Elevation Correction

by pkan

Downloads: 64,344 (30) • Reviews: 11

Version:

1.9

Updated:

Nov 29, 2017

Issues with the plugin - scrambled output

Issues with the plugin - scrambled output

Postby pkiszk » Wed May 06, 2015 3:15 am

I have an issue with this plugin. My Edge 810 returns what seems a correct profile but understated total ascent. Example from GC when elevation correction on GC site is enabled is here (and shows north of 3500m total ascent):
https://connect.garmin.com/modern/activity/766514610

The original Edge's altimeter reports some 3273m total ascent ("Pod górę"):

Image


When I appy the plugin using "Replace with DEM elevation" I get this (196m ascent):

Image

Any ideas how to fix this ?
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Re: Issues with the plugin - scrambled output

Postby texmurphy » Wed May 06, 2015 1:13 pm

I exported the tcx from GC. Note GC does not export elevation. So I applied Elevation Correct Plugin. I used the default SRTM configuration on my ST. Note that I have a lot of elevation zones. Most important I define "Flat" as -1% to +1%. I also have Settings Analysis Smoothing for Elevation ON and set to 1.
Thee result is 3668 meters of over ascent.

Take a look at the Forum FAQ section for comments on Elevation and smoothing. The accuracy of the gps track relative to the elevation databases can really throw off the elevation correction (especially when along side of steep hillsides or crossing bridges or doing tunnels).

As far as the DEM elevation issue - make sure you have the correct database and activity.

What happens when you import the activity.fit for the activity directly from the 810? The .fit from the device is definitely the preferred data source.
ElevCorrect using SRTM.jpg
ElevCorrect using SRTM.jpg (176.37 KiB) Viewed 7895 times
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Re: Issues with the plugin - scrambled output

Postby Z74 » Thu May 07, 2015 5:53 am

Interesting... why did you choose to define -1/1 % slopes as flat?
They are named "falsopiano" in italian, meaning "only appearing to be flat" due to the fact this kind of slope is not consistent enough to be a real descent/climb (frequent fluctuations) but yet not exactly flat.
I'd rather define -0.5/0.5% as really flat... just curiosity.
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Re: Issues with the plugin - scrambled output

Postby texmurphy » Thu May 07, 2015 9:20 am

Depends where you normally live/ride. I consider a meter change in altitude over 0.1 kilometer to be flat.
Also the instruments have an error range for elevation, so it does no good to look below the confidence level.
And garmin changed its recording of elevation to be more stepwise with the later releases (v3.0 and later) of the Edge 500 and subsequent Edge series devices. See https://forums.garmin.com/showthread.ph ... alling-3-0 on the garmin forums. The Edge still shows continuous elevation on its screen, yet recorded only in 2 meter increments. Prior Edge 305/705 recorded with 0.4 meter increments.

The elevation issue is a prime reason many Edge 500 users refused to upgrade beyond v2.8. (Means never use garmin express!!!)
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Re: Issues with the plugin - scrambled output

Postby Z74 » Thu May 07, 2015 10:48 am

What does Garmin Express have to do with it?
I only use it to update the configuration ( add/remove widgets, watch faces, applications).

Does this issue get solved via Wireless connection? My data gets on Garmin Connect as soon as I get off the TacX or I enter the house, I never saw logs being transferred in other ways (which is why I'm basically stranded with OMB's .fit uploader).

Are you sure the inaccuracies are not related to the smart recording? https://forums.garmin.com/showthread.ph ... post135332
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Re: Issues with the plugin - scrambled output

Postby texmurphy » Thu May 07, 2015 4:51 pm

Z74 wrote:What does Garmin Express have to do with it?

Garmin Express will update your device to the latest release - if you want it or not :evil:

Z74 wrote:Are you sure the inaccuracies are not related to the smart recording? https://forums.garmin.com/showthread.ph ... post135332

Red herring - 1 second vs Smart makes no difference re:stepwise elevation recording.
While some claimed smooth elevation traces on releases of Edge 500 v3.0 and above, if you got stepwise elevation then later releases never solved the problem.
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