## 2 Materials and Methods
### Experimental Setup Evaluation and Measurements on Plant Samples
#### 2.3.2 Laboratory Experimental Setup on Lettuce Plants: Image Acquisition and Evaluation Metrics  
As an initial evaluation of the system, lettuce seedlings (_Lactuca sativa_ var. Tanius) with four true leaves were transplanted into plastic pots with a capacity of 10 L. These pots were spaced apart in a fully randomized manner in single rows that were approximately 3 m long, with 5 or 6 pots per row. Two experiments were conducted in the laboratory, with both taking place between April and May 2022. In the first experiment, during which the pots containing the plants remained stationary, six baby lettuce seedlings (named A to F) were subsequently detected, localized, and photographed once on the same day and for 15 iterations. The second experiment was conducted in a 4-week interval, in which 5 different lettuce plants (named A to E) were detected, localized, and photographed once every week (growth days 10 to 31 after transplanting). The spacing between the consecutive pots was again fully randomized throughout this specific experiment. In other words, the plants were randomly shuffled and positioned in a row before the experimental detection and photographed procedure each time in this 4-week interval. The plants were watered daily under all circumstances and manually received a nutrient solution in the laboratory. All measurements were carried out between 10:00 am and 14:00 pm. The LEDs of the device used for illumination proved to be sufficient during both experiments. The degree of detection between the projected leaf area of the lettuce in the ground truth image, which is manually traced to outline the lettuce contour (manual contour delineation), and the corresponding leaf area determined and calculated using the Identify Plant procedure was evaluated using the Intersection Over Union (IoU) metric (Figure 13). This metric provides a ratio that represents the extent of overlap between the projected  
Figure 12: In (**a**), the two laser beams used for the evaluation of the system’s accuracy and repeatability are shown. The red laser is mounted vertically on the carriage, while the green laser is generated by the commercial laser tripod and is adjusted to lie down in a parallel axis with the measuring tape. In (**b**), a detailed close-up view of the measuring tape along with the red laser (spot) and the green laser aligned is shown. -lettuce area detected in the image and the ground truth area relative to the combined area of both the detection and ground truth. The IoU values range from 0 to 1, where a value of 0 indicates no overlap and a value of 1 indicates a perfect overlap. To calculate the projected leaf area as depicted in the images, all the pixels within the plant area that fall within the identified or manually traced plant contour are considered. The contours are treated as convex polygons. The total projected leaf area for each plant is obtained by summing the product of all the pixels within the plant area and the pixel/mm ratio, if available. The metrics Precision, Recall, and F1 score were also calculated. The Precision metric is derived by dividing the intersection area of each pair by the ground truth area, whereas the Recall metric is computed by considering the intersection area of each pair with the detected area (Figure 13). The F1-score metric is calculated as the weighted average of the Precision and Recall as depicted in Equation (2) below. Additionally, for each defined contour, the centroid was computed. The manual tracing of the lettuces' contours in the images of the experimental datasets was accomplished using ImageJ ver. 1.53t software (National Institutes of Health, Bethesda, MD, USA). \[F1\text{-}score=\frac{2\times Precision\times Recall}{Precision+Recall}, \tag{2}\]  
In the second experiment, the morphological characteristics of the plants are further examined by considering certain parameters. These parameters are illustrated in the tables and the images provided.