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Merge pull request #8546 from ahocevar/proj-faq

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Update projection FAQ for v5
This commit is contained in:
Andreas Hocevar
2018-08-27 08:14:28 +02:00
committed by GitHub
parent bb77fbe703 a0e72c7d42
commit bd9635f6ef
1 changed files with 10 additions and 11 deletions
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21
doc/faq.md
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@@ -5,7 +5,7 @@ layout: doc.hbs
# Frequently Asked Questions (FAQ)
Certain questions arise more often than others when users ask for help. This
Certain questions arise more often than others when users ask for help. This
document tries to list some of the common questions that frequently get asked,
e.g. on [Stack Overflow](http://stackoverflow.com/questions/tagged/openlayers).
@@ -65,20 +65,19 @@ var map = new ol.Map({
```
```javascript
// To use other projections, you have to register the projection in OpenLayers:
// To use other projections, you have to register the projection in OpenLayers.
// This can easily be done with [https://proj4js.org](proj4)
//
// By default OpenLayers does not know about the EPSG:21781 (Swiss) projection.
// So we create a projection instance for EPSG:21781 and pass it to
// ol.proj.addProjection to make it available to the library for lookup by its
// code.
var swissProjection = new ol.proj.Projection({
code: 'EPSG:21781',
// The extent is used to determine zoom level 0. Recommended values for a
// projection's validity extent can be found at https://epsg.io/.
extent: [485869.5728, 76443.1884, 837076.5648, 299941.7864],
units: 'm'
});
ol.proj.addProjection(swissProjection);
proj4.defs('EPSG:21781',
'+proj=somerc +lat_0=46.95240555555556 +lon_0=7.439583333333333 +k_0=1 ' +
'+x_0=600000 +y_0=200000 +ellps=bessel ' +
'+towgs84=660.077,13.551,369.344,2.484,1.783,2.939,5.66 +units=m +no_defs');
ol.proj.proj4.register(proj4);
var swissProjection = ol.proj.get('EPSG:21781');
// we can now use the projection:
var map = new ol.Map({
@@ -287,7 +286,7 @@ been populated with features), you should use an event listener function on the
vector.getSource().on('change', function(evt){
var source = evt.target;
if (source.getState() === 'ready') {
var numFeatures = source.getFeatures().length;
var numFeatures = source.getFeatures().length;
console.log("Count after change: " + numFeatures);
}
});