p()
        {
            if(overLayerList!=null && overLayerList.length>0)
            {
                var len= overLayerList.length;
                for(var i=len-1;i>=0;i--)
                {
                    map.removeOverlay(overLayerList[i]);
                }
            }
        }

        /**
        * 测量长度输出
        * @param {ol.geom.LineString} line
        * @return {string}
        */
        function formatLength(line) {
            var length;
            var sphere = new ol