Shuji ISONO

A Study on Paddy Rice Growth Monitoring Method Considering the Influence of Laser Spot Size in UAV-LiDAR Measurements

Kazuyoshi TAKAHASHI

　The authors have been developing a method for estimating paddy plant height and stem number by analyzing the vertical distribution (VD) of paddy rice plant communities acquired by LiDAR measurements. However, VD is known to vary depending on the instruments used and the observation conditions (flight altitude, laser incidence angle, laser divergence angle, etc.), and previous studies have investigated how VD varies under specific observation conditions. However, verifying the relationship between observation conditions and VD requires repeated measurements, which is time-consuming and labor-intensive. In addition, it is difficult to comprehensively verify all observation conditions.
　Therefore, this study investigates a method to evaluate the relevance using a simulation model to estimate the VD under specific observation conditions. In particular, we focus on the laser spot size and aim to clarify the relationship through simulation. Specifically, we will evaluate the usefulness of the simulation model developed in our laboratory by comparing it with the results of measurements made in FY2022 and FY2023. We will also confirm whether VD can be estimated for different fields and investigate the versatility of the model.
　The results showed that the model could generally reproduce VD with RMSE less than 10% in the range of FSI=6 to 9 in FY2022 and FY2023, except in the early growth stage, confirming the usefulness and versatility of the model. However, the similarity was low in the early growth and ear emergence stages, suggesting that the applicable period needs to be determined. It was also pointed out that there is a possibility of overestimation when judging the similarity between distributions based on RMSE alone.