GeoTIFF with Overviews

Rendering a GeoTIFF with external overviews as a layer.

In some cases, a GeoTIFF may have external overviews. This example uses the overviews property to provide URLs for the external overviews. The example composes a false color composite using shortwave infrared (B6), near infrared (B5), and visible green (B3) bands from a Landsat 8 image.

main.js

import 'ol/ol.css';
import GeoTIFF from 'ol/source/GeoTIFF';
import Map from 'ol/Map';
import TileLayer from 'ol/layer/WebGLTile';

// scale values in this range to 0 - 1
const min = 10000;
const max = 15000;

const base =
  'https://landsat-pds.s3.amazonaws.com/c1/L8/139/045/LC08_L1TP_139045_20170304_20170316_01_T1/LC08_L1TP_139045_20170304_20170316_01_T1';

const source = new GeoTIFF({
  sources: [
    {
      url: `${base}_B6.TIF`,
      overviews: [`${base}_B6.TIF.ovr`],
      min: min,
      max: max,
      nodata: 0,
    },
    {
      url: `${base}_B5.TIF`,
      overviews: [`${base}_B5.TIF.ovr`],
      min: min,
      max: max,
      nodata: 0,
    },
    {
      url: `${base}_B3.TIF`,
      overviews: [`${base}_B3.TIF.ovr`],
      min: min,
      max: max,
      nodata: 0,
    },
  ],
});

const map = new Map({
  target: 'map',
  layers: [
    new TileLayer({
      style: {
        saturation: -0.3,
      },
      source: source,
    }),
  ],
  view: source.getView(),
});

index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>GeoTIFF with Overviews</title>
    <!-- Pointer events polyfill for old browsers, see https://caniuse.com/#feat=pointer -->
    <script src="https://unpkg.com/elm-pep"></script>
    <!-- The lines below are only needed for old environments like Internet Explorer and Android 4.x -->
    <script src="https://cdn.polyfill.io/v3/polyfill.min.js?features=fetch,requestAnimationFrame,Element.prototype.classList,TextDecoder"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/core-js/3.18.3/minified.js"></script>
    <style>
      .map {
        width: 100%;
        height:400px;
      }
    </style>
  </head>
  <body>
    <div id="map" class="map"></div>
    <script src="main.js"></script>
  </body>
</html>

package.json

{
  "name": "cog-overviews",
  "dependencies": {
    "ol": "6.12.0"
  },
  "devDependencies": {
    "parcel": "^2.0.0"
  },
  "scripts": {
    "start": "parcel index.html",
    "build": "parcel build --public-url . index.html"
  }
}