Dynamic Data

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index.html<!DOCTYPE html>
<html lang="en">
  <head>
    <title>Dynamic Data</title>
    <!-- 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>
    <style>
      .map {
        width: 100%;
        height:400px;
      }
    </style>
  </head>
  <body>
    <div id="map" class="map"></div>
    <script src="index.js"></script>
  </body>
</html>

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index.jsimport 'ol/ol.css';
import Map from 'ol/Map';
import View from 'ol/View';
import {MultiPoint, Point} from 'ol/geom';
import TileLayer from 'ol/layer/Tile';
import OSM from 'ol/source/OSM';
import {Circle as CircleStyle, Fill, Stroke, Style} from 'ol/style';
import {getVectorContext} from 'ol/render';

var tileLayer = new TileLayer({
  source: new OSM()
});

var map = new Map({
  layers: [tileLayer],
  target: 'map',
  view: new View({
    center: [0, 0],
    zoom: 2
  })
});

var imageStyle = new Style({
  image: new CircleStyle({
    radius: 5,
    fill: new Fill({color: 'yellow'}),
    stroke: new Stroke({color: 'red', width: 1})
  })
});

var headInnerImageStyle = new Style({
  image: new CircleStyle({
    radius: 2,
    fill: new Fill({color: 'blue'})
  })
});

var headOuterImageStyle = new Style({
  image: new CircleStyle({
    radius: 5,
    fill: new Fill({color: 'black'})
  })
});

var n = 200;
var omegaTheta = 30000; // Rotation period in ms
var R = 7e6;
var r = 2e6;
var p = 2e6;
tileLayer.on('postrender', function(event) {
  var vectorContext = getVectorContext(event);
  var frameState = event.frameState;
  var theta = 2 * Math.PI * frameState.time / omegaTheta;
  var coordinates = [];
  var i;
  for (i = 0; i < n; ++i) {
    var t = theta + 2 * Math.PI * i / n;
    var x = (R + r) * Math.cos(t) + p * Math.cos((R + r) * t / r);
    var y = (R + r) * Math.sin(t) + p * Math.sin((R + r) * t / r);
    coordinates.push([x, y]);
  }
  vectorContext.setStyle(imageStyle);
  vectorContext.drawGeometry(new MultiPoint(coordinates));

  var headPoint = new Point(coordinates[coordinates.length - 1]);

  vectorContext.setStyle(headOuterImageStyle);
  vectorContext.drawGeometry(headPoint);

  vectorContext.setStyle(headInnerImageStyle);
  vectorContext.drawGeometry(headPoint);

  map.render();
});
map.render();

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package.json{
  "name": "dynamic-data",
  "dependencies": {
    "ol": "6.1.1"
  },
  "devDependencies": {
    "parcel": "1.11.0"
  },
  "scripts": {
    "start": "parcel index.html",
    "build": "parcel build --experimental-scope-hoisting --public-url . index.html"
  }
}