# Satellite Monitoring of Italian Vineyards and Spatio-Temporal Variability Assessment
## 3 Results
### General Variability  
The overall trend and variability of the VIs is presented below. The Vis' overall average and CV were computed in each vineyard during the six-year monitoring. Then, the statistical indices were compared with the structural and topographic features. The outputs mentioned above aim to respond to the first research question, proving a robust trend along the Italian peninsula and underlining the most divergent features that affect the monitoring through VIs. Figure 8 displays two PCA plots showing the relationship between the vineyard's features and the VIs' mean values and CV in Figures 8a and 8b, respectively. Such analyses explained 40.63% and 35.92% of the variance, respectively. The VIs' averages and CV were split into two analyses because of the means of the statistical indices and to avoid an excessive overlapping of information that could have deflected all the other vectors. On the other hand, NDVI and NDRE were joined to prove their alignment. The plot in Figure 8a reports that the average absolute values of NDVI and NDRE were strongly linked to the latitude effect. On the other hand, the CV of the vineyard showed an opposite relationship with them. Thus, higher variability was found in southern vineyards than in northern ones. Figure 7: The scatter plots describe the seasonal evolution of the VIs from the field in Figure 6 during the 60-day monitoring time. The chart on the top refers to the NDVI, while the chart on the bottom refers to the NDRE. The dashed line is drawn as the regression line between the DOY and VI. Points indicate the average value, while the bars mean the standard deviation. No relevant relationships were found between the VIs and vineyard's size. A foreseeable opposite relation was found between the size and the elevation vector. On the contrary, the row's orientation and spacing showed a weak positive contribution to the VI's absolute value and a negative one to the CV. Table 5 lists the outputs of the ANOVA performed between the VIs' statistical indices (seasonal mean and CV) and the vineyards' categorical features joined with the vintage's effect. The vintage effect was assessed from the VIs' means and CV against the PCA shown in Figure 8. Except for the topography effect, concerned with the CV of the NDRE, all the variables showed a relevant effect on both the VIs' mean and CV. Four classes were compared regarding direction. According to [PERSON]'s test output, the NS orientation retrieved, on average, the highest value for the NDVI and NDRE (0.577 and 0.374, overall mean values, respectively), and no statistical differences were found between NS and SW. The EW orientation retrieved the smallest values for NDVI and NDRE averages (0.515 and 0.330, overall mean values, respectively). In addition to average data, the same trend was repeated in each direction for all vintages, as shown in Figure 9a,b. The results showed that the NS and SW orientations always retrieved higher values than SE and SW, confirming the lowest values in all the vintages. Opposite results were found for the VIs' CV. For example, the NS orientation could be considered the most \"stable\" because it retrieved the smallest CV for NDVI and NDRE (0.090 and 0.111, overall mean values, respectively). The EW orientation showed the highest CV for NDVI and NDRE (0.099 and 0.121, overall mean values, respectively). The boxplots in Figure 10a,b display a constant trend among the vintages in which the vineyards planted in plains seem to reach higher VIs average values than the ones planted in hilly landscapes. Concerning data variability, Figure 10c,d shows a temporal stable CV, and hilly vineyards always showed a higher CV than the ones planted in a plain landscape. Figure 8: Biplots of the numerical morphological features along the first two principal components. Both VIs were plotted in the chart. Chart (**a**) includes the VIs averaged during the six-year monitoring period (NDVI_M and NDRE_M), while chart (**b**) includes the CV of the VIs (NDVI_CV and NDRE_CV).