geocore 0.3.0-nullsafety.0

Geospatial data structures (features, geometry and metadata) and utilities (GeoJSON parser) for Dart.

Geospatial - geocore

Geospatial data structures (features, geometry and metadata) and utilities (GeoJSON parser) for Dart for Dart and Flutter mobile developers.

This package is at the alpha-stage, breaking changes are possible.

This is a Dart code package named geocore under the geospatial repository. The package supports Dart null-safety.

Installing

The package is designed null-safety in mind and requires SDK from beta channel:

environment:
  sdk: '>=2.12.0-0 <3.0.0'

More information about how to switch to the latest beta release of Dart or Flutter SDKs is available in the official null-safety migration guide. Please consult it first about null-safety.

Dependencies defined in the pubspec.yaml when using the package:

dependencies:
  geocore: ^0.3.0-nullsafety.0

All dependencies used by geocore are also ready for null-safety!

Parsing GeoJSON data

The GeoJSON format supports encoding of geographic data structures. Below is an example with sample GeoJSON data and code to parse it.

Imports:

import 'package:geocore/parse_geojson.dart';

The sample code:

  // sample GeoJSON data
  const sample = '''
    {
      "type": "FeatureCollection",
      "features": [
        {
          "type": "Feature",
          "id": "greenwich",
          "geometry": {
            "type": "Point",
            "coordinates": [-0.0014, 51.4778, 45.0]  
          },
          "properties": {
            "title": "Royal Observatory",
            "place": "Greenwich",
            "city": "London"
          }
        }  
      ]
    }
  ''';

  // parse FeatureCollection using the default GeoJSON factory
  final fc = geoJSON.featureCollection(sample);

  // loop through features and print id, geometry and properties for each
  fc.features.forEach((f) {
    print('Feature with id: ${f.id}');
    print('  geometry: ${f.geometry}');
    print('  properties:');
    f.properties.forEach((key, value) => print('    $key: $value'));
  });

At this stage the package supports reading following GeoJSON elements:

• FeatureCollection
• Feature
• Point, LineString and Polygon
• MultiPoint, MultiLineString and MultiPolygon
• GeometryCollection

Using geospatial data structures

It's also possible to create feature, geometry and metadata structure by hand.

Please see example code for more information.

Some samples also below.

Imports:

import 'package:geocore/geocore.dart';

The sample code:

  // Geospatial feature
  final f = Feature.of(
    id: 'greenwich',
    geometry: GeoPoint.from([-0.0014, 51.4778, 45.0]),
    properties: {
      'title': 'Royal Observatory',
      'place': 'Greenwich',
      'city': 'London',
    },
  );

  // Geographical points (lon-lat, lon-lat-m, lon-lat-elev, lon-lat-elev-m)
  final geo2 = GeoPoint2.lonLat(-0.0014, 51.4778);
  final geo2m = GeoPoint2m.lonLatM(-0.0014, 51.4778, 123.0);
  final geo3 = GeoPoint3.lonLatElev(-0.0014, 51.4778, 45.0);
  final geo3m = GeoPoint3m.lonLatElevM(-0.0014, 51.4778, 45.0, 123.0);

Features

Please note that this library is under developement, so classes and their features may still change.

The package contains geospatial data structures:

• Cartesian points using doubles: Point2, Point2m, Point3, Point3m
• Cartesian points using integers: Point2i, Point3i
• Geographical points: GeoPoint2, GeoPoint2m, GeoPoint3, GeoPoint3m
• Geographical camera: GeoCamera
• Geographical bounds: GeoBounds
• More geometries: LineString (any line string or linear ring), Polygon
• Multi geometry: MultiPoint, MultiLineString, MultiPolygon, GeometryCollection
• Custom Iterable interface and sub implementation: Series, SeriesView
• Geometry series: GeometrySeries, PointSeries, LineStringSeries, PolygonSeries
• Features: FeatureId, Feature, FeatureSeries, FeatureCollection
• Coordinate reference system (id): CRS class with two predefined identifiers
• Temporal coordinates: Instant, Interval
• Geospatial extent: Extent
• Web links: Link

An abstraction for parsing geospatial data:

/// A factory to create geospatial geometries and features from source data.
abstract class GeoFactory {
  const GeoFactory();

  /// Parses a geometry from a [data] object.
  Geometry geometry(dynamic data);

  /// Parses a feature from a [data] object.
  Feature feature(dynamic data);

  /// Parses a series of features from a [data] object.
  FeatureSeries featureSeries(dynamic data);

  /// Parses a feature collection from a [data] object.
  FeatureCollection featureCollection(dynamic data);
}

As described on an example earlier there is an implementation for this abstraction to support reading and parsing GeoJSON data.

Authors

This project is authored by Navibyte.

License

This project is licensed under the "BSD-3-Clause"-style license.

Please see the LICENSE.