Is NDVI the best index for vegetation studies?

The vegetative percentage is one of the determinant parameters for energy equations at ground surface and have special importance in various issues such as hydrology, agriculture, and natural resources. There are several methods for decryption vegetation changes, with their own advantages and limitations. One method to study vegetation coverage changes is using plant indices. A review of previous studies shows that the NDVI index is the most widely used plant index in remote sensing which is widely used to study the presence, absence and percentage of vegetation in areas with different climatic, coverage, and topographic characteristics. This index may have completely different performance in different regions. This study tested ۲۱ plant indices statistically (۱۸ true indices, two soil line indices, and one atmospheric impact modifier) to compare other index's performance with the NDVI index. All indicators were obtained using IRS-۱D satellite imagery data. This satellite produces spectral data in four bands (green, blue, red, and near-infrared). This study was conducted in the Gharkhoad protected area of North Khorasan province. Classified random sampling methods were used to harvest canopy percent. Then, the relationship between numerical values in plant indices and the harvested canopy percentage on the ground was tested and the correlation between them was calculated. The results showed that the TSAVI index from the category of soil line indices shows the best correlation with vegetation percentage (R = ۰.۵۴), and NDVI showed the seventh rank in terms of correlation (R = ۰.۴۲) among the ۲۱ studied indices. Based on obtained results, the NDVI index cannot be considered as the best index for studying vegetation by default and the best one should be determined through statistical tests.

کلیدواژه ها:

Satellite imagery ، Gharkhoad ، coverage percentage ، correlation analysis