UAV to measure canopy height and plot biomass in a lucerne variety trial

Complete article published in : Grassland Science in Europe, Vol. 26. "Sensing - New insights into Grassland Science and Practice". [On line], pp. 65-67.

Abstract:

The objective was to test the reliability of height and biomass measurements of lucerne by digital photogrammetry using an unmanned aerial vehicle (UAV). Height measurements were recorded on a variety trial involving 440 microplots of pure stand lucerne over two years from April 2019 to November 2020. For comparison, manual measurements of plant height and dry matter yield (DMY) were performed the same day as the UAV acquisitions at the end of eight growth cycles. The model Phantom 4 Advanced (DJI) with mounted RGB camera equipped with a 20-megapixel CMOS sensor was used for image acquisition. The flights occurred at an altitude of 9 m to achieve a resolution of 2 mm. When UAV heights were calculated using 100% of the pixels of the canopy height model, the correlation between heights and DMY derived from UAV acquisitions were greater than those derived from manual measurements. Regressions on the set of flights per year between UAV heights and DMY were similar with high correlation coefficients in 2019 and 2020 (0.89 and 0.96, respectively). We conclude that UAV equipped with a high-resolution RGB camera allow rapid acquisition and data treatment and predicting reliable results of canopy height and DMY for the lucerne.