• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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• pp.303-306
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• 2006

A roll rate estimation method is proposed using the GPS measurement for spinning vehicles such as guided munitions and smart bombs. Before designing the roll rate estimator, the carrier phase and the carrier frequency deviation caused by spinning have been observed. Based on the observation, the spinning frequency is estimated using I and Q value from the correlator. The proposed method is evaluated through computer simulations using a software defined receiver and a GPS IF signal generator.

• 한국항해항만학회지
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• 제38권2호
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• pp.121-126
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• 2014

본 논문은 저가형 GPS 수신 모듈에 DGPS 서비스를 적용하기 위한 방안으로 NMEA GPGSV 데이터의 위성 배치 정보에 포함된 위성 앙각과 방위각으로 관측 행렬을 구성한 후, 거리기반 보정정보를 위치영역으로 투영하여 기 산출된 위치 오차 벡터를 수정하는 방안을 제시하였다. 저가형 수신기인 U-blox LEA-5H 모델의 출력 데이터에 제안한 알고리즘을 적용한 결과 주 활동 시간인 낮 시간에 수평 오차 RMS를 1.8m에서 1m 이내로 줄였으며, 수직 정확도는 RMS 5.8m에서 1.4m로 75% 향상시킴을 확인하였다. 본 논문에서 제안하는 방식은 하드웨어의 변경없이 소프트웨어만으로 저가형 GPS의 성능을 DGPS 수준으로 향상시키는 기법이므로, 소비자와 제조사의 부담을 경감시켜 향후 제공될 고정밀 측위 서비스 인프라의 활성화에 기여할 수 있을 것으로 기대된다.

• Journal of Positioning, Navigation, and Timing
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• 제4권2호
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• pp.67-72
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• 2015

Power grid techniques are distributed over general power systems ranging from power stations to power transmission, power distribution, and users. To monitor and control the elements and performance of a power system in real time in the extensive area of power generation, power transmission, wide-area monitoring (WAM) and control techniques are required (Sattinger et al. 2007). Also, to efficiently operate a power grid, integrated techniques of information and communication technology are required for the application of communication network and relevant equipment, computing, and system control software. WAM should make a precise power grid measurement of more than once per cycle by time synchronization using GPS. By collecting the measurement values of a power grid from substations located at faraway regions through remote communication, the current status of the entire power grid system can be examined. However, for GPS that is used in general national industries, unexpected dangerous situations have occurred due to its deterioration and jamming. Currently, the power grid is based on a synchronization system using GPS. Thus, interruption of the time synchronization system of the power system due to the failure or abnormal condition of GPS would have enormous effects on each field such as economy, security, and the lives of the public due to the destruction of the synchronization system of the national power grid. Developed countries have an emergency substitute system in preparation for this abnormal situation of GPS. Therefore, in Korea, a system that is used to prepare for the interruption of GPS reception should also be established on a long-term basis; but prior to this, it is required that an evaluation technique for the time synchronization performance of a GPS receiver using an atomic clock within the power grid. In this study, a monitoring system of time synchronization based on GPS at a power grid was implemented, and the results were presented.

• 한국항공운항학회지
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• 제19권4호
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• pp.6-11
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• 2011

Launch of the first Quasi-Zentih Satellite System (QZSS) satellite, dubbed Michibiki, took place September 11, 2010 and technical and application verification of the satellite is being carried out. This paper presents the results obtained from processing of the L5 signal transmitted from the QZSS satellite. The QZSS L5 signal is collected in ETRI, Korea. And then, the acquisition and tracking are performed by the L5 software receiver implemented by ETRI. The tracking loop of FLL, PLL, and DLL, the EPL correlator output, and the C/No output results show that the QZSS L5 signal is normally processed. Finally, the paper demonstrates that the QZSS L5 signal could be used as GPS satellite based augmentation system in Korea as well as Japan.

• 한국측량학회지
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• 제17권1호
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• pp.21-32
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• 1999

항공사진측량에 의한 지도제작과 미지점의 정확한 위치결정은 매우 경제적인 방법이나 외부표정요소를 구하기 위해서는 기준점이 필요하다. 번들조정기법의 성능향상과 횡스트립의 설치로 블럭조정에 요구되어지는 기준점의수가 감소되었음에도 불구하고 기준점 측량은 비용면에서 무시할 수 없는 부분이다. 이러한 단점을 보완하기 위해 연구된 동적 DGPS-위치결정에 의한 GPS-항측은 처음 가능성을 보인 이래 계속 발전되어 오고 있다. 위성배치의 완료, 수신기의 기능 향상 및 동적 DGPS-위치결정을 위한 S/W의 향상 등으로 결합블럭조정의 정확도도 크게 증가하고 있다. 따라서 GPS-항측의 실용화에 대한 연구가 보다 절실히 요청되고 있는 실정이다. 본 연구의 대상지는 60%의 횡중복도와 횡스트립으로 촬영하여 광산지역의 지반침하를 조사하기 위하여 실시되었다. 단지 6개의 기준점만을 사용한 결합블럭조정으로도 21개의 수평기준점과 81개의 연직기준점을 사용한 재래식 블럭조정과 같은 결과를 얻을 수 있었다. 또한 GPS에 의한 노출점의 위치와 블록조정의 정확도는 지상 수신기준점의 거리와는 무관하였으며 결합블럭조정시 정오차 소거를 위한 특별한 모형식이 필요함을 알 수 있었다.

• Journal of Positioning, Navigation, and Timing
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• 제4권2호
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• pp.57-65
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• 2015

Global Navigation Satellite System (GNSS) including Global Positioning System (GPS) is an important element for navigation of both the military and civil Unmanned Aerial Vehicle (UAV). Contrary to the military UAVs, the civil UAVs use the civil signals which are unencrypted, unauthenticated and predictable. Therefore if the civil signals are counterfeited, the civil UAV’s position can be manipulated and the appropriate movement of the civil UAV to the target point is not achieved. In this paper, spoofing on the autonomous navigation UAV is implemented through field experiments. Although the demanded conditions for appropriate spoofing attack exists, satisfying the conditions is restricted in real environments. So, the Way-point of the UAV is assumed to be known for experiments and assessments. Under the circumstances, GPS spoofing signal is generated based on the Software-based GNSS signal generator. The signal is emitted to the target UAV using the antenna of the spoofer and the effect of the signal is analyzed and evaluated. In conclusion, taking the UAV to the target point is hardly feasible. To implement the spoofing as expectation, the position and guidance system of the UAV has to be known. Additionally, the GPS receiver on the UAV could be checked whether it appropriately tracks the spoofing signal or not. However, the effect of the spoofing signal on the autonomous UAV has been verified and assessed through the experimental results. Spoofing signal affects the navigation system of the UAV so that the UAV goes off course or shows an abnormal operation.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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• pp.385-390
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• 2006

This paper examines the sampling and jitter specifications and considerations for Global Navigation Satellite Systems (GNSS) software receivers. Software radio (SWR) technologies are being used in the implementation of communication receivers in general and GNSS receivers in particular. With the advent of new GPS signals, and a range of new Galileo and GLONASS signals soon becoming available, GNSS is an application where SWR and software-defined radio (SDR) are likely to have an impact. The sampling process is critical for SWR receivers, where it occurs as close to the antenna as possible. One way to achieve this is by BandPass Sampling (BPS), which is an undersampling technique that exploits aliasing to perform downconversion. BPS enables removal of the IF stage in the radio receiver. The sampling frequency is a very important factor since it influences both receiver performance and implementation efficiency. However, the design of BPS can result in degradation of Signal-to-Noise Ratio (SNR) due to the out-of-band noise being aliased. Important to the specification of both the ADC and its clocking Phase- Locked Loop (PLL) is jitter. Contributing to the system jitter are the aperture jitter of the sample-and-hold switch at the input of ADC and the sampling-clock jitter. Aperture jitter effects have usually been modeled as additive noise, based on a sinusoidal input signal, and limits the achievable Signal-to-Noise Ratio (SNR). Jitter in the sampled signal has several sources: phase noise in the Voltage-Controlled Oscillator (VCO) within the sampling PLL, jitter introduced by variations in the period of the frequency divider used in the sampling PLL and cross-talk from the lock line running parallel to signal lines. Jitter in the sampling process directly acts to degrade the noise floor and selectivity of receiver. Choosing an appropriate VCO for a SWR system is not as simple as finding one with right oscillator frequency. Similarly, it is important to specify the right jitter performance for the ADC. In this paper, the allowable sampling frequencies are calculated and analyzed for the multiple frequency BPS software radio GNSS receivers. The SNR degradation due to jitter in a BPSK system is calculated and required jitter standard deviation allowable for each GNSS band of interest is evaluated. Furthermore, in this paper we have investigated the sources of jitter and a basic jitter budget is calculated that could assist in the design of multiple frequency SWR GNSS receivers. We examine different ADCs and PLLs available in the market and compare known performance with the calculated budget. The results obtained are therefore directly applicable to SWR GNSS receiver design.

• 대한공간정보학회지
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• 제18권4호
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• pp.93-99
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• 2010

도시에 산재한 각종 시설물의 유지 관리는 대부분 측량지식이 부족한 일반 관리자에 의해 수행되므로, 기 구축된 GIS 도면만으로는 대상물의 정확한 위치를 신속히 찾아내기가 어렵다. 따라서 최근에는 GIS도면이 입력된 UMPC 또는 PDA 등의 단말기에 VRS-RTK 또는 SBAS DGPS 장비 등을 연결하여 대상물의 위치를 신속히 찾아가는 모바일현장시스템이 사용되고 있으나, 2~3층 규모의 주택이 밀집되어 있는 지역에서는 가시위성수의 부족과 위치보정신호의 단절 및 다중경로의 오차 등으로 인해 측위에 많은 어려움이 있다. 본 논문에서는 가시 위성수 증강을 위해 GLONASS 신호 수신이 가능한 휴대용 DGPS 장비를 사용하고, 이에 수신율이 양호한 국토지리정보원의 네트워크 DGPS 보정신호를 적용하여 현장 실험을 실시하였다. 실험결과 네트워크 DGPS 장비는 주택가 밀집지역에서도 0.3~0.84m 이내의 높은 정확도로 측위가 가능하고 측위율도 매우 높게 나타나 향후 골목길에서의 각종시설물 관리에 널리 적용될 수 있을 것으로 사료된다.

• Journal of Positioning, Navigation, and Timing
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• 제13권1호
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• pp.75-83
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• 2024

In order to reduce the time and cost of developing a navigation system, a performance evaluation platform can be used. A User Interface (UI) is required to effectively evaluate the performance, which sets parameters and gives navigation sensor signals and data display, and also displays navigation results. In this paper, a LabVIEW-based UI design method for multi-integrated navigation systems is proposed and implementation results are presented. The UI consists of a signal and data generation part and a signal and data processing part. The signal and data generation part sets parameters for the signal and data generation and displays the navigation sensor signal and data generation results. The signal and data processing part sets parameters for the signal and data processing and displays the navigation results. The signal and data generation part and signal and data processing part are designed to satisfy the requirements of the UI for a performance evaluation of the navigation system. In order to show the usefulness of the proposed UI design method, parameters of the signal and data generation and the signal and data processing are set through the LabVIEW-based UI, and the Global Positioning System (GPS) signal and inertial measurement unit data generation results and the navigation results of a GPS Software Defined Receiver (SDR) and inertial navigation system are confirmed. The implementation results show that the proposed UI design method helps users conduct an effective performance evaluation of navigation systems.

• Journal of Positioning, Navigation, and Timing
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• 제3권1호
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• pp.25-30
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• 2014

Differential Global Positioning System-Correction Projection (DGPS-CP) algorithm, which has been suggested as a method of correcting pre-calculated position error by projecting range-domain correction to positional domain, is a method to improve the accuracy performance of a low price GPS receiver to 1 to 3 m, which is equivalent to that of DGPS, just by using a software program without changing the hardware. However, when DGPS-CP algorithm is actually realized, the error is not completely eliminated in a case where a reference station does not provide correction of some satellites among the visible satellites used in user positioning. In this study, the problem of decreased performance due to the difference in visible satellites between a user and a reference station was solved by applying the Multifunctional Transport Satellites (MTSAT) based Augmentation System (MASA) correction to DGPS-CP, instead of local DGPS correction, by using the Satellite Based Augmentation System (SBAS) operated in Japan. The experimental results showed that the accuracy was improved by 25 cm in the horizontal root mean square (RMS) and by 20 cm in the vertical RMS in comparison to that of the conventional DGPS-CP.