1. Nanjing University, Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology, 22 Hankou Road, Nanjing 210097, ChinabNanjing University, Collaborative Innovation Center for the South China Sea Studies, 22 Hankou Road, Nanjing 2100
2. Nanjing University, Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology, 22 Hankou Road, Nanjing 210097, ChinacNanjing Institute of Surveying, Mapping & Geotechnical Investigation, Co. Ltd, 88 ChuangYi Road, Nanjing 210019,