| Abstrak/Abstract |
Discontinuity position data is the main information of slope stability in an area. Direct discontinuity measurement through geology compass is difficult and dangerous if it is being done in the high and steep cliff so that the measurement is reaching out certain area only. The founded result from direct measurement becomes unrepresentative. The technology development which produces high-resolution topographic data can help the discontinuity measurement in the hard-to-reach cliffs. One method that can be done is Structure from Motion (SfM), which will produce 3D model from acquisition photos with
camera sensor that moves. Further, those photos are processed with Agisoft Metashape and produced dense point cloud that be exported into weld then the discontinuity data be extracted through plug-in Compass and FACET in CloudCompare. The difference between Compass and FACET is in the work process. Compassis semi-automatic because the user must select the discontinuity of measured position visually. Meanwhile, FACET is automatically divides point cloud into some sectors based on some decided parameter. The gathered extraction of discontinuity data is being validated through result of measurement in the real area with geology compass in the same point. This research is focusing in a cliff which is located on the west side of Patuk – Prambanan Street, Ngoro – Oro Village, Patuk, Gunung Kidul. Based on the research result, according to SfM method, there are two discontinuity sets in each plug-in. According to plug-in compass, those are N350oE/80o and N67oE/13o while according to plug-in FACET, there are N354oE/81 and N65oE/13o. The result of validation of discontinuity position shows that plug-in Compass has higher error and has smaller deviation standard than plug-in FACET |
