PLASTIC COVER GREENHOUSES REFLECTANCE SPECTRA FROM DIFFERENT OPTICAL SATELLITE IMAGERY
Keywords: Plastic Covered Greenhouses, Reflectance, Spectral Indexes, OBIA, Landsat 8, WorldView-3, Sentinel-2
Abstract. Mapping the distribution of plastic covered greenhouses (PCG) is essential for any attempts to manage these complex areas of intensive agriculture. It is therefore important to understand how the spectrum of different PCG varies in order to establish its unique absorption features and how these can be utilised for mapping PCG from remote sensing imagery. This paper presents an analysis of the surface reflectance values of satellite image spectra for 50 PCG. The reflectance of these PCG, located in Almería (Spain), was studied in two seasons of the year (summer and winter). All single bands of WorldView-3 (WV3), Sentinel-2 MSI (S2 L2A) and Landsat 8 OLI (L8 L2), together with Normalized Difference Plastic Index (NDPI) and Normalized Difference Vegetation Index (NDVI), were generated through an object-based image analysis (OBIA) approach for each PCG and season. The results showed the variability of absorption features and overall shape of the spectra for all PCG. The main differences in reflectance were attributed to the crops and the specific characteristics of their local management. A relationship between brightness and whitewashing (greenhouse roof painted with lime to provide shade and reduce the temperature inside the greenhouse, especially in summer) was found, showing the ability of whitewashing to temporally mask the spectral signature of the plastic film.