Example of two WMS layers using the projection EPSG:21781, which is unknown to the client.
As long as no coordinate transformations are required, OpenLayers 3 works fine with projections that are only configured with a code and units.
code
units
<!DOCTYPE html> <html> <head> <title>WMS without client projection example</title> <script src="https://code.jquery.com/jquery-1.11.2.min.js"></script> <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css"> <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/js/bootstrap.min.js"></script> <link rel="stylesheet" href="http://openlayers.org/en/3.8.1/css/ol.css" type="text/css"> <script src="http://openlayers.org/en/3.8.1/build/ol.js"></script> </head> <body> <div class="container-fluid"> <div class="row-fluid"> <div class="span12"> <div id="map" class="map"></div> </div> </div> </div> <script> var layers = [ new ol.layer.Tile({ source: new ol.source.TileWMS({ attributions: [new ol.Attribution({ html: '© ' + '<a href="http://www.geo.admin.ch/internet/geoportal/' + 'en/home.html">' + 'Pixelmap 1:1000000 / geo.admin.ch</a>' })], crossOrigin: 'anonymous', params: { 'LAYERS': 'ch.swisstopo.pixelkarte-farbe-pk1000.noscale', 'FORMAT': 'image/jpeg' }, url: 'http://wms.geo.admin.ch/' }) }), new ol.layer.Image({ source: new ol.source.ImageWMS({ attributions: [new ol.Attribution({ html: '© ' + '<a href="http://www.geo.admin.ch/internet/geoportal/' + 'en/home.html">' + 'National parks / geo.admin.ch</a>' })], crossOrigin: 'anonymous', params: {'LAYERS': 'ch.bafu.schutzgebiete-paerke_nationaler_bedeutung'}, serverType: 'mapserver', url: 'http://wms.geo.admin.ch/' }) }) ]; // A minimal projection object is configured with only the SRS code and the map // units. No client-side coordinate transforms are possible with such a // projection object. Requesting tiles only needs the code together with a // tile grid of Cartesian coordinates; it does not matter how those // coordinates relate to latitude or longitude. var projection = new ol.proj.Projection({ code: 'EPSG:21781', units: 'm' }); var map = new ol.Map({ layers: layers, target: 'map', view: new ol.View({ center: [660000, 190000], projection: projection, zoom: 9 }) }); </script> </body> </html>