Elevation profile correction for runs - do it!

TH3 FRB

I'm just starting to log my runs in WKO+ 3.0 (via Garmin 405).  I've been doing the elevation profile correction using Ground Control through WKO+ and it can make a significant difference in the metrics that feed your PMC.  One example -

 

8.55 mile run with 3X800 and 4X400 intervals on the road

 

Before elevation profile correction

6:38/mile NGP, 105 rTSS, .958 IF

elevation gain - 1680ft

elevation loss - 1199ft

 

After correction

7:00/mile NGP, 93.9 rTSS, .906 IF

elevation gain - 112ft

elevation loss - 109ft

 

Just from knowing the roads I ran very well I can tell you that there isn't a single perceivable incline, aside from a bridge over the river, anywhere along the route.  Clearly the original ascent/descent reported in my Garmin file is very wrong.  Honestly, I even doubt the corrected  ascent/descent is accurate although I suppose if it's fine scale and precise enough a bunch of very small undulations could have added up over the course of the 8+ miles.  Also, since I started and ended at the same location the gain/loss should be the same.  The corrected data more or less get's it right but the original data had me gaining almost 500ft more than I lost.  Bottom line is that correcting your elevation profile will likely get you much closer to reality and bring your NGP, rTSS, and IF more in line with what they probably should be.

Tom Glynn

Joel,

I agree that correcting the data makes a big difference. The best way to see the difference is to run an out and back course, preferably hilly and then map the elevation profile. After it's corrected, the graph will be a mirror image. Without it, there can be huge differences from the "out" and "back".

tom

TH3 FRB

Everything around me is nearly dead flat. I've noticed most of my local runs include large "climbs" of as much as 900ft where I know for a fact the road is about as flat as a bowling alley. I've never paid any attention to the ascent/descent data from my runs before, mostly because I know I'm not running any hilly routes where it would be interesting. Now I know that the elevation data from the 405 is junk.

So now I'm curious about my Garmin 500 that I use when riding. Elevation doesn't enter into the NP, TSS, IF equation for riding so it isn't critical to do the corrections but if you are curious about your ascent/descent for a particular ride and have the GPS data then it's probably best to do the correction.

Mark Stovall

The last update at connect.garmin.com does the same thing with my 310xt. If there is elevation data out there for the area you ride/run it has been automatically correcting. Really cool.

TH3 FRB

So I just looked at a ride I did in CO Springs last month where I know I did a good bit of climbing. The Garmin data reported 2722ft gain and 2749ft loss. After correcting I've got 3656ft gain and 3664ft loss. The Garmin was off by almost 1000ft of climbing!!! I'm not sure how that happened though because the original and correct profiles look extremely similar.

 

mancona

@Joel- I believe the edge 500 actually measures elevation with a sensor and does not use GPS data, however to have accurate elevation data you need to have set at least one elevation point on the device that is on your route (so it has a reference point).

That is an interesting example you showed above. Did you also compare waht the Garmin is reporting the elevation as on the edge 500 and in GTC/Garmin connect for the same ride? I'm currious is WKO is reading the GPS data for elevation or using the barometic pressure sensor date on the edge 500. I agree that the correction looks close and would not have thought it would be 1000 ft different.

For the forerunner series this is not the case as they only use GPS for elevation and as you mentioned they are really off if you do not do the correction.

Chris G

 I always run the correction.  Without it the data is pretty useless.  You would think that GPS could measure elevation much better but it just does not seem to on my garmin at least.  

TH3 FRB

I'm pretty sure you're right - 405 uses the elevation data in the GPS signal and 500 uses a pressure sensor to estimate elevation. The 405 is simply using poor data. The 500 is susceptible to changing weather conditions that can impact barometric pressure. It appears that neither the 405 nor the 500 are very good at tracking elevation changes accurately. I've been using the Ground Control service through TrainingPeaks, although WKO+ also lets you select USGS corrections. The Ground Control service incorporates the USGS data as well as other high resolution data so it should be at least as good (or the same) as the USGS and potentially better in some instances.

http://blog.trainingpeaks.com/2008/01/ground-control-elevation-correction-for-your-gps-device.html

The reference point you mentioned should only be important if you care about absolute elevation. Both 405 and 500 should be able to track ascent/descent regardless of the starting point...but only to the accuracy of the method each uses to get elevation data.

Linda Patch

Posted By Chris G on 04 Jun 2010 10:09 AM

 I always run the correction.  Without it the data is pretty useless.  You would think that GPS could measure elevation much better but it just does not seem to on my garmin at least.  

 

Totally agree! And I always run it too. Have to.