code: function(overviewMapPx) {
          var size = this.ovmap.size;
          var res  = this.ovmap.getResolution();
          var center = this.ovmap.getExtent().getCenterLonLat();
      
          var deltaX = overviewMapPx.x - (size.w / 2);
          var deltaY = overviewMapPx.y - (size.h / 2);
  
          return {
              lon: center.lon + deltaX * res,
              lat: center.lat - deltaY * res
          };
      }
docs: Method: getLonLatFromOverviewPx
  Get a map location from a pixel location
  
  Parameters:
  overviewMapPx - {<OpenLayers.Pixel>|Object} OpenLayers.Pixel or
  an object with a
  'x' and 'y' properties.
  
  Returns:
  {Object} Location which is the passed-in overview map
  OpenLayers.Pixel, translated into lon/lat by the overview
  map. An object with a 'lon' and 'lat' properties.