• Journal of Positioning, Navigation, and Timing
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• v.5 no.4
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• pp.213-219
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• 2016

Most existing studies on the wide-area differential global positioning system (WADGPS) employed a grid ionosphere model for error correction in the ionospheric delay. The present study discusses the application of satellite-based ionospheric delay model that provides an error model as a plane function with regard to individual satellites in order to improve accuracy in the WADGPS. The satellite-based ionospheric delay model was developed by Stanford University in the USA. In the present study, the algorithm in the model is applied to the WADGPS system and experimental results using measurements in the Korean Peninsula are presented. Around 1 m horizontal accuracy was exhibited in the existing planar fit grid model but when the satellite-based model was applied, correction performance within 1 m was verified.

• The Journal of the Korean dental association
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• v.41 no.3 s.406
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• pp.180-189
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• 2003

The purpose of this study was to evaluate the accuracy of the soft tissue profile predicted by Quick Ceph Image Pro in mandibular setback surgery. Preoperative and postoperative lateral cephalograms of 24 patients(9 males and 15 females) who had completed treatment that involved orthodontics and mandibular setback by BSSRO were used. Computerized cephalometric lines and video image predictions were generated and compared with the actual postoperative results. In horizontal measurement, predicted values were smaller than actual measurements. And lips were thicker than actual values. Most of the different between values and actual measurement were than 2mm, and it was clinically acceptable.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.161-166
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• 2002

Recently, researches on precision machining of nato-order, especially in the field of optical components and semi-conductors have been under development very actively. A accuracy of machining and positioning in a critical issue in ultra-precision machining. This paper proposes a new positioning system which can give excellent dynamic characteristics and reduce errors in horizontal, vertical, pitching, and yawing motions. In this paper, we suggest a connecting mechanism (the couplings) to reduce motion errors such as chatter and runout while preserving the positioning accuracy. We verified the good performance in the new connecting systems with various coupling types, which we classified into the fixed type, the spring type, the aeroctatic-nozzle type, and the aeroctatic-porous type according to the way of reducing the chatter and error.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.10a
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• pp.527-532
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• 1993

MascMC system is one of the MMC system module which performs measuring and checking of machined workpieces on the machine tools. Accuracy of the MascMC was compensated for developing a reliable measuring system by measurement error calibration. Reference gauges, ring gauges, block gauges,squares, spheres and cylindrical squares, were used for error identification and compensation. .+-. 10 .mu. m accuracy with 95% confidence interval was confirmed on the vertical and the horizontal machining center through the large number of experiments.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.537-540
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• 2005

The attitude control, sensors and camera installed on the spacecraft should be located according to the system alignment requirement. The alignment measurement requirement accuracy for the sensors should be below $\pm$0.1. Therefore, Alignment Measurement System which is combined theodolite, Rotating table and digital inclinometer etc., should be used. As the measurement accuracy is required very precise, the appropriate measurement procedure and alignment angle measurement, calculation and shimming work should is accomplished. Consequently, this paper is accomplished the works to align the measurement requirement accuracy throughout alignment measurement and shimming work of installed module and sensor

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.1393-1398
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• 2009

We once have announced that we developed a horizontal large-area alignment system with an alignment accuracy of < ${\pm}3{\mu}m$ and an alignment time of < 30 seconds, a core process module for RGB direct pattering by using a fine metal mask, which can process a Gen 4 ($730{\times}920mm^2$) substrate for high resolution OLED products. In this article, we presents a brand-new vertical alignment system for a even larger substrate of Gen 5 and beyond which can provide a better alignment accuracy and a higher throughput. The newly developed system exhibits an alignment accuracy of < ${\pm}2{\mu}m$ and an alignment time of < 20 seconds which, we believe, can open a new era for manufacturing large-size OLED monitors and TVs.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.10a
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• pp.417-422
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• 2002

One of the major limitations of productivity and quality in metal cutting is the machining accuracy of machine tools. The machining accuracy is affected by geometric errors, thermally-induced errors, and the deterioration of the machine tools. Geometric and thermal errors of machine tools should be measured and compensated to manufacture high quality products. In metal cutting, the machining accuracy is more affected by thermal errors than by geometric errors. In this study, the compensation device and temperature-based algorithm have been implemented on the machining center in order to compensate thermal error of machine tools under the real-time. The thermal errors are predicted using the neural network and multi-regression modeling methods. In order to compensate thermal characteristics under several operating conditions, experiments performed with five gap sensors and manufactured compensation device on the horizontal machining center.

• Journal of Positioning, Navigation, and Timing
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• v.8 no.2
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• pp.87-94
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• 2019

The Global Navigation Satellite System (GNSS) Real-Time Kinematic (RTK) positioning has been widely used in geodesy, surveying, and navigation fields. RTK can benefit enormously from the integration of multi-GNSS. In this study, we develop a GPS/BeiDou Navigation Satellite System (BDS) RTK integration algorithm for long baselines ranging from 128 km to 335 km in South Korea. The positioning performance with GPS/BDS RTK, GPS-only RTK, and BDS-only RTK is compared in terms of the positioning accuracy. An improvement of positioning accuracy over long baselines can be found with GPS/BDS RTK compared with that of GPS-only RTK and that of BDS-only RTK. The positioning accuracy of GPS/BDS RTK is better than 2 cm in the horizontal direction and better than 5 cm in the vertical direction. A lower Relative Dilution of Precision (RDOP) value with GPS/BDS integration can obtain a better positional precision for long baseline RTK positioning.

• Journal of Positioning, Navigation, and Timing
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• v.10 no.1
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• pp.35-42
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• 2021

The position accuracy of the stand-alone Regional Navigation Satellite System (RNSS) users is more than tens of meters because of various error sources in satellite navigation signals. This paper focuses on wide-area differential (WAD) positioning technique, which is already applied in Global Navigation Satellite System (GNSS), in order to improve the position accuracy of RNSS users. According to the simulation results in the very narrow ground network in regional area, the horizontal position error of stand-alone RNSS is about RMS 11.6 m, and that of RNSS with WAD technique, named the WAD-RNSS, is about RMS 2.5 m. The accuracy performance has improved by about 78%.