Mapping High-Resolution Global Impervious Surface Area: Status and Trends

Impervious surface area (ISA) mapping at the global scale has entered a new era. Currently, the number of high-resolution global ISA products is gradually increasing; however, a literature review that systematically investigates these ISA products is still lacking, which limits the application of these products. Thus, we provide a comprehensive analysis of the existing high-resolution global ISA products, concentrating on the aspects of the data sources, training samples, features, and methods. Moreover, we evaluate these products at multitemporal and multispatial scales, using a series of independent test samples. The results demonstrate that the multitemporal accuracy of the ISA products presents an increasing trend, due to the increase of the available sensors. Among the continuous time-series products [e.g., the updated new global impervious surface area (GISA 2.0), the global impervious surface area (GISA), global annual urban dynamics, global human settlement layer, and global artificial impervious areas], the accuracy of the GISA 2.0 outperforms the others at global, continental, and regional scales. However, the mapping performance of these products in small towns and arid and rural regions needs to be enhanced. In particular, we focus on the spatio-temporal disagreement of the ISA products. We show that the high disagreement regions are predominantly concentrated in eastern Asia, western Europe, and eastern North America. In addition, the high disagreement regions are characterized by low ISA density, high vegetation coverage, and high albedo bare ground coverage. Additionally, this article concludes with some remarks about the future directions of global ISA mapping.