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Now showing items 1 - 4 of 4

  • A Static Displacement Monitoring System for VLBI Antenna Using Close-Range Photogrammetry

    Kim, Hyukgil   Yun, Hongsik   Hwang, Jinsang   Hong, Sungnam  

    In this study, a static displacement monitoring program was developed to maintain the accurate performance of a Very Long Baseline Interferometry (VLBI) antenna by monitoring its structural stability. The monitoring program was designed to measure static displacement, among the many displacements of the antenna's main reflector, which can directly affect its performance. The program measures the position of a monitored object with mm-level accuracy through close-range photogrammetry that uses high-resolution Charge Coupled Device (CCD) cameras. The developed program will be used to evaluate the structural soundness of an antenna based on continuous displacement measurements, which can also be used as basic data for repair and reinforcement work in the future.
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  • A New Window-Based Program for Quality Control of GPS Sensing Data

    Lee, Dongha   Cho, Jaemyoung   Suh, Yongcheol   Hwang, Jinsang   Yun, Hongsik  

    The main purpose of this study is to develop a new Windows-based program that calculates a quality control parameter that shows the quality of Global Positioning System (GPS) observations using GPS data in a Receiver INdependent Exchange (RINEX) format. This new program, Global Positioning System Quality Control (GPSQC), allows general GPS users to easily and intuitively check the quality of GPS observations before post-processing, which will lead to the improvement of GPS positioning precision in diverse areas of GPS applications. The GPSQC is designed to control the multi-path, cycle slip, and ionospheric errors of L-1 and L-2 signals in GPS observations. The GPSQC was developed using C#.NET language for the Window series with Microsoft Graphical User Interfaces (MS GUIs). This program gives brief information for GPS observations, time series plots, graphs of quality control parameters, and a summary report in MS word, Excel and PDF formats. It can simply perform quality checking of GPS observations that is difficult for surveyors conducting field work. We expect that GPSQC can be used to improve the accuracy of positioning and to solve time-consuming problems due to data loss and large errors in GPS observations.
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  • Frequent Unscheduled Updates of the National Base Map Using the Land-Based Mobile Mapping System

    Hwang, Jinsang   Yun, Hongsik   Jeong, Taejun   Suh, Yongcheol   Huang, He  

    This paper focuses on the use of the Land-based Mobile Mapping System (LMMS) for the unscheduled updates of a National Base Map, which has nationwide coverage and was made using aerial photogrammetry. The objectives of this research are to improve the weak points of LMMS surveying for its application to the updates of a National Base Map (NBM), which has rigorous accuracy and quality standards. For this, methods were suggested for the (1) improvement of the accuracy of the Global Positioning System/ Inertial Navigation System (GPS/INS) in the long-term exposure of environments with poor GPS reception; (2) elimination of mutual deviations between LMMS data obtained in duplicate to meet resolution standards; (3) devising an effective way of mapping objects using LMMS data; and (4) analysis of updatable regions and map layers via LMMS. To verify the suggested methods, experiments and analyses were conducted using two LMMS devices in four target areas for unscheduled updates of the National Base Map.
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  • A Study of Shoreline Changes in Antarctica (Terra Nova Bay) Based on SAR Data

    Cho, Jungho   Cho, Jaemyoung   Yun, Hongsik   Kim, Taewoo   Kim, Changwoo  

    Unlike optical imaging, Synthetic Aperture Radar imaging can produce images regardless of the weather and the time of day, which makes it a useful tool for collecting topographical data in tropical rainforests and in the North and South Poles, where traditional optical imaging is ineffective due to the rapidly changing weather. For this study, this researcher acquired SAR imagery of Terra Nova Bay, located near the South Pole, from October 8, 2011 to March 11, 2012 to observe the changes in its shoreline in summer. SAR imagery was captured once every 11th day to determine the exact time in summer when the glaciers and ice along the shore melt. The acquired stereo SAR imagery data were then processed by applying the radargrammetric method along the shoreline to reduce the speckles specific to the SAR data, and to ensure the accuracy of the coordinates and the size of the satellite imagery, before converting them to DEM at 10m intervals, which again generated orthorectified imagery. The generated orthorectified images were then converted to a digital map with the UTM coordinate system via vectorizing, which visually represented on the map the changes that took place in the shoreline in summer. The study showed that the region was covered with ice from March to early November, which affected the activity in the base, including the access of the ice breaker. Due to the warming climate, there was no sea ice in the Terra Nova Bay for about a month in February. The ice in that area started to melt on November 21 and froze again on February 28. Accordingly, it was concluded that the best time to access the South Pole to build the Antarctic base is mid-December, and the construction crew must evacuate the area no later than March to ensure the safety of the mission.
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