Automatic mapping of lineaments and analysis for groundwater targeting using shaded relief images derived from a digital elevation model (DEM) in the Akure North Area of Ondo State, Southwest Nigeria

The study of geological structures (such as lineaments) is one of the most important factors, which gives indications about the locations of ore deposits, landslides, and groundwater propensities. This work involves the mapping of lineaments as an indication of groundwater occurrence using remote sensing and geographic information system. Shaded relief images created from digital elevation models (DEMs) help identify lineaments in different distinct relief and topography. By simulating topographic illumination under varying light directions, the method can enhance lineaments at diverse orientations. Lineaments within the four sun azimuth directions are improved when four shaded relief images are integrated into a single image. Two shaded relief images with multi-directional light were created, the first image with the four azimuth angles of the light sources were 0°, 45°, 90°, and 135°, and the second image with the four azimuth angles of the light sources were 180°, 225°, 270°, and 315°. Both images have been used for lineament extraction using the LINE Algorithm of PCI Geomatica. The results of the analysis show that the longer the lineament, the less frequency at which it appears. In total, 1410 and 1400 lineaments were extracted from the two superimposed images for this investigation. The lowest and maximum lengths of these lineaments are 920.99 and 921.08 meters, respectively, while their total lengths are 2639041.50 and 2607749.35 meters, respectively. The lineaments extracted were analyzed in terms of the total length, the number of lineaments, and orientation. The results of analyses from the extracted lineament map of the area indicate areas of groundwater occurrence. Various analyses were carried out on the extracted lineaments based on the length, density of lineament length, and orientation of lineaments. This study demonstrated the use of shaded relief images created from digital elevation models (DEMs) to extract lineaments. It also led to the delineation of areas where groundwater occurrence can be encountered. A concentration of geophysical surveys can be carried out in the indicated areas with the findings obtained