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Old 12th March 2009, 05:20 AM   #11
Join Date: Aug 2006
Posts: 298

I really don't know what I was thinking there. Of course the 31 is doppler. This proves that I am totally barking.

Good to see you are getting the is44 up to some great speeds.

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Old 12th March 2009, 10:58 AM   #12
Join Date: Aug 2006
Posts: 433

Welcome back Mr. Fox
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Old 28th March 2009, 10:41 PM   #13
Craig Bergh
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Join Date: Sep 2006
Posts: 1
Thumbs up GPS Accuracy...


You have asked a very good question.

The GT11 and GT31 are one of very few GPS units that display AND record Doppler Speeds.

This GPS records satellite location and strength for up to 12 satellites every second. This information can be studied on the computer for every single trackpoint on a run across the water.

When the GT31 displays speeds on screen even when the GPS is not moving, that is due to static from satellites.

The GT11 had filters in the firmware that filtered out this static.

The Windsurfing Tech Group removed the filters on the GT31.

I agree that it seems odd for a GPS to display speed when at rest.

Once the GT31 gets moving, that static does not appear. And the results are very smooth once the file is brought into the computer.

The GT11 and GT31 are extremely accurate tools to measure speed, and the GPS files are quite smooth and precise.

Please let me know if I may provide more information, or samples of files for others to examine.

Thank you everyone. I am lookng forward to a great year of windsurfing.

Craig Bergh
Worthington, Minnesota

email: cbergh@iw.net

web: http://www.midwestspeedquest.com
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Old 1st April 2009, 02:18 AM   #14
Join Date: Aug 2006
Posts: 239

Thanks a lot Craig. Your information is very useful.
Yes it seems odd that a very precise unit shows 2.83 knots when not moving, but my observations are like yours: as soon as the GT31 comes into play at a steady speed it becomes quite precise and updates very quick indeed.

I guess my GT31 doesn't have any problems, so if I dont clock 33 knots on my iSonic this week-end the problem is with... me...... (-;

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