Discontinuity Mapping in Natural Caves: A Comparative Study of Manual Data Collection, Structure from Motion, and iPhone 13 Pro Max

The stability of shallow caves is significantly influenced by analysing rock discontinuities like faults, joints and stratification. Assessing these characteristics and identifying their orientations is essential for evaluating cave stability. Traditionally, this has been done manually with tools like a compass, but accessibility and time constraints limit these methods. Recently, remote sensing methods like Structure from Motion photogrammetry (SfM) and laser scanning have gained popularity for providing high-resolution models. This study compares manual measurements, SfM, and iPhone 13 Pro Max laser scanning for discontinuity mapping in Badajo Cave (Spain), evaluating each method’s accuracy and efficiency. The results show a strong correlation between the methods, with an average measurement difference of around 5° for dip and dip direction, and the variation between methods was less than 7° in the worst case. The findings highlight the strengths and limitations of each method, with SfM providing high-resolution models but requiring considerable time for processing, and the iPhone 13 Pro Max offering quick results with some limitations in scanning range and accuracy.