Thanks for the detailed explanation. On Tue, Nov 11, 2008 at 4:17 PM, <[EMAIL PROTECTED]> wrote:
> This is a very basic GIS calculation. > > Resolution is how many map units per pixel. Map units can be degrees, > meters etc., but the OpenLayers terminology mostly comes from a > degree/latitude/longtitude point of view. > > So if the map is 500 by 600 pixels, and the resolution is 20, then the > width of the map in map units 10.000 and the height in map units is > 12.000. > > The extent then ranges from: > -left: the center X (or longitude) minus half the width (in map units) > -right: the center X (or longitude) plus half the width (in map units) > -bottom: the center Y (or latitude) minus half the height (in map units) > -top: the center Y (or latitude) plus half the height (in map units) > > Hope this helps, if not let us know. > > Best regards, > Bart > > > Can someone please tell me or point me to some literature that explains > > the > > logic behind the below piece of code (Taken from calculateBounds method > of > > Map class)? > > > > var size = this.getSize();<Returns view port size> > > var w_deg = size.w * resolution; > > var h_deg = size.h * resolution; > > extent = new OpenLayers.Bounds(center.lon - w_deg / 2, > > center.lat - h_deg / 2, > > center.lon + w_deg / 2, > > center.lat + h_deg / 2); > > > > -- > > Cheers, > > Abhi > > _______________________________________________ > > Dev mailing list > > Dev@openlayers.org > > http://openlayers.org/mailman/listinfo/dev > > > > > -- Cheers, Abhi
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