Comparison of Scanline and Photogrammetry Survey for Natural Fracture Analysis, Study Case: Jatiluhur Formation and Subang Formation, Bogor

Abstract

This research tries to compare the result of fracture measurement using the scanline as conventional method and photogrammetry method to understand the advantages of each method. This comparison is important to understand the benefit of using the photogrammetry for fracture study compared to the conventional method. The study area is located at three fractured outcrops of Jatiluhur Formation and Subang Formation at Cipamingkis river, Bogor. Two hundred fracture data from the scanline method and 215 aerial photos were collected for the analysis. The analysis found there are three main fracture sets in the study area, namely the Northwest - Southeast (NW-SE), Northeast - Southwest (NE-SW), and East-West (E-W). When measured at the same location, no significant difference in the orientation of the fracture sets can be found between both methods. However, the two different methods give a significantly different result on the fracture density calculation (P10). This difference was caused by the lithological characteristic variation, where it influences the ability to identify fracture from a distance. Additionally, the photogrammetric method enables the better identification of shear fractures and joints pattern that associated with the fold. Therefore, this study concludes that both methods are complementing each other on the natural fracture study. The scanline method is optimal for fracture density measurement, while photogrammetry is better for identification of fracture orientation and pattern in a relatively larger area.