**Document status: Early ideas, subject to change.**

====== Project Goals ======

  * Build a system which allows sending messages between boats which may not be within direct radio communication distance of each other.
  * Allow human written text messages and telemetry.
  * Suitable for small yachts and pleasure fishing boats.
  * Low power usage.
  * Affordable and easy to install.
  * Independent operation: Does not require other infrastructure, central servers, or subscriptions.
  * Open source design.
  * Licence exempt preferably everywhere, initially being developed in/for UK and Canada.

To be implemented with a LoRa mesh network.

===== Purpose and applications of the system =====


  * Wind reports from the next fjord / around the corner.
  * Chatting to your friend on another boat (around corner / out of VHF range?).
  * Race tracking.
  * Weather reporting and forecasting. Local forecasts of remote ocean race areas.
  * Checking on your boat when you are away for a long time. Theft detection / recovery.
  * Storm / high seas / anchor alarms.

===== Onboard Device Specification =====

  * Small, discrete device that can be installed behind a panel.
  * Minimal UI (probably LEDs and a button or two).
  * Configuration method to set some of: boat name, boat type, ID, network settings.
  * "Low power". For monitoring a boat left for the winter: can send occasional position reports or alerts using a typical boat lead acid battery for at least six months to a year without causing problems. May use more power when boat is actively in use / has a battery charging source.
  * Runs on nominal 12V boat power, own wiring or from CAN bus.
  * Battery monitoring. At least report supply voltage.
  * Reduce power usage when battery low. Avoid damaging battery.
  * Builtin GPS receiver and antenna.
  * 9 DoF IMU, to detect movement (security), report sea state...
  * Configurable alarms - e.g. movement or voltage triggered.
  * Data logging: There should be some non-volatile storage, useful for weather reports and buffering messages.
  * At least somewhat waterproof case.
  * Possibly: External enclosure for rail mounting on metal boats.
  * Possibly: Builtin battery. Important for tracking if boat stolen and power is disconnected.

==== Interfaces ====

  * Wind instrument interface for sensors that may be supplied with the device - probably NMEA0183, NMEA2000, or RS485. Possibly wireless or wired analogue for cheaper sensors.
  * NMEA receive interface for GPS (needed if cannot be installed where internal GPS works).
  * LoRa antenna socket? (I think needed for the same reason, if installed below decks on a metal boat)
  * NMEA receive interface for other boat instruments: wind, depth, compass, IMU, temperatures, tanks, ...
  * For the UI: Probably bluetooth to a phone app, or wifi to a computer / web interface.
  * Other sensors, e.g. air quality, humidity, fog, CO2, intruder alarm system. Possibly serial (CAN, RS485) or wifi / IP.

==== UI ====

  * Display own and other boats' sensor readings on a map.
  * Send and receive text messages.

===== Other Possible Devices =====

==== Base Station ====

  * Connects to LoRa network.
  * External antennas
  * Internet linking with ethernet or wifi
  * Mains power
  * Doesn't need NMEA / boat network interfaces. Maybe connects to weather station though.

==== Panel mount UI ====

  * Could be like navtex with weather reports, or a map.
  * Text messages.
  * Maybe keyboard or touchscreen.

==== Portable radio ====

For monitoring an anchored boat when you are ashore. Take with you in dinghy.

===== LoRa Network Design =====

  * Messages should be forwarded between boats to extend range
  * Store and forward possible to allow boats to carry messages to another area.
  * Possible optimisation: replace older messages with new versions
  * Broadcasts. Geographically limited?
  * Addressable messages (maybe not needed at first, ie for simplicity treat everything as public broadcast)

===== Investigate =====

  * Use of satellites to extend range?