Evaluation of similarity-checking methods for reference samples migration to monitor land cover changes in the complex terrain of the Alborz Mountains, Iran
摘要
Mountainous areas are undergoing rapid Land Cover (LC) changes due to climate change and human activity. However, the shortage of reliable training samples still hinders historical LC change monitoring in mountainous areas. Sample migration has recently been introduced to address this obstacle, but its efficiency in mountainous regions has not been well-documented yet. Additionally, previous research has solely utilized Spectral Angle Distance (SAD) and Euclidean Distance (ED) as metrics for similarity checking. In this study, we used a sample migration technique, Landsat imagery, and a cloud computing platform to investigate historical LC changes over the Alborz Mountain range of Iran between 1988 and 2023 at five-year intervals. Initially, we generated the LC map for the reference year (2023) using Landsat data and high-quality reference samples. We then assessed five similarity checking algorithms, namely SAD, ED, Census (CE), Kullback–Leibler (KL), and Multivariate Alteration Detection (MAD), to migrate high-quality samples from the reference year to the target years. Finally, we generated a set of eight 30-m LC maps for the Alborz Mountain at 5-year time intervals. Our analysis showed that the combination of KL and CE yields superior accuracy for migrating high-quality samples. This is because CE considers neighboring pixel information and KL effectively handles non-linear imaging differences. The produced LC maps based on the proposed sample migration technique achieved high overall accuracy, ranging from 88 to 90%. We also observed severe LC changes in the Alborz Mountains, with a dramatic decline in forest areas and a sharp increase in cropland and rangeland.