SailNet Community - View Single Post - Calculating true wind
View Single Post
  #5  
Old 01-22-2013
kellysails's Avatar
kellysails kellysails is offline
Puget Sound Pounder
 
Join Date: Nov 2008
Location: Bainbridge Island, Port Madison, WA
Posts: 593
Thanks: 16
Thanked 6 Times in 6 Posts
Rep Power: 6
kellysails is on a distinguished road
Re: Calculating true wind

Hmmm, so wouldn't the NMEA ($GPVTG - Track made good and ground speed) serve as the current heading? It seems as though the GPS is reporting TMG via Magnetic heading. Jeeze I could be all wet here. But I remember even my ancient old GPS's would provide the current Magnetic heading.



$GPVTG

Track Made Good and Ground Speed.

eg1. $GPVTG,360.0,T,348.7,M,000.0,N,000.0,K*43
eg2. $GPVTG,054.7,T,034.4,M,005.5,N,010.2,K


054.7,T True track made good
034.4,M Magnetic track made good
005.5,N Ground speed, knots
010.2,K Ground speed, Kilometers per hour


eg3. $GPVTG,t,T,,,s.ss,N,s.ss,K*hh
1 = Track made good
2 = Fixed text 'T' indicates that track made good is relative to true north
3 = not used
4 = not used
5 = Speed over ground in knots
6 = Fixed text 'N' indicates that speed over ground in in knots
7 = Speed over ground in kilometers/hour
8 = Fixed text 'K' indicates that speed over ground is in kilometers/hour
9 = Checksum

The actual track made good and speed relative to the ground.

$--VTG,x.x,T,x.x,M,x.x,N,x.x,K
x.x,T = Track, degrees True
x.x,M = Track, degrees Magnetic
x.x,N = Speed, knots
x.x,K = Speed, Km/hr
Reply With Quote Share with Facebook