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I'm beginning with GeoServer and try to display a map of my country (Belgium) as an OpenLayers map (embedded into a MapPanel object). I've downloaded the municipalities limits from gadm.org and copied the file into a PostGIS database (using the tools provided in the GeoServer package). I guess it is a projection issue, but I don't get why since everything is in EPSG:4326.

Here is my code:

panel = new GeoExt.MapPanel({
   title: "MapPanel",
   renderTo: "map-id",
   layers: [
        new OpenLayers.Layer.WMS("Administrative borders",
            "/geoserver/wms",
            {layers: "bel_adm4", projection:"EPSG:4326", format: "image/png"},
            {transitionEffect:'resize', isBaseLayer:true}
   )],
   map:
      {
        projection:"EPSG:4326", 
        maxExtent: new OpenLayers.Bounds(2.5412,49.5100,6.4013,51.502)
       }
 });

Here's a screenshot of the generated map:

enter image description here

Here's how Belgium should be: enter image description here

  • It's worth checking what epsg code is set up for the layer in GeoServer. As it's a wms layer OpenLayers is not going to reproject the images created on the server when it displays them on the client. – pecoanddeco May 14 '13 at 12:28
  • 4
    That's normal and correct. If you want Belgium to be less distorted, you have to use a different projection than 4326 but - as far as I know - OpenLayers only supports reprojection between 4326 and Web Mercator by default. Web Mercator might already look less distorted. – underdark May 14 '13 at 13:52
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A map served by Geoserver as EPSG:4326 and displayed in OpenLayers with this "projection" will look distorted. The units of measure in a EPSG:4326 is degrees, so what you are looking at are an unprojected map.

You'll want to make Geoserver reproject your WMS to eiter EPSG:900913 (or whatever EPSG-code "web/spherical mercator" has nowdays) or a local system that covers Belgium (WGS84 UTM Zone 32N perhaps?)

Geoserver does reprojection on the fly, and supports a wide range of projections, so I would suggest trying to change your layer definition to

   new OpenLayers.Layer.WMS("Administrative borders",
            "/geoserver/wms",
            {layers: "bel_adm4", projection:"EPSG:900913", format: "image/png"},
            {transitionEffect:'resize', isBaseLayer:true}

(sidenote: While libraries like Leaflet and Google Maps makes things easy for developers by letting the user deal with coordinates that are exclusively EPSG:4326, OpenLayers does not. The projection-param set in the layer definition is sent as-is to geoserver)

  • A tad late to mention it here, but anyhow: EPSG:31370 is the one commonly used for belgium (Lambert1972 - Conical) – Tim Couwelier Aug 22 '16 at 15:22

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