Wednesday, September 16, 2009

Garmin Elevation Maps 2

Londell asked about running the same loop again and seeing how the elevation maps change. So today I went ahead and ran the same loop and compared the elevation plots from SportTracks to Bim Active and here are the results.

Here is a map of the run from SportTracks.

SportTracks - Lebanon Hills run - September 15th

SportTracks - Lebanon Hills run - September 16th

My conclusion is that the runs as plotted from SportTracks look similar but not the same. The mileage was identical for both runs 5.61 miles. I am running their plug-in for elevation correction which is supposed to smooth it our a bit. I will need to look into their forum to see if I can improve it any more.

Bim Active - Lebanon Hills run - September 15th

Elevation Avg: 927 ft
Total Uphill: +344 ft
Total Downhill: -370 ft
Elevation Net: -26 ft

Bim Active - Lebanon Hills run - September 16th

Elevation Avg: 928 ft
Total Uphill: +387 ft
Total Downhill: -390 ft
Elevation Net: -3 ft

My conclusion on Bim Active, it looks better than SportTracks but it still isn't quite identical although it looks real close. One difference that I can explain is that in yesterday's run I shut off my Garmin before I got to the top of the hill at the end of the run which is the cause of the difference at the end of the plot. Could the other minor differences be because although I ran the same trail I am sure I did not take the same tangent or is it simply the noise in the data. I did verify that Bim Active uses the USGS data for it's elevation plots but I am not sure how they correct for the noise in the data that SportTracks mentioned. Bim Active is free to use to import your data to, but they do offer a pay service where it appears you can use your cell phone as a GPS by installing an application onto your phone. They do offer a 1 day trial of this service and the yearly cost looks reasonable. What I haven't checked is what do I need from my cell phone provider in order to use this application.

So what next, well I will run the same loop in the next few weeks and plot it out one more time and see if I see anything else worth noting.


Londell said...

Yep, that is what I would expect... Charts have some resemblance but still obvious there is issues... I noted BIM appears much more consistent for the limited time I used is...

Scott Mark said...

This is great stuff, I love the head to head comparisons. I have always considered GPS elevation to be junk data, this confirms it. Frankly, I don't think the SportTracks (which is GPS elevation) profiles even look similar - I think they are significantly different if you look at the details.

I'm hoooked on your little study now. I had never heard of Bim Active, will have to Google that.


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