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Old 04-05-2013, 03:55 PM   #11 (permalink)
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Me, a few buddies, and the gf all have have the same Ski Tracks app. I have an iPhone 5. One of my friends has an android phone and the gf has an iPhone 4. Whenever we all start our apps at the same time and ride together all day and then check our stats at the end of the day we all get different results.

The gf's iPhone 4 is the worst offender. It consistently reads faster and steeper than anyone else's stats. There are days when we all cruise at the same speed all day and ride the same runs then when we check the stats, the gf's phone usually records speeds 5-15 mph faster than all the other phones. One day she had a maximum slope angle of 54 degrees when I'm sure we didn't exceed 30.

I take these ski tracker app stats with a grain of salt. Whenever I achieve a new top speed I'm always skeptical.
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Old 04-05-2013, 04:05 PM   #12 (permalink)
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I guess I mostly just use it to compare one day to the next, not one rider to the next. And for that, it works. Plus it scares my wife, so that's fun!
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Old 04-05-2013, 04:32 PM   #13 (permalink)
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Quote:
Originally Posted by The Deacon View Post
I guess I mostly just use it to compare one day to the next, not one rider to the next. And for that, it works. Plus it scares my wife, so that's fun!
I think even then it may be inaccurate. I think that at times it looses gps reception and that's when some of the stat keeping goes haywire. Sometimes I look over my GPS tracking it shows that I rode a straight line down a trail when I know I was deep in the trees in between two trails.

Accuracy probably depends on the terrain that you are riding.
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Old 04-05-2013, 04:37 PM   #14 (permalink)
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Ok, I get all that. As I mentioned in op, I never took any reading of my max. speed to b 100% spot on. I always assumed that any logged speed would likely b +\- a few mph. So I suppose the argument being made by detractors of these apps. Are the flat out claims of top speed without acknowledging THAT discrepancy?

Or are people claiming that these apps. are unreliable and inconsitantly inaccurate enough that ANY given speed is questionable?
Additionally, that still doesn't address my observation that similar apps used when I ride my MTB seem to B reasonably close to the milage & mph's logged with my bike mounted odometer! Again, usually anywhere within 3-5 mph. Any time I've encountered larger variences than that, they can usually b traced to signal loss or interference.

That level of accuracy is good enough for me to be reasonably confidant that I'm not making wildly inflated, bullshit claims for my snowboarding speeds. Are we arguing about split hairs here?
Average speeds will be accurate but top speeds can be off by a lot. If you look st a series of instantaneous speed indicators from GPS data it can be quite spiky.
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Old 04-05-2013, 07:20 PM   #15 (permalink)
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minute elevation changes on the mountain are very inaccurate. Simple geometry tells you that those inaccuracies get amplified when calculating speed. Hence, completely inaccurate readings even with the best GPS signal.
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Old 04-06-2013, 10:55 AM   #16 (permalink)
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[QUOTE=poutanen;896954]I tracked myself with apps for a couple years, various apps and various phones. My top speeds (after correction) were consistently anywhere from 100-130 kph each day.

Ah, shitty, I read that & was thinkin'....

That was last year?

Fuck, we must be pushin' @ least 150 this year?

Not bad almost 95mph



I've never used one of those things, but I'm really curious.
Done 100kmh on my home made longboard, didn't seem near as fast as I can go on my snowboard.


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