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EncDotNet.S100.DynamicSources.Nmea

EncDotNet.S100.DynamicSources.Nmea shows the ship's own wind, water and air temperature and pressure from its NMEA 0183 instruments on a chart, next to forecasts and buoy observations. NmeaWeatherSource implements IDynamicFeatureSource from EncDotNet.S100.Core and reads sentences with EncDotNet.S100.Nmea; OwnShipWeatherPortrayal draws the feature with the code-defined portrayal toolkit in EncDotNet.S100.Portrayals and the weather styles' wind barbs. The library has no UI or Mapsui dependency. SoundCharts uses it.

Not for navigation.

Install

This package isn't published to NuGet. Reference the project directly:

<ProjectReference Include="path/to/src/EncDotNet.S100.DynamicSources.Nmea/EncDotNet.S100.DynamicSources.Nmea.csproj" />

Example: own-ship wind from a multiplexer

using EncDotNet.S100.DynamicSources.Nmea;
using EncDotNet.S100.Nmea;

await using var weather = new NmeaWeatherSource(new NmeaUdpLineSource(10110));
weather.Changed += (_, _) => Console.WriteLine(weather.Current?.TrueWind);

// Optional: where own ship is drawn, and the motion to use when the stream has none.
weather.UpdateOwnShip(new OwnShipReference(position, heading, cog, sog, DateTimeOffset.UtcNow));

weather.Start(); // reads in the background, retrying after a failure

A host that already reads an NMEA stream passes no input and calls ProcessLine for each line. ReadToEndAsync reads an input once, for a replay.

The feature is a point at own ship, id ownship-weather, Kind weather.observation.ownship, with an OwnShipWeather under the weather attribute (NmeaWeatherSource.GetWeather).

True wind

Best first; OwnShipWeather.TrueWindSource says which:

  1. MWD: the instruments' own true direction and speed (a magnetic-only direction is turned true with the variation from HDG or RMC).
  2. Derived from relative wind (MWV R), the heading and the speed and course over the ground: the wind a buoy or forecast reports, so the barbs compare like with like.
  3. MWV T, turned into a direction with the heading.
  4. Derived from relative wind, the heading and the speed through the water (VHW).

The heading is HDT, else HDG with a variation, else VHW's true heading, else the host's. Speed and course over the ground are RMC or VTG, else the host's; below 0.2 kn the heading stands in for the course. Stream values older than 10 seconds aren't combined with the wind. When none of the four can be had, the feature carries the relative wind only (OwnShipWeather.IsRelativeOnly): it's drawn grey from heading plus the relative angle when the heading is known, and labelled Rel. wind.

Drawing

OwnShipWeatherPortrayal draws a small ring 8 mm right of and above own ship, so it clears the own-ship symbol, with the WMO barb (pennants 50 kn, full barbs 10 kn, half barbs 5 kn) growing from it into the wind, rotated in the geographic frame, and labels for the wind (200° 14 kn) and water temperature (Water 12.4 °C). The barb is picked with WindBarbSymbols.For at own ship's latitude: southern-hemisphere barbs (WXBARBS*) south of the equator, northern ones (WXBARBN*) on and north of it, as for gridded and NDBC barbs. Register a PortrayedDynamicFeatureRenderer over OwnShipWeatherPortrayal.Instance under the renderer key weather.observation.ownship (see EncDotNet.S100.Renderers.Mapsui). The source's metadata places it on S-98 OtherChartOverlays at within-plane priority 110, above NDBC observations.

Main entry points

Type Purpose
NmeaWeatherSource The IDynamicFeatureSource and IDynamicFeatureDescriber. Keeps the latest value of each sentence, drops values after 1 minute without an update, publishes at most once a second, and counts accepted and rejected lines.
NmeaWeatherSourceOptions Id, display name, motion age, drop age, publish interval, retry delay, parse options.
OwnShipWeather / OwnShipReference The weather at own ship; the host's own-ship fix.
OwnShipWeatherPortrayal The glyph as drawing instructions. Implements IDynamicFeaturePortrayal.
NmeaWeatherFormatter The pick-report rows (true wind and its basis, relative wind, heading, temperatures, pressure, update time) and chart labels.

See also

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