signalk-viva-plugin

a plugin that scrapes data from the Svenska sjöfartsverket viva-system from a configurable number of stations around my location to monitor for wind, barometric pressure, configurable alarms for sudden changes in conditions and visualisation in KIP and freeboard-SK.

What it does

• Reads your vessel position from Signal K and finds the nearest ViVa stations within a configurable radius (nearest first, up to a configurable count). Only stations that actually report wind and/or air pressure are selected — stations that only report water level or flow are skipped automatically.
• Re-discovers stations automatically when you have sailed more than ~10 km, so the set of stations follows you along the coast.
• Polls each station's JSON feed (no HTML scraping needed — same service the ViVa app uses) and publishes deltas in SI units.
• Watches for trouble and raises Signal K notifications:
  • Wind rise — average wind increased more than N m/s within a window
  • Wind shift — direction changed more than N degrees within a window
  • Pressure drop — pressure fell more than N hPa within a window

Published paths

For each station, under environment.observations.viva.<station>.:

| Path suffix | ViVa sample | Units | |----------------------|---------------|-------| | wind.averageSpeed | Medelvind | m/s | | wind.gust | Byvind | m/s | | wind.directionTrue | Heading field | rad | | pressure | Lufttryck | Pa | | temperature | Lufttemp | K | | water.temperature | Vattentemp | K | | water.level | Vattenstånd | m | | distance | — (great-circle distance from vessel to station, recalculated every poll) | m |

Example: environment.observations.viva.bonan.wind.averageSpeed

Live data in the Signal K Data Browser (here from Vinga and Svenska Högarna):

Alarms are published as standard Signal K notifications, e.g. notifications.environment.observations.viva.bonan.pressureDrop with state: "alert" and method: ["visual", "sound"], and cleared with state: "normal" when conditions ease (with a small hysteresis to avoid flapping). Any notification-aware app — KIP, WilhelmSK, the server's built-in alarm handling — will show and sound them.

Configuration

In the Signal K admin UI under Server → Plugin Config → Sjöfartsverket ViVa observations:

| Setting | Default | Notes | |--------------------|---------|---------------------------------------------------| | Poll interval | 60 s | ViVa stations update roughly every 1–10 minutes | | Search radius | 50 km | Around current vessel position | | Max stations | 3 | Nearest qualifying stations | | Extra station IDs | — | Always followed, regardless of distance | | Fallback position | — | Used when there is no GPS position — handy at the dock or for testing | | Meteo targets | on | Publish stations as meteo.* contexts for chartplotters (see below) | | Alarm chart notes | on | Place a note at the station when an alarm is active (see below) | | Wind rise alarm | 5 m/s / 30 min | | | Wind shift alarm | 45° / 30 min | | | Pressure drop alarm| 2 hPa / 120 min | ≥ 1 hPa/h sustained usually means real weather coming — tune to taste |

Alarm windows need at least half the window of collected history before they can fire, so you won't get spurious alarms right after startup.

Finding station IDs

Station list with IDs and positions:

https://services.viva.sjofartsverket.se:8080/output/vivaoutputservice.svc/vivastation/

Single station (this is what the plugin polls):

https://services.viva.sjofartsverket.se:8080/output/vivaoutputservice.svc/vivastation/33

Freeboard-SK: stations and alarms on the chart

Two optional features (both on by default) put the stations on the chart:

• Weather station targets — each station is also published as a Signal K meteo.* context with its position, name and observations. Freeboard-SK shows these as windsock icons on the map; tap one to see its current wind, direction and temperature.
• Alarm notes — when an alarm fires (wind rise, wind shift, pressure drop), the plugin places a chart note ("⚠ Vinga") at the station position with the alarm text, and removes it when the alarm clears. Requires a resources provider on the server (the bundled resources-provider plugin — enabled by default on recent servers). Tap the marker in Freeboard-SK to read what happened.

Freeboard-SK setup checklist

The windsocks are easy to lose to a display toggle — if they don't show, walk through this list:

1. Settings → Signal K tab: tick Weather (Meteo) under "Filter Stream data".
2. Same place: keep Max. distance from vessel at None if the vessel has no GPS position — with a distance set, Freeboard cannot compute distances and hides all targets.
3. Map display: in the "⋯" menu on the map toolbar, make sure Show Vessels is on — weather stations are drawn on the same layer as AIS vessels and hide together with them (an eye-with-slash icon on the map means display layers are hidden).
4. Keep Show Notes on to see the ⚠ alarm notes.
5. Diagnostic: the ☰ menu → Weather lists all weather stations Freeboard receives — if your stations are in the list but not on the map, it is one of the display toggles above.

The windsock icon size is currently fixed in Freeboard-SK; there is an open feature request for scalable wind-barb symbols: freeboard-sk#490.

Testing the alarms

Real alarms need real weather, but you can verify the whole chain in minutes by temporarily lowering the thresholds in the plugin config — e.g. wind rise 0.1 m/s / 2 min and pressure drop 0.1 hPa / 5 min. Normal measurement jitter will then raise alarms within a few polls: check for notifications.environment.observations.viva.* paths in the Data Browser, an alert in KIP/Freeboard-SK, and the ⚠ note at the station on the chart. Alarms clear with hysteresis (at 80 % of the threshold), so expect them to come and go. Restore the thresholds afterwards.

Visualization

• KIP: add gauges/wind steering displays on the environment.observations.viva.* paths — units and station names come from the published meta.
• History/graphs: pair with signalk-to-influxdb2 + Grafana (great for watching the pressure trend), or KIP's built-in charts.

Install

Install signalk-viva from the Signal K App Store (admin UI → Appstore), or from npm:

npm install signalk-viva

or from source:

cd ~/.signalk/node_modules
git clone https://github.com/theseal666/signalk-viva-plugin.git signalk-viva

then restart the Signal K server and enable the plugin. Requires Node 18+ (uses the built-in fetch).

Data source

Data comes from Sjöfartsverket's ViVa system via its public JSON service. The service is unofficial/undocumented, so be gentle with poll intervals and expect occasional format changes.