Signal K Weather Station Plugin

This plugin fetches weather data from Finnish Meteorological Institute coastal weather stations for Signal K. It automatically selects nearby stations, providing weather updates for maritime navigation.

Features

• Fetches data from the nearest Finnish Meteorological Institute coastal weather stations
• Automatically selects stations based on vessel position using haversine distance
• Configurable number of monitored stations (1-51)
• Configurable update interval (minimum 10 minutes)
• Fetch timeout (30s) and concurrency guard prevent hangs and overlapping requests
• Handles missing sensor data gracefully (NaN values are excluded)
• Provides the following weather data per station:
  • Station name and short name
  • FMISID (station identifier)
  • Station position (latitude/longitude)
  • Temperature (Kelvin)
  • Wind speed (m/s)
  • Wind gust (m/s)
  • Wind direction (radians, true)
  • Atmospheric pressure (Pa)
  • Observation timestamp

Data Source

This plugin fetches weather observation data directly from the Finnish Meteorological Institute Open Data WFS API (opendata.fmi.fi). The data is freely available under the Creative Commons Attribution 4.0 license. No API key is required.

The plugin queries the fmi::observations::weather::timevaluepair stored query for each station using its FMISID, requesting the following parameters: t2m, ws_10min, wg_10min, wd_10min, p_sea.

Signal K Paths

Weather data is published under the meteo context with the following paths:

| Path | Description | Unit | |------|-------------|------| | environment.station.fmisid | FMI station identifier | - | | navigation.position | Station coordinates | lat/lon | | environment.outside.temperature | Air temperature | Kelvin | | environment.wind.averageSpeed | Wind speed (10 min avg) | m/s | | environment.wind.gust | Wind gust speed | m/s | | environment.wind.directionTrue | Wind direction (true) | radians | | environment.outside.pressure | Sea level pressure | Pascal | | environment.date | Observation timestamp | ISO 8601 |

Usage

Once installed and configured, the plugin will automatically fetch data from the nearest weather stations to your boat's location. Station weather data is available under the meteo context.

Freeboard-SK is able to show meteo data and this needs to be enabled from settings.

Configuration

Plugin settings:

• Data fetching interval -- how often to fetch (minimum 10 minutes)
• Number of stations -- how many nearest stations to monitor (1-51)

Development

Prerequisites

• Node.js 18 or later (uses native fetch)

Setup

npm install        # Install dependencies
npm run build      # Compile TypeScript to dist/

Scripts

npm run clean       # Clean dist/ output folder
npm run build       # Compile TypeScript
npm run typecheck   # Type-check without emitting
npm test            # Build and run tests (Node built-in test runner)
npm run lint        # Run linter (ESLint + TypeScript typecheck)
npm run audit-check # Check for vulnerabilities

Project Structure

src/
  index.ts          # Plugin source
  types.ts          # TypeScript interfaces
test/
  plugin-runtime.test.js   # Comprehensive test suite
  tooling.test.js          # Build artifact verification
dist/               # Compiled output (gitignored)

Support

For any issues or inquiries, please open an issue on the GitHub repository. We welcome any feedback or contributions.

License

This project is licensed under the MIT License. Feel free to modify and distribute it according to the terms of the license.