A ground surface level is the reference position for measuring a plant height by human hands. However, ground surface levels are not uniform in a paddy or among paddies. In addition, in wide area, it is not practical to observe ground surface levels with cm- order and high spatial resolution.
Our proposed method for estimation of rice plants height has following features;
- A position in the top layer of plant canopies is the reference position to calculate a height.
- It assumes that a difference (the relative vertical distance) between the reference position and the arbitrary position in the bottom layer of plant canopies has a linear relationship with a plant height.
By using the reference position and the position in the bottom layer of plant canopies, a process to detect ground surface level is not necessary. Both positions of the reference and the bottom are calculated by using a percentile analysis of a vertical distribution of 3D point cloud data.
According to analyzing field observations data in three seasons, the 1st percentile vertical height is suitable as the reference position. In addition, the 80th to 95th percentile vertical height is suitable as the bottom position. The relative errors of estimation plant height were less than 10%.