SailTimer API - WMM™

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About this app

The wireless, solar-powered SailTimer Wind Instrument RB™ transmits wind speed & direction from the masthead. This app is only for the WMM Edition. See the innovations and features of the Wind Instrument RB™ at

An API is a digital toolkit; this one receives Bluetooth transmissions from the Wind Instrument, does some conversions, then sends the data to other apps for viewing. Use this API with the SailTimer Wind Gauge™ app, the SailTimer™ chartplotter app, or with other navigation, wind gauge or performance apps (

Add your boat name to your Wind Instrument (only visible to you), to be clear that you are always connecting to your own device.

The API remembers your Wind Instrument and reconnects automatically next time you come back to the boat. If you lose the signal, the API will also reconnect automatically if it is open.

The circular Disconnect button on the top bar is handy when leaving the boat, or if you want to save power in your mobile device and Wind Instrument when not in use.

The API maintains the connection to your Wind Instrument when in background, and even if screen is turned off to conserve power. When the API is open, tablet/phone will not go to sleep by itself.

There are two steps for the Bluetooth connection: the initial scan to find devices available, and then the Bluetooth connection to the Wind Instrument you select. The API remembers your Wind Instrument after the first time, and will then reconnect to it automatically without the scan.

Data is shown in green text as the wireless data arrives from the Wind Instrument. Makes it easy to see if you have a Bluetooth connection, and to check the incoming data if needed. Pause/Unpause button if you need to make the green text easier to read. The app also sends official NMEA 0183 sentences for wind direction (MWD) and wind angle (MWV) to other apps for viewing. (Requires English or USA language/keyboard on your device).

Send wind data at 1, 3, 5, 10 or 20 Hz. Wind gauges move more smoothly with faster transmissions, but numerical displays may change too fast. You may want fast transmissions for an autopilot, or may prefer to conserve battery power in your Wind Instrument with fewer transmissions.

Smoothing in the menu is affected by the transmission speed. Use smoothing if a wind gauge is too jumpy (especially at fast transmission rates) because of mast vibration, boat pitching etc. Smoothing makes your wind gauge amazingly fast and smooth.

The GPS in your device needs to identify satellites and detect your location before the green text starts to stream, which may take a moment.

To convert wind direction with Magnetic North to True North, the app calculates compass declination based on your GPS location on Earth.
The app uses the sophisticated new NOAA-British Geological Survey geomagnetic model for compass declination, since magnetic north has been moving around faster than usual in recent years. Compass fine-tuning: not needed in normal circumstances, but this advanced option could fine-tune precision in magnetic wind direction.

New simulator for testing True Wind Direction (TWD) and True Wind Speed (TWS). Long-tap on the wind cup icon to start. Double-tap on the wind cup icon to stop. Allows you to enter boat speed/heading and wind speed/heading, and check TWD and TWS in the first line of green text (MWD in NMEA 0183 format).

Privacy Policy and End-User Licensing Agreement:

There are How-To-Use pages and FAQs at If you have a question or feedback please email We’re here to help.
Updated on
Jun 28, 2022

Data safety

Safety starts with understanding how developers collect and share your data. Data privacy and security practices may vary based on your use, region, and age. The developer provided this information and may update it over time.
No data shared with third parties
Learn more about how developers declare sharing
This app may collect these data types
Data isn’t encrypted
Data can’t be deleted

What's new

• Added smoothing to True Wind Speed & Direction with True North reference, for data shared online for crowdsourced wind maps.
• Bluetooth scan filtered to now only show Wind Instruments. Rename button fixed.
• Transition to new serverless cloud database to better support massive scaling, due to the growing volume of data and users worldwide.