低空无人机遥感在草原监测评价中的应用进展

低空域无人机遥感技术具有高时效性、高分辨率、低成本、易操控等优势,作为地面与高空遥感（航天与航空遥感）间测量尺度空缺的有益补充,低空无人机遥感扩展了样地样方空间尺度,提高了中、小尺度遥感观测信息的精细化程度,实现了草原生境信息的快速采集、处理与分析应用,是草原"星-空-地"一体化监测的重要组成。针对草原监测评价,总结了国内外低空无人机遥感在草原基况调查（草原草层高度监测、草原植被覆盖度监测与草原地上生物量估算）、草原动态监测（草原植被长势监测、草原产草量估测与草畜平衡监测）和草原应急管理（草原火灾、雪灾与生物灾害监测）中的应用。结合大数据、人工智能、云计算与物联网等新型技术,分析了低空无人机遥感在草原生态监测领域存在的不足和未来的发展方向,以期为低空无人机遥感关于草原监测评价与智慧草原的后续研究提供参考。

Advances in applying low-altitude unmanned aerial vehicle remote sensing in grassland ecological monitoring

The low-altitude unmanned aerial vehicle (UAV) remote sensing uses the UAV as a support and transports various sensors to obtain high-resolution ground-based remote sensing data. The low-altitude UAV remote sensing technology has the advantages of high timeliness, high resolution, low cost, and easy control, respectively. As a useful supplement to the gap in the measurement scale between ground and high-altitude remote sensing (aerospace and aerial remote sensing), the low-altitude UAV remote sensing expands the space scale of sample squares and improves the refinement of medium and fine scale remote sensing observation information. It also realizes the rapid collection, processing and application analysis of grassland habitat information, and is an important component of the integrated monitoring of grassland "star-air-ground". The low-altitude UAV comprises the fixed-wing UAV and the multi-rotor UAV at the present time. In anyway, the low-altitude UAV remote sensing enriches data diversity, broadens the depth and scope of data, and provides benefits for monitoring and evaluation of grasslands. Aiming at ecological monitoring of grasslands, this study summarizes the application of the low-altitude UAV remote sensing at home and abroad in grassland base survey (grassland grass height monitoring, grassland vegetation cover monitoring, and grassland aboveground biomass estimation), grassland dynamic monitoring (grassland vegetation growth monitoring, grassland yield estimation and grassland and livestock balance monitoring), and grassland emergency management (grassland fire, snow disaster and biological disaster monitoring). Finally, combined with new technologies such as big data, artificial intelligence, cloud computing and Internet of Things, the shortcomings and future development directions of the low-altitude UAV remote sensing in the field of grassland ecological monitoring are analyzed, in order to provide a reference for the follow-up research on grassland ecological monitoring and smart grassland by low-altitude UAV remote sensing. There are also certain limitations to the application of the low-altitude UAV remote sensing. Firstly, the low-altitude UAV is lightweight and vulnerable to micro-meteorological conditions. Secondly, although the low-altitude UAV may be equipped with multi-source sensors, the sensors have not yet adopted the unified design standards and considered product versatility. Thirdly, the big data processing efficiency of UAV is behind schedule. Lastly, in areas of complex environmental conditions, particularly rough terrain, the operational difficulty of the UAV increased. In the next period of time, the low-altitude UAV remote sensing should fill the above gaps, and the following developments and trends should be highlighted. The low-altitude UAV remote sensing should fully integrated UAV platform and remote sensing sensor, in order to perform integration, built-in and component of UAV flight platform and load. The low-altitude UAV remote sensing should promote the integrated monitoring of "Earth-space stars" and realize the extent of the temporal and spatial scale of grassland ecological observation. The low-altitude UAV remote sensing should combine remote sensing data from multiple sources, and integrate the emerging technologies such as big data, artificial intelligence, cloud computing and the Internet of things, so as to improve the processing efficiency of UAV massive data and mine the application value of images. We believe in that as part of continuing to promote and enhance the grassland ecological monitoring network in the new era, the low-altitude UAV remote sensing with its inherent advantages would foster the development of ecological monitoring of grasslands, from traditional ground-based observation to space-based quantitative remote sensing.