*4.5. Experimental Results from Suburban Areas*

Figures A8–A10 present the representative portions of the original images and Pan sharpening results of the suburban test sites from F3, F7 and F8 frames respectively.

Similar to the urban and rural areas, visual comparison of original MS and Pan sharpened images of this category revealed that all the Pan sharpened images produced higher spatial information than original MS image and benefited from Pan image detail level. However, the visual performance of suburban areas was variable, unlike the urban and rural areas. Results from frame F3 (Figure A8) show that all methods had acceptable performance except Ehlers and HIS. Nevertheless, small amount of distortion in vegetation and shadowed areas is apparent in the results of NNDiffuse and HCS methods.

Figure A9 illustrates the effectiveness of the CIELab method in Pan sharpening process. There is an obvious color distortion in all methods except proposed Lab method's result. Parts e, g and i demonstrate similar distortion in the results of Ehlers, GS and HIS methods with a green dominant color distortion, while other three methods, which are presented in parts d, f and h, have purple dominant color distortion. These color distortions are apparent for all surface types including roads, rooves and other objects. The CIELab was the only method that provided acceptable performance for this test frame. Ehlers and IHS methods could not provide good performance for the last test frame, as is observable in parts c and g of the Figure A10. Parts d and f prove that the results of the GIHS and HCS are blurred and not acceptable. Green and white tones distortion is obvious in the result of GS (Part e from Figure A10). The CIELab method illustrates the best performance again in this frame. Regardless of the distortion in shadowed areas, NNDiffuse provided most similar results to original MS image after the CIELab results.

Numerical results of spectral quality assessment of Pan sharpened images belonging to suburban areas (frames F3, F7 and F8) are presented in Table A5. Once again, CIELab method provides the highest values for the QAVG, PSNR and SSIM metrics, while it achieves the lowest values for the ERGAS, RASE, RMSE and SAM metrics. The GS method has the second place again, similar to the urban and rural test sites by achieving better numeric values for most of the metrics. Similar to previous test site results, the Ehlers and IHS methods have the worst performance between all tested methods.

Spatial quality assessment of Pan sharpening results for the frames F3, F7 and F8 are presented in Table A6. The proposed CIELab method illustrated an unrivaled performance in the case of the spatial quality metrics. For the CC and Zhou index, the highest correlation values that indicate high spatial quality are provided by the CIELab method. Moreover, the lowest SRMSE and SP ERGAS values achieved by the proposed method are another proof of high spatial quality of this method. Ehlers, HCS and IHS methods present the lowest CC and Zhou values with the highest SRMSE and SP ERGAS values, which indicate the poor spatial performances of these methods, like their spectral performances.
