## 2 Materials and Methods
### Agricultural Plastic Surfaces (APS) Analysis
#### 2.2.1 Satellite APS Localization  
The use of satellite images has enabled a first rapid and accurate detection of APSs, so as to reduce the time of manual digitization on orthophotos. For high spatial, temporal, and spectral resolution, the freely downloadable online images of Sentinel-2 were chosen. Sentinel-2 is a mission developed by the European Space Agency (ESA) under the Copernicus program, for monitoring environment and territory, providing support in the management of natural disasters as well. It consists of two identical satellites, Sentinel-2A and Sentinel-2B, and it provides images from 2015. Given its versatility thanks to high revisit time, spectral, and spatial resolution, and free availability of images [28], the Sentinel-2 mission can be also widely used for APS detection. For example, there are several works showing the efficiency of using these images for the detection of plastics in agriculture \begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline \multirow{2}{*}{**Municipality**} & \multirow{2}{*}{**Greenhouse Catering**} & \multicolumn{2}{c}{**Other Greenhouse**} & \multicolumn{2}{c}{**Vegetables in Tunnels and**} & \multirow{2}{*}{**Total of Categories**} \\  & & **Tonatoes** & & & **Vegetables** & & **Other Structures** \\ \hline  & ha & \%\({}^{\,1}\) & ha & \%\({}^{\,1}\) & ha & \%\({}^{\,1}\) & ha & \%\({}^{\,1}\) \\ Bernalda & 2.5 & 10.10 & 24.43 & 5.25 & 7.7 & 3.51 & 34.63 & 4.88 \\ Montalbano jonico & 0 & 0.00 & 4 & 0.86 & 2 & 0.91 & 6 & 0.85 \\ Pisticci & 0.1 & 0.40 & 43.1 & 9.27 & 21.7 & 9.88 & 64.9 & 9.15 \\ Policoro & 1.84 & 7.43 & 151.59 & 32.60 & 34.6 & 15.75 & 188.03 & 26.50 \\ Nova siri & 0 & 0.00 & 6.28 & 1.35 & 7.65 & 3.48 & 13.93 & 1.96 \\ Rotondella & 0 & 0.00 & 3.6 & 0.77 & 3.1 & 1.41 & 6.7 & 0.94 \\ Scanzano jonico & 1 & 4.04 & 169.07 & 36.36 & 84.38 & 38.41 & 254.45 & 35.87 \\ Tursi & 1.5 & 6.06 & 3.98 & 0.86 & 52 & 23.67 & 57.48 & 8.10 \\ \hline Total for study area & 6.94 & 28.04 & 406.05 & 87.32 & 213.13 & 97.02 & 626.12 & 88.26 \\ Total for Basilicata & 24.75 & & 465.01 & & 219.68 & & 709.44 & \\ Region & & & & & & & \\ \hline \hline \end{tabular} \({}^{\,1}\) Percentage compared to the total area of the same category registered in Basilicata Region.  
\end{table} 
Table 1: Area (in ha and %) recorded for major horticultural crops with plastic protection within the study area municipalities. Data processed from the sixth Italian census of agriculture, the last publicly available census [21]. based on different techniques and indices [29; 30]. In this work, only the B2, B3, B4, and B8 bands of the Sentinel-2A satellite were used. These bands all have a spatial resolution of 10 m and the central wavelengths (\(\lambda\)) measure, respectively, of 492.4 nm, 559.8 nm, 664.6 nm, and 832.8 nm. There are many applications that use complex algorithms for semi-automatic detection of APSs. In fact, it is possible to find different works in the literature where different algorithms are implemented with high degrees of accuracy [31; 32]. However, these techniques often require very high scientific skills that are hardly found in local authorities. Satellite images were downloaded through the Theia system, which provides orthorectified surface reflectance images after atmospheric correction. Two images (9 and 26 July 2017) were used to verify the presence of plastic films, avoiding errors due to the temporary absence of greenhouse cover. For the present study, it was chosen to test a Retroprogressive Plastic Greenhouse Index (RPGI) proposed by [PERSON] et al. [33] that can be useful for a more immediate and expeditious methodology. At the same time, this can provide useful data to make a first (but not complete) screening of areas with APSs. RPGI is an index that provides a binary classification (presence, absence of greenhouse plastics) and is very dependent on the vegetation under plastic, since it is higher when crops within the greenhouse are thriving.