Retrieval of soil salinity based on multi-source remote sensing data and differential transformation technology

Rapid and accurate assessments of soil salinity information surrounding saline lakes are crucial for agricultural development and ecological security in arid regions. The Support Vector Machine (SVM) algorithm is currently utilized to derive the relationship between environmental covariates and soil salinity to perform remote sensing inversion of regional soil salinity; however, there is still potential for improvement in the existing SVM algorithm. Therefore, this study aims to improve the remote sensing-based soil salinity content (SSC) extraction from the Landsat 8, DEM and HJ-1A CCD satellite data using the Cuckoo Search Algorithms-Support Vector Machines (CS-SVM) model. In addition, the correlation and principal component analysis were conducted to determine the principal components of environmental covariates. The results show that the differential transformation effectively separates the land and water, which helps to reduce the noise in the raw remote sensing image. The analysis of soil and vegetation factors shows that the first three principal components cumulative variance contributed 99.69% on the raw remote sensing image, while the first two principal components cumulative variance contributed 88.01% and 85.28% on the first- and second-order differential transformation remote sensing images, respectively. Interestingly, L-S2 is the only factor correlated with SSC in the third order differential transform remote sensing image, with the R value of 0.325. The slope direction and plane curvature under the topographic factors had negative correlations with SSC, with the R values of -0.521 and -0.325, respectively. Finally, the SSC inversion model was developed using the first order differential transformation remote sensing images, which has high accuracy and good stability (R-2 = 0.68 and RMSE = 3.80 g(-1)). The cuckoo algorithm is helpful for determining the best support vector machine parameters and offers new perspectives in improving the reliability of remote sensing-based soil salinity inversion in arid regions.