*4.6. Thematic Accuracy Evaluation with Spectral Index*

The performance of the conventional and proposed Pan sharpening methods were evaluated with several quality indices and visual interpretation in this research. However, the effects of Pan sharpening on the information extraction, process such as image classification, segmentation and index-based analysis is another important concern that requires conservation of spectral properties of the MS image after Pan sharpening. One of the indirect methods frequently used to evaluate the abovementioned situation is to apply the spectral index on the MS and Pan sharpened images, and investigate their consistency. As only visible bands of the images were used in this research, the visible atmospherically resistant index (VARI) proposed by Gitelson et al., 2002 [54] was used for the evaluation as it uses the all visible bands for calculation.

$$VARI = \frac{Green - Red}{Green + Red - Blue}.\tag{9}$$

The test site F3 was selected for this evaluation, as it is one of the most challenging sites in the dataset due to complex and heterogeneous land cover characteristics. The VARI index was applied on both the MS and CIELab Pan sharpened images, and a binary classification was performed with the use of the same threshold to map the manmade and natural lands in the region. According to results presented in Figure 4, same level of information extraction could be achieved with CIELab Pan sharpened image and it even provided better thematic representation by providing better geometric representations of the objects and less of the salt and pepper effect observed in the vegetated areas located in the north and south parts of the image.
