• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2004.04a
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• pp.51-55
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• 2004

In this study, the levelling and the GPS levelling were carried out with 6 points in 2km${\times}$2km area and the results were analysed. As a result of this research, we had to observe more than 15 minutes to get the height accuracy of 10mm by single frequency GPS receiver in relative surveying. We could not get more better accuracy than 10mm. we could get the height accuracy of within 10mm from observing only more than 5 minutes by double frequency GPS receiver, and of within about 3mm from observing more than 10 minutes. When the number of fixed points is within 3, the level net adjustment result is very close to the one of direct levelling survey. When the number of fixed points is 3, the less the area of triangle the better the adjustment result, and the case of including measure point has more better accuracy than that of non-including measure point.

• Atmosphere
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• v.14 no.3
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• pp.41-54
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• 2004

In this study, a brief overview on a WMO/WWRP program - The Observing System Research and Predictability Experiment (THORPEX) and discussions on perspectives and potential benefits of Asian countries are provided. THORPEX is aimed at accelerating improvements in the accuracy of 1 to 14-day high-impact weather forecasts with research objectives of: 1) predictability and dynamical processes; 2) observing systems; 3) data assimilation and observing strategies; and 4) societal and economic applications. Direct benefits of Asian countries from THORPEX include improvement of: 1) forecast skills in global models, which exerts positive impact on mesoscale forecasts; 2) typhoon forecasts through dropwindsonde observations; and 3) forecast skills for high-impact weather systems via increased observations in neighboring countries. Various indirect benefits for scientific researches are also discussed. Extensive adaptive observation studies are recommended for all high-impact weather systems coming into the Korean peninsula, and enhancement of observations in the highly sensitive regions for the forecast error growth is required to improve forecast skills in the peninsula, possibly through international collaborations with neighboring countries.

• Journal of Astronomy and Space Sciences
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• v.10 no.1
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• pp.94-102
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• 1993

We have develped a four-channel photoelectric photometer for the 61cm telescope of Sobaeksan Astronomy Observatory using optical fiber. We observed a standard star with each channel to check the efficiency difference between the channels, and found no differences. To calibrate the observing accuracy and efficiency, we have observed a short period W UMa type eclipsing binary star, BV Dra. Test observations show that the photometer is very stabel and the accuracy of the data is also increased. The observing efficiency is very increased compared with that of single channel photometer ; at least five times faster than older one in the case of one filter observation.

• Atmosphere
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• v.18 no.2
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• pp.147-158
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• 2008

Domestic IOP (intensive observing period) has mostly been represented by the KEOP (Korea Enhanced Observing Period), which started the 5-yr second phase in 2006 after the first phase (2001-2005). During the first phase, the KEOP had focused on special observations (e.g., frontal systems, typhoons, etc.) around the Haenam supersite, while extended observations have been attempted from the second phase, e.g., mountain and downstream meteorology in 2006 and heavy rainfall in the mid-central region and marine meteorology in 2007. So far the KEOP has collected some useful data for severe weather systems in Korea, which are very important in understanding the development mechanisms of disastrous weather systems moving into or developing in Korea. In the future, intensive observations should be made for all characteristic weather systems in Korea including the easterly in the central-eastern coastal areas, the orographically-developed systems around mountains, the heavy snowfall in the western coastal areas, the upstream/downstream effect around major mountain ranges, and the heavy rainfall in the mid-central region. Enhancing observations over the seas around the Korean Peninsula is utmost important to improve forecast accuracy on the weather systems moving into Korea through the seas. Observations of sand dust storm in the domestic and the source regions are also essential. Such various IOPs should serve as important components of international field campaign such as THORPEX (THe Observing system Research and Predictability EXperiment) through active international collaborations.

• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.635-638
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• 1998

This paper proposes a simple method to measure system's performance in target tracking problems. Essentially employing the Cramer-Rao lower bound (CRLB) on trakcing accuracy, an algorithm of predicting system's performance under various scenarios is developed. The input data is a collection of measurements over time fromsensors embedded in gaussian noise. The target of interest may not maneuver over the processing time interval while the own ship observing platform may maneuver in an arbitrary fashion. Th eproposed approach is demonstrated and discussed through simulation results.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.4
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• pp.429-438
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• 2017

Cranke-Nicolson scheme in native OpenFOAM source libraries was not able to provide 2nd order temporal accuracy of velocity and pressure since the volume flux of convective nonlinear terms was 1st accurate in time. In the present study the simplest way of getting the volume flux with 2nd order accuracy was proposed by using old fluxes. A possible numerical instability originated from an explicit estimation of volume fluxes could be handled by introducing a weighting factor which was determined by observing the ratio of the finally corrected volume flux to the intermediate volume flux at the previous step. The new calculation of volume fluxes was able to provide temporally accurate velocity and pressure with 2nd order. The improvement of temporal accuracy was validated by performing numerical simulations of 2D Taylor-Green vortex of which an exact solution was known and 2D vortex shedding from a circular cylinder.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.2
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• pp.18-28
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• 1989

In this paper, we describe a pointing accuracy establishment and efficiency measurement of 13.7 m antenna for observing cosmic radio wave which is in the first stage just after finishing its installation. The initial stage of pointing model, 1 and 2 were set up with the observational data of Sun and Moon which are large in visual diameter and also strong in radio intensity. Based on this model, model 3 and 4 were established within the available operational range, i.e., 3.8" in azimuth deviation, 10.5" in elevation deviation, with the observational data of SiO maser source which is a point source and distributed in overall sky. Both apeture efficiency anhd beam efficiency were measured by observing Venus whose brightness temperature is well-known. The resulting corrected efficiencies were 35% and 50% respectively.

• Atmosphere
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• v.23 no.3
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• pp.275-282
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• 2013

In this study, the numerical model was developed to evaluate the observational environment of sunshine duration and, for evaluating the accuracy and utility of the model, it was verified against the observational data measured at Dae-gu Automated Synoptic Observing System (ASOS) located in an urban area. Three-dimensional topography and building configuration as the surface input data of the model were constructed using a Geographic Information System (GIS) data. First, the accuracy of the computing planetary positions suggested by Paul Schlyter was verified against the data provided by Korea Astronomy and Space Science Institute (KASI) and the results showed that the numerical model predicted the Sun's position (the solar azimuth and altitude angles) quite precisely. Then, this model was applied to reproduce the sunshine duration at the Dae-gu ASOS. The observed and calculated sunshine durations were similar to each other. However, the observed and calculated sunrise (sunset) times were delayed (curtailed), compared to those provided by KASI that considered just the ASOS's position information such as latitude, longitude, and elevation height but did not consider the building and topography information. Further investigation showed that this was caused by not only the topographic characteristic (higher in the east and lower in the west) but also the buildings located in the southeast near the sunrise and the southwest near the sunset. It was found that higher building resolution increased the accuracy of the model. It was concluded that, for the accurate evaluation of the sunshine duration, detailed building and topography information around the observing sites was required and the numerical model developed in this study was successful to predict and/or the sunshine duration of the ASOS located in an urban area.

• Journal of the Korean Society for Precision Engineering
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• v.4 no.2
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• pp.36-46
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• 1987

An optical technique using laser for non-contact measurement of surface roughness and form accuracy of ground surfaces is presented. It is found that, when a ground surface is illuminated by a beam of laser light, the roughness height and slope distribution has significant influence on the pattern of reflection and it maintains an unique Gaussian distribution relationship with the surface roughness. The principle idea of the optical measurement system is therefore monitor the radiation, and then calibrate it in process against surface roughness by means of necessary digital data processing. On the other hand, measuring the form accuracy of a ground surface is accomplished by using a triangular method, which is based on observing the movement of an image of a spot of light projected onto the surface. The image is focused, through a series of lenses for magnification, on a photodetector array lf line configur- ation. Then the relative movement of image and consequently the form accuracy of the surface can be obtained through appropriate calibration procedures. Experimental test showed that the optical roughness measurement technique suggested in this work is very efficient for most industrial applications being capable of monitoring the roughness heights ranging 0.1 to 0.6 .$\mu$m CLA values. And form accuracy can be measured in process with a resolution of 10 .$\mu$m.

• Journal of Fisheries and Marine Sciences Education
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• v.10 no.1
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• pp.53-62
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• 1998

Accuracy of positions by GPS receiver at Tongyoung Port were measured and analysed in order to get more credible information on GPS positioning for vessels. Positions were automatically recorded every 5-Min from 1st October, 1997 to 30th of November, 1997 by two identical GPS receivers at the Laboratory of Navigation in the College of Marine Science, Gyeongsang University ($34^{\circ}$ 49' 57.985"N, $128^{\circ}$ 24' 06.562") and at the training ship "Gyeongyang" alongside in the tongyoung passenger port ($34^{\circ}$ 50" 10.080"N, $128^{\circ}$ 25' 16.415") as fixed positions. The results are as follows ; 1. Number of the usable satellites observing Zenith angle between $9^{\circ}$ and $82^{\circ}$ was normally 4 during a day 24 hours except for 3 hours with total Number 20. 2. Accuracy of position with time was widely dispersed around center of standard position as well as directional deviation around mean position. 3. Specific error of GPS receiver showed a little deviation by alternative measurements for consecutive 5 days at each fixed position respectively. 4. Accuracy of GPS position at 2 fixed positions of Tongyoung port was revealed 27.2 m as minimum value while normal accuracy for all day could be less than 50 m.