geocore 0.10.2

Geospatial data structures (points, geometry, features, meta) and parsers (GeoJSON, WKT) for Dart.

example/geocore_example.dart

// Copyright (c) 2020-2024 Navibyte (https://navibyte.com). All rights reserved.
// Use of this source code is governed by a “BSD-3-Clause”-style license that is
// specified in the LICENSE file.
//
// Docs: https://github.com/navibyte/geospatial

// NOTE : lint rules disabled for the purpose of making sample code readable
//
// ignore_for_file: avoid_print, avoid_redundant_argument_values
// ignore_for_file: cascade_invocations, unused_local_variable
// ignore_for_file: prefer_const_constructors
// ignore_for_file: prefer_const_literals_to_create_immutables

import 'package:equatable/equatable.dart';

import 'package:geocore/geocore.dart';

/*
To test run this from command line: 

dart example/geocore_example.dart
*/

void main() {
  // configure Equatable to apply toString() default impls
  EquatableConfig.stringify = true;

  // call simple demos
  _parseGeoJSON();
  _readmeIntro();

  print('\nWrite Point values as string');
  _pointValuesAsString();

  print('\nWrite Point to different formats');
  _pointToGeoJsonAndWKT();

  print('\nFeatureCollection as GeoJSON');
  _geoJsonFeatureCollection();
}

void _parseGeoJSON() {
  print('Parse GeoJSON sample data.');

  // sample GeoJSON data
  const sample = '''
    {
      "type": "FeatureCollection",
      "features": [
        {
          "type": "Feature",
          "id": "ROG",
          "geometry": {
            "type": "Point",
            "coordinates": [-0.0014, 51.4778, 45.0]  
          },
          "properties": {
            "title": "Royal Observatory",
            "place": "Greenwich",
            "city": "London",
            "isMuseum": true,
            "code": "000",
            "founded": 1675,
            "prime": "1884-10-22", 
            "measure": 5.79
          }
        }  
      ]
    }
  ''';

  // parse FeatureCollection using a GeoJSON parser with geographic coordinates
  final format = GeoJSON();
  final parser = format.parserGeographic(geographicPoints);
  final fc = parser.featureCollection(sample);

  // loop through features and print id, geometry and properties for each
  for (final f in fc.features) {
    print('Feature with id: ${f.id}');
    print('  geometry: ${f.geometry}');
    print('  properties:');
    for (final key in f.properties.keys) {
      print('    $key: ${f.properties[key]}');
    }
  }
}

void _readmeIntro() {
  // Some samples for README
  //    (https://github.com/navibyte/geospatial/tree/main/dart/geocore).
  // Note that following samples are just created, not used, even printed.

  // -----------

  // Spatial bounds

  Bounds.of(min: Point2(x: 10.1, y: 10.1), max: Point2(x: 20.2, y: 20.2));
  Bounds.of(min: Point3i(x: 10, y: 10, z: 3), max: Point3i(x: 20, y: 20, z: 5));
  GeoBounds.bboxLonLat(-20.3, 50.2, 20.5, 60.9);

  // A feature (a geospatial entity) contains an id, a geometry and properties:

  Feature(
    id: 'ROG',
    geometry: GeoPoint3(lon: -0.0014, lat: 51.4778, elev: 45.0),
    properties: {
      'place': 'Greenwich',
      'city': 'London',
    },
  );

  // Parsing GeoJSON data.

  final geoJsonParser = GeoJSON().parserGeographic(GeoPoint3.coordinates);
  geoJsonParser.feature(
    '''
    {
      "type": "Feature",
      "id": "ROG",
      "geometry": {
        "type": "Point",
        "coordinates": [-0.0014, 51.4778, 45.0]  
      },
      "properties": {
        "place": "Greenwich",
        "city": "London"
      }
    }  
  ''',
  );

  // Parsing WKT data.

  // Parse using specific point factories for coordinates with and without M
  final wktParser = WKT().parser(Point2.coordinates, Point2m.coordinates);
  wktParser.parse('POINT (100.0 200.0)'); // => Point2;
  wktParser.parse('POINT M (100.0 200.0 5.0)'); // => Point2m;

  // Projected (or cartesian) coordinates (Point2, Point2m, Point3 or Point3m)
  WKT().parserProjected().parse('LINESTRING (200.1 500.9, 210.2 510.4)');

  // Geographic coordinates (GeoPoint2, GeoPoint2m, GeoPoint3 or GeoPoint3m)
  WKT().parserGeographic().parse(
        'POLYGON ((40 15, 50 50, 15 45, 10 15, 40 15),'
        ' (25 25, 25 40, 35 30, 25 25))',
      );

  // -----------

  // Projected point with X, Y and Z coordinates in two ways.
  Point3(x: 708221.0, y: 5707225.0, z: 45.0);
  Point3.xyz(708221.0, 5707225.0, 45.0);

  // The same point created from `Iterable<num>`.
  Point3.from([708221.0, 5707225.0, 45.0]);

  // The same point parsed from WKT compatible text.
  // Actually WKT representation would be : "POINT (708221.0 5707225.0 45.0)",
  // but this parser takes only coordinate data between paranthesis.
  Point3.parse('708221.0 5707225.0 45.0');

  // The `parse` method throws when text is invalid, but `tryParse` returns null
  // in such case. This can be utilized for fallbacks.
  Point3.tryParse('nop') ?? Point3.parse('708221.0 5707225.0 45.0');

  // The same point parsed using the WKT parser for projected geometries.
  // Here `wktProjected` is a global constant for a WKT factory implementation.
  WKT().parserProjected().parse('POINT Z (708221.0 5707225.0 45.0)');

  // -----------

  // A sample point with x, y, z and m coordinates.
  final source = Point3m.xyzm(708221.0, 5707225.0, 45.0, 123.0);

  // Return new points of the same type by changing only some coordinate values.
  source.copyWith(m: 150.0);
  source.copyWith(x: 708221.7, z: 46.2);

  // Returns a point of the same type, but no previous values are preserved
  // (result here is Point3m.xyzm(1.0, 2.0, 3.0, 0.0)) with default 0.0 for m).
  source.newWith(x: 1.0, y: 2.0, z: 3.0);

  // This returns also Point3m.xyzm(1.0, 2.0, 3.0, 0.0)).
  source.newFrom([1.0, 2.0, 3.0, 0.0]);

  // -----------

  // Geographic point with longitude, latitude, elevation and measure.
  GeoPoint3m(lon: -0.0014, lat: 51.4778, elev: 45.0, m: 123.0);
  GeoPoint3m.lonLatElevM(-0.0014, 51.4778, 45.0, 123.0);

  // Someone might want to represent latitude before longitude, it's fine too.
  GeoPoint3m.latLonElevM(51.4778, -0.0014, 45.0, 123.0);

  // When creating from value array, the order is: lon, lat, elev, m.
  GeoPoint3m.from([-0.0014, 51.4778, 45.0, 123.0]);

  // Also here it's possible to parse from WKT compatible text.
  GeoPoint3m.parse('-0.0014 51.4778 45.0 123.0');

  // The WKT parser for geographic coordinates parses full representations.
  WKT().parserGeographic().parse('POINT ZM (-0.0014 51.4778 45.0 123.0)');

  // -----------

  // A point series of `Point2` composed of list of points that are of `Point2`
  // or it's sub classes.
  PointSeries<Point2>.from([
    Point2(x: 10.0, y: 10.0),
    Point2(x: 20.0, y: 20.0),
    Point2m(x: 30.0, y: 30.0, m: 5.0),
    Point3(x: 40.0, y: 40.0, z: 40.0),
    Point3m(x: 50.0, y: 50.0, z: 50.0, m: 5.0),
  ]);

  // Making a point series of `Point3` from a list of a list of nums.
  PointSeries.make(
    // three points each with x, y and z coordinates
    [
      [10.0, 11.0, 12.0],
      [20.0, 21.0, 22.0],
      [30.0, 31.0, 32.0],
    ],
    // This is `PointFactory` that converts `Iterable<num>` to a point instance,
    // in this example using a factory creating `Point3` instances.
    Point3.coordinates,
  );

  // Parsing a point series of `GeoPoint` from WKT compatible text with
  // `GeoPoint3` as a concrete point class.
  PointSeries<GeoPoint>.parse(
    '10.0 11.0 12.0, 20.0 21.0 22.0, 30.0 31.0 32.0',
    GeoPoint3.coordinates,
  );

  // -----------

  // This makes a a line string of `Point3m` from a list of points.
  LineString.make(
    [
      [10.0, 11.0, 12.0, 5.1],
      [20.0, 21.0, 22.0, 5.2],
      [30.0, 31.0, 32.0, 5.3],
    ],
    Point3m.coordinates,
  );

  // Using the WKT factory produces the same result as the previous sample.
  WKT().parserProjected().parse<Point3m>(
        'LINESTRING ZM(10.0 11.0 12.0 5.1, 20.0 21.0'
        ' 22.0 5.2, 30.0 31.0 32.0 5.3)',
      );

  // Also this sample, parsing from WKT compatible text, gives the same result.
  LineString.parse(
    '10.0 11.0 12.0 5.1, 20.0 21.0 22.0 5.2, 30.0 31.0 32.0 5.3',
    Point3m.coordinates,
  );

  // -----------

  // Making a polygon of `GeoPoint2` from a list of a list of a list of nums:
  Polygon.make(
    [
      // this is an exterior boundary or an outer ring
      [
        [35, 10],
        [45, 45],
        [15, 40],
        [10, 20],
        [35, 10],
      ],
      // this is an interior boundary or an inner ring representing a hole
      [
        [20, 30],
        [35, 35],
        [30, 20],
        [20, 30],
      ],
    ],
    GeoPoint2.coordinates,
  );

  // The same polygon geometry as above, but parsed from a WKT compatible text.
  Polygon.parse(
    '(35 10, 45 45, 15 40, 10 20, 35 10) (20 30, 35 35, 30 20, 20 30)',
    GeoPoint2.coordinates,
  );

  // -----------

  // A multi point of `GeoPoint2` with four lon-lat points.
  MultiPoint.parse('10 40, 40 30, 20 20, 30 10', GeoPoint2.coordinates);

  // A multi line string of `Point2` with two line strings.
  MultiLineString.parse(
    '(10 10, 20 20, 10 40), (40 40, 30 30, 40 20, 30 10)',
    Point2.coordinates,
  );

  // A multi polygon of `GeoPoint2` with two polygon (both with exterior
  // boundary without holes).
  MultiPolygon.parse(
    '((30 20, 45 40, 10 40, 30 20)), ((15 5, 40 10, 10 20, 5 10, 15 5))',
    GeoPoint2.coordinates,
  );

  // -----------

  // A geometry collection can contain any other geometry types. Items for such
  // a collection can be constructed using different ways.
  GeometryCollection([
    // A point with integer values using a constructor with named parameters.
    Point2(x: 40, y: 10),
    // A line string made from a list of points (each a list of nums).
    LineString.make(
      [
        [10, 10],
        [20, 20],
        [10, 40],
      ],
      Point2.coordinates,
    ),
    // A polygon parsed from WKT compatible text.
    Polygon.parse('(40 40, 20 45, 45 30, 40 40)', Point2.coordinates),
  ]);

  // A geometry collection can also be parsed from WKT text.
  WKT().parserProjected().parse<Point2>(
    '''
      GEOMETRYCOLLECTION (
        POINT (40 10),
        LINESTRING (10 10, 20 20, 10 40),
        POLYGON ((40 40, 20 45, 45 30, 40 40)))
      ''',
  );

  // -----------

  // Bounds (2D) or bounding box from minimum and maximum 2D projected points.
  Bounds.of(min: Point2(x: 10.0, y: 10.0), max: Point2(x: 20.0, y: 20.0));

  // Bounds (3D) made from a list of list of nums.
  Bounds.make(
    [
      [10.0, 10.0, 10.0],
      [20.0, 20.0, 20.0],
    ],
    Point3.coordinates,
  );

  // Bounds (3D with measure) parsed from WKT compatible text.
  Bounds.parse('10.0 10.0 10.0 5.0, 20.0 20.0 20.0 5.0', Point3m.coordinates);

  // -----------

  // Geographical bounds (-20.0 .. 20.0 in longitude, 50.0 .. 60.0 in latitude).
  GeoBounds.bboxLonLat(-20.0, 50.0, 20.0, 60.0);

  // The same bounds created of 2D geographic point instances.
  GeoBounds.of(
    min: GeoPoint2(lon: -20.0, lat: 50.0),
    max: GeoPoint2(lon: 20.0, lat: 60.0),
  );

  // -----------

  // Geospatial feature with an identification, a point geometry and properties.
  Feature(
    id: 'ROG',
    geometry: GeoPoint3(lon: -0.0014, lat: 51.4778, elev: 45.0),
    properties: {
      'title': 'Royal Observatory',
      'place': 'Greenwich',
      'city': 'London',
      'isMuseum': true,
      'code': '000',
      'founded': 1675,
      'prime': DateTime.utc(1884, 10, 22),
      'measure': 5.79,
    },
  );

  // -----------

  // get WKT format
  final format = WKT();

  // Parse projected points from WKT (result is different concrete classes).
  final parser1 = format.parserProjected();
  parser1.parse('POINT (100.0 200.0)'); // => Point2
  parser1.parse('POINT M (100.0 200.0 5.0)'); // => Point2m
  parser1.parse('POINT (100.0 200.0 300.0)'); // => Point3
  parser1.parse('POINT Z (100.0 200.0 300.0)'); // => Point3
  parser1.parse('POINT ZM (100.0 200.0 300.0 5.0)'); // => Point3m

  // Parse geographical line string, from (10.0 50.0) to (11.0 51.0).
  final parser2 = format.parser(GeoPoint2.coordinates);
  parser2.parse('LINESTRING (10.0 50.0, 11.0 51.0)');

  // Parse geographical polygon with a hole.
  final parser3 = format.parserGeographic();
  parser3.parse(
    'POLYGON ((40 15, 50 50, 15 45, 10 15, 40 15),'
    ' (25 25, 25 40, 35 30, 25 25))',
  );
}

void _pointValuesAsString() {
  // create a point (XYZ)
  final point = Point3(x: 10.123, y: 20.25, z: -30.95);

  // print value list as string
  print('Values: ${point.valuesAsString()}');
  print('Values (delimiter = ";"): ${point.valuesAsString(delimiter: ';')}');
}

void _pointToGeoJsonAndWKT() {
  // create a point (XYZ)
  final point = Point3(x: 10.123, y: 20.25, z: -30.95);

  // print with default format
  print('Default format: $point');
  print('Default format (decimals = 0): ${point.toStringAs(decimals: 0)}');

  // print with WKT format
  print('WKT format: ${point.toStringAs(format: WKT.geometry)}');

  // print with GeoJSON format
  print('GeoJSON format: ${point.toStringAs(format: GeoJSON.geometry)}');
  print(
    'GeoJSON (decimals = 1) format: ${point.toStringAs(
      format: GeoJSON.geometry,
      decimals: 1,
    )}',
  );
}

void _geoJsonFeatureCollection() {
  // feature text encoder for GeoJSON
  final encoder = GeoJSON.feature.encoder();

  // create a feature collection with two features
  final collection = FeatureCollection(
    bounds: GeoBounds.of(
      min: GeoPoint2(lon: -1.1, lat: -3.49),
      max: GeoPoint2(lon: 10.12, lat: 20.25),
    ),
    features: [
      Feature(
        id: 'fid-1',
        geometry: GeoPoint2(lon: 10.123, lat: 20.25),
        properties: {
          'foo': 100,
          'bar': 'this is property value',
        },
      ),
      Feature(
        geometry: LineString.make(
          [
            [-1.1, -1.1],
            [2.1, -2.5],
            [3.5, -3.49],
          ],
          GeoPoint2.coordinates,
          type: LineStringType.any,
          bounds: GeoBounds.make(
            [
              [-1.1, -3.49],
              [3.5, -1.1],
            ],
            GeoPoint2.coordinates,
          ),
        ),
        properties: {},
      ),
    ],
  );

  // write the feture collection to the content writer of the encoder
  // (encoder.writer is FeatureContent)
  collection.writeTo(encoder.writer);

  // print GeoJSON text
  print(encoder.toText());

  // the previous line prints (however without line breaks):
  //    {"type":"FeatureCollection",
  //     "bbox":[-1.1,-3.49,10.123,20.25],
  //     "features":[
  //        {"type":"Feature",
  //         "id":"fid-1",
  //         "geometry":{"type":"Point","coordinates":[10.123,20.25]},
  //         "properties":{"foo":100,"bar":"this is property value"}},
  //        {"type":"Feature",
  //         "geometry":{"type":"LineString",
  //                     "bbox":[-1.1,-3.49,3.5,-1.1],
  //                     "coordinates":[[-1.1,-1.1],[2.1,-2.5],[3.5,-3.49]]},
  //         "properties":{}}]}
}