1760 yards

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Jezza
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Re: 1760 yards

Post by Jezza »

John Gray wrote: It's actually 2Ï€" ~= 6.28".
Oohhh ppuullease John ~= 6.28 ~= 6 9/32

One must not mix imperial with decimal....it is just so passe :angel:
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Goshute
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Re: 1760 yards

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jezza wrote:I have theory this may have something to do with it WAAS
That link mentions Selective Availability (the US Government's way of saying "we are messing with the signal to try to limit the effectiveness of our enemies in using GPS in targeting algorithms"). SA was discontinued in May 2000 at the request of the US FAA. Wikipedia has more information on GPS than I ever want to read: http://en.wikipedia.org/wiki/Global_Positioning_System" onclick="window.open(this.href);return false;
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Don Wells
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Re: 1760 yards

Post by Don Wells »

Hi Jerry
    What model GPS are you using?
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Don

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Jezza
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Re: 1760 yards

Post by Jezza »

Don

Garmin Forerunner 405
Jerry
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jonwallace
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Re: 1760 yards

Post by jonwallace »

I still think it's down to you swinging your arms, try covering the distance with your arms taped to your sides, perhaps with the assistance of this thread or even the thread of your choice...
John

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Kiwi Keith
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Re: 1760 yards

Post by Kiwi Keith »

JoeP wrote:Accuracy of the GPS unit?

Joe
There are two factors in any measurement: "accuracy"- how close to the real value and "precision" - how consistent the measurement is.

Many GPS units give an Estimated Position Error (EPE) which is the unit's guess of its own error, typically +/- 3 metres. But the EPE is going to vary with how many satellites are in the sky at one time and their position in the sky. I have a handheld GPS receiver that has a mapping function. You can set it up to show your "track", a dotted line on the map. If I leave it sitting in the one spot and come back to it after a while the track for that position will look like a spider web as the reported position wanders.

I use the GPSr for the sport of geocaching where you use the GPSr to hunt down treasure someone else has hidden and provided the location online. When setting a geocache it is recommended that you average the reading over a time period for the simple purpose of eliminating the wander.

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Don Wells
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Re: 1760 yards

Post by Don Wells »

Are you taking someone's word for the track measurements? Or have you intimate knowledge of it? I would suspect that the track is in fact a 440 yard oval.
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Don

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Jezza
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Re: 1760 yards

Post by Jezza »

Sorry, been distracted for various reason so couldn't reply. I have checked and this is a certified 400 metre track with metric markers all the way around. I spoke to the groundsman who assures me it is. My research shows
Lane 1400.0 Metres
Lane 2407.2 Metres
Lane 3414.9 Metres
Lane 4422.6 Metres
Lane 5430.4 Metres
Lane 6438.2 Metres
Lane 7446.1 Metres
Lane 8453.6 Metres
Due to the nature of the run I have a very strong feeling that as I run on the white line between Lane 1 and 2 I could potentially be adding 7.2 metres to my laps.

:whisper: I have a feeling atmospherics may have an effect as well
Jerry
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ChrisGreaves
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Re: 1760 yards

Post by ChrisGreaves »

John Gray wrote:
ChrisGreaves wrote:Quite easily worked out as the difference between the two circumferences
Quite so.
Now if Jezza thinks about his comment "... I run in the inside half of the inside track, I suppose there could be a potential for extra distance. " very carefully ....
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Don Wells
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Re: 1760 yards

Post by Don Wells »

Due to the nature of the run I have a very strong feeling that as I run on the white line between Lane 1 and 2 I could potentially be adding 7.2 metres to my laps.
Hi Jerry
    As the attached spreadsheet shows, I calculate your lap discrepancy as a consequence of running on the lane divider to be 5.84 Metres per lap (23.39 total). This leaves an unexplained error of 14.05 Metres which I believe is explained by the time taken for the GPS to establish your position. During this time it assumes you are traveling in a straight line. I previously read that the Garmin capture time was in the neighbourhood of 15 seconds. My rough calculations show that a capture time of 16.39 seconds will account for the error.

H.T.H.
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Don

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Jezza
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Re: 1760 yards

Post by Jezza »

Thanks Don

I had to have a cup of tea and a quiet moment to go through that and does explain it very well. I am of a strong belief that atmospherics has a big thing to play on this and also the number of satellites that are connecting to the device as it has varied considerably of late.

Although this does sound a trivial conundrum I will be running 250 laps and adding 3-10 metres per lap can make a big difference.
Jerry
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Don Wells
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Re: 1760 yards

Post by Don Wells »

Hi Jerry
    Good luck on your run.     100 Km? :flee:
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Don