True vs Sailing Master M

The wind you feel on a moving boat isn't the real wind. True-Wind Calculator turns the apparent wind you measure into the true wind you need — in two taps, no wind instruments required. In use since 2013, completely rebuilt in 2026. HOW IT WORKS Enter boat speed, apparent wind speed, apparent wind angle and heading. The app does exact vector math — no lookup tables, no approximations — and gives you true wind speed and true wind direction instantly. Boat speed and heading can be filled automatically from GPS and compass with one tap. FREE • True wind speed, direction and angle — unlimited calculations • One-tap GPS fill for boat speed and heading • The formula explained, so you can trust the numbers • Works completely offline — no account, no ads, no tracking PRO (one-time purchase, no subscription) • Performance — live VMG, target boat speed, % of target VMG and point of sail, driven by your boat's polar • Tactics — tack preview, windward-mark laylines, and whether you can lay the mark • Boat polars — pick a preset or build your own in the editor • Compass rose view — heading, apparent and true wind on one dial • Calculation history — every result logged with its inputs • All speed units — knots, m/s, km/h, mph Bought the app back when it was paid? Pro is already yours — it unlocks automatically. PRIVACY Everything stays on your device. Location is read only to fill the input fields and never leaves your phone. No analytics, no third-party SDKs.

Sailing Master M offers comprehensive sailing data and performance optimization information on iPhones, iPads, iWatches, and ActiveLook smart glasses. The application provides configurable pages and data displays, utilizing over 35 sailing measurements from the boat’s instruments, polars tables, and nautical charts. On phones and pads, the Data and Analog Displays can include minimum and maximum values and time series graphs. The Wind Display provides wind, heading, route, and speed information. The Route Display shows the expected wind conditions on the next legs. The Map Display shows the vessel with direction, tacking and downwind laylines on a nautical chart, or the wind laylines in another location. The connectivity is through NMEA 0813 Wi-Fi gateways such as B&G Vulcan, Zeus, GoFree, Yacht Devices, Signal K, Actisense, and ShipModul. The application has evolved from its initial focus on NMEA data display to encompass a comprehensive suite of features. Consequently, the app’s name has been revised from 'Display0183M' to 'Sailing Master M'. For further information, please refer to the user’s guide available on the app’s website or within the app itself. Terms of use: The app is delivered under the Apple End User License Agreement (EULA, https://www.apple.com/legal/internet-services/itunes/dev/stdeula/) The following libraries and services are used: - Kitura/BlueSocket, published under the Apache 2.0 license - A modified version of GPX package, published under BSD 3-Clause License and copyrighted by Ioannis Silks - OpenStreetMap licensed under the Open Data Commons Open Database License (ODbL, https://opendatacommons.org/licenses/odbl/) by the OpenStreetMap Foundation Licence, and ©OpenStreetMap contributors. OpenSeaMap, which is licensed under the Open Data Commons (ODbL) license, and ©OpenSeaMap contributors The supported NMEA 0183 sentences are: - BWR: Bearing and distance to waypoint - DBS: Depth below surface - DBT: Depth below transducer. - DPT: depth of water. - CGA: Global Positioning System Fix data - GLL: Geographic position Latitude/Longitude - HDG: Heading magnetic - HDM: Heading magnetic - HDT: Heading true - MWD: undocumented, wind direction, wind speed - MTW: water temperature °C - MWV: Wind speed and angle (A,T) - RMB: XTE, range to destination, bearing to destination, destination closing velocity . - RMC: Speed over ground - RSA: Rudder sensor angle - VHW: Water speed and heading - VLW: Distance travelled through water - VPW: Speed - measured parallel to wind - VTG: Course over ground (T or M), speed over ground - VWR: Wind direction (A), wind speed (A) - WCV: Waypoint closure velocity - XDR: air temperature (°C), water temperature (°C) and barometric pressure (mbar). - XTE: Cross track error The data items from NMEA and polars are: - Waypoint bearing - Waypoint distance - Time to Waypoint - VMG waypoint - Cross track error - Depth - Heading - Heading - Course - Course - Water speed - Speed over ground - Water temperature - Air temperature - Air pressure - Wind speed apparent - Wind angle apparent - Wind speed true - Wind direction - Wind direction - VMG Wind - Latitude, Longitude - Waypoint laititude, longitude - Water Distance after reset - Total water distance - Ground distance after reset - Total ground distance - Velocity made good towards wind - Heel - Rudder - Boat target speed through the water - Boat speed of target speed (%) - Beat VMG boat target speed through the water - Run VMG boat target speed through the water - GPS based trip distance - Leeway