Automatic extraction of lineaments (linear features like faults, fractures, and dykes) from Landsat 8 and Sentinel 2 images can be performed using various remote sensing and image processing techniques. Here are some common techniques used for this purpose:
Edge Detection Algorithms: Edge detection algorithms, such as the Canny edge detector or the Sobel operator, are commonly used to identify abrupt changes in pixel intensity, which often correspond to linear features. These algorithms can highlight potential lineaments in the images.
Hough Transform: The Hough transform is a technique used to detect straight lines in an image. It converts the Cartesian coordinates of image points into a parameter space, where lines are represented by peaks. Hough transform can be applied to identify linear features in Landsat 8 and Sentinel 2 images.
Image Fusion: Combining different bands or sensors from Landsat 8 and Sentinel 2 images using image fusion techniques can enhance the visibility of lineaments by highlighting their spectral characteristics and reducing noise.
Principal Component Analysis (PCA): PCA is a dimensionality reduction technique that can be used to enhance linear features by emphasizing variations in the data. By transforming the original bands into principal components, lineaments may become more distinguishable.
Texture Analysis: Texture analysis methods, such as the gray-level co-occurrence matrix (GLCM) or local binary patterns (LBP), can help identify lineaments based on their distinct textural properties compared to the surrounding terrain.
Supervised and Unsupervised Classification: Applying supervised or unsupervised classification techniques can help separate lineaments from other land cover types based on their spectral characteristics.
Object-Based Image Analysis (OBIA): OBIA is an image segmentation approach that groups pixels into meaningful objects based on their spectral, spatial, and contextual characteristics. It can be used to identify linear features as cohesive objects.
Remote Sensing Indices: Specific remote sensing indices, such as the Normalized Difference Vegetation Index (NDVI) or the Normalized Difference Water Index (NDWI), can help emphasize lineaments by highlighting their differences from the surrounding landscape.
Machine Learning Algorithms: Machine learning techniques, such as random forests or support vector machines, can be trained to recognize lineaments based on labeled training data and then applied to automatically detect them in new images.
It's important to note that the choice of technique depends on the specific characteristics of the study area, the desired level of automation, and the complexity of the lineament extraction task. In some cases, a combination of multiple techniques may yield the best results. Additionally, post-processing and validation are crucial to ensure the accuracy of the extracted lineaments.
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