[OpenLayers-Users] Changing Resolution in Spherical Mercator

Linda Rawson linda.rawson at gmail.com
Fri Nov 16 09:17:59 EST 2007


I am using the following to define my map:

options = {
    projection: "EPSG:900913",
    units: "m",
    maxResolution: 156543.0339,
    numZoomLevels: 18,
    maxExtent: new OpenLayers.Bounds(-20037508, -20037508,
                                     20037508, 20037508.34)
};

map = new OpenLayers.Map('map',options);

Then my layer:

var sat = new OpenLayers.Layer.Google(
                "Google",
                {'sphericalMercator': true}
    );

What the sphericalMercator true does is run the

initMercatorParameters: function() {
        // set up properties for Mercator - assume EPSG:900913
        this.RESOLUTIONS = [];
        var maxResolution = 156543.0339;
        for(var zoom=0; zoom<=this.MAX_ZOOM_LEVEL; ++zoom) {
            this.RESOLUTIONS[zoom] = maxResolution / Math.pow(2, zoom);
        }
        this.units = "m";
        this.projection = "EPSG:900913";
    },

The maxResolution of 156543.0339 is based on (20037508.34 + 20037508) / 256.

I need a different Resolution but I still want the forward and inverse
mercator functions to work.  Where are all the different places to change
the resolution?  I need it based on a tile that is not 256 in size.  I have
tried changing this in initMercatorParameters, the map, but It still does
not seem to play nice.

Thanks,

Linda Rawson
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