Considering the difficulties associated with the creation of deterioration maps for stone cultural heritages, quantitative determination of chemical and biological contaminants in them is still challenging. Hyperspectral image analysis has been proposed to overcome this drawback. In this study, hyperspectral imaging was performed on Stone Buddhas Temple in Four Directions at Gulbulsa Temple Site(Treasure 121), and several surface contaminants were observed. Based on the color and shape, these chemical and biological contaminants were classified into ten categories. Additionally, a method for establishing each class as a reference image was suggested. Simultaneously, with the help of Spectral Angle Mapper algorithm, two classification methods were used to classify the surface contaminants. Method A focused on the region of interest, while method B involved the application of the spectral library prepared from the image. Comparison of the classified images with the reference image revealed that the accuracies and kappa coefficients of methods A and B were 52.07% and 63.61%, and 0.43 and 0.55, respectively. Additionally, misclassified pixels were distributed in the same contamination series.

In this study, vegetation index, the vegetation index calculated based on hyperspectral images was used to monitor Petroglyphs of Cheonjeon-ri, Ulju from 2014 to 2020. To select suitable the vegetation index for monitoring, indoor analysis was performed, and considering the sensitivity to biocontamination, Normalized Difference Vegetation Index (NDVI) and Triangular Vegetation Index (TVI) were selected. As a result of monitoring using the selected vegetation index, NDVI increased from 2014 to 2018 and then decreased in 2020, after preservation treatment. On the other hand, TVI was difficult to confirm the tendency during the monitoring. This difference was due to the variation in spectral reflectance according to the photographing conditions by year. Therefore NDVI is less sensitive to spectral reflectance deviation than TVI, so it can be used for monitoring. In order for TVI to be used, however, in-depth study is needed.

VNIR hyperspectral images can be analyzed in situations involving color changes, such as before and after cleaning, without pre-treatment. In this study, to analyze the application of the VNIR hyperspectral system, we compared the black contaminants on the surface of the Jigwangguksa Pagoda upper stereobate at Beopcheonsa Temple, Wonju before and after cleaning with laser. After a preliminary experiment to evaluate the applicability of VNIR hyperspectral imaging, we took images of the four sides (north, south, east, and west). The 823 nm band image was used for comparing before and after cleaning. As per the result of the image differencing analysis about before and after cleaning, the spectral reflectance of the area where the cleaning was performed showed a tendency to increase. Additionally, it was found that not only the washed area but also the extent of change could be calculated through monochrome for quantitative comparison, and imaging analysis using the VNIR hyperspectral system was sufficiently effective for comparison before and after cleaning.

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