EncDotNet.S57 0.4.1

EncDotNet.S57

A .NET 10 library for reading and working with IHO S-57 Electronic Navigational Charts (ENCs) — the international standard for digital hydrographic data used in maritime navigation systems worldwide.

Features

• Parse S-57 .000 chart files into a strongly-typed domain model
• Access dataset metadata, feature records, vector/spatial records, and attributes
• Query features by S-57 object code (DEPARE, SOUNDG, LIGHTS, BOYLAT, etc.)
• Navigate chain-node topology: features → faces → edges → connected nodes
• Higher-level S57Chart model with indexed, typed feature and spatial record collections
• Apply incremental updates (.001, .002, …) to base charts
• Read exchange set catalogs (CATALOG.031) with geographic bounds
• Read full exchange sets with all referenced chart files
• Immutable data model using ImmutableArray<T> and ImmutableDictionary<K,V>

Installation

dotnet add package EncDotNet.S57

This package depends on EncDotNet.Iso8211 for ISO 8211 binary parsing (installed automatically).

Quick Start

Reading a Chart File

using EncDotNet.S57;

// Parse an S-57 chart file
var document = S57DocumentReader.ReadFromFile("US5CA11M.000");

// Access dataset metadata
Console.WriteLine($"Dataset: {document.DataSetIdentification?.DataSetName}");
Console.WriteLine($"Scale:   1:{document.DataSetParameters?.CompilationScale}");

// Coordinate multiplication factor — divide raw integers by this
// to get decimal degrees (typically 10,000,000)
int comf = document.CoordinateMultiplicationFactor;

// Query features by S-57 object code
var depthAreas = document.GetFeaturesByObjectCode(S57ObjectCode.DEPARE);

foreach (var feature in depthAreas)
{
    Console.WriteLine($"Depth Area {feature.RecordName} — {feature.Primitive}");

    // Feature attributes (e.g. DRVAL1, DRVAL2 for depth range)
    foreach (var attr in feature.Attributes)
    {
        Console.WriteLine($"  ATTL {attr.AttributeCode} = {attr.Value}");
    }

    // Follow spatial pointers to geometry
    foreach (var ptr in feature.SpatialPointers)
    {
        var vector = document.GetVectorRecord(ptr.Name);

        if (vector is not null)
        {
            foreach (var coord in vector.Coordinates2D)
            {
                double lon = coord.X / (double)comf;
                double lat = coord.Y / (double)comf;
                Console.WriteLine($"  ({lat:F6}, {lon:F6})");
            }
        }
    }
}

Higher-Level Chart Model

S57Chart provides indexed, strongly-typed access to features and spatial records:

using EncDotNet.S57.Charts;

var chart = S57Chart.FromFile("US5CA11M.000");

// Typed feature collections
Console.WriteLine($"Point features: {chart.PointFeatures.Length}");
Console.WriteLine($"Line features:  {chart.LineFeatures.Length}");
Console.WriteLine($"Area features:  {chart.AreaFeatures.Length}");

// Spatial record dictionaries (keyed by record name)
Console.WriteLine($"Edges:          {chart.Edges.Count}");
Console.WriteLine($"Connected nodes:{chart.ConnectedNodes.Count}");
Console.WriteLine($"Isolated nodes: {chart.IsolatedNodes.Count}");

Applying Incremental Updates

S-57 supports incremental updates distributed as .001, .002, etc. files:

var baseDoc = S57DocumentReader.ReadFromFile("chart.000");
var update  = S57DocumentReader.ReadFromFile("chart.001");

// Merge insert/delete/modify operations into the base document
var merged = baseDoc.ApplyChanges(update);

Reading an Exchange Set Catalog

Each S-57 exchange set contains a CATALOG.031 file listing all chart files and their geographic bounds:

using EncDotNet.S57.ExchangeSets;

var catalog = S57CatalogReader.ReadFromFile("ENC_ROOT/CATALOG.031");

foreach (var entry in catalog.Entries)
{
    Console.WriteLine($"{entry.FileName}");
    Console.WriteLine($"  Bounds: ({entry.SouthernmostLatitude}, {entry.WesternmostLongitude}) " +
                      $"to ({entry.NorthernmostLatitude}, {entry.EasternmostLongitude})");
}

Key Types

Core (Document-Level)

Charts (Higher-Level Model)

Exchange Sets

Background

IHO S-57 (Edition 3.1) is the International Hydrographic Organization's transfer standard for digital hydrographic data. It defines how nautical chart data — depth areas, soundings, buoys, lights, coastlines, and hundreds of other maritime features — is encoded into binary files using ISO/IEC 8211 as the container format.

S-57 uses a chain-node topology model where features reference spatial records (faces, edges, connected nodes, isolated nodes) to define their geometry. Raw coordinates are stored as integers and must be divided by the Coordinate Multiplication Factor (COMF) to get decimal degrees.

Related Packages

• EncDotNet.Iso8211 — The underlying ISO 8211 binary parser
• EncDotNet.Noaa — NOAA ENC product catalog client for downloading chart data

License

MIT — see LICENSE for details.