Colour to Greyscale Pixels: Re‐seeing Greyscale Archived Aerial Photographs and Declassified Satellite CORONA Images Based on Image Fusion Techniques

Abstract

To date, archived aerial photographs or recently declassified satellite CORONA images have been used to support archaeological research. However the use of such images is limited to the interpretation of greyscale images, which can be improved by image analysis processes including filters, edge detection techniques, etc. This article presents a methodology to improve the interpretation of these images by adding colour from recently acquired satellites or airborne sensors. The methodology followed in this article, is based on the use of pan-sharpening algorithms which are applied to a set of an archived greyscale image and a recently colour image taken over the same area. These two images are geometrically corrected while their histograms are matched. Then, the two images are merged based on different pan-sharpening techniques such as Brovey transformation, high pass filters, multiplicative transformation, principal component analysis and wavelet decomposition. The final result is a colour image which can be further studied for interpretation purposes. A coherence image is also calculated since differences due to time might be also observed in the images (e.g. land use changes). The results presented here from different cases studies of Cyprus indicate that the proposed methodology may be applied in any other greyscale archive dataset. From the results is was shown that Brovey and high pass filter transform seem to be able to support better the interpretation of such archive information. Figure 3. CORONA and Landsat 8 LDCM images used over the 'Kourion' archaeological site (34°40.367ʹN; 32°51.830ʹE, WGS 84, 36 N). Fusion results based on Brovey, PCA, and wavelet transformations are also presented. This figure is available in colour online at wileyonlinelibrary.com/journal/arp Figure 4. CORONA and Landsat 8 LDCM images used over the 'Palaepaphos' archaeological site (34°42.357ʹN; 32°34.867ʹE; WGS 84, 36 N). Fusion results based on Brovey, PCA, and wavelet transformations are also presented. This figure is available in colour online at wileyonlinelibrary.com/journal/arp 235 Colour to Greyscale Pixels Based on Image Fusion Techniques

Fusion of Satellite Multispectral Images Based on Ground-Penetrating Radar (GPR) Data for the Investigation of Buried Concealed Archaeological Remains

“…However, the fusion and integration of data gathered from different sensors is quite challenging. Although some fusion techniques already exist, like pan-sharpening between multi-spectral and panchromatic bands of the same or different satellite sensors [26,27], or as more recently shown, fusion between archive greyscale and recent multispectral satellite images [28], fusion methodologies of more diverse datasets need to be developed and tested for archaeological research. Studies have shown that it is feasible to scale-up ground spectroradiometric data (i.e., ground spectral signatures) to existing [29] or even forthcoming satellite sensors [30].…”

From Space to Ground. Digital Techniques for the Investigation of Monuments and Sites

“…To detect and map potential traces of the remains, archive and recent aerial photographs have been used. Towards this end, identification of potential crop and soil marks [7], which are considered as a proxy for buried archaeological remains was studied. Based on pan-sharpening techniques these marks could be enhanced and identified from recent orthophotos (see [7]).…”

“…Towards this end, identification of potential crop and soil marks [7], which are considered as a proxy for buried archaeological remains was studied. Based on pan-sharpening techniques these marks could be enhanced and identified from recent orthophotos (see [7]). Several marks were also identified after photo-interpretation and in situ inspections, using Global Navigation Satellite Systems (GNSS).…”

Searching data for supporting archaeo-landscapes in Cyprus: an overview of aerial, satellite, and cartographic datasets of the island

“…However, in other aerial images, interpretation can be problematic due to the noise of the datasets. It has been demonstrated in [17] that such datasets might be fused together using pan-sharpening techniques in order to retrieve the lost archaeological marks and therefore assist archaeologists for better understanding a site. Other aerial images taken during the 70's are also available from the Department of Land and Surveyors.…”

“…CORONA images have been used in other areas in order to support archaeological research [20]. Some first studies from the potential use of CORONA images for archaeological research in Cyprus can be found in [17] although it should be mentioned that the quality of the images over Cyprus is relative poor (low SNR) compare to other areas of the world. CORONA were acquired at different spatial resolution, acquisition modes such as stereo etc.…”