[GIS] Openlayers + WMS layer. Use scale or resolution + DPI

openlayers-2resolutionscalewms

I have a problem with displaying map with WMS layer in Openlayers. I'm able to display it but the image of the map is not sharp especially at higher zooms.

I have a documentation from the map provider and below is part of description:
The data scale set is:

1:20 mil., 1:6 200 000, 1:3 000 000, 1:1mil., 1:500 000, 1:200 000,
1:75 000, 1:25 000, 1:12 500 , 1:6 250

For the best quality of displayed data while zooming is recommended to count with recalculation
96dpi/200dpi (Map DPI = 200), it means 0,48 x default scale set.

I'm not sure if this DPI setting that is wrong in my code. I found out that Openlayers standard DPI is 72 DPI.

Can you suggest anything how can I fix it?

WMS getcapabilities:

<SRS>EPSG:32633</SRS>
<LatLonBoundingBox minx="-8.060897" miny="32.143274" maxx="56.352488" maxy="66.324824"/>
<BoundingBox SRS="EPSG:32633" minx="-1700000" miny="3800000" maxx="2300000" maxy="8000000"/>

My code:

<!DOCTYPE html>
<html>
  <head>
    <title>WMS map</title>
    <script src="http://openlayers.org/api/OpenLayers.js"></script>

<script type='text/javascript'> 


var map; function init() {

{ 
   var mapoptions = {
      maxExtent: new OpenLayers.Bounds(-1700000, 3800000, 2300000, 8000000),
      numZoomLevels:14,
      scale: [20000000, 6200000, 3000000, 1000000, 500000, 200000, 75000, 
      25000, 12500, 6250],
      maxResolution: "auto",
      projection: "EPSG:32633",
      displayProjection: new OpenLayers.Projection("EPSG:32633")

    }};
    map = new OpenLayers.Map( 'map',mapoptions );



   var wms = new OpenLayers.Layer.WMS( "layer_name" ,'https://wms.dot.com', 
   {layers: 'layer_name',
   format: "image/png"}, 
   {} 
); 
map.addLayer(wms); 
if(!map.getCenter()){ map.zoomToMaxExtent(); } } 
</script>
</head>

<body onload='init();'>
    <div id='map' style='width: 1000px; height: 1000px;'>
</div>
</body>
</html>

Best Answer

This article should help you Configuring ZoomLevels in OpenLayers

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