viewer.entities.add({
        position: Cesium.Cartesian3.fromDegrees(112.816525, 28.413053,78),
        name: ‘point‘,
        billboard: {
            // 图像地址，URI或Canvas的属性
            image: image,
            show: true,
        　　 heightReference: Cesium.HeightReference.CLAMP_TO_GROUND   //设置HeightReference高度参考类型为CLAMP_TO_GROUND贴地类型
          }
    });