• The Journal of the Korea Contents Association
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• v.13 no.10
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• pp.574-583
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• 2013

The coastal area, which is managed by local governments, geographically, culturally and economically has been transformed into more influential space. In recent years, new type of fusion researches about coastal areas that have economic, cultural and engineering aspects, have been conducted. In this study, the multiple observations information was used to analyze change of Ilsan beach shoreline which is located in Dong-gu, Ulsan, Korea. For the shoreline analysis, we used VRS-RTK(Virtual Reference System by Real-Time Kinematic) GPS survey, aerial photograph, terrestrial LiDAR survey and fixed reference station survey. Specially fixed reference station method was suggested for shoreline observation and maintenance. In the case of Ilsan beach shoreline, according to the result of multiple observations information, coastline erosion(6~12m) appeared in medium and lower part and sedimentation(3~14m) in the upper part of coastline.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.159.2-159.2
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• 2012

In this study, we propose an effective strategy for precise orbital and geodetic parameter estimation using SLR (Satellite Laser Ranging) observations for ILRS AAC (Associate Analysis Center). The NASA/GSFC GEODYN II software and SLR normal point observations of LAGEOS-1, LAGEOS-2, ETALON-1, and ETALON-2 are utilized for precise orbital and geodetic parameter estimation. Weekly-based precise orbit determination strategy is applied to process SLR observations, and Precise Orbit Ephemeris (POE), TRF (Terrestrial Reference Frame), and EOPs (Earth Orientation Parameters) are obtained as products of ILRS AAC. For improved estimation results, selection strategies of dynamic and measurement models are experimently figured out and configurations of various estimation parameters are also carefully chosen. The results of orbit accuracy assessment of POE and precision analysis of TRF/EOPs for each case are compared with those of existing results. Finally, we find an appropriate strategy for precise orbital and geodetic parameter estimation using SLR observations for ILRS AAC.

• Journal of the Korean Ceramic Society
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• v.51 no.6
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• pp.591-597
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• 2014

A poled lead zirconate titanate (PZT) rectangular parallelepiped specimen was subjected to through-thickness electric fields at five loading rates and four temperatures. The rates of the electric field were 0.01, 0.10, 0.25, 0.50, and $1.00MVm^{-1}s^{-1}$; the temperatures were 20, 50, 80, and $110^{\circ}C$. From the measured polarization hysteresis responses, the so-called reference remnant polarization and strains were calculated. Using the calculated reference remnant polarization hysteresis loops, the effects of loading rates and temperature were discussed; using the calculated reference remnant strains, strain butterfly loops were calculated and compared with observations.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.1
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• pp.100.1-100.1
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• 2012

Lunar limb profiles are needed for analyses of lunar occultations and solar eclipses. The lunar limb profile data by C.B. Watts (1963) have been used for such analyses, but it has been found that there are many kinds of errors in the data by Watts, which seriously affected the results obtained from the analyses of the observations. Recently very precise lunar topographic data were obtained by the Japanese lunar explorer Kaguya and NASA's Lunar Reconnaissance Orbiter. I obtained lunar limb profiles for any lunar librations from them. I will show how well the lunar limb profiles fit to observed ones from lunar grazing occultations. By combining the accurate lunar limb profiles with observations of lunar occultations we can detect errors in the Hipparcos stellar reference frame. By analyzing Baily's beads timing observations of past total and annular solar eclipses using the accurate lunar limb profiles we will be able to detect solar diameter variations.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.59.2-59.2
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• 2015

We present the results of simultaneous observations of the H2O and SiO masers emitted from the circumstellar envelopes of the late-type stars. These observations have been carried out at the K and Q bands using KVN since 2014 August and were scheduled to test the feasibility of multi-frequency phase referencing analysis on the maser lines. In order to increase the accuracy of group delay solution in the fringe search on the continuum source, the IF channels were randomly distributed within the available bandwidth of 500 MHz in each band. The positions of all maser spots are relatively described with respect to the position of the reference continuum source through the source frequency phase referencing technique, and this provides the astrometric position accuracy. Therefore, the relative locations of the H2O maser spots with respect to the SiO maser spots are determined from our observations, and the capability of the simultaneous multi-band observation of KVN is proved to be powerful to study the maser pumping mechanism around the late-type stars.

• Journal of Astronomy and Space Sciences
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• v.30 no.4
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• pp.269-277
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• 2013

In this study, we present results of precise orbital geodetic parameter estimation using satellite laser ranging (SLR) observations for the International Laser Ranging Service (ILRS) associate analysis center (AAC). Using normal point observations of LAGEOS-1, LAGEOS-2, ETALON-1, and ETALON-2 in SLR consolidated laser ranging data format, the NASA/GSFC GEODYN II and SOLVE software programs were utilized for precise orbit determination (POD) and finding solutions of a terrestrial reference frame (TRF) and Earth orientation parameters (EOPs). For POD, a weekly-based orbit determination strategy was employed to process SLR observations taken from 20 weeks in 2013. For solutions of TRF and EOPs, loosely constrained scheme was used to integrate POD results of four geodetic SLR satellites. The coordinates of 11 ILRS core sites were determined and daily polar motion and polar motion rates were estimated. The root mean square (RMS) value of post-fit residuals was used for orbit quality assessment, and both the stability of TRF and the precision of EOPs by external comparison were analyzed for verification of our solutions. Results of post-fit residuals show that the RMS of the orbits of LAGEOS-1 and LAGEOS-2 are 1.20 and 1.12 cm, and those of ETALON-1 and ETALON-2 are 1.02 and 1.11 cm, respectively. The stability analysis of TRF shows that the mean value of 3D stability of the coordinates of 11 ILRS core sites is 7.0 mm. An external comparison, with respect to International Earth rotation and Reference systems Service (IERS) 08 C04 results, shows that standard deviations of polar motion $X_P$ and $Y_P$ are 0.754 milliarcseconds (mas) and 0.576 mas, respectively. Our results of precise orbital and geodetic parameter estimation are reasonable and help advance research at ILRS AAC.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.16 no.1
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• pp.27-40
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• 1998

This paper addresses the suitability of GPS positioning technology to monitoring deformation and movement of structures. The first part of the study is an empirical quantitative study of the repeatability of GPS observations and the second part is a performance evaluation of kinematic GPS, which requires only a few minutes per a point, for monitoring deformation of an engineering structure. On the test network for monitoring of a earth am, four observations have been conducted repeatedly on different seasons and water levels. The reference network was observed in static mode, and monitoring points were observed respectively in rapid-static mode as well as in kinematic mode in each epoch and then the results were compared with those obtained by conventional surveying techniques. The repeatability of baseline vectors to better than average 7 mm in three dimensions was achieved in base line observations between reference points and also the unclosure of reference networks showed the range of 4 ppm to 27 ppm. Compared with conventional surveying techniques, the kinematic approach showed the differences of 3∼4 m in slope distances which were observed from reference points to monitoring points, and showed the differences of 4∼8 m in height. It was ascertained that the kinematic GPS technology provides an efficient alternative to deformation monitoring by conventional means which are capable of detecting movements in the order of 5 mm.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1D
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• pp.135-143
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• 2009

Integrating the Global Positioning System (GPS) and Inertial Navigation System (INS) sensor technologies using the precise GPS Carrier phase measurements is a methodology that has been widely applied in those application fields requiring accurate and reliable positioning and attitude determination; ranging from 'kinematic geodesy', to mobile mapping and imaging, to precise navigation. However, such integrated system may not fulfil the demanding performance requirements when the baseline length between reference and mobil user GPS receiver is grater than a few tens of kilometers. This is because their positioning/attitude determination is still very dependent on the errors of the GPS observations, so-called "baseline dependent errors". This limitation can be remedied by the integration of GPS and INS sensors, using multiple reference stations. Hence, in order to derive the GPS distance dependent errors, this research proposes measurement processing algorithms for multiple reference stations, such as a reference station ambiguity resolution procedure using linear combination techniques, a error estimation based on Kalman filter and a error interpolation. In addition, all the algorithms are evaluated by processing real observations and results are summarized in this paper.

• Journal of Korean Society on Water Environment
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• v.29 no.1
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• pp.55-65
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• 2013

It is very difficult to apply stream flow data directly to the management of Total Maximum Daily Loads because there are some differences between the unit watershed and the stream flow monitoring network in their characteristics such as monitoring locations and its intervals. Flow duration curve can be developed by linking the daily flow data of stream monitoring network to 8 day interval flow data of the unit watershed. This study investigated the current operating conditions of the stream flow monitoring network and the flow relationships between the unit watershed and the stream flow monitoring network. Criteria such as missing and zero value data, and correlation coefficients were applied to select the stream flow reference sites. The reference sites were selected in 112 areas out of 142 unit watersheds in 4 river basins, where the stream flow observations were carried out in relatively normal operating conditions. These reference sites could be utilized in various ways such as flow variation analysis, flow duration curve development and so on for the management of Total Maximum Daily Loads.

• Journal of the Korean earth science society
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• v.40 no.2
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• pp.135-148
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• 2019

Although the technology for the observation of solar radiation is rapidly developing worldwide, in Korea the guidelines for comparing observations of solar radiation are only now under preparation. In this study, a procedure for intercomparison observations of solar radiation was established which accounts for meteorological and geographical conditions. The intercomparisons among observations by national reference pyranometers were carried out at the Asia Regional Radiation Center, Japan, in 2017. Recently, the result of the calibration of the reference pyranometer of the Korean Meteorological Administration (KMA) has been reported. Using the KMA pyranometer as a reference, comparisons between observations and calibrations were carried out for the standard (B to J) pyranometers of the KMA, and for the reference (A) and the standard pyranometers of the Gangneung-Wonju National University. The intercomparisons were carried out between October 24 and October 25, 2018. The sensitivity constants were adjusted according to the results of the data analysis performed on October 24. On October 25, a post-comparison observation was also performed, and the data of the participating pyranometers were verified. The sensitivity constants were calculated using only data corresponding to a solar radiation of $450.0W\;m^{-2}$ or higher. The B and I pyranometers exhibited a small error (${\pm}0.50W\;m^{-2}$), and the applied sensitivity constants were in the range $0.08-0.16{\mu}V(W\;m^{-2})^{-1}$. For the C pyranometer, the adjustment of the sensitivity constant was the largest, i.e., $-0.16{\mu}V(W\;m^{-2})^{-1}$. As a result, the nine candidate pyranometers could be calibrated with an average error of $0.06W\;m^{-2}$ (0.08%) with respect to the KMA reference, which falls within the allowed tolerance of ${\pm}1.00%$ (or ${\pm}4.50W\;m^{-2}$).