Ground Speed Calculator

• θ = wind direction − track
• Drift = asin( (wind × sin θ) ÷ TAS )
• GS = TAS × cos(drift) − wind × cos θ

TAS 120 kt on track 360°, wind 300° at 30 kt.

1. 1.θ = 300° − 360° = −60° (wind from the left-front).
2. 2.Crosswind component = 30 × sin(60°) = 26 kt from the left.
3. 3.Drift = asin(26 ÷ 120) ≈ 12.5° to the right; correct 12.5° left.
4. 4.Headwind = 30 × cos(60°) = 15 kt; GS = 120 × cos(12.5°) − 15 ≈ 102 kt.

Ground speed ≈ 102 kt, drift 12.5° right, hold 348°.

The wind triangle links true airspeed, wind, and the path over the ground. Ground speed drives your ETA and fuel; the wind-correction angle is the heading offset that keeps you on the desired track. Both fall straight out of resolving the wind along and across the track.

The maximum drift angle equals the crosswind component divided by TAS, in radians — or, as a rule of thumb, (crosswind ÷ TAS) × 60 in degrees. Handy when the E6B isn't to hand.