EncDotNet.S100.DynamicSources.Ndbc

EncDotNet.S100.DynamicSources.Ndbc shows NOAA National Data Buoy Center (NDBC) observations on a chart: the latest wind, waves, pressure and temperatures from the moored buoys and C-MAN stations in view. NdbcObservationSource implements IDynamicFeatureSource from EncDotNet.S100.Core, and NdbcStationPortrayal draws each station as a station-model glyph with the code-defined portrayal toolkit in EncDotNet.S100.Portrayals. 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.Ndbc/EncDotNet.S100.DynamicSources.Ndbc.csproj" />

Example: observations for the visible area

using EncDotNet.S100.DynamicSources.Ndbc;
using EncDotNet.S100.Pipelines;

using var http = new HttpClient();
http.DefaultRequestHeaders.UserAgent.ParseAdd("MyApp/1.0 (+https://example.org)");

await using var ndbc = new NdbcObservationSource(http);
ndbc.Changed += (_, _) => Console.WriteLine($"{ndbc.CurrentFeatures.Count} stations");

// South latitude, west longitude, north latitude, east longitude.
ndbc.UpdateArea(new BoundingBox(40.5, -71.5, 43.0, -69.5));
ndbc.Start(); // polls every 10 minutes; or call PollAsync on your own schedule

Each feature is a point at the station with Kind weather.observation.ndbc (or weather.observation.ndbc.stale), and its NdbcObservation under the observation attribute (NdbcObservationSource.GetObservation).

Main entry points

Type	Purpose
`NdbcObservationSource`	The `IDynamicFeatureSource`. Fetches the station table once a day and the head of each `realtime2/{station}.txt` file for the meteorological stations in the area plus a margin, every 10 minutes per station, with exponential backoff on errors. Nothing is fetched until `UpdateArea` sets an area, while the area is wider than 25°, or while `IsActive` is false. Marks observations older than 3 hours stale and drops them after 12. Also an `IDynamicFeatureDescriber`, so a pick report lists every value with its unit and the observation time.
`NdbcObservationSourceOptions`	Base address, paths, poll interval, ageing, backoff, margin, span gate, per-poll and concurrency limits, and the HTTP `Range` size.
`NdbcRealtimeParser` / `NdbcObservation`	The `realtime2` standard meteorological format: wind direction, speed and gust; wave height, dominant and average period and mean direction; pressure, air, water and dew-point temperature, visibility, pressure tendency and tide. `MM` is missing (`null`). `NdbcObservation.Combine` merges a station's newest rows, since buoys report waves less often than wind (half-hourly or hourly, against every 10 minutes).
`NdbcStationTable` / `NdbcStation`	The `activestations.xml` station table: ids, positions, types and whether a station reports meteorological data.
`NdbcStationPortrayal`	The station-model glyph as drawing instructions: a station marker, the weather styles' WMO wind barb rotated into the wind (the mirrored southern-hemisphere barb for a station south of the equator, through `WindBarbSymbols`), and the wave height as a label. Stale stations are grey. Implements `IDynamicFeaturePortrayal`.
`NdbcObservationFormatter`	The pick-report rows for an observation.

Draw the stations

The source's RendererKey is weather.observation.ndbc. With Mapsui, register a PortrayedDynamicFeatureRenderer over NdbcStationPortrayal.Instance under that key (see EncDotNet.S100.Renderers.Mapsui). Headless, pass NdbcStationPortrayal.Instance.Portray(feature) and a DynamicFeatureGeometryProvider to the Skia renderer. The source's metadata places it on the S-98 OtherChartOverlays plane at within-plane priority 100.

Network use

The files come from https://www.ndbc.noaa.gov/ (US government data, public domain). Each station request asks for the first 16 KiB of its file with an HTTP Range header, about a day of rows. NDBC answers with 206 Partial Content, so the last line is usually cut off; the parser skips it, and stops at rows older than 12 hours either way. Set a User-Agent that identifies your application on the HttpClient you pass in. The client stays yours to dispose.