Garmin for devices with internal barometer as it’s considered more accurate. If you enable it for the Garmin 200 it uses elevation overlays e.g. OS contour data which again doesn’t show every up & down so is better than GPS but still not perfect.

oddly enough though, my mate’s 705 and my 500, which as far as I know both use barometric readings for altitude, still come out quite different at the end of a ride. Not nearly so far as the 200 but it does show how approximate these things can be.

Zigzag has it- the 800 is by far the most reliable for altitude due to the internal barometer.

GPS only elevation is notorious for being wrong.

Although in windy / mountainous conditions the 200 will actually be the most accurate. The barometric altimeter will tend to over-read.

Also you won’t be able to enable elevation correction on Garmin for devices with internal barometer as it’s considered more accurate.

Odd, I certainly get the option for tracks recorded on an edge 800 and 500.

Hi, I have an 810 which seems to double the Altitude of my Friends 800, and my iPhone recorded Strava

Today I set my home altitude as i had never done it before and it was still double that of Strava

Although in windy / mountainous conditions the 200 will actually be the most accurate. The barometric altimeter will tend to over-read.

I’ve found baro altimeters highly accurate in mountainous and windy conditions. The only times they tend to have a problem is if you get a front come through with a large pressure change.

Interestingly though, last weekend there was a significant difference in measured ascent between my 910XT and scotroutes’ Edge (I don’t know which model, but it had a baro altimeter just like mine). Strangely he measured a lot more ascent than me one day and the other day I measured a lot more than him! Having IT problems and haven’t yet got round to uploading my tracks, maybe it will be more obvious when I do.

Odd, I certainly get the option for tracks recorded on an edge 800 and 500.

Seems you’re right; it’s just disabled by default. I’m sure when I tried to change it for my Fenix the other day it wouldn’t let me, but I stand corrected.

Barometer will be more accurate but it won’t be out of the box. They require calibration, and really should be set on every ride.

That’s why Garmin have a location feature where you can specify a known height for a specific location. Whenever you ride from that location it will effectively calibrate it.

However atmospheric changes, wind and such will also affect it.

I’m lazy about calibrating and I find places I haven’t set a location height will vary in height each time I ride the same place. However even when I’ve set the location on my 510, I’ve started off and gone in a loop back to the start and then it tells me I finished 100ft lower than I started.

All said, GPS altitude is by comparison poor. GPS isn’t designed for accurate altitude readings.

Then there’s another factor. Some sites you upload to, such as Strava, will auto adjust to topographical elevation if the device doesn’t have a barometer.

Ultimately I’m not fussed about the accuracy of the elevation, only the accuracy of the elevation change.