code: function() {
          var mapRes = this.map.getResolution();
          var targetRes = this.ovmap.getResolution();
          var resRatio = targetRes / mapRes;
          if(resRatio > this.maxRatio) {
              // zoom in overview map
              targetRes = this.minRatio * mapRes;            
          } else if(resRatio <= this.minRatio) {
              // zoom out overview map
              targetRes = this.maxRatio * mapRes;
          }
          var center;
          if (this.ovmap.getProjection() != this.map.getProjection()) {
              center = this.map.center.clone();
              center.transform(this.map.getProjectionObject(),
                  this.ovmap.getProjectionObject() );
          } else {
              center = this.map.center;
          }
          this.ovmap.setCenter(center, this.ovmap.getZoomForResolution(
              targetRes * this.resolutionFactor));
          this.updateRectToMap();
      }
docs: Method updateOverview
  Called by <update> if <isSuitableOverview> returns true