Aus öffentlichen Paketdaten erstellte Orientierung.
Geobase ist ein umfassendes Dart-Paket zur Verarbeitung geospatialer Daten, einschließlich geometrischer Operationen, Geodäsieberechnungen, Kartenprojektionen, Tile-Schemata und Unterstützung für Vektorformate wie GeoJSON, WKT und WKB. Für den plattformübergreifenden Einsatz konzipiert, ermöglicht es präzise räumliche Berechnungen und Datenmanipulation auf Android, iOS, Web, macOS, Windows und Linux. Ideal für Entwickler, die Kartenanwendungen, Navigationswerkzeuge oder ortsbasierte Dienste erstellen, die überzeugende geospatiale Funktionalität erfordern.
Anwendungsfälle
Kartenanwendungen
Navigationsysteme
Standortbasierte Analyse
räumliche Datenverarbeitung
Geoinformationssysteme (GIS)
interaktive Web-Karten
Hauptmerkmale
Unterstützung für GeoJSON, WKT, WKB
Geodätische Distanz- und Flächenberechnungen
Mehrere Kartenprojektionen
Implementierungen des Kachelungsschemas
Geometrische Operationen (Vereinigung, Schnitt)
Plattformübergreifende Kompatibilität
Geeignet für
Entwickler, die GIS-Anwendungen erstellen
Mobile und Web-Mapping-Lösungen
Anwendungen, die genaue geospatial Mathematik benötigen
Backend-Dienste zur Verarbeitung räumlicher Daten
Echtzeit-Standortverfolgungssysteme
Hinweise
Erfordert Verständnis geospatialer Konzepte
Kann bei großen Datensätzen Leistungsbeeinträchtigungen verursachen
Beschränkte Dokumentation über die Kern-APIs hinaus
Am besten geeignet für fortgeschrittene Benutzer mit geospatialen Anforderungen
Nicht für Echtzeit-Streaming-Szenarien optimiert
Original-README
Originaler README-Schnappschuss aus dem verknüpften Quell-Repository. Aktuelle Inhalte finden Sie im Repository.
:compass: Geospatial tools for Dart
Geospatial data structures, tools and utilities for
Dart and Flutter - coordinates,
geometries, feature objects, metadata, spherical geodesy, projections, tiling
schemes, vector data models and formats, and geospatial Web APIs.
✨ New (2024-11-10): The stable release with ellipsoidal geodesy functions letting you calculate distances, bearings, destination positions and intermediate points along the Earth surface accurately.
✨ New (2024-07-26): The stable version 1.3.0 with centroid, polylabel, point-in-polygon and other cartesian 2D calculations enhanced - read more!
Geospatial data structures (coordinates, geometries, features, metadata), ellipsoidal and spherical geodesy, projections and tiling schemes. Vector data format support for GeoJSON, WKT and WKB.
Partially supported (conformance classes, queryables, features filter).
:keyboard: Sample code
Geodesy functions with geobase
Ellipsoidal and spherical geodesy functions to calculate distances etc.:
final greenwich = Geographic.parseDms(lat: '51°28′40″ N', lon: '0°00′05″ W');
final sydney = Geographic.parseDms(lat: '33.8688° S', lon: '151.2093° E');
// How to calculate distances using ellipsoidal Vincenty, spherical// great-circle and spherical rhumb line methods is shown first.// The distance along a geodesic on the ellipsoid surface (16983.3 km).
greenwich.vincenty().distanceTo(sydney);
// By default the WGS84 reference ellipsoid is used but this can be changed.
greenwich.vincenty(ellipsoid: Ellipsoid.GRS80).distanceTo(sydney);
// The distance along a spherical great-circle path (16987.9 km).
greenwich.spherical.distanceTo(sydney);
// The distance along a spherical rhumb line path (17669.8 km).
greenwich.rhumb.distanceTo(sydney);
// Also bearings, destination points and mid points (or intermediate points)// are provided for all methods, but below shown only for great-circle paths.// Destination point (10 km to bearing 61°): 51° 31.3′ N, 0° 07.5′ E
greenwich.spherical.initialBearingTo(sydney);
greenwich.spherical.finalBearingTo(sydney);
// Destination point: 51° 31.3′ N, 0° 07.5′ E
greenwich.spherical.destinationPoint(distance: 10000, bearing: 61.0);
// Midpoint: 28° 34.0′ N, 104° 41.6′ E
greenwich.spherical.midPointTo(sydney);
// Vincenty ellipsoidal geodesy functions provide also `inverse` and `direct`// methods to calculate shortest arcs along a geodesic on the ellipsoid. The// returned arc object contains origin and destination points, initial and// final bearings, and distance between points.
greenwich.vincenty().inverse(sydney);
greenwich.vincenty().direct(distance: 10000, bearing: 61.0);
Geospatial data structures with geobase
As a quick sample, this is how geometry objects with 2D coordinate are created
using geobase:
Geospatial feature and feature collections can be instantiated easily too:
// A geospatial feature collection (with two features):FeatureCollection([
Feature(
id: 'ROG',
// a point geometry with a position (lon, lat, elev)
geometry: Point.build([-0.0014, 51.4778, 45.0]),
properties: {
'title': 'Royal Observatory',
'city': 'London',
'isMuseum': true,
},
),
Feature(
id: 'TB',
// a point geometry with a position (lon, lat)
geometry: Point.build([-0.075406, 51.5055]),
properties: {
'title': 'Tower Bridge',
'built': 1886,
},
),
]);
GeoJSON, WKT and WKB formats are supported as input and output:
// Parse a geometry from GeoJSON text.final geometry = LineString.parse(
'{"type": "LineString", "coordinates": [[30,10],[10,30],[40,40]]}',
format: GeoJSON.geometry,
);
// Encode a geometry as GeoJSON text.print(geometry.toText(format: GeoJSON.geometry));
// Encode a geometry as WKT text.print(geometry.toText(format: WKT.geometry));
// Encode a geometry as WKB bytes.final bytes = geometry.toBytes(format: WKB.geometry);
// Decode a geometry from WKB bytes.LineString.decode(bytes, format: WKB.geometry);
A sample showing more deeply how to handle WKB and EWKB binary data:
// to get a sample point, first parse a 3D point from WKT encoded stringfinal p = Point.parse('POINT Z(-0.0014 51.4778 45)', format: WKT.geometry);
// to encode a geometry as WKB/EWKB use toBytes() or toBytesHex() methods// encode as standard WKB data (format: `WKB.geometry`), prints:// 01e9030000c7bab88d06f056bfb003e78c28bd49400000000000804640final wkbHex = p.toBytesHex(format: WKB.geometry);
print(wkbHex);
// encode as Extended WKB data (format: `WKB.geometryExtended`), prints:// 0101000080c7bab88d06f056bfb003e78c28bd49400000000000804640final ewkbHex = p.toBytesHex(format: WKB.geometryExtended);
print(ewkbHex);
// otherwise encoded data equals, but bytes for the geometry type varies// there are some helper methods to analyse WKB/EWKB bytes or hex strings// (decodeFlavor, decodeEndian, decodeSRID and versions with hex postfix)// prints: "WkbFlavor.standard - WkbFlavor.extended"print('${WKB.decodeFlavorHex(wkbHex)} - ${WKB.decodeFlavorHex(ewkbHex)}');
// when decoding WKB or EWKB data, a variant is detected automatically, so// both `WKB.geometry` and `WKB.geometryExtended` can be usedfinal pointFromWkb = Point.decodeHex(wkbHex, format: WKB.geometry);
final pointFromEwkb = Point.decodeHex(ewkbHex, format: WKB.geometry);
print(pointFromWkb.equals3D(pointFromEwkb)); // prints "true"// SRID can be encoded only on EWKB data, this sample prints:// 01010000a0e6100000c7bab88d06f056bfb003e78c28bd49400000000000804640final ewkbHexWithSRID =
p.toBytesHex(format: WKB.geometryExtended, crs: CoordRefSys.EPSG_4326);
print(ewkbHexWithSRID);
// if you have WKB or EWKB data, but not sure which, then you can fist check// a flavor and whether it contains SRID, prints: "SRID from EWKB data: 4326"if (WKB.decodeFlavorHex(ewkbHexWithSRID) == WkbFlavor.extended) {
final srid = WKB.decodeSRIDHex(ewkbHexWithSRID);
if (srid != null) {
print('SRID from EWKB data: $srid');
// after finding out CRS, an actual point can be decoded// Point.decodeHex(ewkbHexWithSRID, format: WKB.geometry);
}
}
Using Newline-delimited GeoJSON (or "GeoJSONL") is as easy as using the
standard GeoJSON:
/// a feature collection encoded as GeoJSONL and containing two features that/// are delimited by the newline character \nconst sample = '''
{"type":"Feature","id":"ROG","geometry":{"type":"Point","coordinates":[-0.0014,51.4778,45]},"properties":{"title":"Royal Observatory","place":"Greenwich"}}
{"type":"Feature","id":"TB","geometry":{"type":"Point","coordinates":[-0.075406,51.5055]},"properties":{"title":"Tower Bridge","built":1886}}
''';
// parse a FeatureCollection object using the decoder for the GeoJSONL formatfinal collection = FeatureCollection.parse(sample, format: GeoJSONL.feature);
// ... use features read and returned in a feature collection object ...// encode back to GeoJSONL dataprint(collection.toText(format: GeoJSONL.feature, decimals: 5));
Access GeoJSON resources with geodata
The geodata package has the following
diagram describing a decision flowchart how to select a client class to access
GeoJSON features:
Quick start code to access a Web API service conforming to OGC API Features:
// 1. Get a client instance for a Web API endpoint.final client = OGCAPIFeatures.http(endpoint: Uri.parse('...'));
// 2. Access/check metadata (meta, OpenAPI, conformance, collections) as needed.final conformance = await client.conformance();
if (!conformance.conformsToFeaturesCore(geoJSON: true)) {
return; // not conforming to core and GeoJSON - so return
}
// 3. Get a feature source for a specific collection.final source = await client.collection('my_collection');
// 4. Access (and check) metadata for this collection.final meta = await source.meta();
print('Collection title: ${meta.title}');
// 5. Access feature items.final items = await source.itemsAll(limit: 100);
// 6. Check response metadata.print('Timestamp: ${items.timeStamp}');
// 7. Get an iterable of feature objects.final features = items.collection.features;
// 8. Loop through features (each with id, properties and geometry)for (final feat in features) {
print('Feature ${feat.id} with geometry: ${feat.geometry}');
}
:rocket: Demos and samples
More guidance and code examples are provided on the
geospatial.navibyte.dev documentation site.
✨ See also the
Geospatial demos for Dart code
repository for demo and sample apps demonstrating the usage of
geobase and
geodata packages along with other topics.
Shows earthquakes fetched from the USGS web service on a basic map view. The demo uses both geobase and geodata packages for geospatial data accesss. Discusses also state management based on Riverpod. The map UI is based on the Google Maps Flutter plugin.
✨ The stable release with ellipsoidal geodesy functions letting you calculate distances, bearings, destination positions and intermediate points along the Earth surface accurately.
Proj4dart is a Dart library to transform point coordinates from one coordinate system to another, including datum transformations (Dart version of proj4js/proj4js).
