Demonstrates client-side raster reprojection of OSM to arbitrary projection
This example shows client-side raster reprojection capabilities from OSM (EPSG:3857) to arbitrary projection by searching in MapTiler Cloud Coordinates API. Note: Make sure to get your own API key at https://www.maptiler.com/cloud/ when using this example.
import Graticule from 'ol/layer/Graticule.js';
import Map from 'ol/Map.js';
import OSM from 'ol/source/OSM.js';
import Stroke from 'ol/style/Stroke.js';
import TileDebug from 'ol/source/TileDebug.js';
import TileLayer from 'ol/layer/Tile.js';
import View from 'ol/View.js';
import proj4 from 'proj4';
import {applyTransform} from 'ol/extent.js';
import {get as getProjection, getTransform} from 'ol/proj.js';
import {register} from 'ol/proj/proj4.js';
const key = 'Get your own API key at https://www.maptiler.com/cloud/';
const osmSource = new OSM();
const debugLayer = new TileLayer({
source: new TileDebug({
tileGrid: osmSource.getTileGrid(),
projection: osmSource.getProjection(),
}),
visible: false,
});
const graticule = new Graticule({
// the style to use for the lines, optional.
strokeStyle: new Stroke({
color: 'rgba(255,120,0,0.9)',
width: 2,
lineDash: [0.5, 4],
}),
showLabels: true,
visible: false,
wrapX: false,
});
const map = new Map({
layers: [
new TileLayer({
source: osmSource,
}),
debugLayer,
graticule,
],
target: 'map',
view: new View({
projection: 'EPSG:3857',
center: [0, 0],
zoom: 1,
}),
});
const queryInput = document.getElementById('epsg-query');
const searchButton = document.getElementById('epsg-search');
const resultSpan = document.getElementById('epsg-result');
const renderEdgesCheckbox = document.getElementById('render-edges');
const showTilesCheckbox = document.getElementById('show-tiles');
const showGraticuleCheckbox = document.getElementById('show-graticule');
function setProjection(code, name, proj4def, bbox) {
if (code === null || name === null || proj4def === null || bbox === null) {
resultSpan.innerHTML = 'Nothing usable found, using EPSG:3857...';
map.setView(
new View({
projection: 'EPSG:3857',
center: [0, 0],
zoom: 1,
}),
);
return;
}
resultSpan.innerHTML = '(' + code + ') ' + name;
proj4.defs(code, proj4def);
register(proj4);
const newProj = getProjection(code);
const fromLonLat = getTransform('EPSG:4326', newProj);
newProj.setWorldExtent(bbox);
// approximate calculation of projection extent,
// checking if the world extent crosses the dateline
if (bbox[0] > bbox[2]) {
bbox[2] += 360;
}
const extent = applyTransform(bbox, fromLonLat, undefined, 8);
newProj.setExtent(extent);
const newView = new View({
projection: newProj,
});
map.setView(newView);
newView.fit(extent);
}
function search(query) {
resultSpan.innerHTML = 'Searching ...';
fetch(
`https://api.maptiler.com/coordinates/search/${query}.json?exports=true&key=${key}`,
)
.then(function (response) {
return response.json();
})
.then(function (json) {
const results = json['results'];
if (results && results.length > 0) {
for (let i = 0, ii = results.length; i < ii; i++) {
const result = results[i];
if (result) {
const id = result['id'];
const code = id['authority'] + ':' + id['code'];
const name = result['name'];
const proj4def = result['exports']['wkt'];
const bbox = result['bbox'];
if (
code &&
code.length > 0 &&
proj4def &&
proj4def.length > 0 &&
bbox &&
bbox.length == 4
) {
setProjection(code, name, proj4def, bbox);
return;
}
}
}
}
setProjection(null, null, null, null);
});
}
/**
* Handle click event.
* @param {Event} event The event.
*/
searchButton.onclick = function (event) {
search(queryInput.value);
event.preventDefault();
};
/**
* Handle checkbox change events.
*/
function onReprojectionChange() {
osmSource.setRenderReprojectionEdges(renderEdgesCheckbox.checked);
}
function onGraticuleChange() {
graticule.setVisible(showGraticuleCheckbox.checked);
}
function onTilesChange() {
debugLayer.setVisible(showTilesCheckbox.checked);
}
showGraticuleCheckbox.addEventListener('change', onGraticuleChange);
renderEdgesCheckbox.addEventListener('change', onReprojectionChange);
showTilesCheckbox.addEventListener('change', onTilesChange);
onReprojectionChange();
onGraticuleChange();
onTilesChange();
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Reprojection with coordinate system search</title>
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/[email protected]/dist/css/bootstrap.min.css">
<link rel="stylesheet" href="node_modules/ol/ol.css">
<style>
.map {
width: 100%;
height: 400px;
}
</style>
</head>
<body>
<div id="map" class="map"></div>
<form class="row">
<span class="col-auto">
<span class="input-group">
<label class="input-group-text" for="epsg-query">Search projection: </label>
<input type="text" id="epsg-query" placeholder="4326, 27700, 3031, US National Atlas, Swiss, France, ..." class="form-control" size="50" />
<button class="btn btn-outline-secondary" id="epsg-search">Search</button>
</span>
</span>
<span class="mt-2" id="epsg-result"> </span>
</form>
<form>
<div class="form-check mt-2">
<input class="form-check-input" type="checkbox" id="render-edges" />
<label class="form-check-label" for="render-edges">Render reprojection edges</label><br>
</div>
<div class="form-check">
<input class="form-check-input" type="checkbox" id="show-tiles" />
<label class="form-check-label" for="show-tiles">Show tile coordinates</label><br>
</div>
<div class="form-check">
<input class="form-check-input" type="checkbox" id="show-graticule" />
<label class="form-check-label" for="show-graticule">Show graticule</label>
</div>
</form>
<script type="module" src="main.js"></script>
</body>
</html>
{
"name": "reprojection-by-code",
"dependencies": {
"ol": "10.3.1",
"proj4": "2.15.0"
},
"devDependencies": {
"vite": "^3.2.3"
},
"scripts": {
"start": "vite",
"build": "vite build"
}
}