cesium獲取czml模型所在位置

viewer.dataSources.add(Cesium.CzmlDataSource.load(czml)).then(function (ds) {
            setInterval(function() {
                var vehicleEntity = ds.entities.getById('path');// 獲取id獲取czml
                var positionProperty = vehicleEntity.position;// 獲取czml當前所在位置
                console.log(positionProperty._property._interpolationResult);// 笛卡爾座標
            }, 3000);
        });