GeoJSON

A .NET Standard implementation of GeoJSON (RFC 7946) for spatial data interchange: read and write features, and convert to/from the library's Geometry<T> types.

Supported capabilities

Capability	Supported
Read	Yes — GeoJson.DeserializeGeometry, GeoJson.LoadFromFile, GeoJsonFeatureSet.Parse / LoadAsync
Write	Yes — IGeoJsonGeometry.Serialize, GeoJson.SaveFeatures, GeoJsonFeatureSet.SaveAsync
Z coordinates	Yes (3rd position element, per RFC 7946)
M coordinates	Yes, as a non-standard 4D extension (Geometry<PointZM>)
GeometryCollection	No — conversion throws

Geometry types: Point, MultiPoint, LineString, MultiLineString, Polygon, MultiPolygon, plus Feature and FeatureCollection.

Coordinate reference system

Per RFC 7946 §4, GeoJSON coordinates are WGS 84 (longitude, latitude in decimal degrees), equivalent to urn:ogc:def:crs:OGC::CRS84. An optional third position element is height in meters. Conversion methods take an isLongitudeFirst flag and an srid so you can adapt to non-default inputs.

4D coordinate support (extension)

This implementation supports 4D coordinates (PointZM with measure) as an extension beyond RFC 7946. While RFC 7946 Section 3.1.1 states that implementations SHOULD NOT extend position arrays beyond 3 elements, this library provides 4D support for compatibility with systems that require measure values. This is provided as extra functionality and is not part of the GeoJSON standard.

Polygon rings (RFC 7946 section 3.1.6)

Rings MUST be closed — the first and last positions contain identical values:

{
  "type": "Polygon",
  "coordinates": [
    [[30, 10], [40, 40], [20, 40], [10, 20], [30, 10]]
  ]
}

Rings MUST follow the right-hand rule: external rings counterclockwise, holes clockwise. Maptor's Geometry<Point> uses the same orientation invariant, and GeoJsonPolygon / GeoJsonMultiPolygon provide a validation method:

var polygon = GeoJson.DeserializeGeometry(polygonJson) as GeoJsonPolygon;
var (isValid, errors) = polygon.ValidateRingOrientations();
if (!isValid)
{
    foreach (var error in errors)
        Console.WriteLine(error);
}

Usage

All types live in IRI.Maptor.Core.Spatial.GeoJsonFormat; the geometry extension methods live in IRI.Maptor.Extensions.

Reading

using IRI.Maptor.Core.Spatial.GeoJsonFormat;

// Read features from a .geojson file
IEnumerable<GeoJsonFeature> features = GeoJson.LoadFromFile("path/to/file.geojson");

// Deserialize a single geometry from a string
IGeoJsonGeometry? point = GeoJson.DeserializeGeometry("{\"type\":\"Point\",\"coordinates\":[30,10]}");

// Parse a FeatureCollection from a string
GeoJsonFeatureSet featureSet = GeoJsonFeatureSet.Parse(featureCollectionJson);

Writing

// Write a list of features to a file
GeoJson.SaveFeatures("output.geojson", features);

// Or save a feature set (async)
var set = new GeoJsonFeatureSet { Features = features.ToList(), TotalFeatures = features.Count() };
await set.SaveAsync("output.geojson", indented: true);

// Serialize a single geometry to a string
string json = point.Serialize(indented: true);

Converting GeoJSON to geometry

using IRI.Maptor.Core.Spatial.Primitives;

IGeoJsonGeometry geoJson = GeoJson.DeserializeGeometry("{\"type\":\"Point\",\"coordinates\":[30,10]}");

// Returns Geometry<Point>, Geometry<PointZ>, or Geometry<PointZM> based on coordinate dimensions
IGeometry geometry = geoJson.Parse(isLongitudeFirst: true, srid: 4326);

Converting geometry to GeoJSON

using IRI.Maptor.Extensions;
using IRI.Maptor.Core.Spatial.Primitives;

var point = Geometry<Point>.Create(30, 10);
IGeoJsonGeometry geoJsonPoint = point.AsGeoJson(isLongitudeFirst: true);

string json = geoJsonPoint.Serialize(indented: true);

Format details

Aspect	GeoJSON in Maptor
Coordinate system	Spec mandates WGS 84 (urn:ogc:def:crs:OGC::CRS84), longitude/latitude in degrees. Parse(isLongitudeFirst, srid) lets you set axis order and SRID; Maptor does not reproject or enforce WGS 84.
Z / M	Z (elevation) is part of the spec (3rd position element). M is a non-standard extension surfaced as Geometry<PointZM>; it is not part of RFC 7946 output.
Polygon rings	Right-hand rule — exterior CCW, holes CW (same as Geometry<Point>). The writer repeats the first vertex as the last to close each ring.
Serialization	System.Text.Json. Deserialize: GeoJson.DeserializeGeometry, GeoJsonFeatureSet.Parse, GeoJson.LoadFromFile. Serialize: IGeoJsonGeometry.Serialize, GeoJson.SaveFeatures, GeoJsonFeatureSet.SaveAsync.
Specification	GeoJSON — RFC 7946

Limitations

• AsGeoJson covers Point/MultiPoint/LineString/MultiLineString/Polygon/MultiPolygon. GeometryCollection and curve geometries are not supported and throw.
• Measure (M) values are a 4D extension and are not part of standard RFC 7946 output.

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