[GIS] Zoom Scale in OpenLayers 3

coordinate systemopenlayersscalezoom

Need to change the default zoom of OpenLayers 3 to do so adapted scales, type [1: 100000, 1: 50000.1: 25000.1: 10000.1: 1000.1: 500] have seen in Openlayers2 if you can, but at 3 I have not found a way to create it.

I tried to create a new projection, to create a new resolution, but no resolution to these scales are calculated.

The projection anyway not well created not because the coordinates of a town of Spain, are in the middle of Africa. I leave the code creating the projection.

 var etrs89 = new ol.proj.Projection({
     code: 'EPSG:25830',
     global:false,
     extent: [-729785.83,3715125.82,940929.67,9518470.69]
 });
var pucol=[729016.6720,4387551.5079]; 
var vista= new ol.View({
   projection: etrs89,
   center: pucol,
   resolutions: [65536, 32768, 16384, 8192, 4096, 2048,500,200,30,10], // TEST
   zoom: 0
 });

Best Answer

I have test it a bit and seems to work correct. Inspired from this

var res = getResolutionFromScale(200000);
alert(res);
function getResolutionFromScale(scale){
    var units = map.getView().getProjection().getUnits();
    var dpi = 25.4 / 0.28;
    var mpu = ol.proj.METERS_PER_UNIT[units];
    var resolution = scale/(mpu * 39.37 * dpi);
    return resolution;
}
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