Fig. 18

a Comparison between spectra from the transparent area inside the stained glass and the vegetation. The spectra are taken from all the acquisitions of LM-8368. Each spectrum is an average signal obtained by selecting the entire transparent area (Fig. 14a). The red line refers to the spectra obtained when the transmittance reference is taken inside the stained glass, which appears flat due to the division occurring during the image processing phase. The characteristic bands of the transparent glass can be observed when the reference is taken from the windows’ panes. b Comparison between spectra of an area painted with stained yellow and vegetation, taken from all the acquisitions of LM-8368. The red line refers to the spectra obtained when the transmittance reference is taken inside the stained glass and appears slightly different from the others due to effects related to the radiometric correction. c Comparison of spectra of the transparent area inside the stained glass (Fig. 15c), taken from all the acquisitions of LM-749. d Comparison between spectra from an area painted with stained yellow, taken from all the acquisitions of LM-749