WMTS Tile Transitions

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WMTS Tile Transitions

Sea-level

Example of smooth tile transitions when changing the dimension of a WMTS layer.

Demonstrates smooth reloading of layers when changing a dimension continuously. The demonstration layer is a global sea-level computation (flooding computation from SCALGO, underlying data from CGIAR-CSI SRTM) where cells that are flooded if the sea-level rises to more than x m are colored blue. The user selects the sea-level dimension using a slider.

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index.html<!DOCTYPE html>
<html lang="en">
  <head>
    <title>WMTS Tile Transitions</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>
    <label>
      Sea-level
      <input id="slider" type="range" value="10" max="100" min="-1">
    </label>
    <span id="theinfo"></span>
    <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 {getWidth, getTopLeft} from 'ol/extent';
import TileLayer from 'ol/layer/Tile';
import {get as getProjection} from 'ol/proj';
import OSM from 'ol/source/OSM';
import WMTS from 'ol/source/WMTS';
import WMTSTileGrid from 'ol/tilegrid/WMTS';


// create the WMTS tile grid in the google projection
var projection = getProjection('EPSG:3857');
var tileSizePixels = 256;
var tileSizeMtrs = getWidth(projection.getExtent()) / tileSizePixels;
var matrixIds = [];
var resolutions = [];
for (var i = 0; i <= 14; i++) {
  matrixIds[i] = i;
  resolutions[i] = tileSizeMtrs / Math.pow(2, i);
}
var tileGrid = new WMTSTileGrid({
  origin: getTopLeft(projection.getExtent()),
  resolutions: resolutions,
  matrixIds: matrixIds
});

var scalgoToken = 'CC5BF28A7D96B320C7DFBFD1236B5BEB';

var wmtsSource = new WMTS({
  url: 'http://ts2.scalgo.com/olpatch/wmts?token=' + scalgoToken,
  layer: 'SRTM_4_1:SRTM_4_1_flooded_sealevels',
  format: 'image/png',
  matrixSet: 'EPSG:3857',
  attributions: [
    '<a href="http://scalgo.com">SCALGO</a>',
    '<a href="https://cgiarcsi.community/data/' +
        'srtm-90m-digital-elevation-database-v4-1">CGIAR-CSI SRTM</a>'
  ],
  tileGrid: tileGrid,
  style: 'default',
  dimensions: {
    'threshold': 100
  }
});

var map = new Map({
  target: 'map',
  view: new View({
    projection: projection,
    center: [-9871995, 3566245],
    zoom: 6
  }),
  layers: [
    new TileLayer({
      source: new OSM()
    }),
    new TileLayer({
      opacity: 0.5,
      source: wmtsSource
    })
  ]
});

var updateSourceDimension = function(source, sliderVal) {
  source.updateDimensions({'threshold': sliderVal});
  document.getElementById('theinfo').innerHTML = sliderVal + ' meters';
};

updateSourceDimension(wmtsSource, 10);

document.getElementById('slider').addEventListener('input', function() {
  updateSourceDimension(wmtsSource, this.value);
});

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package.json{
  "name": "wmts-dimensions",
  "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"
  }
}