Using UAV-Based Photogrammetric Data for Pegmatitic Lineament Extraction in the Angarf Area (Zenaga Inlier, Morocco)

Data acquisition using unmanned aerial vehicles (UAV) has increased interest in the geological field. This instrument allows capturing of high-resolution images of the rock surface and the analysis of those datasets remotely. In this study, a lineaments extraction approach was applied to highlight the pegmatitic veins in the Angarf area (Zenaga inlier, Central Anti-Atlas, Morocco) using UAV photogrammetry. The photographs were acquired by Phantom 4Pro with a flight altitude set at 100 m. The resulting spatial resolution is about 3 cm/pixel. First, several preprocessing techniques were applied to the raw data to obtain a Digital Elevation Model (DEM) and an orthophoto. Then, a comparison between the two methods was conducted. The first consists of automatically extracting the lineaments from the shading of the DEM, and the second is based on manual interpretation to list the pegmatite veins directly from the aerial photographs. As a result, the approach using automatic extraction from shading provided little information since the elevation is almost invariant in the study area. This is in contrast to the manual interpretation of the orthophoto, where many veins were identified. Although the latter method is more time-consuming and relies mainly on human experience and capacity, it remains the most suitable for the case of our study.