## 3 Results and Discussion
### Determination of Relevant Visual Information
#### 3.2.3 Information Gained from Test Clips  
Screen shots from the ten clips used in this study are shown in Figure 7. Participant responses regarding the information gained from each video clip and how that information could be used (i.e., two of the open-ended questions from the questionnaire) are tabulated in the Appendix A. A summary of the responses to questions 4-6 is provided in Table 2, with full details provided in the Appendix A. Only two of the video clips (1 and 2) were typically viewed by a majority of the participants when operating their sprayers (Table 2). Not surprisingly, these were the only two video clips where a majority of participants identified the level of importance of the information provided to be \"very important\" or \"extremely important\". Video clips 3 through 7 were not perceived to provide visual information that is relevant to the task of operating an agricultural sprayer. The utility of the information provided in the video clips is more difficult to summarize. Generally, participants used the video clips to obtain information about the boom status, the location and movement of the sprayer within the field, the weather conditions (especially the wind), obstacles to be avoided, crop conditions, and field conditions. However, not all video clips were equally effective at providing information for these relevant parameters. Participants were able to gather information regarding the field conditions and travel speed of the sprayer from almost all of the clips. This outcome is not surprising given that the field was present in all the video clips and all clips featured some aspect of the sprayer against the stationary background of the field. It should be noted, however, that information about many of the other parameters was available in only a subset of the  
Figure 6: A screen shot of the practice video clip (clip P). Figure 7: Screen shots from clips 1–10. clips. Information about boom height, leaks, crop condition, wheel alignment with previous tracks, machine integrity, weather (wind), and obstacles could be determined from five to seven video clips. Information about the sprayer's location, spray pattern, nozzle status (not plugged), spray drift, and how close the boom end was from the field boundary could be determined from only three or four video clips. Features such as sprayer clearance, section control, boom stability, turning at headland, size of the field, object behind the sprayer, field boundary, side of the sprayer, and knowing that the sprayer was in the right field could be determined from only one or two clips. Participants' ability to identify any useful visual information from the sprayer and its surrounding environment was not dependent on how frequently such information was presented. As an example, 28% of participants considered \"turning at headland\" to be valuable, even though it was only presented in one of the clips (as perceived by participants), while fewer participants identified the \"approximate travel speed\" as visually important, even though it was perceived in all the video clips (see Appendix A). Furthermore, environmental cues were considered important by participants when such cues were presented in relation to the spraying operation. For example, a higher number of participants perceived the field boundary to be valuable information when the end of the boom was visible with respect to the field boundary. However, fewer participants perceived the \"field boundary\" to be useful in clips that didn't relate it to the spraying operation (boom), despite being visible. In other words, the field boundary is only important with respect to the position of the sprayer--the user does not care about the location of the field boundary unless it is presented in relation to the position of the boom. A summary of the information gained by operators based their look zones is presented in Figure 8.