SailStats is a project to install a small embedded (or non-embedded but Micro-ATX sized) computer on a sailboat and log data from the various instruments. This page serves as a notebook of sorts for ideas and information relating to the project.


  • Brookhouse NMEA Combiner / Multiplexer w/ Seatalk and USB
  • Milltech Marine SR161 AIS Receiver
  • Garmin Chartplotter
  • RayMarine ST60 Plus Instruments

The Brookhouse NMEA Combiner / Multiplexer is the data hub of the whole system. It accepts data from up to four NMEA talkers at 4800 bps, an AIS receiver at 38400 bps, and RayMarine Instruments via their proprietary SeaTalk data bus. Finally, the device has two outputs, a 4800 bps NMEA output for an autopilot and USB for a computer. For the USB output, the Brookhouse device uses the Prolific Technology PL2303 controller for RS232 (Serial) to USB conversion. It has a USB Vendor/Product code of 0x067B/0x2303 and is supported well under most platforms including OpenBSD and Mac OS X.

Available NMEA Messages

  • AIS Receiver
    • AIVDM - AIS Message Format
  • Garmin Chartplotter
    • GPBWC - Bearing to waypoint using great circle route
    • GPRMC - Minimum recommend data
    • GPGGA - Fix Data
    • GPGSA - Overall satellite reception data
    • GPGSV - Detailed satellite data
    • GPGLL - Lat/Lon data
    • GPBOD - Bearing, origin to destination
    • GPRMB - Minimum recommended data when following a route
    • GPRTE - Route data, only when there is an active route
    • GPVTG - Vector track and speed over ground
    • GPWPL - Waypoint data
    • GPXTE - Cross track error
    • PGRME - Estimated error, not sent if set to 0183 1.5
    • PGRMM - Map datum
    • PGRMZ - Altitude
  • RayMarine (definitions need more analysis)
    • IIDBT - Depth below transducer
    • IIHDM - Fluxgate Compass Heading
    • IIMTW - Water temperature
    • IIMWV - Apparent wind angle, Apparent wind speed in knots
    • IIRMB - Unknown
    • IIRMC - Lat/Long, Speed over ground, Course over ground, Time (GMT), Date, Compass Variation
    • IIVHW - Speed through water
    • IIVTG - Course over ground
    • IIVWR - Apparent wind angle, Apparent wind speed in knots

Posted Event Derived Data Products

Track / Wind Overlay
Overlay measured wind data on recorded track.
Pointing Ability
True Wind Direction, Heading, Water Speed. Upwind plotted against time.
Wind Efficiency
True Wind Speed, Heading, Water Speed. Entirety plotted over time.

Real-time Calculations

Launch Control
Distance to starting line at the gun. Use wind efficiency to calculate maximum distance from starting line for final approach.
Competitor Distance
Timers to track competitors at rounding to calculate distance to/from competitors.