Evaluation of Pixel and Object-Oriented Classification Techniques for Detection and Zoning of Erosion Lands Using Sentinel-2 Remote Sensing Data (Case Study: Lighvan Watershed)

Water erosion is one of the most important causes of soil destruction, and it is considered a serious environmental hazard all over the world. Recently, remote sensing is customarily used in conservation and erosion projects that most of them use air photography which, despite the many benefits, bot have limitations. The present study was aimed to detect and zoning soil erosion levels using high resolution of Sentinel-2 satellite image, its integration with aerial photographs, base maps, and implementation of various classification methods, including pixel-based and object-oriented techniques. After the staff operations, atmospheric and geometric corrections, pre-processing, and processing done on images of Sentinel-2 for detecting the area of erosion in the Lighvan watershed. In order to evaluate the correctness and accuracy of each method in this study, the criterions of user and producer accuracy, accuracy and kappa coefficient were compared. Based on the results, the supervised tuning method with user accuracy equal 77.78 and 33.33, has the highest and lowest accuracy for classification using spectral angle map algorithm and Mahalanubis distance, respectively. The maximum of overall accuracy and kappa coefficients, 72 and 62 percent, respectively, indicate the medium accuracy of the produced maps with pixel based algorithms. The results of object-oriented processing show that based on user and producer accuracy, object-oriented methods have increased accuracy (12 %) compared to pixel-based methods. Classification results with object-oriented algorithms and based on overall accuracy, 88 and 84 percent, respectively, for the brightness and the combination of brightness and slope, and the kappa coefficient for these two algorithms was 0.86 and 0.79, respectively. This result represents an acceptable increase in classification accuracy in the use of object-oriented algorithms compared to pixel base algorithms.