이 연구는 GPS를 이용한 서울-제천지역에 대한 대류층 천정 지연 분석에 관한 것이다. 다양한 기상조건하에서 정확도를 보장하는 GPS 측위를 위하여 대류층 천정 지연과 GPS 정밀도와의 연관성을 분석하였다. Bernese 4.0소프트웨어로 산출한 대류층 천정 지연값의 증가시 GPS 측위 오차도 증가하였다. 대류층에 의한 오차는 평균 20 cm 였으며, 보정 모델 사용시 모두 5cm 범위내로 줄일 수 있었으며, 보정 모델 간에는 차이가 거의 없었다. GPS 측위오차와 대류층 천정 지연의 상관관계를 밝힘으로써 전선의 이동상황을 모니터링할 수 있으며 이는 GPS 기준망의 확장으로 가능할 것이다.

We determined the precise three dimensional WGS84 Coordinates and the sea level height of Seoul Radio Astronomy Observatory (SRAO). In this study, we performed the simultaneous GPS observations at SRAO and Seoul GPS Reference Station(SGRS) of Korea Astronomy Observatory(KAO) for 3.5 hours from 17KST on October 27, 1999. We employed two different antennas, i.e., chokering antenna at SGRS of KAO and L1/L2 compact with groundplane antenna at SRAO. But we employed same type of receivers, i.e., Trimble 4000SSI at both observing places. The observed data were processed by GPSURVEY 2.30 software of Trimble with L1/L2 ION Free technique and broadcasting ephemeris of GPS Satellites because of very short baseline between SGRS of KAO and SRAO. We determined WGS84 latitude, longitude, height and the sea level height of SRAO with 37∘27′15.′6846N±0.′0004,126∘57′19.′0727E±0.′0002,204.89m±0.02m,181.38m±0.17m 37∘27′15.′6846N±0.′0004,126∘57′19.′0727E±0.′0002,204.89m±0.02m,181.38m±0.17m , respectively.

Si3N4에 2wt% Al2O3와 6wt% Y2O3을 첨가한 분말을 가스압 소결 방법으로 시편을 제조하였다. 이때 소결시 시간변화에 따른 공기 중에서 마모 특성을 비교하였다. 소결 시간에 따른 마모 특성의 변화는 기계적 성질, 즉, 파괴인성 등이 영향을 주는 것으로 나타났다. 소결 시간이 길어지면 큰 elongated 입자의 과잉성장에 따라 곡강도 및 파괴인성이 낮아져 이 결과 마모가 증가되었다. 이때 나타난 결과에 의하면 공기 중에서 질화규소의 마모특성에 영향을 주는 인자는 여러 가지 기계적 특성 중에서 파괴인성 및 곡강도가 미치는 영향이 크게 나타났다.

The experimented rangefinder consist of sets of V/A-Code GPS and sets of L1 C/A-code & carrier phase receivers connected by two spread spectrum radio modems in order to measure relative range and bearing between two ship antennas by real time, comparing and analyzing accuracy of both GPS receivers at the fix point on the land by means of executing zero baseline test by C/A code and by carrier phase as well as measuring distance range 5m, 10m, 15m between each other receivers. The results from the measurement of relative range and bearing are as follows as ;1. According to the results from zero baseline test, the average error by C/A-code receiver is less than 0.1m, which proves theories from published books but when each GPS receivers track different satellites, the range accuracy error becomes up to 100m by means of S/A. Because of this sudden wide range error, rangefinder is not appropriate at relative range measurement without additional modification of the algorism of the GPS receiver itself.2. According to relative range measurement by Carrier Phase and zero baseline test at static condition, the range error is less than 3.5cm in case that it passes more than 5 minutes after GPS sets can track simultaneously more than 6 satellites. Its main reason is understood that the phase center of antenna is bigger than geodetic antenna.3. When range measurement of two receivers from 5m, to 10m to 15m, the each range error is 0.340m, 0.190m, 0.011m and each standard variation is 0.0973m, 0.0884m, 0.0790m. The range error and standard variation are in inverse proportion to distance between two receivers. 4. L1 Carrier Phase GPS generally needs 5 minutes to fix and during this ambiguity search, the relative range and bearing angle is shown to be various.

본 논문은 1994년 8월 1일부터 10월 5일 사이에 대변항을 중심으로 조업하고 있는 근해 멸치유자망 어선의 멸치유자망 표류상태를 측정하기 위하여 멸치유자망에 GPS 3개를 설치하여 유자망의 흐름을 측정하고, 조류계로 유향.유속을 측정하여 어구의 표류상태와 이들 상호간의 관계에 대해 검토, 분석하였다. 그 결과를 요약하면 다음과 같다. 1) 육상 고정점에 대한 GPS의 95% 확률원 오차는 대변항에서 79.8m였고 표준위치로부터 평균편위거리는 21.0m였다. 2) 대변항에서 GPS의 PDOP와 HDOP의 평균값은 각각 3.5, 1.9로서 비교적 안정된 측위를 얻을 수 있음을 알 수 있었다. 3) Lat 35˚ 41.5'N에서 35˚ 43.5'N, Long 129˚ 30.1'E에서 129˚ 31.2'E 사이의 어장에서 그물의 뻗친 방향은 190˚ 였고 투망이 완료된 시점네서 전체 어구의 방향은 200˚ 였다. 양망 당시 어구의 전개된 형태는 직각으로 휘어진 모양이며 투망 완료 후 양망이 시작될 때까지 그물 전체는 170˚ ~ 180˚ 방향으로 표류하였다. 평균표류속도는 0.82kt였다. 4) Lat 35˚ 44.0'N에서 35˚ 45.2'N, Long 129˚ 33.0'E에서 129˚ 34.0'E 사이의 어장에서 그물을 뻗친 방향은 20˚ 였으며, 투망 완료시 어구의 전개는 20˚ 방향이고 양망 당시 어구의 전개된 형태는 N에서 S로 바뀌었는데, 투망 완료후 양망이 시작될 때까지 평균적으로 210~220˚ 방향으로 표류함을 알 수 있었다. 평균표류속도는 0.75kt였다. 5) Lat 35˚ 44.9'N에서 35˚ 46.0'N, Long 129˚ 34.0'E 사이의 어장에서 그물 뻗친 방향은 35˚ 였으며, 투망 완료된 어구의 형태는 50˚ 였고 양망 시작시 그물의 방향은 E에서 S방향으로 바뀌었다. 그물은 330˚ ~ 340˚ 방향으로 표류하였다. 평균표류속도는 0.63kt였다.

군산대학교 실습선 해림 3호의 조종성능을 파악하기 n이하여 GPS 보다 그 측립정도가 더 높은 DGPS를 이용하여 종회권 측정을 행하고, 이를 재래식 측정방법인 부표방입반법과 비교 검토하였으며, 그 결과를 요약하면 다음과 같다. 1. DGPS에 의한 선회권측정의 정도를 파악하기 위하여 육상에서 50m의 선회시험을 행한 결과 측위오차는 1.5m 이내 였다. 2. DGPS에 의한 선회권측정은 속력별, 타각별, 좌우선회별로 각각 그 특성이 잘 나타낼 수 있도록 정확하게 측정 할 수 있었다. 3. 부표방위반법에 의한 선회권측정은 타각을 크게 하여 그 선회권이 작을 때는 DGPS의 것과 같이 비교적 정확하게 측정할 수 있으나, 타각을 작게하여 선회권이 클 때는 방위오차가 크기 때문에 정확하게 측정할 수 없었다. 4. DGPS에 의한 해림 3호의 선회경(DT)은 타각 35。~5。일 때, 미속에서는 선박의 수선간장 (Lpp)상의 2.6~15.0배, 반속에서는 2.8~16.6배, 전속에서는 3.1~17.4배로 나타났었고, 부표방위반법에 의한 선회경은 각각 2.4~9.5배, 2.6~9.6배, 3.2~12.2배로 나타났었다

This paper is described on the positioning accuracy of GPS which has observed from November. 1991 to September, 1992 in Korean southeast coast. The main results give as follows. 1) A daily variance of positioning error is irregularly, and the average error of the latitude and the longitude are 15.1m, 22.7m respectively. 2) The usable satellites in Korean southeast coast from Panggojin to Chisepo are SV satellite number 2, 3, 11～21, 23～26 and sv 28, of all these sv 3, 16, 17, 23, 24 and 26 can be observed in all the area. 3) A circle of the average radius enclose 95% of the measurement points are 72.9m and the average shift distances from standard position are 34.6m. 4) The variation of PDOP(HDOP) at each measurement points are coincide with the one of distance error.

This paper describes an alignment algorithm that estimates the initial heading angle of AUVs (Autonomous Underwater Vehicle) for starting navigation in a sea area. In the basic dead reckoning system, the initial orientation of the vehicle is very important. In particular, the initial heading value is an essential factor in determining the performance of the entire navigation system. However, the heading angle of AUVs cannot be measured accurately because the DCS (Digital Compass) corrupted by surrounding magnetic field in pointing true north direction of the absolute global coordinate system (not the same to magnetic north direction). Therefore, we constructed an experimental constraint and designed an algorithm based on extended Kalman filter using only inertial navigation sensors and a GPS (Global Positioning System) receiver basically. The value of sensor covariance was selected by comparing the navigation results with the reference data. The proposed filter estimates the initial heading angle of AUVs for navigation in a sea area and reflects sampling characteristics of each sensor. Finally, we verify the performance of the filter through experiments.

This paper presents a satellite relative navigation strategy for formation flying, which chooses an appropriate navigation algorithm according to the operating environment. Not only global positioning system (GPS) measurements, but laser measurements can also be utilized to determine the relative positions of satellites. Laser data is used solely or together with GPS measurements. Numerical simulations were conducted to compare the relative navigation algorithm using only laser data and laser data combined with GPS data. If an accurate direction of laser pointing is estimated, the relative position of satellites can be determined using only laser measurements. If not, the combined algorithm has better performance, and is irrelevant to the precision of the relative angle data between two satellites in spherical coordinates. Within 10 km relative distance between satellites, relative navigation using double difference GPS data makes more precise relative position estimation results. If the simulation results are applied to the relative navigation strategy, the proper algorithm can be chosen, and the relative position of satellites can be estimated precisely in changing mission environments.

As a part of collaborative efforts to understand ionospheric irregularities, the Korea ionospheric scintillation sites (KISS) network has been built based on global positioning system (GPS) receivers with sampling rates higher than 1 Hz. We produce the rate of TEC index (ROTI) to represent GPS TEC fluctuations related to ionospheric irregularities. In the KISS network, two ground-based GPS sites at Kiruna (marker: KIRN; geographic: 67.9° N, 21.4° E; geomagnetic: 65.2° N) and Chuuk (marker: CHUK; geographic: 7.5° N, 151.9° E; geomagnetic: 0.4° N) were selected to evaluate the ROTI value for ionospheric irregularities during the occurrence of the 2015 St. Patrick’s Day storm. The KIRN ROTI values in the aurora region appear to be generally much higher than the CHUK ROTI values in the EIA region. The CHUK ROTI values increased to ~0.5 TECU/min around UT=13:00 (LT=23:00) on March 16 in the quiet geomagnetic condition. On March 17, 2015, CHUK ROTI values more than 1.0 TECU/min were measured between UT=9:00 and 12:00 (LT=19:00 and 22:00) during the first main phase of the St. Patrick’s Day storm. This may be due to ionospheric irregularities by increased pre-reversal enhancement (PRE) after sunset during the geomagnetic storm. Post-midnight, the CHUK ROTI showed two peaks of ~0.5 TECU/min and ~0.3 TECU/min near UT=15:00 (LT=01:00) and UT=18:00 (LT=04:00) at the second main phase. The KIRN site showed significant peaks of ROTI around geomagnetic latitude=63.3° N and MLT=15:40 on the same day. These can be explained by enhanced ionospheric irregularities in the auroral oval at the maximum of AE index

In order to simulate a typhoon precisely, the satellite observation data has been assimilated using WRF (Weather Research and Forecasting model) three-Dimensional Variational (3DVAR) data assimilation system. The observation data used in 3DVAR was GPS Radio Occultation (GPS-RO) data which is loaded on Low-Earth Orbit (LEO) satellite. The refractivity of Earth is deduced by temperature, pressure, and water vapor. GPS-RO data can be obtained with this refractivity when the satellite passes the limb position with respect to its original orbit. In this paper, two typhoon cases were simulated to examine the characteristics of data assimilation. One had been occurred in the Western Pacific from 16 to 25 October, 2015, and the other had affected Korean Peninsula from 22 to 29 August, 2012. In the simulation results, the typhoon track between background (BGR) and assimilation (3DV) run were significantly different when the track appeared to be rapidly change. The surface wind speed showed large difference for the long forecasting time because the GPS-RO data contained much information in the upper level, and it took a time to impact on the surface wind. Along with the modified typhoon track, the differences in the horizontal distribution of accumulated rain rate was remarkable with the range of 600~500 mm. During 7 days, we estimated the characteristics between daily assimilated simulation (3DV) and initial time assimilation (3DV_7). Because 3DV_7 demonstrated the accurate track of typhoon and its meteorological variables, the differences in two experiments have found to be insignificant. Using observed rain rate data at 79 surface observatories, the statistical analysis has been carried on for the evaluation of quantitative improvement. Although all experiments showed underestimated rain amount because of low model resolution (27 km), the reduced Mean Bias and Root-Mean-Square Error were found to be 2.92 mm and 4.53 mm, respectively.

The efficiencies of Gang-Byeon sewage treatment facilities, which are based on GPS-X modelling, were analysed and used to design recycle water treatment processes. The effluent of an aeration tank contained total kjeldahl nitrogen (TKN) of 1.8 mg/L with both C-1 and C-2 conditions, confirming that most ammonia nitrogen (NH3 +-N) was converted to nitrate nitrogen (NO3 --N). The concentrations of NH3 +-N and NO3 --N were found to be 222.5 and 227.2 mg/L, respectively, with C-1 conditions and 212.2 and 80.4 mg/L with C-2 conditions. Although C-2 conditions with higher organic matter yielded a slightly higher nitrogen removal efficiency, sufficient denitrification was not observed to meet the discharge standards. For the total nitrogen (T-N) removal efficiency, the final effluent concentrations of T-N were 293.8 mg/L with biochemical oxygen demand (BOD) of 2,500 mg/L, being about 1.5 times lower than that (445.3 mg/L) with BOD of 2,000 mg/L. Therefore, an external carbon source to increase the C/N ratio was required to get sufficient denitrification. During the winter period with temperature less than 10 , the denitrification efficiency was dropped rapidly even with a high TKN concentration (1,500 mg/L). This indicates that unit reactors (anoxic/aerobic tanks) for winter need to be installed to increase the hydraulic retention time. Thus, to enhance nitrification and denitrification efficiencies, flexible operations with seasons are recommended for nitrification/anoxic/denitrification tanks.

This study has been considering cable stayed bridge for structural health monitoring purpose . To monitor the bridge, 6 different locations (like 2 points from deck, 2 points from pylon, 1 points from side span and 1 points from girder) were introduce to find the satellite signal received from the GPS antenna. According to the World Geodetic System 1984(WGS-84) coordinate system, the GPS station signal was measured in the 6 observed points. After that, Statistical moment analysis is applied to assess the condition of those 6 position of this long span bridge. Finally, the Statistical moment analysis results clearly indicate the present condition of the long span bridge at 6 different locations. The time series statistical moments really able to detect the damage condition and localization of the long span bridge.

This study presents a precise relative navigation algorithm using both laser and Global Positioning System (GPS) measurements in real time. The measurement model of the navigation algorithm between two spacecraft is comprised of relative distances measured by laser instruments and single differences of GPS pseudo-range measurements in spherical coordinates. Based on the measurement model, the Extended Kalman Filter (EKF) is applied to smooth the pseudo-range measurements and to obtain the relative navigation solution. While the navigation algorithm using only laser measurements might become inaccurate because of the limited accuracy of spacecraft attitude estimation when the distance between spacecraft is rather large, the proposed approach is able to provide an accurate solution even in such cases by employing the smoothed GPS pseudo-range measurements. Numerical simulations demonstrate that the errors of the proposed algorithm are reduced by more than about 12% compared to those of an algorithm using only laser measurements, as the accuracy of angular measurements is greater than 0.001° at relative distances greater than 30 km.

Using the Total Electron Content (TEC) data from the Global Navigation Service System (GNSS) site in Jeju, operated by the Korea Astronomy and Space Science Institute (geographic location: 33.3° N, 126.5° E; geomagnetic location: 23.6° N) for 2002– 2014 in Korea, the results of the statistical analysis of positive and negative ionospheric storms are presented for the first time. In this paper, ionospheric storms are defined as turbulences that exceed 50% of the percentage differential Global Positioning System (GPS) TEC ratio (ΔTEC) with monthly median GPS TEC. During the period of observations, the total number of positive ionospheric storms (ΔTEC > 50%) was 170, which is greater than five times the number of negative ionospheric storms (ΔTEC < - 50%) of 33. The numbers of ionospheric storms recorded during solar cycles 23 and 24 were 134 and 69, respectively. Both positive and negative ionospheric storms showed yearly variation with solar activity during solar cycle 23, but during solar cycle 24, the occurrence of negative ionospheric storms did not show any particular trend with solar activity. This result indicates that the ionosphere is actively perturbed during solar cycle 23, whereas it is relatively quiet during solar cycle 24. The monthly variations of the ionospheric storms were not very clear although there seems to be stronger occurrence during solstice than during equinox. We also investigated the variations of GPS positioning accuracy caused by ionospheric storms during November 7–10, 2004. During this storm period, the GPS positioning accuracies from a single frequency receiver are 3.26 m and 2.97 m on November 8 and 10, respectively, which is much worse than the quiet conditions on November 7 and 9 with the accuracy of 1.54 m and 1.69 m, respectively.