External PDA wind not correct?

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mattm
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Joined: Thu Jan 24, 2008 4:38 pm

External PDA wind not correct?

Post by mattm » Fri Aug 28, 2020 10:44 pm

Has anyone noticed that the external PDA does not report the same wind as the one on Condor? Today I was doing some wave flying, where the winds aloft were higher than at the ridge tops, but my external PDA reported the same wind all the time. To make sure it wasn't the external PDA (running TopHat) I checked the NMEA monitor, which showed me this:

$LXWP0,Y,184.6,6321.9,-0.40,,,,,,74,315,21.9*59

If I remember my NMEA parsing, that "21.9" is the reported wind in km/hr, which computes to 11.8kts. TopHat is reporting 12kts of wind. The PDA in Condor is reporting 35kts at the same time.

Thanks,
Matt

Rotareneg
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Re: External PDA wind not correct?

Post by Rotareneg » Sat Aug 29, 2020 3:52 am

Yeah, I've noticed that too, I set XCSoar to use its own wind calculations because of that.
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Bre901
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Re: External PDA wind not correct?

Post by Bre901 » Sat Aug 29, 2020 10:39 am

If you take a closer look at the NMEAlog.txt, you notice that the windcourse and speed remain constant.

In the flightplan I set wind from 225°, 36km/h, in the NMEAlog.txt I get: 053,32.6

Apparently the "windcourse" is something like wind direction - 180°

Edited to add that wind speed and direction variation were set respectively to "low" and "medium"
I'll re-do some tests later
CN: MPT — CondorUTill webpage: https://condorutill.fr/

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Bre901
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Re: External PDA wind not correct?

Post by Bre901 » Sat Aug 29, 2020 3:05 pm

I did another test with no wind speed or direction variation

Flightplan.fpl :
WindDir=336.44775390625 -180 = 156
WindSpeed=5.08165550231934 =18.29395980834962‬ km/h

NMEALog.txt (same values in all the fixes)
$LXWP0,Y,8.2,38.8,0.00,,,,,,336,156,18.3*4D

This proves clearly that Condor sends the flightplan wind data, not the real-time ones.
CN: MPT — CondorUTill webpage: https://condorutill.fr/

mattm
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Joined: Thu Jan 24, 2008 4:38 pm

Re: External PDA wind not correct?

Post by mattm » Fri Sep 04, 2020 12:37 am

My take on this is that it a hole in Condor function. I spent a lot of money on my RL vario so I could have one that would provide decent wind data to my flight computer.

So far TopHat seems to always believe that number, rather than compute it for itself. Maybe I'll go back to XCSoar, since it always seemed to prefer its own ideas on wind (even in the RL glider!).

Matt

k6chris
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Re: External PDA wind not correct?

Post by k6chris » Sun Jan 17, 2021 5:14 pm

Just discovered this bug too. The data that Condor passes to XCSoar as "external wind" is wrong, strength seems always to be about 60% too low. If you disable the "external" input in XCSoar's wind calcs, then it uses GPS drift, either circling or from two straight glides, and calculates it correctly. It's actually a useful thing to practice to see how quickly XCSoar can get wind strength and data the same as the Condor input (as shown on the Condor PDA).

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