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Author Topic: Difference between GPS and Sporttracks distance  (Read 3566 times)

canadien

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Difference between GPS and Sporttracks distance
« on: September 24, 2010, 11:41:36 am »

Hi,

I wanted to ask this for a while. Hope it hasn't been talked before. If yes, please be kind and point out the related thread...

I would like to know what can be the cause of the difference -in distance- between GH625 and the distance shpwed in sports track. Ex, on a 21.1km there is a différence of about 100m.

Slope, viaduc (lost of signal), any idea?

What is the real distance???


Thx
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zingo

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Re: Difference between GPS and Sporttracks distance
« Reply #1 on: September 24, 2010, 01:23:48 pm »

I think they use different smoothing algorithms, You can press the "calculator" top-right of "overview" panel (about middle of the screen) and change it to a pencil, to get the values from the watch.
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canadien

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Re: Difference between GPS and Sporttracks distance
« Reply #2 on: September 24, 2010, 03:25:38 pm »

Thanks Zingo, but what you think are the more realistic data between both?
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zingo

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Re: Difference between GPS and Sporttracks distance
« Reply #3 on: September 27, 2010, 01:36:16 pm »

Don't know, I think that if you record GPS points at 4s intervals instead of the 1s (factory reset) SportTracks got it's number nearer the watch one's but this does not help you decide who wins...
If you have access something with know's length like a measured race track you could give it a test. I myself usually put in the number from the watch in my training website, but that is since it easier to do then any other reason.
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TWG_TECH8

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Re: Difference between GPS and Sporttracks distance
« Reply #4 on: October 06, 2010, 01:10:37 am »

Dear all

Let me clearify the puzzle. :D
For Globalsat, we calculate the distance by every incoming point, no matter you decide the interval time to record.

For Sporttracks, it just calculate regarding the all points from record.

Sincerely,

Geoffrey
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canadien

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Re: Difference between GPS and Sporttracks distance
« Reply #5 on: October 06, 2010, 11:15:49 am »

Hi Geoffrey,

So if I understand correctly what you are saying, the time/distance from the watch (or GYM software) is more precise than sportstracks. It should show the real distance compare to SporTracks wich always extended distance (altough good for the ego as the pace is also faster).

Am I right in my declaration? Recorded incoming points can lead to a false interpretation?
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Longjog @ GS-Sport-Servicecenter

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Re: Difference between GPS and Sporttracks distance
« Reply #6 on: October 07, 2010, 01:43:58 am »

Hi canadien,
Quote
So if I understand correctly what you are saying, the time/distance from the watch (or GYM software) is more precise than sportstracks.

If there are small errors caused by GPS-accuracy, they are cumulated to a bigger error. So the result of the watch shlould be longer than the calculated distance point to point (the shortest way between to points is a straight line). The shorter the recording interval of the watch the smaller the difference between watch and sporttracks.

Regards

Longjog
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http://www.gs-sport-servicecenter.de.vu/

GH-625M, GH-625XT, GH-505, GH-561, GB-580P, BT-338
Germany

canadien

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Re: Difference between GPS and Sporttracks distance
« Reply #7 on: October 08, 2010, 04:48:24 pm »

Hi canadien,
Quote
So if I understand correctly what you are saying, the time/distance from the watch (or GYM software) is more precise than sportstracks.

If there are small errors caused by GPS-accuracy, they are cumulated to a bigger error. So the result of the watch shlould be longer than the calculated distance point to point (the shortest way between to points is a straight line). The shorter the recording interval of the watch the smaller the difference between watch and sporttracks.

Regards

Longjog

Hi Longjog 8),


I do understand, but my recorded points have always been set to the minimum available (see 1sec). So I still wonder why there is there a difference between ST and GH watch/software...?
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zingo

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Re: Difference between GPS and Sporttracks distance
« Reply #8 on: October 09, 2010, 08:40:21 am »

I think Sporttrack does some smoothing.
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canadien

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Re: Difference between GPS and Sporttracks distance
« Reply #9 on: October 13, 2010, 11:45:37 am »

I think Sporttrack does some smoothing.
Yes, me too think you are right. Do you know if this smoothing can be set or is it automatic?


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zingo

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Re: Difference between GPS and Sporttracks distance
« Reply #10 on: October 13, 2010, 12:25:20 pm »

No, remember that due to GPS error the smoothing can be a good thing.
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TWG_TECH8

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Re: Difference between GPS and Sporttracks distance
« Reply #11 on: October 14, 2010, 06:49:06 am »

Hi,

GPS chipset has smoothing mode, but the testing result wasn't satisified at some case than normal mode. Likes trace accuracy. So we decided disable.

It is hard to say what methold of distance calculation is better, it depends what activity you did and how long interval time to record you set.

Regards,

Geoffrey
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