1、Feature 轉WKT 且帶座標系的轉換

     var strwkt = new ol.format.WKT().writeFeature(feature, {                dataProjection: targetcrs,//目標座標系                featureProjection:crs  //當前座標系            });

 2、WKT轉Feature 

  var newfeature = new ol.format.WKT().readFeature(strwkt);

3、Feature 座標系轉換（支援所有圖形）

  var geom = feature.getGeometry().transform(crs, targetcrs);  feature.setGeometry(geom);

4、利用WKT轉換Feature座標系（這種不支援GEOMETRY不為Circle）

  var strwkt = new ol.format.WKT().writeFeature(feature, {                dataProjection: targetcrs,                featureProjection:crs            });            var newfeature = new ol.format.WKT().readFeature(strwkt);

注意：方法4得到的Feature 會沒有原始Feature對應的Properties