turf-union
Combines two polygons into one.
<!doctype html>
<html lang="en">
<head>
<link rel="stylesheet" href="https://rawcdn.githack.com/openlayers/openlayers.github.io/master/en/v5.3.0/css/ol.css" type="text/css">
<link rel="stylesheet" href="assets/css/styles.css" type="text/css">
<script src="//cdn.jsdelivr.net/npm/@turf/turf@5/turf.min.js"></script>
<script src="https://rawcdn.githack.com/openlayers/openlayers.github.io/master/en/v5.3.0/build/ol.js"></script>
<script src="assets/js/es6-promise.min.js"></script>
<script src="https://cdn.polyfill.io/v2/polyfill.min.js?features=requestAnimationFrame,Element.prototype.classList,URL,fetch"></script>
<script src="assets/js/helpers.js"></script>
<title>Turf and OpenLayers 3 - Union</title>
</head>
<body>
<div id="map" class="map"></div>
<button id="switchlayer" type="button">Show polygons union</button>
<script type="text/javascript">
// Declare a source for points and
// for future convex polygon deduced from them
var vectorUnionPolygon = new ol.source.Vector();
var vectorLayerUnionPolygon = new ol.layer.Vector({
source: vectorUnionPolygon
});
// Instanciate a map and add layers
var map = new ol.Map({
target: 'map',
layers: [
new ol.layer.Tile({
source: new ol.source.OSM()
}),
vectorLayerUnionPolygon
],
view: new ol.View({
center: ol.proj.fromLonLat([-1.555493, 47.216151]),
zoom: 12
})
});
var polygons, union;
fetch('assets/data/union.geojson').then(function(response) {
return response.json().then(function(polygons_fc) {
console.log(polygons_fc.features);
polygons = polygons_fc;
var features = polygons_fc.features;
// Simple way but we could also use recursive function
for (var i = 1, len = features.length; i < len; i++) {
if (i == 1) {
union = turf.union(features[i - 1], features[i]);
} else {
union = turf.union(union, features[i]);
}
}
console.log(union);
vectorUnionPolygon.addFeatures(geojsonToFeatures(polygons_fc, {
featureProjection: 'EPSG:3857'
}));
});
});
var button = document.getElementById('switchlayer');
button.addEventListener('click', function(e) {
if (this.innerHTML === 'Show polygons union') {
this.innerHTML = 'Show polygons before union';
vectorUnionPolygon.clear();
vectorUnionPolygon.addFeatures(geojsonToFeatures(union, {
featureProjection: 'EPSG:3857'
}));
} else {
this.innerHTML = 'Show polygons union';
vectorUnionPolygon.clear();
vectorUnionPolygon.addFeatures(geojsonToFeatures(polygons, {
featureProjection: 'EPSG:3857'
}));
}
})
</script>
</body>
</html>