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Author Topic: GH 505 & Doppler  (Read 4651 times)

davva

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GH 505 & Doppler
« on: November 02, 2010, 10:03:57 am »

Im not sure what a Doppler Device is but I was mentioning to some windsurfing people the GH 505 comparing to what people used at the moment - the Genie GT31 - http://www.locosystech.com/product.php?zln=en&id=30 and they said the GT31 was a "Doppler Device"

Is "Doppler" something the GH 505 can do or is it something that can be in a future firmware release. Is a "Doppler Device" a big deal.
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TWG_TECH8

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Re: GH 505 & Doppler
« Reply #1 on: November 02, 2010, 10:51:40 am »

Im not sure what a Doppler Device is but I was mentioning to some windsurfing people the GH 505 comparing to what people used at the moment - the Genie GT31 - http://www.locosystech.com/product.php?zln=en&id=30 and they said the GT31 was a "Doppler Device"

Is "Doppler" something the GH 505 can do or is it something that can be in a future firmware release. Is a "Doppler Device" a big deal.

Dear customer,

Do you mean GT31 be able to record doppler information or done by software?

Sincerely,

Geoffrey
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davva

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Re: GH 505 & Doppler
« Reply #2 on: November 02, 2010, 11:10:54 am »

I think im a bit out of my depth talking about doppler and I think its based on the chip rather than anything else. Is there anything than can be logged regarding doppler?

On my windsurfing forum someone posted this article

http://www.mikeg.me.uk/guides/GPS_Devices_-_Speed_Sailing_-_Feature_Comparison.pdf

and id be really interested how the GH 505 compares to the products in section 4.1.10 in particular whether the GH 505 logs the num sats, hdop and sdop info.
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davva

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Re: GH 505 & Doppler
« Reply #3 on: November 02, 2010, 11:25:01 am »

Apparently the GT-31 records records the speed over ground - This was posted on the windsurfing forum.

"The important thing is for the Doppler speed (i.e. speed over ground) to be written to the track log so that it is available for subsequent analysis (GPSResults, GpsarPro or RealSpeed).

Few devices save anything other than the postional data and there isn't any supporting data to give any degree of confidence in the readings. That's one of the reasons why the GT-31 is so good for speedsurfing... it's basically a great data logger but also has the speed genie, etc.

I haven't any first hand experience of the GH 505 so I can't say what data it records."
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christophe

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Re: GH 505 & Doppler
« Reply #4 on: December 02, 2010, 03:59:33 am »

Is the GH505 recording the speed from the Doppler shifts of the satellite signals or from calculations using the positional measurments?

It seems calculation the (horizontal only since we're on water) speed by using doppler shift values and SDOP and VSDOP would give a very precise speed measurement. That's what the GT31 does and that's why it's been approved for speed sailing.

(check http://nujournal.net/SDOP.pdf for more technical information)
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TWG_TECH8

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Re: GH 505 & Doppler
« Reply #5 on: December 08, 2010, 06:51:50 am »

Is the GH505 recording the speed from the Doppler shifts of the satellite signals or from calculations using the positional measurments?

It seems calculation the (horizontal only since we're on water) speed by using doppler shift values and SDOP and VSDOP would give a very precise speed measurement. That's what the GT31 does and that's why it's been approved for speed sailing.

(check http://nujournal.net/SDOP.pdf for more technical information)

Dear christophe,

Thanks for providing detail information. GH-505 calculate instant speed base on the average of 8 continuous coming pure speed data which comes from Ground speed (Horizontal speed).
The total average speed bases on (total distance/ total time).

To come out SDOP,VSDOP, it seems need more simultaneous recording data to do calibration. I am not sure GH-505 can get precise data or not. Maybe we have to a try. Do you have a simulation tool?

Please let me know if any suggestions.


Geoffrey
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christophe

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Re: GH 505 & Doppler
« Reply #6 on: December 12, 2010, 03:41:00 pm »

Hello Geoffrey,

i don't have more information or simulation tool, sorry...

Is there a way to get the instant speed really coming from ground speed and not an average calculated on 8 samples?

thank you
 
Christophe
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TWG_TECH8

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Re: GH 505 & Doppler
« Reply #7 on: December 15, 2010, 08:37:26 pm »

Hello Geoffrey,

i don't have more information or simulation tool, sorry...

Is there a way to get the instant speed really coming from ground speed and not an average calculated on 8 samples?

thank you
 
Christophe

Hi Christophe,

Sure thing, just to modify firmware to save instant speed. I am studying SDOP algorithm now. ;D


Sincerely,

Geoffrey
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TWG_TECH8

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Re: GH 505 & Doppler
« Reply #8 on: December 17, 2010, 03:39:01 am »

Hello Geoffrey,

i don't have more information or simulation tool, sorry...

Is there a way to get the instant speed really coming from ground speed and not an average calculated on 8 samples?

thank you
 
Christophe

Hi Christophe

We plan to add Surfing Mode to record the raw speed data instead current if you active it. Do you have any comments?


Sincerely,

Geoffrey

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christophe

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Re: GH 505 & Doppler
« Reply #9 on: December 17, 2010, 04:06:08 am »

sweet :o)

thanks
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TWG_TECH8

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Re: GH 505 & Doppler
« Reply #10 on: December 18, 2010, 05:14:41 am »

sweet :o)

thanks

We will process it soon. ;D
But it is not the right season for surfing. :(

Have a nice weekend,

Geoffrey
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zingo

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Re: GH 505 & Doppler
« Reply #11 on: December 20, 2010, 10:11:27 am »

Quote
But it is not the right season for surfing.

I's seems to always be season for surfing, kitsurfing friends are out (swedish winter) now surfing with skies on the snow.
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TWG_TECH8

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Re: GH 505 & Doppler
« Reply #12 on: December 21, 2010, 12:44:46 am »

Quote
But it is not the right season for surfing.

I's seems to always be season for surfing, kitsurfing friends are out (swedish winter) now surfing with skies on the snow.

So it always is the season for surfing and kitsurfing.
But it is really cold now.

Geoffrey
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TWG_TECH8

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Re: GH 505 & Doppler
« Reply #13 on: December 28, 2010, 05:14:54 am »

Is the GH505 recording the speed from the Doppler shifts of the satellite signals or from calculations using the positional measurments?

It seems calculation the (horizontal only since we're on water) speed by using doppler shift values and SDOP and VSDOP would give a very precise speed measurement. That's what the GT31 does and that's why it's been approved for speed sailing.

(check http://nujournal.net/SDOP.pdf for more technical information)

Hi christophe

I read the paper and discussed with our team, we would like to implement VMG and speed avg, but we don't have idea to generate SDOP and how to join GPSSpeed club, do you have idea?

We create new topic for sailing and windsurfing proposes, welcome to leave there.


Sincerely,

Geoffrey ;D
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seglare86

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Re: GH 505 & Doppler
« Reply #14 on: January 04, 2011, 02:25:09 am »

Posted the following in the thread in the main forum before I saw this thread. Apologies for repretition but maybe everyone is not reading the main forum. Also apologies for repetition of the device info from previous posts in this thread.

A good place to read about and get in contact with windsurfers using GPS is http://www.seabreeze.com.au/forums/Windsurfing/Gps/

The organisation that approves GPS devices for speed measurements and records is GPS Speedsurfing http://www.gps-speedsurfing.com/default.aspx

A good device to look at is Locosys Genie GT 31 http://www.locosystech.com/product.php?zln=en&id=30. This is the most commonly used device for measuring speed for windsurfers. 

This guy has developed a custom firmware specialised on windsurfing for the device http://mtbest.net/setting-up-navi-GT31.htm where I am sure you can draw some conclusions on required features and algoritms etc.

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