Fig 1.
Schematic drawing of the relationship between camera, maize plant and related two-dimensional maize plant projection.
Fig 2.
The schema of maize planting rows construction and maize plant distance calculation.
(A) Randomly selected adjusted centroids (pi). (B) Determination of the buffer design. (C) Calculate the center points (Pc) of the chosen maize point collection. (D) Updated line that crossed Pc point with the predefined crop row angle d.
Fig 3.
Flowchart of maize planting interval distance calculation.
Fig 4.
Example of images acquired by UAV platform.
(a) S9cm_1m. (b) S18cm_1m.
Table 1.
Parameters used to detect maize plant location to determine plant distance.
Fig 5.
Estimated distance of the maize interval at 1m camera height with different plant distances.
(a) 9cm, (b) 18cm, (c)27cm and (d) 36cm.
Table 2.
The estimated distance of maize interval (cm).
Fig 6.
Enlarged view of Fig 1 and related estimated distance of maize intervals.
(a) Leaves inteact, and (b) leaves separate.
Fig 7.
Relative error of crop distance interval estimation.
Fig 8.
The letter i indicates different distances of maize interval. (a) S18cm_5m, (b) S27cm_5m, and (c) S36cm_5m.
Fig 9.
Flight and related plot area covered by UAV imagery.
Fig 10.
Estimated maize distance with different flight heights.
(a) 1m, (b) 2cm, (c) 3m, (d) 4m, and (e) 5m.
Table 3.
Accuracy assessment of average crop interval distance.
Fig 11.
Maize segmentation from the threshold based method at different heights.
(a) 1m, and (b) 2m.