• Journal of Advanced Navigation Technology
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• v.18 no.6
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• pp.546-554
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• 2014

For improvement of network RTK performance in survey field, Spatial Information Research Institute (SIRI), LX Korea Cadastral Survey Corporation installed 30 GNSS permanent stations in Korea Peninsula, and has been running the MAC-based network RTK service as a test version. In this paper, we introduce the LX GNSS network and analyze the positioning accuracy of the LX MAC RTK service. For field test of the LX MAC RTK service, we installed temporally fixed anchor points and observed simultaneously with VRS of National Geographic Information Institute. As a result, the horizontal position differences and initial times of LX MAC with respect to NGII VRS are $1{\sim}2{\pm}1cm$ and <10 seconds, respectively.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.11
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• pp.138-147
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• 2001

Alignment systems are frequently used under various semiconductor manufacturing environment. Particularly in PDP(Plasma Display Panel) manufacturing process, the alignment system is applied to the combining and sealing processes of the upper and lower glass panels of PDP, where these processes are performed in the vacuum chamber of high vacuum and high temperature. In this paper, the XYΘ-alignment stage is developed to align PDP panels. Because of high vacuum and high temperature environment, the alignment chamber has been designed to isolate the inner part of the alignment chamber from the outer environment of high vacuum and high temperature, in which every part of the alignment stage is inserted. As it is difficult to attach feedback sensors to the alignment stage in the alignment chamber, the alignment stage is implemented with the open loop algorithm, where the parallel link structure has been designed using step-motors and ball-screws for structural simplicity. The kinematic analysis is performed to drive the parallel link structure, based on the experiments of actuation-compensation of the alignment stage. For the error compensation, the hyperpatch model has been used to model the errors. From the experiments, the positional accuracy of the alignment stage can be improved significantly.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.15 no.2
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• pp.165-173
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• 1997

The combined bundle block adjustment with projection center coordinates determined by kinematic DGPS-positioning has reached a high level of accuracy. Standard deviations of the ground coordinates of $\pm{10cm}$ or even better can be reached. On this accuracy level also smaller error components are becoming more important. One major point of this is the interpolation of the projection centers as a function of time between the GPS-antenna locations. A just linear interpolation is not respecting the not linear movement of the aircraft. Based on a least squares polynomial fitting the aircraft maneuver can be estimated more accurate and blunders of the GPS-positions caused by loss of satellite and cycle slips are determinable. The interpolation with a time interval of 3sec in the study area RHEINKAMP is quite different to the interpolation with a time interval of 6-7sec in the study area MAAS. The GPS-positions of the study area are identified as blunders based on a local polynomial regression. This cannot be neglected for precise block adjustment.

• Physical Therapy Korea
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• v.13 no.4
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• pp.23-29
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• 2006

The purpose of the present study was to examine gaze effects on spatial and kinematic characteristics during a pointing task. Subjects were asked to watch and point to an aimed target (2 mm in diameter) displayed on a vertically mounted board. Four gaze conditions were developed as combinations of "seeing-aiming" in terms of the eye movements: Focal-Focal (F-F), Focal-Fixing (F-X), Fixing-Focal (X-F), and Fixing-Fixing (X-X). Both the home target and an aimed target were presented for 1 second and then were disappeared in F-F and X-F. In X-F and X-X, only an aimed target disappeared after 1 second. Subjects were asked to point (with index finger tip) to an aimed target accurately as soon as the aimed target was removed. A significant main effect of gaze was found (p<.01) for normalized movement time. Peripheral retina targets had significantly larger absolute error compared to central retina targets on the x (medio-lateral) and z (superior-inferior) axes (p<.01). A significant undershooting to peripheral retina targets on the x axis was found (p<.01). F-F and X-F had larger peak velocities compared to F-X and X-X (p<.01). F-F and X-F were characterized by more time spent in the deceleration phase compared to F-X and X-X (p<.01). The present study demonstrates that central vision utilizes a form of on-line visual processing to reach to an object, and thus increases spatial accuracy. However, peripheral vision utilizes a relatively off-line visual processing with a dependency on proprioceptive information.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.327-332
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• 2006

In airborne gravimetry, there are two data streams. One is the specific force measured by an air/sea gravimeter or accelerometers, the other is kinematic acceleration measured by DGPS. And the difference of them provides the gravity disturbance information. To satisfy the requirement of most applications, an accuracy of 1mGal $(1mCal=10^{-5}m/s^{2})$ with a spatial resolution of 1km is the aim of current airborne gravimetry. There are two different methods to derive the kinematic acceleration. The generally used method is to differentiate the position twice, and the position can be calculated by commercial DGPS software. The main defect of this method is that integer ambiguities need to be fixed to get the precise position solution, but it's not a trivial thing for long base line. And to fix integer ambiguities, the noisier iono-free measurement is used. When differentiation is applied, noise is amplified and will influence the accuracy of acceleration. The other method is to get carrier phase acceleration by differentiate the carrier phase first, and then using the acceleration of GPS satellite to derive the vehicle acceleration. The main advantages include that fixing integer ambiguities is not needed anymore, position can be relaxed to about 10 meters, and smoother acceleration can be got since iono-free measurement is not needed. In some literatures, it's considered that the dynamic performance of the second method is inferior to that of the first. Through analysis, it is found that the performance degradation in dynamic environment results from the simplification of the GPS carrier phase observable model. And an iterative algorithm is presented to compensate the model error. Using a dynamic GPS data from an aeromagnetic survey, the importance of this compensation is showed at last.

• Journal of Korea Water Resources Association
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• v.52 no.12
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• pp.1057-1066
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• 2019

The storage function method is used as a flood prediction model for four flood control offices in Korea as a method to analyze the actual rainfall-runoff relationship with non-linearity. It is essential to accurately estimate the parameters of the storage function method for accurate runoff analysis. However, the parameters of the storage function method currently in use are estimated by the empirical formula developed by the limited hydrological analysis in 2012; therefore, they are somewhat inaccurate. The kinematic wave method is a method based on physical variables of watershed and channel and is widely used for rainfall-runoff analysis. By adopting the two-term storage function method by the conversion of the kinematic wave method, parameters can be estimated based on physical variables, which can increase the accuracy of runoff calculation. In this research, the reproducibility of the kinematic wave method by the two-term storage function method was investigated. It is very easy to estimate the parameters because equivalent roughness, which is an important physical variable in watershed runoff, can be easily obtained by using land use and land cover, and the physical variable of channel runoff can be easily obtained from the basic river planning report or topographic map. In addition, this research examined the applicability of the two-term storage function method to runoff simulation of Naechon Stream, a tributary of the Hongcheon River in the Han River basin. As a result, it is considered that more accurate runoff calculation results could be obtained than the existing one-term storage function method. It is expected that the utilization of the storage function method can be increased because the parameters can be easily estimated using physical variables even in unmeasured watersheds and channels.

• Journal of Positioning, Navigation, and Timing
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• v.2 no.1
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• pp.19-31
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• 2013

It is well known that the accident of vehicles carrying hazardous materials incurs huge losses economically and socially. To detect and respond rapidly against the accident of a vehicle carrying hazardous materials, it is essential to estimate the relative navigation information between the forward tractor module and the backward trailer module of the vehicle reliably and accurately. In this paper, a precise relative positioning system based on GPS is designed, implemented, and evaluated as a prerequisite to design an effective relative navigation system for the vehicle carrying hazardous materials. An experiment using field-collected 10 Hz real GPS measurements showed that the designed relative positioning system achieves 22 cm accuracy within 15 epochs by float solutions. Also, it was found that cm-level integer solutions can be generated reliably after the quick convergence of float solutions.

• Journal of Astronomy and Space Sciences
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• v.32 no.4
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• pp.403-409
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• 2015

The Quasi-Zenith Satellite System (QZSS), a dedicated regional Japanese satellite system currently under development, was designed to complement the performance of the Global Positioning System (GPS). The high elevation angle of the QZSS satellite is expected to enhance the effectiveness of GPS in urban environments. Thus, the work described in this paper, aimed to investigate the effect of QZSS on GPS performance, by processing the GPS and QZSS measurements recorded at the Bohyunsan reference station in South Korea. We used these data, to evaluate the satellite visibility, carrier-to-noise density (C/No), performance of single point positioning, and Dilution of Precision (DOP). The QZSS satellite is currently available over South Korea for 19 hours at an elevation angle of more than 10 degrees. The results showed that the impact of the QZSS on users' vertical positioning is greatest when the satellite is above 80 degrees of elevation. As for Precise Point Positioning (PPP) performance, the combined GPS/QZSS kinematic PPP was found to improve the positioning accuracy compared to the GPS only kinematic PPP.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.148-151
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• 2003

In order to achieve reliable but cost-effective crash simulations of stamped parts, sheet forming process effects were incorporated in simulations using the ideal forming theory mixed with the 3D hybrid membrane/shell method, while the subsequent crash simulations were carried out using a dynamic explicit finite element code. Example solutions performed for forming and crash simulations of I- and S-shaped rails verified that the proposed approach is cost-effective without sacrificing accuracy. The method required a significantly small amount of additional computation time, less than 3% for the specific examples, to incorporate sheet forming effects to crash simulations. As for the constitutive equation, the combined isotropic-kinematic hardening law and the non-quadratic anisotropic yield stress potential as well as its conjugate strain-rate potential were used to describe the anisotropy of AA6114-T4 aluminum alloy sheets.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.4
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• pp.377-386
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• 2015

Joint force/torque estimation by inverse dynamics is a traditional tool in biomechanical studies. Conventionally for this, kinematic data of human body is obtained by motion capture cameras, of which the bulkiness and occlusion problem make it hard to capture a broad range of movement. As an alternative, inertial motion sensing using cheap and small inertial sensors has been studied recently. In this research, the performance of inertial motion sensing especially to calculate inverse dynamics is studied. Kinematic data from inertial motion sensors is used to calculate ground reaction force (GRF), which is compared to the force plate readings (ground truth) and additionally to the estimation result from optical method. The GRF estimation result showed high correlation and low normalized RMSE(R=0.93, normalized RMSE<0.02 of body weight), which performed even better than conventional optical method. This result guarantees enough accuracy of inertial motion sensing to be used in inverse dynamics analysis.