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Rock slope excavation is unpreventable due to some location of infrastructure development must cut through rock hills. Therefore, an appropriate rock slope characterization should be carried out in order to prevent any possible failure. Recent advancement of drone technology has enabled the preliminary assessment on geotechnical characterization to be done in a short period of time. This paper mainly focuses on extraction of orientation and discontinuity features from drone imagery through the application of photogrammetry for rock slope stability assessment. Kinematic analysis is a method used to analyze the various modes of potential rock slope failures such as planar sliding, wedge sliding and flexural toppling that occur due to the presence of unfavorable oriented discontinuities. A drone was used to capture images from aerial and sideways, then imported to photogrammetry software to be processed. The output of the photogrammetry which is the dense cloud point would then be imported into a cloud compare software for the kinematic analysis. The orientations of discontinuities that has been extracted from the rock slope using CloudCompare software was imported into Rocscience Dips Version 7.0 software. The kinematic analysis feature of this software provides a quick check for various rock slope stability failure modes on a stereonet plot, such as planar sliding, wedge sliding and flexural toppling with just input on slope orientation, friction angle and lateral limits, before selecting the failure modes. By using discontinuity data, the kinematic analysis shows that the rock slope has 15.40% risk for planar sliding, 7.16% for wedge sliding and 1.33% for flexural toppling. Hence, the use of UAV as a tool in rock slope characterization is reliable because it can provide valuable preliminary information on rock slope stability assessment.

Photogrammetry advancement in the field of geotechnics is able to provide useful preliminary data in a short time and with minimum resources. The data acquisition for photogrammetry processing was done utilizing the imagery from a low-cost unmanned aerial vehicle (UAV). Commercial drone by DJI, Phantom 4 Pro was used to take aerial and side images of the rock slope. Good overlapping of the images is very important to generate a very dense 3D model. Ground control point was established to georeferenced the output of photogrammetry, so that it represents the real site scale and coordinates. Photogrammetry using structure from motion technique (SfM) is able to generate three-dimensional model of the specified study area. 3-D model of the rock slope was analyzed to extract the geological planes using CloudCompare software with the aid of FACET plugin. 3-D dense cloud point generated from the photogrammetry process was the input file to the CloudCompare software. Traditional method of using scan line survey was carried out to check the adequacy of the geological plane extraction data from photogrammetry survey output. Extraction of geological planes through FACET plugin provides information on major discontinuity sets and the orientation of the planes. Then, the dip/ dip direction obtained was compared with scanline survey. The discontinuity datasets obtained from the CloudCompare was compared with the scan line survey. Results showed the difference is not more than 20 %. Therefore, application of photogrammetry through CloudCompare software provides reliable and accurate measurement.