Elevation Correction

by pkan

Downloads: 64,344 (30) • Reviews: 11

Version:

1.9

Updated:

Nov 29, 2017

Smoothing Factor for Elevation

Smoothing Factor for Elevation

Postby dbrillha » Fri Jan 31, 2014 11:42 am

I've corrected my data with SRTM 1" elevation correction.

But on a 30 mile run in Florida where there is some climbing and lots of undulating trail.... I get wildly differing "climb" stats depending on how I set the ST elevation slider.

I have kept it on a value of "15" because I found that on a bike century (Six Gap) that is well known to have about 11,000 feet of climb, SportTracks reported 11,200. So I thought that a smoothing factor of 15 was about right.

But on this 30 mile run in Florida, it reported 2700 feet of climb. That is WAY to much. I disabled smoothing and it reported 6000 feet of climb. I set smoothing to 60 and it reported 1200 feet of climb.

So, it seems that a low smoothing factor may work better in mountains and a higher smoothing factor works better in more flat terrain. But, this setting is global, not per workout. And, there is no intelligence to try to set it based on the type of elevation change.

I'm curious what slider value most of you find works best for most of your runs/rides....
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Re: Smoothing Factor for Elevation

Postby gerhard » Fri Jan 31, 2014 1:43 pm

dbrillha wrote:So, it seems that a low smoothing factor may work better in mountains and a higher smoothing factor works better in more flat terrain. But, this setting is global, not per workout. And, there is no intelligence to try to set it based on the type of elevation change.


Yes, the perceived setting depends on the activity type, the elevation data and terrain.
At least it is possible to change the smoothing in ST, not possible everywhere.
Maybe some other smoothing algorithm could work better.

Some info in the FAQ: viewtopic.php?p=30032#p30032
The Elevation Correction page has more info: http://web.comhem.se/pkanpa/ElevationCo ... lugin.html
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Re: Smoothing Factor for Elevation

Postby texmurphy » Fri Jan 31, 2014 4:23 pm

For Road Bicycling, I set Elevation Smoothing to 1. (I also smooth Pace/Speed to 5, all else not smoothed).
Garmin Edge 305/500 and others will smooth elevation on the device (proprietary so who knows what they do?).
Also a problem with some recent Garmin device software where elevation is "stepped" in 2 meter increments on some versions of devices. E.g. for my Edge 500 and its firmware after v2.80 - I rolled back to v2.80 for this reason!

If you are using Elevation Correction, then your elevation values are very dependent on you gps accuracy.
Cycling tends to place the rider in the roadway and the data points are further apart then when running where you are likely on the shoulder or path and data points are closer together. Edges of roadway with ditches or hillsides will be very sensitive to elevation correction - even in the flats of Florida.
Use the Elevation Correction Activity screen for your run for further analysis. Maybe compare the run to a route created with autorouting with applied elevation.
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Re: Smoothing Factor for Elevation

Postby dbrillha » Tue Mar 11, 2014 8:12 am

I use a Garmin 910XT with a barometric sensor, which avoids all the GPS noise in elevation. But does introduce barometric shift over time. Still it is clear that ST should allow the SLIDER values to be set by activity types. And the elevation slider should by dynamic (less smoothing when there is lots of elevation change, more when there isn't so much).

Like the Calorie Calculations are done... by activity type.
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Re: Smoothing Factor for Elevation

Postby old_man_biking » Wed Mar 12, 2014 2:42 am

Waypoints and Courses plugin provides elevation correction as well.
And this correction detects in a first step, if the elevation track is one that comes GPS based elevation recording (spiky) or from a device with a barometric altimeter (drifting).
It then applies the appropriate correction (replace elevation by DEM elevation or just remove drift).

Cheers,
OMB
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