Precise remote measuring system for building 3D spatial information on rocks that cover and uncover

For this study, a system capable of measuring the absolute position and shape of nearby rocks that cover and uncover along the shore precisely and remotely was devised. The system, consisting of a GPS/INS and a stereo digital camera, can be attached to the side of a ship. A surveying ship equipped with the system may sail around the rocks, obtaining GPS and INS data on the rocks, and digital images captured with a stereo cameras. The data can then be post-processed to obtain precise 3D spatial information on the rocks. The key methods used to realize the system was GPS/INS integration method, real-time direct geo-referencing method for a digital camera, and 3D scanning technology that automatically matches stereo images. Among these methods, the stereo image matching method was developed for this study. The method was realized by combining the conventional SURF descriptor generation algorithm, the matching methods using the scanning area reduction method based on the epipolar geometric theory, and matching line-based filtering, thus allowing faster and more accurate image matching and 3D surveying on the rocks. To verify the feasibility of the technology, a test survey was conducted on a rock and a dyke near Incheon, South Korea. The test run showed that the system could obtain 3D spatial data on the rocks with an average 10.45 cm planar and 14.32 cm elevation errors.