Total ascent variation Garmin Fenix 5X and Edge 1000

[Jehosefat]

The error was taken out of civilian GPS units years ago because by connecting to more satellites it is fairly trivial to error correct on the device itself and achieve the same accuracy as the military units.

 

In terms of altitude changes, GPS is notoriously inaccurate in terms of measuring altitude and most devices that use GPS altitude actually use the GPS to get the co-ordinates and then survey maps to read off the surveyed altitude that corresponds to said set of co-ordinates. And iirc surveyed altitudes are done at approximately a 30m grid so the accuracy isn't spectacular on that either.

 

As a side note pretty much no military equipment uses GPS for altitude measurement even with their apparently "enriched" spec GPS.