• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2003.04a
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• pp.55-60
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• 2003

As the distance between GPS rover station and GPS base station increases, more decorrelated positioning errors limit the ability for PDGPS(Precise Differential GPS). The objective of this paper is to present the improvement of using VRS(virtual reference station) based on multiple GPS reference station network to single reference station for static positioning in post-processing mode. For this, the VRS observations from GPS observations of real reference stations are derived by using Web service in post-mode. The coordinates of check point post-processed by 27 kind of VRS observations compared with the known ones.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.4C
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• pp.379-383
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• 2003

A simpler nonparametric detector test statistic based on reference observation in addition to the rank statistics of regular observations is suggested in this letter. Using reference observations instead of sign statistics helps us a simpler detector structure especially for random signals buried in multiplicative noise.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.410-413
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• 2007

Water vapor in the atmosphere is an influential factor of the hydrosphere cycle, which exchanges heat through phase change and is essential to precipitation. Because of its significance in altering weather, the estimation of water vapor amount and distribution is crucial to determine the precision of the weather forecasting and the understanding of regional/local climate. It is shown that it is reliable to measure precipitable water (PW) using long baseline (500-2000km) GPS observations. However, it becomes infeasible to derive absolute PW from GPS observations in Taiwan due to geometric limitation of relatively short-baseline network. In this study, a method of deriving Near-Real-Time PW from short baseline GPS observations is proposed. This method uses a reference station to derive a regression model for wet delay, and to interpolate the difference of wet delay among stations. Then, the precipitable water is obtained by using a conversion factor derived from radiosondes. The method has been tested by using the reference station located on Mt. Ho-Hwan with eleven stations around Taiwan. The result indicates that short baseline GPS observations can be used to precisely estimate the precipitable water in near-real-time.

• Journal of Positioning, Navigation, and Timing
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• v.12 no.4
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• pp.359-367
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• 2023

In order to ensure the high-integrity of reference stations of satellite navigation system, cycle slip should be precisely monitored and compensated. In this paper, we proposed a cycle slip algorithm for the integrity monitoring of the reference stations. Unlike the legacy method using the Melbourne-Wübbena (MW) combination and ionosphere combination, the proposed algorithm is based on ionosphere combination only, which uses high precision carrier phase observations without pseudorange observations. Two independent and complementary ionosphere combinations, Ionospheric Negative (IN) and Ionospheric Positive (IP), were adopted to avoid insensitive cycle slip pairs. In addition, a second-order time difference was applied to the IN and IP combinations to minimize the influence of ionospheric and tropospheric delay even under severe atmosphere conditions. Then, the cycle slip was detected by the thresholds determined based on error propagation rules, and the cycle slip was identified through weighted least square method. The performance of the proposed cycle slip algorithm was validated with the 1 Hz dual-frequency carrier phase data collected under the difference levels of ionospheric activities. For this experiment, 15 insensitive cycle slip pairs were intentionally inserted into the raw carrier phase observations, which is difficult to be detected with the traditional cycle slip approach. The results indicate that the proposed approach can successfully detect and compensate all of the inserted cycle slip pairs regardless of ionospheric activity. As a consequence, the proposed cycle slip algorithm is confirmed to be suitable for the reference station where real time high-integrity monitoring is crucial.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.8C
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• pp.709-712
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• 2010

In this paper, the two sample locally optimum rank detector is obtained in the weakly dependent noise with non-zero temporal correlation between noise observations. The test statistic of the locally optimum rank detector is derived from the Neyman-Pearson lemma suitable for the two sample observation models, where it is assumed that reference observations are available in addition to regular observations. Two-sample locally optimum rank detecter shows the same performance with the one-sample locally optimum rank detector asymptotically. The structure of the two-sample rank detector is simpler than that of the one-sample rank detector because the sign statistic is not processed separately.

• Journal of Positioning, Navigation, and Timing
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• v.4 no.4
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• pp.205-211
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• 2015

The Global Navigation Satellite System (GNSS) is undergoing dramatic changes. Nowadays, much more satellites are transmitting navigation data at more frequencies. A multi-GNSS analysis is performed to improve the positioning accuracy by processing combined observations from different GNSS. The multi-GNSS technique can improve significantly the positioning accuracy. In this paper, we present a combined Global Positioning System (GPS), the GLObal NAvigation Satellite System (GLONASS), the China Satellite Navigation System (BeiDou), and the Quasi-Zenith Satellite System (QZSS) standard point positioning (SPP) method to exploit all currently available GNSS observations at Mokpo (MKPO) station in South Korea. We also investigate the multi-GNSS data recorded at MKPO reference station. The positioning accuracy is compared with several combinations of the satellite systems. Because of the different frequencies and signal structure of the different GNSS, intersystem biases (ISB) parameters for code observations have to be estimated together with receiver clocks in multi-GNSS SPP. We also present GPS/GLONASS and GPS/BeiDou ISB values estimated by the daily average.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.529-534
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• 2006

New geocentric geodetic datum has recently been realized in Korea, Korean Geodetic Datum 2002- KGD2002, to overcome problems due to the existing Tokyo datum, which had been used in this country since early 20th century. This transition will support modern surveying techniques, such as Global Navigation Satellite Systems (GNSS) and ensures that spatial data is compatible with other international systems. For this realization, very long baseline interferometry (VLBI) observations were initially carried out in 1995 to determine the coordinates of the origin of KGD2002 based on the International Terrestrial Reference Frame (ITRF). Continuous GPS observations were collected from 14 reference stations across Korea to compute the coordinates of 1st order horizontal geodetic control points. During the campaign, GPS observations were also collected at about 9,000 existing geodetic control points. In 2006, network adjustment with all data obtained using GPS and EDM since 1975 has been performed under the condition of fixing the coordinates of GPS continuous observation stations to compute coordinate measurements of the 2nd and 3rd geodetic control points. This paper describes the GPS campaigns which have been undertaken since 1996 and details of the network adjustment schemes. This is followed

• Publications of The Korean Astronomical Society
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• v.19 no.1
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• pp.39-46
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• 2004

We have carried out the high-resolution spectroscopic observations of Titan using BOES (Bohyunsan Echelle Spectrometer) to establish a standard spectral atlas of Titan. The observations were made on November 3, 4, 16 and 17, 2003 using a 300 11m fiber optics with a spectral resolving power of 30,000. The spectral atlas will be served as a reference for the future spectroscopic researches of Titan and other planetary objects. We were able to confirm $CH_4$ absorption lines of the Kuiper bands, and find unidentified lines near $7500{\AA}$.

• Journal of the Korean Society for Library and Information Science
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• v.32 no.2
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• pp.121-142
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• 1998

Based on the comprehensive literature search and the sample library surveys, some observations are made on the impact of online information technologies for reference services. Various issues specifically with OPAC, CD-ROM, remote database access, and internet environment are overviewed as the source of and trigger for change in reference librarianship and in terms of expectations as well as difficulties. The paper then focuses on how these technologies influence on the roles of reference librarians as intermediaries in information providing, instructing, consulting, and evaluating functions. This leads to rethinking the conceptual basis of today's reference service and the competencies for reference librarians with new functions and responsibilities.

• Journal of the Korean Society of Clothing and Textiles
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• v.25 no.6
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• pp.1069-1078
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• 2001

Pattern grading is a technique used to increase or decrease the size of a garment pattern according to the measurements in a given size chart. The original pattern is graded and laid out for cutting before mass production. This study tried to classify body types for pattern grading of jacket by applying a concept of "drop"defined as the difference between chest girth and waist girth and the difference between hip girth and waist girth for pants. Data were collected through the stratified sampling method. 138 subjects were selected out of 1,290 subjects of our sample population. Findings were as follows : 1) For pattern grading of jacket, the cell with the chest girth of 96cm and the waist girth of 87cm had the highest frequency rate and body type was 87H type and the coverage of this type was 9.52%. Then, the size specification 87-96 was the center of distribution. H type had seven ones such as 72H, 75H, 78H, 81H, 84H. 87H and 90H. H type had 33 observations and frequency ratio of 26.19%. Same types could be graded up and down from the reference size for the age group. And this reference size became to the starting point for developing the grading system. 2) For pattern grading of pants, fatty types, H10 type had six ones such as 80H10. 82H10, 84H10, 86H10, 88H10 and 90H10. H10 type had 28 observations and frequency ratio of 20.29%. H6 type had 6 ones such as 84H6, 86H6, 88H6, 90H6. 92H6 and 94H6. H6 type had 27 observations and frequency ratio of 19.57%. If lower body types were classified as same ones, these types could be graded up and down proportionately.