Tissot Indicatrix

EPSG:4326

EPSG:3857

Draw Tissot's indicatrices on maps.

Example of Tissot indicatrix maps. The map on the top is an EPSG:4326 map. The one on the bottom is EPSG:3857.

<!DOCTYPE html>
<html>
  <head>
    <title>Tissot Indicatrix</title>
    <link rel="stylesheet" href="https://openlayers.org/en/v4.6.4/css/ol.css" type="text/css">
    <!-- The line below is only needed for old environments like Internet Explorer and Android 4.x -->
    <script src="https://cdn.polyfill.io/v2/polyfill.min.js?features=requestAnimationFrame,Element.prototype.classList,URL"></script>
    <script src="https://openlayers.org/en/v4.6.4/build/ol.js"></script>
  </head>
  <body>
    <h4>EPSG:4326</h4>
    <div id="map4326" class="map"></div>
    <h4>EPSG:3857</h4>
    <div id="map3857" class="map"></div>
    <script>
      var vectorLayer4326 = new ol.layer.Vector({
        source: new ol.source.Vector()
      });

      var vectorLayer3857 = new ol.layer.Vector({
        source: new ol.source.Vector()
      });

      var map4326 = new ol.Map({
        layers: [
          new ol.layer.Tile({
            source: new ol.source.TileWMS({
              url: 'https://ahocevar.com/geoserver/wms',
              params: {
                'LAYERS': 'ne:NE1_HR_LC_SR_W_DR',
                'TILED': true
              }
            })
          }),
          vectorLayer4326
        ],
        target: 'map4326',
        view: new ol.View({
          projection: 'EPSG:4326',
          center: [0, 0],
          zoom: 2
        })
      });

      var map3857 = new ol.Map({
        layers: [
          new ol.layer.Tile({
            source: new ol.source.TileWMS({
              url: 'https://ahocevar.com/geoserver/wms',
              params: {
                'LAYERS': 'ne:NE1_HR_LC_SR_W_DR',
                'TILED': true
              }
            })
          }),
          vectorLayer3857
        ],
        target: 'map3857',
        view: new ol.View({
          center: [0, 0],
          zoom: 2
        })
      });

      var wgs84Sphere = new ol.Sphere(6378137);

      var radius = 800000;
      var x, y;
      for (x = -180; x < 180; x += 30) {
        for (y = -90; y < 90; y += 30) {
          var circle4326 = ol.geom.Polygon.circular(wgs84Sphere, [x, y], radius, 64);
          var circle3857 = circle4326.clone().transform('EPSG:4326', 'EPSG:3857');
          vectorLayer4326.getSource().addFeature(new ol.Feature(circle4326));
          vectorLayer3857.getSource().addFeature(new ol.Feature(circle3857));
        }
      }
    </script>
  </body>
</html>