Bright shiney new Training Infographic question

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K5 Gus Jul 2019 4:20pm, 2 Jul 2019 3,053 posts	0 K5 Gus I did a hilly 14 miler today, using a Fenix 5 with built in altimeter : Garmin : 819m Fetch : 815m ~~strava~~ : 819m Never seen it as close as that before, agree that there is often quite a difference
Sam Jelfs Jul 2019 4:21pm, 2 Jul 2019 369 posts	0 Sam Jelfs If I go to GC and turn elevation correction on, so ignoring altimeter data, then I get 1200m elev gain for the same run.
becca7 Jul 2019 4:21pm, 2 Jul 2019 7,870 posts	0 becca7 Not much variation for Comrades Garmin: 1844m Strava: 1859m Fetch: 1834m
jabberknit Jul 2019 4:28pm, 2 Jul 2019 2,906 posts	0 jabberknit I thought yours was a Suunto, becca7 - have you changed to Garmin?
larkim Jul 2019 4:31pm, 2 Jul 2019 7,972 posts	0 larkim A while back on Fetch I posted this which compares the elevation data recorded by my watch (Vivoactive, no built in altimeter) on two identical runs. The data recorded by the watch on the two occasions was markedly different, but after uploading to Garmin Connect and then downloading the resultant GPX files, you can see that they've applied a new elevation overlay which is identical on both runs, because the route was the same. fetcheveryone.com/viewtopic.php?id=59792 I don't know what, if anything, Fetch does to elevation data, as there is no export function (that I know of!) from Fetch to pull out the GPX files that would result from it's interpretation of the elevation data.
oi you Jul 2019 4:33pm, 2 Jul 2019 436 posts	0 oi you It's always worth bearing in mind that the Garmin doesn't actually measure distance at all, horizontal or vertical. It's all calculated after the event, so the result can change depending on measurement frequency and what map info is used to work out the route from the position data that it has recorded.
larkim Jul 2019 4:39pm, 2 Jul 2019 7,973 posts	0 larkim The garmin does measure horizontal distance as it goes (otherwise you wouldn't get pace / distance measurements!), unless I'm misunderstanding what you mean? It doesn't snap the data back to roads etc afterwards either, so the map used for horizontal distances isn't relevant. It simply calculates the distance between point a (recorded by the watch) and point b (recorded by the watch) on a theoretical ellipsoid representing the "roundness" of the world.
larkim Jul 2019 4:42pm, 2 Jul 2019 7,974 posts	0 larkim And of course, then does that X times (often one reading per second, some watches do more, some do fewer). THey also do some error correction / smoothing to the data points to avoid lines which are too zig-zag due to the inherent inaccuracy of each measurement point.
K5 Gus Jul 2019 4:55pm, 2 Jul 2019 3,054 posts	0 K5 Gus oi you, as well as what larkim said above, watches with barometric altimeters do indeed measure altitude gain during the event. You can switch this off in Garmin Connect afterwards and it will re-calculate altitude based on mapping ( as shown above by Sam ) but this will be less accurate. Caveat : barometric altitude can be a bit inaccurate if there is a large change in air pressure during your run ( at the same point ), ie if a big weather front moves through the area
um Jul 2019 5:12pm, 2 Jul 2019 1,086 posts	0 um Today's run .... GC 262ft elevation, Fetch 577ft