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GPS Out - NMEA wind sentences

Skymaster 9999

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Hallo to all users and authors of this useful sw. I have a a plea to the authors - would you please consider extension of NMEA out senteces for $GPMWV / $GPMWD (wind info)? With the appearance of gliders in MSFS I would like to use XCSoar on my phone but because FSUIPC 7 sends only position and baro height, wind estimates are way off (in this case XCSoar calculates wind from circling only with very unprecise results). To be more precise, XCSoar require IAS/TAS info, send via customized NMEA sentences (LX / Borgelt etc extensions of NMEA protocols) to calculate wind or use wind info directly from external source. Thank you for your kind help and keep the good work.

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sorry for the delay in replying. This is an area of FSUIPC that I am not that familiar with (at the moment!), but I have discussed this with Pete.
First, it seems that you would like one of two options:
   1. Adding NMEA out sentences for $GPMWV / $GPMWD, or
   2. Add IAS/TAS info, via custom NMEA sentences, so that wind info can be calculated from external sources

Is this correct?

For 1, I am not sure that this information is available. There are simvars for ambient wind relative wind velocity:

AMBIENT WIND DIRECTION:	Wind direction	Degrees	(TRUE, not relative)
AMBIENT WIND VELOCITY:	Wind velocity	Knots	
AMBIENT WIND X:	Wind component in East/West direction.	Meters per second	
AMBIENT WIND Y:	Wind component in vertical direction.	Meters per second	
AMBIENT WIND Z:	Wind component in North/South direction.	Meters per second	
STRUCT AMBIENT WIND	X: (latitude), Y (vertical) and Z (longitude) components of the wind.	Feet per second	

RELATIVE WIND VELOCITY BODY X:	Lateral speed relative to wind	Feet (ft) per second	
RELATIVE WIND VELOCITY BODY Y:	Vertical speed relative to wind	Feet (ft) per second	
RELATIVE WIND VELOCITY BODY Z:	Longitudinal speed relative to wind	Feet (ft) per second	

I could possibly construct a MWC sentence using these ambient wind simvars - from the NMEA 0183 protocol:

MWV Wind Speed and Angle
1 2 3 4 5
| | | | |
1) Wind Angle, 0 to 360 degrees
2) Reference, R = Relative, T = True
3) Wind Speed
4) Wind Speed Units, K/M/N
5) Status, A = Data Valid
6) Checksum

However, I have no details on the sentence to be used for MWD - from the same document:

MWD Wind Direction & Speed
Format unknown

Do you have any details on how to construct such a sentence? Or would just adding the MWV sentence suffice?

For 2, do you have any information on the custom sentences required? IAS is already included in the RPY sentence (as speed KIAS*10). but not TAS.


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Also, are you sure that it is IAS/TAS that you need? No wind element can be derived from IAS/TAS. You would need TAS and GS. The wind only affects GS not the craft’s airspeed. The difference between IAS and TAS is caused by air density. At low altitudes they are pretty nearly identical, but at higher altitudes the measured airspeed (IAS) is lower than the true airspeed (TAS) because there’s less pressure.


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18 minutes ago, Skymaster 9999 said:

I am not a big expert on this matter

Me neither! Let me know how you get on. I could look into adding an MWV sentence at some point if absolutely required, although I'm not sure when I will have time to look into this at the moment. I will add it to my 'todo / to investigate' list, and let you know when I get time to look into this in more detail. I am currently very busy just keeping up with the MSFS releases  (as well as the P3D ones....)!


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