**Acknowledgements**

The content in this chapter was supported by the National Key Research and Development Program of China (2016YFD0300601) and the National Natural Science Foundation of China (41571354, 41501468, and 41301389) and the Innovation Foundation of Director of Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, China (Grant No. Y6XS560030, Y5ZZ01101B). The authors would like to thank those who helped with the field campaign at the National Experimental Station for Precision Agriculture.
