geodata

🌎 Geodata

Geodata is a library package for Dart and Flutter mobile developers to help on accessing OGC API and other geospatial data sources.

Currently the package has a partial (and still quite limited) support for OGC API Features services with functions to read metadata and feature items.

📦 Package

This is a Dart code package named geodata under the geospatial repository.

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

The package is associated with and depending on the datatools package containing non-geospatial Web API data structures and utilities that are extended and utilized by the geodata package to provide client-side access for geospatial APIs.

This package also utilizes the geocore package for geometry, metadata and feature data structures and GeoJSON parser, and the attributes package for non-geospatial data structures.

🔌 Installing

The package supports Dart null-safety and using it requires the latest SDK from a beta channel. However your package using it doesn't have to be migrated to null-safety yet.

Please see the official null-safety migration guide how to switch to the latest beta release of Dart or Flutter SDKs.

In the pubspec.yaml of your project add the dependency:

dependencies:
  geodata: ^0.4.1-nullsafety.0  

Please note that following dependencies used by geodata (indirect dependencies via datatools) are not yet migrated to null-safety or null-safety version is not depended from the datatools package:

• http
• http_parser

🗃️ Libraries

The package contains following mini-libraries:

Library	Description
model_base	Data structures for client access of generic Web API clients.
model_common	Data structures for client access of common geospatial Web APIs.
model_features	Data structures for client access of "geospatial features" Web APIs.
provider_common	An abstract client-side data provider to read common geospatial Web APIs.
provider_features	An abstract client-side data provider to read "geospatial features" APIs.
source_oapi_common	An abstract client-side data provider to read OGC API Common services.
source_oapi_features	A client-side data provider to read services conforming to OGC API Features.

For example to access a mini library you should use an import like:

import 'package:geodata/source_oapi_features.dart';

To use all libraries of the package:

import 'package:geodata/geodata.dart';

⌨️ Usage

An example how to setup an API client and a provider for OGC API Features service.

Imports:

import 'package:datatools/datatools.dart';
import 'package:geodata/geodata.dart';

Setting up an API client and a feature provider:

// Create an API client accessing HTTP endpoints.
final client = HttpApiClient.endpoints([
  Endpoint.url(baseURL),
]);

// Create a feature provider for OGC API Features (OAPIF).
final provider = FeatureProviderOAPIF.client(client);

Now it's possible to access metadata (the provider implementation calls a landing page or '/', '/conformance' and '/collections' resources under a base URL and combines all metadata fetched):

// Read metadata 
final meta = await provider.meta();

// do something with meta data accessed

Fetching items (or features of a OGC API Features service) as paged sets:

// Get feature resource for a collection by id
final resource = await provider.collection(collectionId);

// fetch feature items as paged results with max 10 features on one query
final items1 = await resource.itemsPaged(FeatureFilter(limit: 10));

// do something with feature items fetched

// check for next set (of max 10 features) and fetch it too if available
if (items1.hasNext) {
  final items2 = await items1.next();

  // do something with next set of feature items fetched
}

Please see full example code for more details.

🏡 Authors

This project is authored by Navibyte.

More information and other links are available at the geospatial repository from GitHub.

©️ License

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

Please see the LICENSE.