Buffer su punti

by Francesco Boccacci

HTML

<link rel="stylesheet" href="https://cdn.jsdelivr.net/gh/openlayers/openlayers.github.io@master/en/v6.4.3/css/ol.css">
<script src="https://cdn.jsdelivr.net/gh/openlayers/openlayers.github.io@master/en/v6.4.3/build/ol.js"></script>
<script src="https://code.jquery.com/jquery-3.2.1.min.js"></script>
<body>
  <label for="buffer">Buffer (metri)</label>
  <select id="buffer">
    <option value=1000>1000</option>
    <option value=2000>2000</option>
    <option value=5000>5000</option>
  </select>
  <div id="map" class="map"></div>
</body>

CSS

html, body {
    height: 100%;
    width: 100%;
    margin:0;
  }
  .map {
        height: 90%;
        width: 100%;
      }

JavaScript

var pois = {
    "type": "FeatureCollection",
    "crs": {
      "type": "name",
      "properties": {
        "name": "urn:ogc:def:crs:EPSG::3857"
      }
    },
    "features": [{
      "type": "Feature",
      "properties": {
        "id": 1,
        "tipo": "A",
        "quota": 91.63
      },
      "geometry": {
        "type": "Point",
        "coordinates": [1246198.7546599496, 5435469.6013667583]
      }
    }, {
      "type": "Feature",
      "properties": {
        "id": 3,
        "tipo": "B",
        "quota": 7.75
      },
      "geometry": {
        "type": "Point",
        "coordinates": [1251597.8380584808, 5431734.189015449]
      }
    }, {
      "type": "Feature",
      "properties": {
        "id": 2,
        "tipo": "A",
        "quota": 51.26
      },
      "geometry": {
        "type": "Point",
        "coordinates": [1247579.9155293412, 5426382.1906465562]
      }
    }, {
      "type": "Feature",
      "properties": {
        "id": 21,
        "tipo": "B",
        "quota": 18.34
      },
      "geometry": {
        "type": "Point",
        "coordinates": [1244064.2333163442, 5429066.0373359425]
      }
    }, {
      "type": "Feature",
      "properties": {
        "id": 5,
        "tipo": "C",
        "quota": 68.02
      },
      "geometry": {
        "type": "Point",
        "coordinates": [1255254.7753603929, 5427182.6361504076]
      }
    }, {
      "type": "Feature",
      "properties": {
        "id": 4,
        "tipo": "B",
        "quota": 77.34
      },
      "geometry": {
        "type": "Point",
        "coordinates": [1255992.4408247273, 5432267.81935135]
      }
    }, {
      "type": "Feature",
      "properties": {
        "id": 20,
        "tipo": "B",
        "quota": 85.33
      },
      "geometry": {
        "type": "Point",
        "coordinates": [1252806.3538191987, 5435296.9562580846]
      }
    }, {
      "type": "Feature",
      "properties": {
        "id": 19,
        "tipo": "B",
        "quota": 54.03
     ...