Contact
Email n.landeker@gmail.com and I'll get back to you. It helps to include your iOS version and iPhone model. Bug reports, feature ideas and "the math looks off" notes are all welcome.
Frequently asked
How do I calculate true wind?
Enter four values — boat speed, apparent wind speed, apparent wind angle, and heading — and the app returns true wind speed, direction and angle instantly. Tap the GPS button to fill boat speed and heading automatically.
How accurate is it? What's the formula?
The app uses exact vector math, not lookup tables or approximations. It resolves the apparent-wind and boat-velocity vectors into north/east components, subtracts the boat's motion, and converts the result back to a true wind speed and bearing. The 3.0 version fixed a bug in the older formula that produced wrong wind directions in some cases; the new math is verified against 10,800 reference cases. Tap "the formula explained" inside the app to see the working.
The GPS fill button isn't working.
Auto-fill needs location permission. Go to Settings → True-Wind Calculator → Location and allow access "While Using the App." You'll also get the best speed and heading readings outdoors with a clear view of the sky. You can always enter values by hand instead — nothing requires GPS.
What's in Pro, and is it a subscription?
Pro is a one-time purchase — no subscription, ever. It adds the compass rose view (heading, apparent and true wind on one dial), calculation history, and all speed units (knots, m/s, km/h, mph). The free app gives you unlimited true-wind calculations and one-tap GPS fill.
I bought the app years ago when it was paid. Do I have to pay again?
No. Pro unlocks automatically for anyone who bought the app before it became free. If it doesn't appear, make sure you're signed in with the same Apple ID you used originally, then tap Restore Purchases on the Pro screen.
I bought Pro but it's not showing on my other device.
Tap Restore Purchases on the Pro screen while signed in with the same Apple ID. Purchases are tied to your Apple ID, so there's no extra charge.
Does the app work offline?
Yes — completely. There's no account and no network requirement. GPS works offline too.
What does the app collect about me?
Nothing. No tracking, no analytics, no ads. Location is read only to fill the input fields and never leaves your phone. See the Privacy Policy for detail.
Which devices and languages are supported?
iPhone on iOS 16 or later. The app is localized in English, Slovenian, German, Italian and French.