Edge 520: displayed elevation data is not saved elevation data

Could you post the activity FIT file for that ride? What it shows at the UI level is what it should have recorded.

How soon in the ride was the high elevation? Did you make any manual elevation settings? When an elevation setting is made on the 520 the offset is also made to the points that where previously logged. Unless there had been a manual setting, GPS elevation is used to make a setting and if that happens after the activity has been started the previously recorded data is modified.

Thanks TIGERMOUNTRIDER and AWEATHERALL for your responses. The max elevation was in the middle of the ride, after one and a half hours riding. I have no manual elevation settings done (no reference points with elevation introduced). The thing is that it seems the edge 520 modifies the elevation displayed while riding always at the end when recording the route. Sometimes the correction is higher and sometimes lower. For the ride I was talking about, it was about 50m, but I remember another one with a max elevation displayed while riding of 1780m and the recorded one was 1697m. I'm posting the FIT file for both rides. Thanks!!!!

Best

After using the garmin edge 520 during August (about 1000 Km in total using both a MTB and a road bike) I’m still with the same issue: displayed data is not saved data. I’ve been making some tests in order to try to understand this strange behavior.

Test 1. No reference points with elevation saved: When I start riding, it seems that the device makes an initial elevation correction according to GPS elevation. The initial elevation is quite accurate (+-10m). During the ride, it seems that there are more elevation corrections taking the GPS elevation as reference and the displayed elevation is more or less accurate (+-10m). BUT when I finish riding and I save the data, only the initial calibration is taken into account and the other calibrations are removed when saving the data. For example, initial elevation is set to 830 m and during the ride there is another elevation correction that adds 40m to the initial calibration. When riding, after the second calibration I can see 1840 m but when saving, that points are saved with an altitude of 1800m as if the second elevation never happened.

Test2. One initial reference point with elevation saved at the beginning. When I start riding, the elevation is corrected according to the initial point elevation and no more elevation corrections happen so the saved data is the displayed data. But it seems the barometric altimeter is not very precise because although the initial elevation is correctly set (say 830m) after riding 25km and at an altitude of 1950m (I know for sure this elevation because it is marked on the road) the barometric altimeter reports 1900m. I was riding with a friend using a Garmin Fenix , we both calibrated the elevation at the begging and we both obtained more or less the same elevation readings during the ride. I finished that ride in the same point I started it, but the edge didn’t calibrate again with the initial elevation, obtaining a different reading (initial and final points in the saved route didn’t have the same elevation)

Is this the normal behavior of the edge 520 or is something wrong with my device and I should contact garmin support for a replacement? And regarding the barometric altimeter, should I expect more accuracy or this is the normal behavior of barometric altimeters? I know readings are affected by changes in the atmosphere during riding but I consider that a difference of 50m in an altitude of 1950m is quite a bit. The thing is that the garmin fenix barometric altimeter seems to behave the same … Any thoughts? Thanks a lot!

See my other thread in altitude gain error, for me a firmware reset fixed the issue!

After using the garmin edge 520 during August (about 1000 Km in total using both a MTB and a road bike) I’m still with the same issue: displayed data is not saved data. I’ve been making some tests in order to try to understand this strange behavior.

Test 1. No reference points with elevation saved: When I start riding, it seems that the device makes an initial elevation correction according to GPS elevation. The initial elevation is quite accurate (+-10m). During the ride, it seems that there are more elevation corrections taking the GPS elevation as reference and the displayed elevation is more or less accurate (+-10m). BUT when I finish riding and I save the data, only the initial calibration is taken into account and the other calibrations are removed when saving the data. For example, initial elevation is set to 830 m and during the ride there is another elevation correction that adds 40m to the initial calibration. When riding, after the second calibration I can see 1840 m but when saving, that points are saved with an altitude of 1800m as if the second elevation never happened.

Test2. One initial reference point with elevation saved at the beginning. When I start riding, the elevation is corrected according to the initial point elevation and no more elevation corrections happen so the saved data is the displayed data. But it seems the barometric altimeter is not very precise because although the initial elevation is correctly set (say 830m) after riding 25km and at an altitude of 1950m (I know for sure this elevation because it is marked on the road) the barometric altimeter reports 1900m. I was riding with a friend using a Garmin Fenix , we both calibrated the elevation at the begging and we both obtained more or less the same elevation readings during the ride. I finished that ride in the same point I started it, but the edge didn’t calibrate again with the initial elevation, obtaining a different reading (initial and final points in the saved route didn’t have the same elevation)

Is this the normal behavior of the edge 520 or is something wrong with my device and I should contact garmin support for a replacement? And regarding the barometric altimeter, should I expect more accuracy or this is the normal behavior of barometric altimeters? I know readings are affected by changes in the atmosphere during riding but I consider that a difference of 50m in an altitude of 1950m is quite a bit. The thing is that the garmin fenix barometric altimeter seems to behave the same … Any thoughts? Thanks a lot!

I think it is normal behavior.

Unless it is powered off and on, the 520 uses one setting for all of the recorded elevation data. It makes that setting after GPS reception is accurate. The setting is applied to the previously recorded data if the activity had been started prior to good reception. That is different from the earlier Edge models which make periodic setting adjustments for the recorded data based on drift between GPS elevation and pressure measured elevation.

From your observation it appears that the 520 still makes the periodic setting adjustment for the displayed elevation. My guess is that is by design and there is logic for adjusting the displayed but not the recorded.

Measuring height change based on pressure is more consistent and precise than using GPS elevation data. That is why pressure sensors are used. Two inaccuracies that affect pressure measurements are a change in ambient pressure and non standard temperate of the air mass. Since GPS data gives absolute elevation, it can be used to try to correct for those two inaccuracies. But, because GPS data is not that precise, using it can introduce additional errors in the elevation profile. One of the problems with making a setting change for the recorded data is that it will not be done at the same time or by the same amount for two units side by side. The elevation profiles from two 520s riding side by side will be exactly the same down to the noise level. The profiles from two older models will drift apart from time to time. For the displayed elevation, being closer to the absolute elevation is more desirable so adjusting it throughout the ride is better.

For your ride, the recorded data being 50 m lower than the expected 1950 is because the air mass was warmer than standard. The elevation to pressure curve is based on a temperature of 15 deg C at sea level. Warmer air is less dense and the pressure changes less for any given climb. Airplanes fly closer to the ground on cold days. A correction to the recorded data based on GPS data would probably result in it being closer to 1950 but at the cost of ramping in distortions to the elevation profile from time to time.

It is a tradeoff but I like the way the 520 works.