Precision Assessment of Near Real Time Precise Orbit Determination for Low Earth Orbiter

최종연,이상정 한국우주과학회 2011 Journal of Astronomy and Space Sciences Vol.28 No.1

The precise orbit determination (POD) of low earth orbiter (LEO) has complied with its required positioning accuracy by the double-differencing of observations between International GNSS Service (IGS) and LEO to eliminate the common clock error of the global positioning system (GPS) satellites and receiver. Using this method, we also have achieved the 1 m positioning accuracy of Korea Multi-Purpose Satellite (KOMPSAT)-2. However double-differencing POD has huge load of processing the global network of lots of ground stations because LEO turns around the Earth with rapid velocity. And both the centimeter accuracy and the near real time (NRT) processing have been needed in the LEO POD applications--atmospheric sounding or urgent image processing--as well as the surveying. An alternative to differential GPS for high accuracy NRT POD is precise point positioning (PPP) to use measurements from one satellite receiver only, to replace the broadcast navigation message with precise post processed values from IGS, and to have phase measurements of dual frequency GPS receiver. PPP can obtain positioning accuracy comparable to that of differential positioning. KOMPSAT-5 has a precise dual frequency GPS flight receiver (integrated GPS and occultation receiver, IGOR) to satisfy the accuracy requirements of 20 cm positioning accuracy for highly precise synthetic aperture radar image processing and to collect GPS radio occultation measurements for atmospheric sounding. In this paper we obtained about 3-5 cm positioning accuracies using the real GPS data of the Gravity Recover and Climate Experiment (GRACE) satellites loaded the Blackjack receiver, a predecessor of IGOR. And it is important to reduce the latency of orbit determination processing in the NRT POD. This latency is determined as the volume of GPS measurements. Thus changing the sampling intervals,we show their latency to able to reduce without the precision degradation as the assessment of their precision.

Accuracy Analysis of Code-based PPP-RTK Positioning Utilizing K-SSR Correction Messages Outside the Reference Network

Yoon, Woong-Jun,Park, Kwan-Dong,Kim, Hye-In,Woo., Seung,Park, Junpyo The Institute of Positioning 2017 Journal of Positioning, Navigation, and Timing Vol.6 No.2

Precise Point Positioning-Real Time Kinematic (PPP-RTK) refers to a technology that combines PPP with network-RTK in which a user does not directly receive observed data from a reference station but receives State-Space Representation (SSR) messages corrected for error components from a central processing station through Networked Transport of RTCM via Internet Protocol (NTRIP) or Digital Multimedia Broadcasting (DMB) for purposes of positioning. SSR messages, which refer to corrections used in PPP-RTK, are generated by a central processing station using real-time observed data collected from reference stations and account for corrections needed due to the ionosphere, troposphere, satellite orbital errors, satellite time offsets, and satellite biases. This study used a type of SSR message provided in South Korea, known as Korea-SSR (K-SSR), to implement a PPP-RTK algorithm based on code-pseudorange measurements and validated its accuracy within the reference station network. In order to validate the accuracy of the implemented algorithm outside of the network, the K-SSR was extrapolated and applied to positioning in reference stations in Changchun, China (CHAN) and Japan (AIRA). This also entailed a quantitative evaluation that measured improvements in accuracy in comparison with point positioning. The results of the study showed that positioning applied with extrapolated K-SSR correction data was more accurate in both AIRA and CHAN than point positioning with improvements of approximately 20~50%.

Performance Analysis of GPS/BDS Integrated Precise Positioning System Considering Visibility in Urban Environments

Noh, Jae Hee,Lee, Sun Yong,Lim, Deok Won,Lee, Sang Jeong The Institute of Positioning 2019 Journal of Positioning, Navigation, and Timing Vol.8 No.1

In recent years, Intelligent Transport Systems (ITS) and Autonomous Vehicle Technology have actively studied around the world. In order to achieve the purpose of Advanced Driver Assistance System (ADAS) and Autonomous Vehicle Technology, it must be obtained accurate and reliable positioning. However, the problem of positioning in the urban area is a low position accuracy caused by the reduction of the number of visible satellites due to high buildings. In this paper, we analyzed the availability of precise positioning system in urban area are using GPS/BDS integrated system. For this study, GPS and BDS satellite signals were collected using two low-cost receivers in the open sky and a designed software based platform for precise positioning performance analysis. And we analyzed the precise positioning performance by changing the mask angle considering the urban area. From the results, it can be confirmed that the performance of precise positioning of GPS only and BDS only decrease in the environment where mask angle is $40^{\circ}$ to $45^{\circ}$, however, GPS/BDS integrated system maintains high performance of precise positioning.

Performance Analysis of GPS/BDS Integrated Precise Positioning System Considering Visibility in Urban Environments

노재희,이선용,임덕원,이상정 사단법인 항법시스템학회 2019 Journal of Positioning, Navigation, and Timing Vol.8 No.1

In recent years, Intelligent Transport Systems (ITS) and Autonomous Vehicle Technology have actively studied around the world. In order to achieve the purpose of Advanced Driver Assistance System (ADAS) and Autonomous Vehicle Technology, it must be obtained accurate and reliable positioning. However, the problem of positioning in the urban area is a low position accuracy caused by the reduction of the number of visible satellites due to high buildings. In this paper, we analyzed the availability of precise positioning system in urban area are using GPS/BDS integrated system. For this study, GPS and BDS satellite signals were collected using two low-cost receivers in the open sky and a designed software based platform for precise positioning performance analysis. And we analyzed the precise positioning performance by changing the mask angle considering the urban area. From the results, it can be confirmed that the performance of precise positioning of GPS only and BDS only decrease in the environment where mask angle is 40° to 45°, however, GPS/BDS integrated system maintains high performance of precise positioning.

논문 : 정보처리 및 복합기술 ; 다중 GPS 수신기에 의한 농업용 차량의 정밀 위치 계측(1) -오차추정 시뮬레이션 및 고정위치계측-

김상철 ( S. C. Kim ),조성인 ( S. I. Cho ),이승기 ( S. G. Lee ),이운용 ( W. Y. Lee ),홍영기 ( Y. G. Hong ),김국환 ( G. H. Kim ),조희제 ( H. J. Cho ),강지원 ( G. W. Gang ) 한국농업기계학회 2011 바이오시스템공학 Vol.36 No.2

This study was conducted to develop a robust navigator which could be in positioning for precision farming through developing a plural GPS receiver with 4 sets of GPS antenna. In order to improve positioning accuracy by integrating GPS signals received simultaneously, the algorithm for processing plural GPS signal effectively was designed. Performance of the algorithm was tested using a simulation program and a fixed point on WGS 84 coordinates. Results of this study are aummarized as followings. 1. 4 sets of lower grade GPS receiver and signals were integrated by kalman filter algorithm and geometric algorithm to increase positioning accuracy of the data. 2. Prototype was composed of 4 sets of GPS receiver and INS components. All Star which manufactured by CMC, gyro compass made by KVH, ground speed sensor and integration S/W based on RTOS(Real Time Operating System)were used. 3. Integration algorithm was simulated by developed program which could generate random position error less then 10 m and tested with the prototype at a fixed position. 4. When navigation data was integrated by geometrical correction and kalman filter algorithm, estimated positioning erros were less then 0.6 m and 1.0 m respectively in simulation and fixed position tests.

이중 차분된 도플러 측정치의 특성을 이용한 위치 영역에서 평활화 기법

이병현,지규인,이달호 제어로봇시스템학회 2011 제어로봇시스템학회 각 지부별 자료집 Vol.2011 No.7

Precise positioning using differenced measurement is one of the most commonly used techniques. And in general for precise positioning, pseudo-range and carrier phase measurement is used. In this paper, double differenced pseudo-range and phase measurements are used for precise positioning. Furthermore, Doppler measurement is used to enhance the performance of velocity estimation. And the properties of double differenced Doppler enhance the performance of positioning by smoothing in position domain.

Practical Control of Non-Friction Mechanism for Precision Positioning

Shin-Horng CHONG,Kaiji SATO 제어로봇시스템학회 2008 제어로봇시스템학회 국제학술대회 논문집 Vol.2008 No.10

This paper describes the practical control of non-friction mechanism for precision positioning. Non-friction mechanism is often used for precision positioning. Even though it has a simple structure, still, plant identification is compulsory needed during designing a conventional controller. This makes the controller non-user-friendly and non-practical-used in industry. For overcoming this problem, practical controller design procedure based on NCTF (Nominal Characteristic Trajectory Following) controller is proposed. NCTF controller consists of a nominal characteristic trajectory (NCT) and a PI compensator, which is free from exact modeling and parameter identification. The NCT is determined using an open-loop time responses of the mechanism. The PI compensator is used to make the mechanism motion to follow the NCT and it is tuned without given model parameters. Non-friction mechanism has non-damping a characteristic and often has a short-working range. A suitable current input to stop the non-damping mechanism within a short working range in open-loop condition and to be able to improve the damping characteristic of the mechanism is necessary. The positioning performances of two different current inputs are examined and discussed. The positioning performance of NCTF control system is evaluated based on simulation and experimental results.

Accuracy Analysis of Code-based PPP-RTK Positioning Utilizing K-SSR Correction Messages Outside the Reference Network

윤웅준,박관동,김혜인,서승우,박준표 사단법인 항법시스템학회 2017 Journal of Positioning, Navigation, and Timing Vol.6 No.2

Precise Point Positioning-Real Time Kinematic (PPP-RTK) refers to a technology that combines PPP with network-RTK in which a user does not directly receive observed data from a reference station but receives State-Space Representation (SSR) messages corrected for error components from a central processing station through Networked Transport of RTCM via Internet Protocol (NTRIP) or Digital Multimedia Broadcasting (DMB) for purposes of positioning. SSR messages, which refer to corrections used in PPP-RTK, are generated by a central processing station using real-time observed data collected from reference stations and account for corrections needed due to the ionosphere, troposphere, satellite orbital errors, satellite time offsets, and satellite biases. This study used a type of SSR message provided in South Korea, known as Korea-SSR (K-SSR), to implement a PPP-RTK algorithm based on code-pseudorange measurements and validated its accuracy within the reference station network. In order to validate the accuracy of the implemented algorithm outside of the network, the K-SSR was extrapolated and applied to positioning in reference stations in Changchun, China (CHAN) and Japan (AIRA). This also entailed a quantitative evaluation that measured improvements in accuracy in comparison with point positioning. The results of the study showed that positioning applied with extrapolated K-SSR correction data was more accurate in both AIRA and CHAN than point positioning with improvements of approximately 20~50%.

Nanometric Positioning Over a One-Millimeter Stroke Using a Flexure Guide and Electromagnetic Linear Motor

Shigeo Fukada,Kentaro Nishimura 한국정밀공학회 2007 International Journal of Precision Engineering and Vol.8 No.2

In this study, we investigated experimentally the potential of a planer positioning mechanism with three degrees of freedom using a flexure guide and an electromagnetic linear motor. The goal was to produce a multi-axis positioning system with nanometric resolution over a 1-㎜ stroke. An X-Y-θ stage was designed based on previous results from a single-axis prototype and was constructed with a flexure guide mechanism and voice coil motor type linear actuators. We examined the necessity of a driving method and control system to ensure high resolution for multi-axis positioning. Experiments were conducted to evaluate the performance, and the results confirmed the mechanism's potential: fine point-to-point (PTP) positioning was achieved over a 1-㎜ stroke, with a resolution of 2 ㎚ for translation in X- Y and 0.01 asec for yaw in θ.

Reference Particles-based LTE Base Station Positioning

Cho, Seong Yun,Kwon, Jae Uk 항법시스템학회 2021 Journal of Positioning, Navigation, and Timing Vol.10 No.3

A new positioning technique for positioning of LTE base stations is proposed. The positioning information of the base station is absolutely necessary for model-based wireless positioning, and is required in some of the various merhodologies for estimating signals in an uncorrected area when construnting a database for fingerprinting-based positioning. Using the acquired location-based Reference Signal Received Power (RSRP) information to estimate the location of the base station, it is impossible with the existing trilateration methods. Therefore, in this paper, a method using reference particles is proposed. Particles are randomly generated in the application area, and signal propagation modeling is performed assuming that a base station is located in each particle. Based on this, the errors of measurements are calculated. The particle group with the minimum measurement errors is selected, the position of the base station is estimated through weighted summation, and the signal propagation model of the corresponding base station is built at the same time. The performance of the proposed technology is verified using data acquired in Seocho-dong, Seoul.