Geojson #

Utilities to work with geojson data in Dart.

Example #

import 'dart:io';
import 'package:geojson/geojson.dart';

void main() async {
  multipolygons();
  lines();
}

void multipolygons() async {
  final file = File("lakes_of_europe.geojson");
  final features = await featuresFromGeoJsonFile(file, nameProperty: "label");
  for (final feature in features.collection) {
    final geom = feature.geometry as MultiPolygon;
    for (final polygon in geom.polygons) {
      print("Polygon ${polygon.name}");
      for (final geoSerie in polygon.geoSeries) {
        print("- ${geoSerie.geoPoints.length} geopoints");
      }
    }
  }
}

void lines() async {
  final file = File("railroads_of_north_america.geojson");
  final features = await featuresFromGeoJsonFile(file);
  for (final feature in features.collection) {
    print("${feature.geometry.geoSerie.name}: " +
        "${feature.geometry.geoSerie.geoPoints.length} geopoints");
  }
}

Api #

featuresFromGeoJson: get a FeaturesCollection from geojson string data. Parameters:

• data: a string with the geojson data, required
• nameProperty: the property used for the geoserie name, automaticaly set if null
• verbose: print data if true

featuresFromGeoJsonFile: get a FeaturesCollection from a geojson file. Parameters:

• file: the file to load, required
• nameProperty: the property used for the geoserie name, automaticaly set if null
• verbose: print data if true

Supported geojson features #

All the data structures use GeoPoint and GeoSerie from the GeoPoint package to store the geometry data. Data structures used:

FeatureCollection:

• String name
• List<Feature> collection

Feature:

• FeatureType type: one of FeatureType.point, FeatureType.multipoint, FeatureType.line, FeatureType.multiline, FeatureType.polygon, FeatureType.multipolygon
• Map<String, dynamic> properties: the json properties of the feature
• dynamic geometry: the geometry data, depends on the feature type, see below

Point:

• String name
• GeoPoint geoPoint: the geometry data

MultiPoint:

• String name
• GeoSerie geoSerie: the geometry data: this will produce a geoSerie of type GeoSerieType.group

Line:

• String name
• GeoSerie geoSerie: the geometry data: this will produce a geoSerie of type GeoSerieType.line

MultiLine:

• String name
• List<Line> lines

Polygon:

• String name
• List<GeoSerie> geoSeries: the geometry data: this will produce a list of geoSerie of type GeoSerieType.polygon*

MultiPolygon:

• String name
• List<Polygon> polygons

Note: none of the parameters is final for all of these data structures