UAS, Lidar Tested in Chinese Grasslands to Gather Data
Unmanned aircraft may provide advantages when it comes to gathering data about grassland ecosystems, according to a recent study conducted in the Hulunber grasslands of northeast China.
Grasslands cover about 27 percent of the Earth’s surface, providing forage for livestock, storing carbon and protecting soil. Chinese researchers funded by the National Science Foundation of China, China Agricultural Research System, and others, conducted a study to see if unmanned aircraft could provide an alternative to field-based data collection for attributes such as grassland canopy height, ground cover and biomass.
The researchers concluded that a UAS carrying a light detection and ranging, or lidar, system could “yield vital returns” for these purposes, and do so on a large scale. However, they decided that further testing should be conducted.
The investigators used a lightweight Velodyne HDL-32E lidar mounted on a UAS to gather data that was necessary to estimate the grassland canopy height, fractional cover, and biomass, and was able to provide a substitute to field-based date collection.
Lidar data is primarily used in the grassland to retrieve information and is said to be the best for calculating canopy height and fractional cover data. Space borne lidar data gives the highest level of spatial coverage and lowers economic costs over the large tested areas. Terrestrial or airborne lidar is usually too pricey to use for a broad-scale data collection. On the other hand, the photogrammetric data method is low in cost compared to lidar, but fails to estimate grassland canopy heights.
The lidar sensor was limited by the larger laser beam being used in the test. Future studies will be held to determine the benefits of lidar systems with a short transmit pulse widths and a smaller laser beam in the calculation of grassland parameters.
