1 Chongqing Engineering Research Center for Remote Sensing Big Data Application, Chongqing Key Laboratory of Karst Environment, School of Geographical Sciences, Southwest University, Chongqing, 400715, China. hongyanghy@gmail.com.
2 Department of Geography and Environmental Science, University of Reading, Reading, RG6 6AB, UK.
3 Chongqing Engineering Research Center for Remote Sensing Big Data Application, Chongqing Key Laboratory of Karst Environment, School of Geographical Sciences, Southwest University, Chongqing, 400715, China.
4 UCL Department of Geography, University College London, London, WC1E 6BT, UK.