Old 09-29-15, 06:20 AM
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rm -rf
don't try this at home.
 
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That's interesting that MapMyRide was higher. Some years ago, before I switched to ridewithgps.com (which is way better for drawing routes and viewing recordings), I drew maps on mapmyride. They always were the lowest elevation total, since they ignored any hill less than 10 meters/33 feet high. So repeated small rollers were ignored. This sounds like what strava is doing now. I can see the arguments both ways.

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Smoothing GPS data

I'll repeat my comment from another thread:

All gps software uses smoothing. My Garmin 705 records once a second, and is accurate enough to show which side of the road I was on. But even so, there's "jitter" in recordings, and the different sites have their own way of fixing the raw data.

I have a wheel sensor feeding the Garmin, so it knows when I'm stopped. A phone GPS needs to guess, since even when stopped, the current location drifts, and it looks like you are moving at random.

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I often get three different average speeds on ridewithgps.com, strava.com and My Tourbook running on my PC.

For instance, here's 4 minutes of My Tourbook with smoothing turned off. Notice the huge Feet per Hour in yellow. In real life, I can sustain about 2000 feet per hour, and maybe 3000 for a very short hill.



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And the same thing with the smoothing settings I use. The max speed is lower. The rest of the chart looks more reasonable. And even here, the yellow feet per hour is still not right. But if I increase the smoothing even more, it just rounds off all the highs and lows too much.



My Tourbook is free software that runs on your own computer. It has tons of features for tracking rides and viewing them on maps.

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Here's a zoomed in My Tourbook map showing each one-per-second data point, color coded by speed. First, heading uphill to the top of the map, then returning downhill and turning right.

You'd think that something this accurate wouldn't need any smoothing.


Last edited by rm -rf; 06-02-16 at 09:09 AM.
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