Update concepts
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Tim Schaub
@@ -6,27 +6,34 @@ layout: doc.hbs
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# Basic Concepts
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## Map
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The core component of OpenLayers is the map (`Map`). It is rendered to a `target` container (e.g. a `div` element on the web page that contains the map). All map properties can either be configured at construction time, or by using setter methods, e.g. `setTarget()`.
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The core component of OpenLayers is the map (`ol/Map`). It is rendered to a `target` container (e.g. a `div` element on the web page that contains the map). All map properties can either be configured at construction time, or by using setter methods, e.g. `setTarget()`.
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The markup below could be used to create a `<div>` that contains your map.
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```xml
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<div id="map" style="width: 100%, height: 400px"></div>
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<script>
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import Map from 'ol/Map';
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```
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var map = new Map({target: 'map'});
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</script>
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The script below constructs a map that is rendered in the `<div>` above, using the `map` id of the element as a selector.
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```js
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import Map from 'ol/Map';
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var map = new Map({target: 'map'});
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```
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## View
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`Map` is not responsible for things like center, zoom level and projection of the map. Instead, these are properties of a `View` instance.
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The map is not responsible for things like center, zoom level and projection of the map. Instead, these are properties of a `ol/View` instance.
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```js
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import View from 'ol/View';
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import View from 'ol/View';
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map.setView(new View({
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center: [0, 0],
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zoom: 2
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}));
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map.setView(new View({
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center: [0, 0],
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zoom: 2
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}));
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```
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A `View` also has a `projection`. The projection determines the coordinate system of the `center` and the units for map resolution calculations. If not specified (like in the above snippet), the default projection is Spherical Mercator (EPSG:3857), with meters as map units.
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@@ -35,54 +42,49 @@ The `zoom` option is a convenient way to specify the map resolution. The availab
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## Source
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To get remote data for a layer, OpenLayers uses `source/Source` subclasses. These are available for free and commercial map tile services like OpenStreetMap or Bing, for OGC sources like WMS or WMTS, and for vector data in formats like GeoJSON or KML.
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To get remote data for a layer, OpenLayers uses `ol/source/Source` subclasses. These are available for free and commercial map tile services like OpenStreetMap or Bing, for OGC sources like WMS or WMTS, and for vector data in formats like GeoJSON or KML.
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```js
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import OSM from 'ol/source/OSM';
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import OSM from 'ol/source/OSM';
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var osmSource = OSM();
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var osmSource = OSM();
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```
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## Layer
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A layer is a visual representation of data from a `source`. OpenLayers has four basic types of layers: `layer/Tile`, `layer/Image`, `layer/Vector` and `layer/VectorTile`.
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`layer/Tile` is for layer sources that provide pre-rendered, tiled images in grids that are organized by zoom levels for specific resolutions.
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A layer is a visual representation of data from a `source`. OpenLayers has four basic types of layers:
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`layer/Image` is for server rendered images that are available for arbitrary extents and resolutions.
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`layer/Vector` is for vector data that is rendered client-side.
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`layer/VectorTile` is for tiled vector data that is rendered client-side.
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* `ol/layer/Tile` - Renders sources that provide tiled images in grids that are organized by zoom levels for specific resolutions.
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* `ol/layer/Image` - Renders sources that provide map images at arbitrary extents and resolutions.
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* `ol/layer/Vector` - Renders vector data client-side.
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* `ol/layer/VectorTile` - Renders data that is provided as vector tiles.
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```js
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import TileLayer from 'ol/layer/Tile';
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import TileLayer from 'ol/layer/Tile';
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var osmLayer = new TileLayer({source: osmSource});
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map.addLayer(osmLayer);
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var osmLayer = new TileLayer({source: osmSource});
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map.addLayer(osmLayer);
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```
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## Putting it all together
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The above snippets can be combined into a single script that renders a map with a single tile layer:
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The above snippets can be conflated to a self contained map configuration with view and layers:
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```js
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import Map from 'ol/Map';
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import View from 'ol/View';
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import OSM from 'ol/source/OSM';
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import TileLayer from 'ol/source/Tile';
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```xml
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<div id="map" style="width: 100%, height: 400px"></div>
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<script>
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import Map from 'ol/Map';
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import View from 'ol/View';
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import OSM from 'ol/source/OSM';
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import TileLayer from 'ol/source/Tile';
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new Map({
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layers: [
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new TileLayer({source: new ol.source.OSM()})
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],
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view: new View({
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center: [0, 0],
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zoom: 2
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}),
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target: 'map'
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});
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</script>
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new Map({
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layers: [
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new TileLayer({source: new OSM()})
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],
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view: new View({
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center: [0, 0],
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zoom: 2
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}),
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target: 'map'
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});
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```
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