• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2015.07a
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• pp.60-62
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• 2015

Dynamic Positioning System(DPS)은 동력, DP control 장치, DP 컴퓨터, 위치참조시스템(PRS), 센서, thruster 시스템 및 DP 운용자(DPO) 7가지로 구성되어 있다. DP 선박은 이들 구성요소들에 문제가 발생하면 그 기능을 상실할 수 있다. 본 연구에서는 2001~2010년까지 10년 동안 IMCA 보고된 DP 선박 관련사고 612건에 대한 분석을 바탕으로 DPS의 7가지 구성요소와 관련된 사고 원인을 파악하고 이들 중 가장 높은 비율을 차지하는 원인을 정성적, 정량적으로 상세 분석하여 요소별 관계와 주요 작용 요소를 확인하고자 한다. 이를 통해 DP 선박의 LOP사과 관련 분석에 있어 베이지안 네트워크의 활용성을 확인해 보았다. 10년 평균 가장 높은 비율을 차지한 DPS 사고원인 요인은 PRS이었으며 이를 전문가 브레인스토밍을 통해 작성된 flowchart를 바탕으로 베이지안 네트워크를 통해 상세 분석해 본 결과 PRS의 각 요소별 조건부 확률 확인할 수 있었다. DP 선박의 drive off를 발생시키는데 주요한 영향을 미치는 것은 DGPS, microwave radar 및 HPR 이었고 DGPS에 주요한 영향을 미치는 에러 요인은 signal blocked, electric components failure, relative mode error 및 signal weak or fail 이었다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.1
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• pp.54-60
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• 2013

This paper presents a ground altitude determination algorithm using a laser altimeter and GPS for automatic take-off and landing of UAV. The characteristics of the laser altimeter was analyzed in ground tests and a low-pass filter was designed to reduce the effect of signal interruption due to reflectivity problem. The paper shows that a single sensor cannot measure ground altitude appropriately in terms of reliability and accuracy. To complement shortcomings of the laser altimeter, the linear Kalman filter was designed using DGPS vertical speed. Designed filter was validated and tuned through the steps of simulation, ground test and flight test. It was confirmed that the accuracy for automatic landing is achievable.

• Journal of Biosystems Engineering
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• v.27 no.3
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• pp.259-266
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• 2002

It is crucial to know spatial soil variability for precision farming. However, it is time-consuming, and difficult to measure spatial soil properties. Therefore, there are needs fur sensing technology to estimate spatial soil variability, and for electronic mapping technology to store, manipulate and process the sampled data. This research was conducted to develop a real-time soil organic matter sensor and an electronic mapping system. A soil organic matter sensor was developed with a spectrophotometer in the 900∼1,700 nm range. It was designed in a penetrator type to measure reflectance of soil at 15cm depth. The signal was calibrated with organic matter content (OMC) of the soil which was sampled in the field. The OMC was measured by the Walkeley-Black method. The soil OMCs were ranged from 0.07 to 7.96%. Statistical partial least square and principle component regression analyses were used as calibration methods. Coefficient of determination, standard error prediction and bias were 0.85 0.72 and -0.13, respectively. The electronic mapping system was consisted of the soil OMC sensor, a DGPS, a database and a makeshift vehicle. An algorithm was developed to acquire data on sampling position and its OMC and to store the data in the database. Fifty samples in fields were taken to make an N-fertilizer dosage map. Mean absolute error of these data was 0.59. The Kring method was used to interpolate data between sampling nodes. The interpolated data was used to make a soil OMC map. Also an N-fertilizer dosage map was drawn using the soil OMC map. The N-fertilizer dosage was determined by the fertilizing equation recommended by National Institute of Agricultural Science and Technology in Korea. Use of the N-fertilizer dosage map would increase precision fertilization up to 91% compared with conventional fertilization. Therefore, the developed electronic mapping system was feasible to not only precision determination of N-fertilizer dosage, but also reduction of environmental pollution.

• Journal of Advanced Navigation Technology
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• v.21 no.3
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• pp.272-278
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• 2017

In order to meet performance requirements specified by the ICAO in drone operation, a system that provides augmentation information such as SBAS is needed. However, the operating range of the drone is limited in situation where the drone can not received the SBAS message continuously. In this paper, we propose a system to transmit SBAS augmentation message using a separate communication channel assuming the SBAS satellite signal to the drone has been shielded. We implemented the proposed system and verified its performance in the static environment. The DGPS positioning results showed that the accuracy difference is about 10cm, which means the accuracy performance was very similar. In addition, the protection level calculated by the system also shows the difference within 2m from the value calculated by the airborne receiver.

• Journal of Korean Society for Geospatial Information Science
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• v.18 no.4
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• pp.87-92
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• 2010

With recent localized heavy rain, the collapsing accident of the cut slopes occur repeatedly every year. The maintenance of the cut slopes is very crucial as the collapsing of cut slopes causes various calamities such as human causalities and sweeping away of the roads. By looking at the study of current situation of the cut slopes, designed for maintenance of cut slopes, the locations of the damaged districts are hard to figure out as they are represented through distance mark and longitude and latitude. In this paper has used NDGPS methods and VRS service through GPS signal corrections that are received by DGPS standard department to correctly analyze the exact location and the shape of the slope. The result of this analysis shows that both methods produce similar shape of the slope. Therefore, these two methods, NDGPS methods and VRS service, can be applied to other analysis of cut slopes in different areas.

• Journal of Biosystems Engineering
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• v.41 no.4
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• pp.319-327
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• 2016

Purpose: Automated guidance systems (AGSs) for mobile farm machinery have several advantages over manual operation in the crop production industry. Many researchers and companies have tried to develop such a system. However, it is not easy to evaluate the performance of an AGS because there is no established device used to evaluate it that complies with the ISO 12188 standard. The objective of this study was to develop a tracking sensor system using five laser distance measurement sensors. Methods: One sensor-for long-range distance measurement-was used to measure travel distance and velocity. The other four sensors-for mid-range distance measurement-were used to measure lateral deviation. Stationary, manual driving, and A-B line tests were conducted, and the results were compared with the real-time kinematic differential global positioning system (RTK-DGPS) signal used by the AGS. Results: For the stationary test, the average error of the tracking sensor system was 1.99 mm, and the average error of the RTK-DGPS was 15.19 mm. For the two types of driving tests, the data trends were similar. A comparison of the changes in lateral deviation showed that the data stability of the developed tracking system was better. Conclusions: Although the tracking system was not capable of measuring long travel distances under strong sunlight illumination because of the long-range sensor's limitations, this dilemma could be overcome using a higher-performance sensor.

• Journal of Korea Multimedia Society
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• v.18 no.12
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• pp.1427-1431
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• 2015

In the salvage area, the location of the incident vessel and diver to rescue the victim are very important. But there are no ways but to rely on the GPS satellites to obtain the location in the salvage sites. Because the positioning using GPS satellites has a measurement error of up to 50 meters caused by the status of the atmosphere, a new positioning method with more accuracy should be devised. So if studies on measuring the position of the ships and divers accurately in the sea are performed, it will be helpful in the field of the salvage positioning. In this paper, a high precision positioning system in salvage using DGPS signal through mobile broadcasting is proposed with positioning error of up to 1 meter.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.05a
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• pp.771-772
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• 2016

The paper is the basic study on the investigation that MSAS system can be usable around Korean Peninsula. The general issues of DGNSS were mostly investigated referred to previous published materials. And it is verified that the sufficient GPS satellites, which are more than 4 satellites, for positioning using MSAS service are available around Korean Peninsula.

• Journal of the Korea Institute of Military Science and Technology
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• v.6 no.1
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• pp.39-48
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• 2003

A GPS translator system is used to get the precise and reliable trajectory data for the high dynamic test vehicles, such as missiles or artillery shells. The missile system with high dynamics, vibration and shock needs to determine its position and velocity in particular. The proposed GPS translator on the test vehicle receives GPS signals, amplifies, down-converts, digitally samples, BPSK modulates, up-converts them to S-band, and then retransmits them to the ground translator processing station. It has doppler variation and signal noise, so design method for resolving them is proposed. The performance of the translator is proved by environmental test and real flight test.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.1015-1017
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• 2003

Recently, DGPS or RTK-GPS techniques enable us to use satellite based positioning systems with high accuracy. But in urban area, navigation systems suffer from problems such as signal blockage by high-rise buildings, multi-path problems, and so on. So we have to know numbers of visible satellites and quality of signals received at the ground level in urban area as accurate as possible. In this paper, we developed a simulation system called LoQAS [Location service Quality Assessment System, 2002, the University of Tokyo] which can simulate numbers of visible satellites and DOP values using accurate satellite orbital data and 3-D digital map. In this time, we evaluated this system and extended it to deal with reflected signals to assess multi-path problems.