Algorithm 1. Radius neighborhood search algorithm.

Input: The point cloud of stem cross-section or rice plant

1: Project the point data onto the X-Y plane

2: Calculate the centroid position of the horizontal projection point: Z(${\mathit{x}}_{\mathit{i},}{\mathit{y}}_{\mathit{i}}$)

3: Count the horizontal projection point cloud: n

4: Build Kd-tree structure for point clouds

5: Set initial search radius and step size

6: for R in the radius range

7:  Neighborhood search with Z($x_{i,}{y}_i$) as the center and R as the radius, and record the number of points searched: k

8:  if k = n:

9:   return R

10: end

Output: Calculate the perimeter of stem or crown diameter of rice plant