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Attackpoint - performance and training tools for orienteering athletes

Discussion: altitude

in: JayXC; JayXC > 2016-06-19

Jun 19, 2016 10:35 PM # 
Your altitude is steadily decreasing - is that the canoe slowly filling with water? :)
Jun 20, 2016 5:47 PM # 
Lambo Shih Tzu:
From DC Rainmaker...

The FR920XT contains a barometric altimeter, which in theory means that it would be able to track your elevation gains and losses more accurately, as well as your exact elevation more accurately. This is different than many running watches that just use GPS based altimeters, which while having improved significantly in recent years – still aren’t quite as precise.

But Garmin has made some changes in how the latest multisport device establishes initial elevation. Previously, with every other Garmin sport/fitness device ever made the unit would get a reading of the elevation from GPS first, allowing it to establish the initial GPS elevation to a rough degree. From there, the barometric altimeter would kick in and more precisely hone in on the exact elevation.

Unfortunately, the first step is skipped in the case of the FR920XT. This means that it attempts to determine the elevation using only the barometric altimeter. The problem is this takes forever – and even when it does decide where you are, it’s inaccurate. In case you’re looking for a more clear definition of ‘forever’, it’s at least an hour after you’ve turned the device on and are ready to run/ride/etc…
Jun 20, 2016 6:05 PM # 
Lambo Shih Tzu:
I just learned that AP replaces all uploaded file data climb to database (map) climb and smooths the results. So I am not sure why the elevation appears on AP like this.
Jun 20, 2016 6:11 PM # 
It was the beginning of a Matrix inversion.
Jun 20, 2016 6:12 PM # 
AP has several different settings with regards to whether or not it does elevation correction (configurable under Settings).
Jun 20, 2016 6:30 PM # 
Lambo Shih Tzu:
Wow. Thanks. So if i am using a device with barometric altimeter, what setting do i want selected?

i was on 'auto select mode' and that was producing the climb on the flatwater paddles...

Jun 20, 2016 6:32 PM # 
I'm on autoselect s well. I'm comfortable with 100' error over 8 miles.
Jun 20, 2016 7:11 PM # 
I think I saw a description of the settings once, but I don't remember the distinctions. I did come across something from a few years ago where ken mentioned that for barometric devices AP only looks up the elevation at the start and end instead of all along the track, so my guess is that the GPS and GPS+baro modes might do that (using the device's measurements as relative changes instead of absolute values) while "disabled" relies solely on whatever the device records. But it looks like you've asked the question where ken will see it, so you should get a definitive answer from him.

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