## 3 Results and Discussion  
### Identification of Look Zones during Manual Sprayer Operation  
Analysis of the in-cab video footage (camera M) revealed nine look zones: (i) the view ahead of the operator from his seated position (i.e., front view); (ii) right side; (iii) right boom; (iv) left side; (v) left boom; (vi) upper display/mapping system (located at the top right corner from the operator's seated position); (vii) a second display (located close to the right arm rest); (viii) sprayer's dashboard/steering wheel; and (ix) left mirror/other (Figure 3). The participant was also seen making adjustments to the sprayer settings (through the displays) and checking his phone. Overall, he spent 39% of his time looking at the front view (Figure 3). This finding is consistent with the results of [15], who noted that sprayer operators spent the most time looking at the field ahead (i.e., front view), while the least attention was given to the dashboard information. When asked why he was looking at these regions, his reasons were (i) to determine how close the booms were to the field boundary, (ii) to assess if the nozzles were working properly, and (iii) to ensure that there were no obstacles close to the field boundaries and along the sprayer's path that would require him to manually raise the boom. He also stated that the front view helped him to determine when to take over the steering wheel to initiate turning at the headland.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Camera** & **Rationale** \\ \hline M & Ability to observe the operator’s head and eye movement (from his seated position) during the spraying operation. \\ \hline
1 & To capture the field ahead of the sprayer and other environmental cues. \\ \hline P and 2 & To capture the view of the right and left boom, respectively, as perceived from the typical seated position of an operator in the cab of a self-propelled sprayer. \\ \hline
3, 4, 6, 7, 8, and 10 & To capture regions around the sprayer that are currently not visible to operators (from their seated position). \\ \hline
5 and 9 & To capture off-field (third party) views and assess their usefulness to the remote supervisor of the autonomous sprayer(s). \\ \hline \hline \end{tabular}
\end{table}
Table 1: Rationale for choosing each camera position.  
Another method for interpreting eye-tracking data is to represent the data as a function of time to give a sense of the cyclical nature of the task [14]. The data collected in this study are presented as a function of time in Figure 4. The data show that the operator was focused primarily on four look zones (front view, upper display, right side, and right boom) during the first 9 min of video footage--this corresponded to the time when he was spraying the field boundary. The front view enables the operator to assess where he is going and when to initiate turning, while the look zones to the right (i.e., right side and right boom) enable the operator to guide the sprayer along the field's boundary. Therefore, when the operator was spraying along the field boundary, his attention was split between looking ahead and watching the right side of the sprayer. Once the field boundary was completed, the time spent viewing the right boom decreased noticeably.  
Figure 4: Video data represented as a function of time to demonstrate the monitoring behavior of the operator during spraying operation. Each dot represents 10 s of the recorded video. Additionally, the gap at the beginning of the graph indicates the time interval between when the GoPro camera was turned on and when the spraying operation began.  
Figure 3: Look zones from the operator’s perspective during spraying operation.