Elevation/altimeter accuracy

I know this is a common topic for 'discussion' and I'm fine with accepting the margins for accuracy but thought I'd share this elevation profile for a 3-lap course. I just find it interesting that it looks like the park I was running in was sinking. I presume the elevation is measured by GPS but my track appears to be within 1 metre of the route (paths) so it's interesting that the error is greater in one dimension.

0 tess over 4 years ago

DJGShef said:
I presume the elevation is measured by GPS

Your elevation is measured by the barometric altimeter. You can go into Garmin Connect on your computer and enable elevation correction after your run and elevation will be displayed using surveyed maps based on your GPS position. Anyway, your laps look similar with the gain/loss on each lap. This tells me that your barometer reading was rising during your run. Do you recall the the start, during and finish barometer readings? The question is why the barometer changed. Was the barometer calibrated along with elevation prior to your start? (I'm assuming you can do this on the Instinct). Did the barometer port become obstructed with sweat? Was there a head wind at the start that decreased during your run? Did the pressure actually rise during your run? There's a few things to check here, but as far as the barometric altimeter recording elevation gain/loss it looks quite good.