• Korean Journal of Remote Sensing
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• v.37 no.5_3
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• pp.1425-1434
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• 2021

Continuous and periodic data acquisition must be preceded to maintain and manage the river facilities effectively. Adapting the existing general facilities methods, which include river surveying methods such as terrestrial laser scanners, total stations, and Global Navigation Satellite System (GNSS), has limitation in terms of its costs, manpower, and times to acquire spatial information since the river facilities are distributed across the wide and long area. On the other hand, the Mobile Mapping System (MMS) has comparative advantage in acquiring the data of river facilities since it constructs three-dimensional spatial information while moving. By using the MMS, 184,646,009 points could be attained for Anyang stream with a length of 4 kilometers only in 20 minutes. Levee points were divided at intervals of 10 meters so that about 378 levee cross sections were generated. In addition, the waterside maximum and average slope could be automatically calculated by separating slope plane form levee point cloud, and the accuracy of RMSE was confirmed by comparing with manually calculated slope. The reference slope was calculated manually by plotting point cloud of levee slope plane and selecting two points that use location information when calculating the slope. Also, as a result of comparing the water side slope with slope standard in basic river plan for Anyang stream, it is confirmed that inspecting the river facilities with the MMS point cloud is highly recommended than the existing river survey.

• Journal of Positioning, Navigation, and Timing
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• v.7 no.4
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• pp.295-305
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• 2018

Network RTK is a highly practical technology that can provide high positioning accuracy at levels between cm~dm regardless of user location in the network by extending the available range of RTK using reference station network. In particular, unlike other carrier-based positioning techniques such as PPP, users are able to acquire high-accuracy positions within a short initialization time of a few or tens of seconds, which increases its value as a future navigation system. However, corrections must be continuously received to maintain a high level of positioning accuracy, and when a time delay of more than 30 seconds occurs, the accuracy may be reduced to the code-based positioning level of meters. In case of SSR, which is currently in the process of standardization for PPP service, the corrections by each error source are transmitted in different transmission intervals, and the rate of change of each correction is transmitted together to compensate the time delay. Using these features of SSR correction is expected to reduce the performance degradation even if users do not receive the network RTK corrections for more than 30 seconds. In this paper, the simulation data were generated from 5 domestic reference stations in Gunwi, Yeongdoek, Daegu, Gimcheon, and Yecheon, and the network RTK and SSR corrections were generated for the corresponding data and applied to the simulation data from Cheongsong reference station, assumed as the user. As a result of the experiment assuming 30 seconds of missing data, the positioning performance compensating for time delay by SSR was analyzed to be horizontal RMS (about 5 cm) and vertical RMS (about 8 cm), and the 95% error was 8.7 cm horizontal and 1cm vertical. This is a significant amount when compared to the horizontal and vertical RMS of 0.3 cm and 0.6 cm, respectively, for Network RTK without time delay for the same data, but is considerably smaller compared to the 0.5 ~ 1 m accuracy level of DGPS or SBAS. Therefore, maintaining Network RTK mode using SSR rather than switching to code-based DGPS or SBAS mode due to failure to receive the network RTK corrections for 30 seconds is considered to be favorable in terms of maintaining position accuracy and recovering performance by quickly resolving the integer ambiguity when the communication channel is recovered.

• Journal of Advanced Navigation Technology
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• v.22 no.6
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• pp.591-601
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• 2018

This paper discusses methods to effectively operates and evaluates an infrastructure system for lane-level positioning based on satellite navigation. The lane-level positioning infrastructure provides correction information on range measurements with integrity information on the correction to a user with a single frequency (cheap) satellite navigation receiver in order to perform lane-level positioning and integrity monitoring on the position estimate. The architecture and configuration of the lane-level positioning system are described from the systematic level in order to provide a comprehensive insight of the system. The operation/evaluation system for the integrated infrastructure is then presented. The evaluation results of the real implemented system are provided. Based on the results, we discuss requirements to increase the system stability from the operation perspective.

• Journal of Advanced Navigation Technology
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• v.22 no.2
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• pp.49-56
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• 2018

As the energy generated by earthquake, tsunami, etc. propagates through the air and disturbs the electron density in the ionosphere, the perturbation can be detected by analyzing the ionospheric delay in satellite signal. The electron density in the ionosphere is affected by various factors such as solar activity, latitude, season, and local time. To distinguish from the anomaly, therefore, it is required to inspect the normal trend of the ionosphere. Also, as the perturbation magnitude diminishes by distance it is necessary to develop an appropriate algorithm to detect long-distance disturbances. In this paper, normal condition ionosphere trend is analyzed via IONEX data. We selected monitoring value that has no tendency and developed an algorithm to effectively detect the long-distance ionospheric disturbances by using the lasting characteristics of the disturbances. In the end, we concluded the $2^{nd}$ derivative of ionospheric delay would be proper monitoring value, and the false alarm with the developed algorithm turned out to be 1.4e-6 level. It was applied to 2011 Tohoku earthquake case and the ionospheric disturbance was successfully detected.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.8 no.3
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• pp.467-475
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• 2018

Recently earthquakes have been increasing worldwide, and the largest earthquake of 5.8 on the Richter scale occurred on September 12, 2016 in the Gyeongju area. After the earthquake, more than 200 aftershocks have occurred from January 2017 to December 2017. The largest earthquake in 2017 was a 4.3-magnitude earthquake near Pohang on November 15. In this study, we tried to analyze the coordinate change due to the earthquake using the data of the CORS(Continuously Operating Reference Station) in Korea. In order to analyze the change of coordinates due to the earthquake in Pohang area on November 15, 2017, data processing was performed by kinematic method. And from January 2017 to December 2017, observation data of 9 stations in Korea were analyzed by relative positioning method and the change of coordinates due to earthquake was analyzed. As a result of the study, it was possible to estimate the instantaneous coordinate change due to the earthquake through the kinematic positioning, and it was suggested that there is no change in the coordinates of the domestic CORS by the relative positioning results. After the 2017 Gyeongju earthquake, aftershocks continue to occur, and it is necessary to monitor the area continuously.

• Journal of Environmental Policy
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• v.14 no.2
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• pp.149-170
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• 2015

The purpose of this paper is to figure out the research direction and information regarding Mt. Baekdu in Korea through analyses of the research field and trends. Firstly, we made inventory of journal papers, conference proceedings, and research reports published related to Mt. Baekdu. A total of 255 data, spanning the 34 years from the 1980s to the middle of 2014, were acquired and classified into categories according to the year, field, contents and study area. Results show that research on Mt. Baekdu has been performed more than twice since 2010 and study regarding prediction has been carried out in 54.7% cases. In addition, the importance of geo-spatial information is expected to increase in order to study Mt. Baekdu. Secondly, we made and analyzed a geospatial information using inventory of 234 detailed research contents in research reports by Korea Meteorological Administration (KMA) and National Institute of Meteorological Research (NIMR). Statistics on categories show that research regarding prediction accounted for 81.6% of cases and the study of geo-spatial information utilization accounted for 54.7% of cases. However, the focus on studying the Mt. Baekdu region accounted for only 20.1% of cases. Thus, this indicates that it is necessary to do research at Mt. Bakdu itself. If the directly available geo-spatial information system is developed related to Mt. Baekdu, it will save research costs and analysis time. This study can be used to manage information about the research field of Mt. Baekdu by analysing inventory of research references and geospatial information using inventories when the Mt. Baekdu area is the focus of future research.

• Korean Journal of Remote Sensing
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• v.37 no.5_1
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• pp.1135-1147
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• 2021

In order to geometrically correct high-resolution satellite imagery, the sensor modeling process that restores the geometric relationship between the satellite sensor and the ground surface at the image acquisition time is required. In general, high-resolution satellites provide RPC (Rational Polynomial Coefficient) information, but the vendor-provided RPC includes geometric distortion caused by the position and orientation of the satellite sensor. GCP (Ground Control Point) is generally used to correct the RPC errors. The representative method of acquiring GCP is field survey to obtain accurate ground coordinates. However, it is difficult to find the GCP in the satellite image due to the quality of the image, land cover change, relief displacement, etc. By using image maps acquired from various sensors as reference data, it is possible to automate the collection of GCP through the image matching algorithm. In this study, the RPC of KOMPSAT-3A satellite image was corrected through the extracted matching point using the UAV (Unmanned Aerial Vehichle) imagery. We propose a pre-porocessing method for the extraction of matching points between the UAV imagery and KOMPSAT-3A satellite image. To this end, the characteristics of matching points extracted by independently applying the SURF (Speeded-Up Robust Features) and the phase correlation, which are representative feature-based matching method and area-based matching method, respectively, were compared. The RPC adjustment parameters were calculated using the matching points extracted through each algorithm. In order to verify the performance and usability of the proposed method, it was compared with the GCP-based RPC correction result. The GCP-based method showed an improvement of correction accuracy by 2.14 pixels for the sample and 5.43 pixelsfor the line compared to the vendor-provided RPC. In the proposed method using SURF and phase correlation methods, the accuracy of sample was improved by 0.83 pixels and 1.49 pixels, and that of line wasimproved by 4.81 pixels and 5.19 pixels, respectively, compared to the vendor-provided RPC. Through the experimental results, the proposed method using the UAV imagery presented the possibility as an alternative to the GCP-based method for the RPC correction.