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Abstract. The underwater environment has substantial properties for underwater research such as marine archaeology, monitoring coral reefs, and shipwrecks. SfM, as a major step of photogrammetry, has been widely used in the field. For a high 3D construction quality, images must have a clear visual sight environment and known orientations of the images. However, underwater images have various types of visual disturbances, but also GPS/INS, commonly used on the ground, are not accepted. Finding more feature points or using more images for SfM are solutions to the problems. However, these methods take high computational costs. An alternative to this problem is to provide the known orientations of the images. For a solution to provide known orientations of images, the presented method in this study uses visual SLAM that processes the localization of a vehicle system and mapping of surroundings. The experiment aims to verify whether SLAM improves the quality of underwater 3D reconstruction and the computation efficiency of SfM. We examine the two aqualoc datasets with the results of the number of cloud points, SfM processing time, and the number of matched images/total images and mean reprojection errors. The outcome shows SLAM-determined orientations improved the quality of 3D reconstruction and the computation efficiency of SfM with results of the increased number of point clouds and the decreased processing time.

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<p>The potential seismic hazard in South Korea is known to be that mid-sized earthquakes could occur nationwide. Because the damages of mid-sized earthquake are concentrated only in the vicinity of the epicenter, on-site EEW technology is known to be effective as a means to reduce absence of alarm near the epicenter and to ensure safety from earthquake threat. This study aims to simulate on-site EEW suitable for South Korea's seismic observation environment and verify its reliability. Seismic observations of 267 events occurred in South Korea, have been collected over the past five years for the simulation . Filter Picker was utilized to detect P-wave features from more than 37,000 data sets using a time window suitable for mid-sized earthquakes. The ground noises are removed from the detected P-waves, and a linear empirical relationship between the maximum P-wave amplitudes in vertical direction and observed PGVs on the base rock are derived. Convert the forecasted and observed PGVs to MMI, respectively. Assuming a successful prediction within the MMI±1 margin of error by comparing the two values, the results of this study showed an 80% success rate in the range above MMI 4. Through this study, feasibility and performance of on-site EEWS using domestic earthquake records were verified in South Korea. It is expected that this will contribute to the reduction of earthquake damage near the epicenter through an on-site warning in Korea.</p>

When a disaster occurs, effective alerts will reduce human life and property loss. The Integrated Emergency Alert System is a national disaster management system which integrates existing alert systems to deliver effective disaster alerts. Alert message exchange protocol is the essential technology for the System. In Korea, the first specification for "Common Alerting Protocol Profile for Integrated Emergency Alert System" was established in 2014. In this paper, we derive two additional requirements for more enhanced alert service and propose revision of the specification: multilingual alert service for foreigners and more flexible representation of target area. We review the associated foreign profile specifications as well as the domestic specifications to analyze these requirements. Finally, we propose the most efficient way to deliver multilingual alert message and to represent target area.

<p><strong>Abstract.</strong> Most of the existing public transit routing algorithms were developed on the basis of graph theory. Recently, algorithms are being developed that can compute for O-D public transit paths by using timetable information only, not using network structure consisting of nodes and links. The timetable-based public transit routing algorithm produces one shortest path to destination, using departure time and arrival time by stop. But it has limitations in reflecting additional factors, such as transfer penalty and alternative path selection, in the process of path calculation. In addition, since public transit passengers tend to choose one among various alternative paths, it is necessary to calculate multiple paths rather than a single path as in the existing methods. Therefore, this study proposes an improved RAPTOR algorithm that can consider transfer penalty and produce multiple paths, while it is based on RAPTOR, the existing timetable-based public transit routing algorithm. The transfer penalty was applied at the point of transfer, and differently according to transfer types. As a result of analyzing computed paths of the algorithms before and after improvement, it was found that computed paths with the improved RAPTOR algorithm proposed by this study were more similar to Seoul public transit passengers' actual travel paths than computed paths by the existing RAPTOR alone.</p>

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