docs: 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
          };
      }