# Introduction of a New Index of Field Operations Efficiency
## 4 Discussion and Conclusions  
In this paper, a new index for the efficiency of field operations was presented. This new index, FTE, provides an objective measure for the operational productivity since it is a function of well-defined and measurable features, including the field area and shape (field features), the machines' operating width and turning radius (machinery features), the driving direction and the field-work pattern (operating features). A number of scenarios, in terms of the above-mentioned features interaction, have been generated in order to demonstrate the sensitivity of the FTE to that features. The values of the FTE ranged between 70% and 98% for all tested scenarios. It is worth noting that the selection of the machinery features to be tested, provides a representative range in terms of operating width of the implements (4.5 m to 12 m) and the tractors' size (minimum turning radius between 3 m and 6 m), and field-work patterns selected regard the most common patterns in agricultural field area coverage. An average value of the FTE has been also calculated based on the mix of all (realistic) combinations between the machinery and operating features for a specific field. To this end, this average can provide an index for a specific field that represents its operability as a function solely of its shape and total area. However, generating a field operability index is an issue of further research, since a more comprehensive and well-defined group of alternatives have to be generated to provide this average value. These alternatives include, as an example, the exhaustive enumeration of all feasible driving directions (and not just the use of the indicative directions of \(0^{\circ}\), \(30^{\circ}\), \(60^{\circ}\), and \(90^{\circ}\) in the case of artificial fields and the two perpendicular directions, namely the parallel and the vertical to the longest field edge, in the case of real fields. The total longest productive travel length depends on the operating width (shorter operating width results to higher productive travelled distance) and for the same operating width depends on the area overlaps which are a function (given a fixed operating width) of the travelling direction. For the cases presented in Table 2, it is clear that for the cases of SQR, STD, R21, REN, and BPL the maximum FTE corresponds to longest travelled productive distances, while in the case of R41 the diversion between the min and max FTE values is attributed to the driving direction. The method can be easily implemented in real fields. As an example, Figure 13 shows the generated continuous paths with corresponding FTE for two fields implementing three different field-work patterns. Figure 12: Average FTE for all template field shapes in each driving direction. Figure 13: Demonstration of the effect of the field-work pattern on FTE. Other parameters are the same for all cases (operating width: 9 m; turning radius: 6 m; number of headlands: 2). The approach can also be implemented also as decision support system for the field operational planning since the process of selecting the optimal combination of features such as operating width, driving direction, and field-work pattern it is not a trivial one. As for example, Figure 14 depicts a field implementation showing the variability of FTE in different operational setups for this field. It can be seen that by comparing the FTE between the configurations in Figure 14a,b, the one with the narrower operating width (b) results to a higher FTE compared with the larger width (a) due to the selection of the SF pattern in the former case. Analogously, by comparing the FTE configurations between Figure 14c,d, the shorter operating width results to a higher FTE due to the selection of another field-work pattern. [PERSON] et al., (2015) was shown that the improvement in the field efficiency can be up to 7% by adopting an appropriate fieldwork pattern [PERSON] et al. (2015). This first approach on FTE definition and estimation process presents a number of limitations.