Это просто картинка прибора. А вот формула VMG, и в обоих случаях присутствует значение угла направления движения куда вам надо (travel direction):
"...
True VMGThe general concept of a boat's VMG as stated above is:
VMG,y^=Vocosθ{textstyle VMG,{hat {y}}=V_{o}costheta }
Obviously this is a quick way to determine your VMG while sailing. The truth is though that the overview of the physics is much more complicated than that. Some instances to take into consideration is that a sailboats Speed Over Ground increases or decreases relative to the wind direction. In theory, a sailboats speed increases while sailing from upwind to a downwind direction, not before slowing down ( while officially going downwind) before sailing parallel to wind direction ( downwind). Some other factors to include is the sail boat specifics that exists for each manufacturer. This would include things such as 'Velocity Increase Constant', which is normally given by the manufacturer as a 'The sail boat increases speed by 10% for every X degrees from the wind'. Considering these factors in mind; a True VMG can be calculated with the equation:
VMGD,y^=Vwcosθs(1+β100)|θo−θs|icosθγ{displaystyle VMG_{D},{hat {y}}={V_{w} over costheta _{s}}(1+{beta over 100})^{|theta _{o}-theta _{s}| over i}costheta _{gamma }}
The above equation is for finding the True VMG for a sail boat going UPWIND ONLY.
VMGD,y^=Vwcosθs(1+β100)|180∘−θs−θo|icosθγ{displaystyle VMG_{D},{hat {y}}={V_{w} over costheta _{s}}(1+{beta over 100})^{|180^{circ }-theta _{s}-theta _{o}| over i}costheta _{gamma }}
The above equation is for finding the True VMG for a sail boat going DOWNWIND ONLY.
Where:
Vw{displaystyle V_{w}} = Velocity of the Wind
θo{displaystyle theta _{o}} = Angle between the direction of travel and the direction of the wind
θγ{displaystyle theta _{gamma }} = Angle between the direction of travel and the direction of destination..."
https://en.wikipedia...ocity_made_good