Garmin Edge 810 here.
Phones ok but are pretty shoot when it comes to measuring altitude.
On a regular ride two different phones show 2400ft, both my Garmin and a friends show 1900 ft, both use built Barometric sensors to determine altitude.
Had a good look at an ordnance survey map of the route and have no idea where the two phones get 2400ft from.
Some phones have barometric altimeters too, so its a little unfair to write off all phones on that basis.
Angus Young wrote:
I just ride till I'm knackered.