Example of using custom coordinate transform functions.
With ol.proj.addCoordinateTransforms(), custom coordinate transform functions can be added to configured projections.
OpenLayers Examples<!DOCTYPE html>
<html>
<head>
<title>Custom Tiled WMS</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=""></script>
<script src="https://openlayers.org/en/v4.6.4/build/ol.js"></script>
</head>
<body>
<div id="map" class="map"></div>
<script>
// By default OpenLayers does not know about the EPSG:21781 (Swiss) projection.
// So we create a projection instance for EPSG:21781 and pass it to
// ol.proj.addProjection to make it available to the library for lookup by its
// code.
var projection = new ol.proj.Projection({
code: 'EPSG:21781',
// The extent is used to determine zoom level 0. Recommended values for a
// projection's validity extent can be found at https://epsg.io/.
extent: [485869.5728, 76443.1884, 837076.5648, 299941.7864],
units: 'm'
});
ol.proj.addProjection(projection);
// We also declare EPSG:21781/EPSG:4326 transform functions. These functions
// are necessary for the ScaleLine control and when calling ol.proj.transform
// for setting the view's initial center (see below).
ol.proj.addCoordinateTransforms('EPSG:4326', projection,
function(coordinate) {
return [
WGStoCHy(coordinate[1], coordinate[0]),
WGStoCHx(coordinate[1], coordinate[0])
];
},
function(coordinate) {
return [
CHtoWGSlng(coordinate[0], coordinate[1]),
CHtoWGSlat(coordinate[0], coordinate[1])
];
});
var extent = [420000, 30000, 900000, 350000];
var layers = [
new ol.layer.Tile({
extent: extent,
source: new ol.source.TileWMS({
url: 'https://wms.geo.admin.ch/',
crossOrigin: 'anonymous',
attributions: '© <a href="http://www.geo.admin.ch/internet/geoportal/' +
'en/home.html">Pixelmap 1:1000000 / geo.admin.ch</a>',
params: {
'LAYERS': 'ch.swisstopo.pixelkarte-farbe-pk1000.noscale',
'FORMAT': 'image/jpeg'
},
serverType: 'mapserver'
})
}),
new ol.layer.Tile({
extent: extent,
source: new ol.source.TileWMS({
url: 'https://wms.geo.admin.ch/',
crossOrigin: 'anonymous',
attributions: '© <a href="http://www.geo.admin.ch/internet/geoportal/' +
'en/home.html">National parks / geo.admin.ch</a>',
params: {'LAYERS': 'ch.bafu.schutzgebiete-paerke_nationaler_bedeutung'},
serverType: 'mapserver'
})
})
];
var map = new ol.Map({
controls: ol.control.defaults().extend([
new ol.control.ScaleLine({
units: 'metric'
})
]),
layers: layers,
target: 'map',
view: new ol.View({
projection: projection,
center: ol.proj.transform([8.23, 46.86], 'EPSG:4326', 'EPSG:21781'),
extent: extent,
zoom: 2
})
});
/*
* Swiss projection transform functions downloaded from
* http://www.swisstopo.admin.ch/internet/swisstopo/en/home/products/software/products/skripts.html
*/
// Convert WGS lat/long (° dec) to CH y
function WGStoCHy(lat, lng) {
// Converts degrees dec to sex
lat = DECtoSEX(lat);
lng = DECtoSEX(lng);
// Converts degrees to seconds (sex)
lat = DEGtoSEC(lat);
lng = DEGtoSEC(lng);
// Axiliary values (% Bern)
var lat_aux = (lat - 169028.66) / 10000;
var lng_aux = (lng - 26782.5) / 10000;
// Process Y
var y = 600072.37 +
211455.93 * lng_aux -
10938.51 * lng_aux * lat_aux -
0.36 * lng_aux * Math.pow(lat_aux, 2) -
44.54 * Math.pow(lng_aux, 3);
return y;
}
// Convert WGS lat/long (° dec) to CH x
function WGStoCHx(lat, lng) {
// Converts degrees dec to sex
lat = DECtoSEX(lat);
lng = DECtoSEX(lng);
// Converts degrees to seconds (sex)
lat = DEGtoSEC(lat);
lng = DEGtoSEC(lng);
// Axiliary values (% Bern)
var lat_aux = (lat - 169028.66) / 10000;
var lng_aux = (lng - 26782.5) / 10000;
// Process X
var x = 200147.07 +
308807.95 * lat_aux +
3745.25 * Math.pow(lng_aux, 2) +
76.63 * Math.pow(lat_aux, 2) -
194.56 * Math.pow(lng_aux, 2) * lat_aux +
119.79 * Math.pow(lat_aux, 3);
return x;
}
// Convert CH y/x to WGS lat
function CHtoWGSlat(y, x) {
// Converts militar to civil and to unit = 1000km
// Axiliary values (% Bern)
var y_aux = (y - 600000) / 1000000;
var x_aux = (x - 200000) / 1000000;
// Process lat
var lat = 16.9023892 +
3.238272 * x_aux -
0.270978 * Math.pow(y_aux, 2) -
0.002528 * Math.pow(x_aux, 2) -
0.0447 * Math.pow(y_aux, 2) * x_aux -
0.0140 * Math.pow(x_aux, 3);
// Unit 10000" to 1 " and converts seconds to degrees (dec)
lat = lat * 100 / 36;
return lat;
}
// Convert CH y/x to WGS long
function CHtoWGSlng(y, x) {
// Converts militar to civil and to unit = 1000km
// Axiliary values (% Bern)
var y_aux = (y - 600000) / 1000000;
var x_aux = (x - 200000) / 1000000;
// Process long
var lng = 2.6779094 +
4.728982 * y_aux +
0.791484 * y_aux * x_aux +
0.1306 * y_aux * Math.pow(x_aux, 2) -
0.0436 * Math.pow(y_aux, 3);
// Unit 10000" to 1 " and converts seconds to degrees (dec)
lng = lng * 100 / 36;
return lng;
}
// Convert DEC angle to SEX DMS
function DECtoSEX(angle) {
// Extract DMS
var deg = parseInt(angle, 10);
var min = parseInt((angle - deg) * 60, 10);
var sec = (((angle - deg) * 60) - min) * 60;
// Result in degrees sex (dd.mmss)
return deg + min / 100 + sec / 10000;
}
// Convert Degrees angle to seconds
function DEGtoSEC(angle) {
// Extract DMS
var deg = parseInt(angle, 10);
var min = parseInt((angle - deg) * 100, 10);
var sec = (((angle - deg) * 100) - min) * 100;
// Avoid rounding problems with seconds=0
var parts = String(angle).split('.');
if (parts.length == 2 && parts[1].length == 2) {
min = Number(parts[1]);
sec = 0;
}
// Result in degrees sex (dd.mmss)
return sec + min * 60 + deg * 3600;
}
</script>
</body>
</html>