geobase 0.2.0-dev.8 
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navibyte.comGeospatial coordinates (geographic and projected), projections and data writers (GeoJSON, WKT) for Dart.
// Copyright (c) 2020-2022 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
// ignore_for_file: avoid_print, cascade_invocations
// ignore_for_file: avoid_redundant_argument_values
import 'package:geobase/geobase.dart';
/*
To test run this from command line:
dart example/geobase_example.dart
*/
void main() {
// Coordinates
_geographicPosition();
_geographicBbox();
_projectedPosition();
_projectedBbox();
// WKT samples
_wktPointGeometry();
_wktPointGeometryWithZ();
_wktPointGeometryWithM();
_wktPointGeometryWithZM();
// GeoJSON samples
_geoJsonPointGeometry();
_geoJsonPointGeometryDecimals();
_geoJsonPointGeometryCustomStringBuffer();
_geoJsonLineStringGeometryWithBbox();
_geoJsonGeometryCollection();
_geoJsonFeature();
_geoJsonFeatureCollection();
// time objects
_intervalAndInstant();
// extents
_geoExtent();
// projection samples
_wgs84Projections();
// transform samples
_basicTransfroms();
}
void _geographicPosition() {
// Geographic position with longitude and latitude
const Geographic(lon: -0.0014, lat: 51.4778);
// Geographic position with longitude, latitude and elevation.
const Geographic(lon: -0.0014, lat: 51.4778, elev: 45.0);
// Geographic position with longitude, latitude, elevation and measure.
const Geographic(lon: -0.0014, lat: 51.4778, elev: 45.0, m: 123.0);
// The last sample also from num iterable or text.
Geographic.fromCoords(const [-0.0014, 51.4778, 45.0, 123.0]);
Geographic.fromText('-0.0014,51.4778,45.0,123.0');
Geographic.fromText('-0.0014 51.4778 45.0 123.0', delimiter: ' ');
}
void _geographicBbox() {
// Geographic bbox (-20.0 .. 20.0 in longitude, 50.0 .. 60.0 in latitude).
const GeoBox(west: -20.0, south: 50.0, east: 20.0, north: 60.0);
// Geographic bbox with limits on elevation coordinate too.
const GeoBox(
west: -20.0,
south: 50.0,
minElev: 100.0,
east: 20.0,
north: 60.0,
maxElev: 200.0,
);
// The last sample also from num iterable or text.
ProjBox.fromCoords(const [-20.0, 50.0, 100.0, 20.0, 60.0, 200.0]);
ProjBox.fromText('-20.0,50.0,100.0,20.0,60.0,200.0');
// Geographic bbox with limits on elevation and measure coordinates too.
const GeoBox(
west: -20.0,
south: 50.0,
minElev: 100.0,
minM: 5.0,
east: 20.0,
north: 60.0,
maxElev: 200.0,
maxM: 6.0,
);
}
void _projectedPosition() {
// Projected position with x and y.
const Projected(x: 708221.0, y: 5707225.0);
// Projected position with x, y and z.
const Projected(x: 708221.0, y: 5707225.0, z: 45.0);
// Projected position with x, y, z and m.
const Projected(x: 708221.0, y: 5707225.0, z: 45.0, m: 123.0);
// The last sample also from num iterable or text.
Projected.fromCoords(const [708221.0, 5707225.0, 45.0, 123.0]);
Projected.fromText('708221.0,5707225.0,45.0,123.0');
Projected.fromText('708221.0 5707225.0 45.0 123.0', delimiter: ' ');
}
void _projectedBbox() {
// Projected bbox with limits on x and y.
const ProjBox(minX: 10, minY: 10, maxX: 20, maxY: 20);
// Projected bbox with limits on x, y and z.
const ProjBox(minX: 10, minY: 10, minZ: 10, maxX: 20, maxY: 20, maxZ: 20);
// The last sample also from num iterable or text.
ProjBox.fromCoords(const [10, 10, 10, 20, 20, 20]);
ProjBox.fromText('10,10,10,20,20,20');
// Projected bbox with limits on x, y, z and m.
const ProjBox(
minX: 10,
minY: 10,
minZ: 10,
minM: 10,
maxX: 20,
maxY: 20,
maxZ: 20,
maxM: 20,
);
}
void _wktPointGeometry() {
// geometry writer for WKT
final writer = wktFormat().geometriesToText();
// prints:
// POINT(10.123 20.25)
print(
writer
..geometryWithPosition(
type: Geom.point,
coordinates: const Projected(x: 10.123, y: 20.25),
)
..toString(),
);
}
void _wktPointGeometryWithZ() {
// geometry writer for WKT
final writer = wktFormat().geometriesToText();
// prints:
// POINT Z(10.123 20.25 -30.95)
print(
writer
..geometryWithPosition(
type: Geom.point,
coordType: Coords.xyz,
coordinates: const Projected(x: 10.123, y: 20.25, z: -30.95),
)
..toString(),
);
}
void _wktPointGeometryWithM() {
// geometry writer for WKT
final writer = wktFormat().geometriesToText();
// prints:
// POINT M(10.123 20.25 -1.999)
print(
writer
..geometryWithPosition(
type: Geom.point,
coordType: Coords.xym,
coordinates: const Projected(x: 10.123, y: 20.25, m: -1.999),
)
..toString(),
);
}
void _wktPointGeometryWithZM() {
// geometry writer for WKT
final writer = wktFormat().geometriesToText();
// prints:
// POINT ZM(10.123 20.25 -30.95 -1.999)
print(
writer
..geometryWithPosition(
type: Geom.point,
coordType: Coords.xyzm,
coordinates:
const Geographic(lon: 10.123, lat: 20.25, elev: -30.95, m: -1.999),
)
..toString(),
);
}
void _geoJsonPointGeometry() {
// geometry writer for GeoJSON
final writer = geoJsonFormat().geometriesToText();
// prints:
// {"type":"Point","coordinates":[10.123,20.25]}
print(
writer
..geometryWithPosition(
type: Geom.point,
coordinates: const Geographic(lon: 10.123, lat: 20.25),
)
..toString(),
);
}
void _geoJsonPointGeometryDecimals() {
// geometry writer for GeoJSON, with number of decimals for text output set
final writer = geoJsonFormat().geometriesToText(decimals: 1);
// prints:
// {"type":"Point","coordinates":[10.1,20.3]}
print(
writer
..geometryWithPosition(
type: Geom.point,
coordinates: const Geographic(lon: 10.123, lat: 20.25),
)
..toString(),
);
}
void _geoJsonPointGeometryCustomStringBuffer() {
// geometry writer for GeoJSON with a custom string buffer
final buf = StringBuffer();
final writer = geoJsonFormat().geometriesToText(buffer: buf);
// write both directly to buffer and via geometry writer
buf.write('{"geometry":');
writer.geometryWithPosition(
type: Geom.point,
coordinates: const Geographic(lon: 10.123, lat: 20.25),
);
buf.write('}');
// prints:
// {"geometry":{"type":"Point","coordinates":[10.123,20.25]}}
print(buf.toString());
}
void _geoJsonLineStringGeometryWithBbox() {
// geometry writer for GeoJSON
final writer = geoJsonFormat().geometriesToText();
// prints (however without line breaks):
// {"type":"LineString",
// "bbox":[-1.1,-3.49,3.5,-1.1],
// "coordinates":[[-1.1,-1.1],[2.1,-2.5],[3.5,-3.49]]}
print(
writer
..geometryWithPositions1D(
type: Geom.lineString,
bbox: const GeoBox(west: -1.1, south: -3.49, east: 3.5, north: -1.1),
coordinates: [
const Geographic(lon: -1.1, lat: -1.1),
const Geographic(lon: 2.1, lat: -2.5),
const Geographic(lon: 3.5, lat: -3.49),
],
)
..toString(),
);
}
void _geoJsonGeometryCollection() {
// geometry writer for GeoJSON
final writer = geoJsonFormat().geometriesToText();
// prints (however without line breaks):
// {"type":"GeometryCollection",
// "geometries":[
// {"type":"Point",
// "coordinates":[10.123,20.25,-30.95]},
// {"type":"Polygon",
// "coordinates":[[[10.1,10.1],[5,9],[12,4],[10.1,10.1]]]}]}
print(
writer
..geometryCollection(
geometries: (gw) => gw
..geometryWithPosition(
type: Geom.point,
coordinates:
const Geographic(lon: 10.123, lat: 20.25, elev: -30.95),
coordType: Coords.xyz,
)
..geometryWithPositions2D(
type: Geom.polygon,
coordinates: [
[
const Geographic(lon: 10.1, lat: 10.1),
const Geographic(lon: 5, lat: 9),
const Geographic(lon: 12, lat: 4),
const Geographic(lon: 10.1, lat: 10.1)
],
],
),
)
..toString(),
);
}
void _geoJsonFeature() {
// feature writer for GeoJSON
final writer = geoJsonFormat().featuresToText();
// prints (however without line breaks):
// {"type":"Feature",
// "id":"fid-1",
// "geometry":
// {"type":"Point","coordinates":[10.123,20.25]},
// "properties":
// {"foo":100,"bar":"this is property value","baz":true}}
print(
writer
..feature(
id: 'fid-1',
geometries: (gw) => gw.geometryWithPosition(
type: Geom.point,
coordinates: const Geographic(lon: 10.123, lat: 20.25),
),
properties: {
'foo': 100,
'bar': 'this is property value',
'baz': true,
},
)
..toString(),
);
}
void _geoJsonFeatureCollection() {
// feature writer for GeoJSON
final writer = geoJsonFormat().featuresToText();
// 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":{}}]}
print(
writer
..featureCollection(
bbox: const GeoBox(
west: -1.1,
south: -3.49,
east: 10.123,
north: 20.25,
),
features: (fw) => fw
..feature(
id: 'fid-1',
geometries: (gw) => gw.geometryWithPosition(
type: Geom.point,
coordinates: const Geographic(lon: 10.123, lat: 20.25),
),
properties: {
'foo': 100,
'bar': 'this is property value',
},
)
..feature(
geometries: (gw) => gw.geometryWithPositions1D(
type: Geom.lineString,
bbox: const GeoBox(
west: -1.1,
south: -3.49,
east: 3.5,
north: -1.1,
),
coordinates: [
const Geographic(lon: -1.1, lat: -1.1),
const Geographic(lon: 2.1, lat: -2.5),
const Geographic(lon: 3.5, lat: -3.49),
],
),
),
)
..toString(),
);
}
void _intervalAndInstant() {
// Instants can be created from `DateTime` or parsed from text.
Instant(DateTime.utc(2020, 10, 31, 09, 30));
Instant.parse('2020-10-31 09:30Z');
// Intervals (open-started, open-ended, closed).
Interval.openStart(DateTime.utc(2020, 10, 31));
Interval.openEnd(DateTime.utc(2020, 10, 01));
Interval.closed(DateTime.utc(2020, 10, 01), DateTime.utc(2020, 10, 31));
// Same intervals parsed (by the "start/end" format, ".." for open limits).
Interval.parse('../2020-10-31');
Interval.parse('2020-10-01/..');
Interval.parse('2020-10-01/2020-10-31');
}
void _geoExtent() {
// An extent with spatial (WGS 84 longitude-latitude) and temporal parts.
GeoExtent.single(
crs: 'EPSG:4326',
bbox: const GeoBox(west: -20.0, south: 50.0, east: 20.0, north: 60.0),
interval: Interval.parse('../2020-10-31'),
);
// An extent with multiple spatial bounds and temporal interval segments.
GeoExtent.multi(
crs: 'EPSG:4326',
boxes: const [
GeoBox(west: -20.0, south: 50.0, east: 20.0, north: 60.0),
GeoBox(west: 40.0, south: 50.0, east: 60.0, north: 60.0),
],
intervals: [
Interval.parse('2020-10-01/2020-10-05'),
Interval.parse('2020-10-27/2020-10-31'),
],
);
}
void _wgs84Projections() {
// Built-in coordinate projections (currently only between WGS 84 and
// Web Mercator)
// Geographic (WGS 84 longitude-latitude) to Projected (WGS 84 Web Mercator)
final forward = wgs84ToWebMercator.forward();
final projected =
forward.project(const Geographic(lon: -0.0014, lat: 51.4778));
// Projected (WGS 84 Web Mercator) to Geographic (WGS 84 longitude-latitude)
final inverse = wgs84ToWebMercator.inverse();
final unprojected = inverse.project(projected);
print('$unprojected <=> $projected');
}
void _basicTransfroms() {
// Create a point and transform it with the built-in translation that returns
// `Position(x: 110.0, y: 220.0, z: 50.0, m: 1.25)` after transform.
print(
const Projected(x: 100.0, y: 200.0, z: 50.0, m: 1.25)
.transform(translatePosition(dx: 10.0, dy: 20.0)),
);
// Create a point and transform it with a custom translation that returns
// `Position(x: 110.0, y: 220.0, z: 50.0, m: 1.25)` after transform.
print(
const Projected(x: 100.0, y: 200.0, z: 50.0, m: 1.25)
.transform(_sampleFixedTranslate),
);
}
/// Translates X by 10.0 and Y by 20.0, other coordinates (Z and M) not changed.
T _sampleFixedTranslate<T extends Position>(T source) =>
source.copyWith(x: source[0] + 10.0, y: source[1] + 20.0) as T;Metadata
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Geospatial coordinates (geographic and projected), projections and data writers (GeoJSON, WKT) for Dart.
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