# Near Real-Time Irrigation Detection at Plot Scale Using Sentinel-1 Data
## 4 Results
### Results over Catalonia
This increase in the SAR signal is related to the transition between the heading phase (minimum point on 19/04) and the soft dough phase (maximum point at 19/05). However, these points were eliminated using the proposed cereal phenology filter discussed in Section 3.4. The proposed method was applied over a wide area of Catalonia region including 159,850 plots (123,428 non-irrigated and 36,423 irrigated plots) of different crop types. Despite the absence of information about the exact irrigation dates over Catalonia, a quantitative analysis was performed by comparing the results obtained by applying the method over irrigated and non-irrigated plots. Over Catalonia, the morning acquisition was 12 h prior to the evening acquisition. Figure 8 presents the histogram of the distribution of the number of events detected over irrigated and non-irrigated plots. Figure 8a corresponds to the morning SAR acquisition and Figure 8b corresponds to the evening SAR acquisition. The intersection between the evening and morning acquisitions is presented in Figure 8c. The intersection means that at each SAR date the point is considered as irrigation point if it exists within both the ascending and the descending acquisition modes (only 12 h difference between the two acquisitions is approximately equal to same day). Finally, Figure 8d shows the result of the combined use of both acquisitions. The combination between the results of the both acquisition modes means that at a given SAR date, the point is considered irrigation point if it exists in either the ascending or the descending acquisition modes. For morning acquisition mode (Figure 8a), the distribution shows that 68.3% of the non-irrigated plots had no detected irrigation events for the period between September 2017 and December 2018 (82 SAR images). Moreover, 20.3% of the non-irrigated plots encountered only one detected event. Therefore, 88.6% of the non-irrigated plots have maximum one detected irrigation point in the morning acquisition mode. The non-irrigated plots with 2 and 3 detected irrigation points represent only 6% and 2% respectively. On the other hand, only 12.1% of the irrigated plots failed to register any irrigation event. Thus, 87.9% of the irrigated plots had one and more detected irrigation points. The percentage then increases gradually where 54.9% of the irrigated plots had between two and five detected irrigation points. In addition, 20.4% of the irrigated plots encountered between five and 10 detected irrigation points. Similar results are obtained for the evening acquisition (Figure 8b). For example, 58.2% of the non-irrigated plots had no detected irrigation events while 25.1% had only one detected event. Thus, 83.3% of the non-irrigated plots encountered a maximum of one detected point for evening acquisition mode. In contrast, only 9.1% of the irrigated plots failed to gain any detected irrigation point and therefore 91.9.% of the irrigated plots had one and more detected irrigation point in the evening acquisition mode. Moreover, 51.1% of the irrigated plots had between two and five events and 27.3% of the irrigated plots had between six and ten detected points. The intersection between the morning and evening acquisitions modes (Figure 8c) shows that 90.2% of the non-irrigated plots have no detected peaks whereas 72.4% of the irrigated plots had one or more detected irrigation peak. The combination of both acquisition modes (Figure 8d) increases the number of detected irrigation points but leads to an accuracy of the same order of magnitude as in the case of a separate use of the two SAR acquisition modes or in the case of the intersection of the two acquisition modes. For non-irrigated plots, 45.9% of the plots had no detected points and 27.0% had one detected points. The percentage decreases gradually to then reach 7% for three detected irrigation points. Inversely, the irrigated plots with no detected irrigation points consist of only 6.8% while the percentage of plots varies between 5% and 10% for irrigation points between 1 and 14 points.