Simplified Noise Modeling of GPS Measurements for a Fast and Reliable Cycle Ambiguity Resolution

Byungwoon Park,Changdon Kee 한국항해항만학회 2006 한국항해항만학회 학술대회논문집 Vol.1 No.-

The relationship between the observable noise model and the satellite elevation angle can be modeled quite well by an exponential function.[Jin, 1996] Noise size and dependence on the elevation angle are, however, different for each observation and receiver type. Therefore, the coefficient determination of this model is an issue, and various methods including PR-CP, single difference, and time difference have been suggested. The limitations of them are difficulty to model the carrier phase noise and to eliminate bias. To overcome these disadvantages for using Jin’s model, we suggest zero baseline double difference (DD) and noise sorting algorithm. Data DD technique in zero baseline is useful to eliminate all the troublesome GPS biases, and the remaining error is the sum of GPS measurement noises from two satellites. These DD residuals for hours should be sorted by the combination of satellite elevation angles, and then variance value of the residual for each combination can be estimated. Using these values, we construct an over-determined linear equation whose solution is a set of noise variance for each satellite elevation angle. With 24hr Trimble 4000ssi data, we easily worked out the coefficients of the noise model not only for pseudorange but also for carrier phase. We estimated the standard deviation of the measurement DD using our model, and plotted 1 and 3 sigma lines for every epoch to verify the representation of the residual error. 63.3% of pseudorange residual and 65.9% of phase error did not exceed the 1 sigma lines. Additionally, 99.2% and 99.5% of them lied within 3sigma line. These figures prove that the Gaussian property of measurement noise, and that the suggested model by our algorithm corresponds to the observable noise information.

Study on reducing GNSS temporal and spatial decorrelation error using Compact Network RTK

Park, Byungwoon(박병운),Songi, Junesol(송준솔),Kee, Changdon(기창돈) 한국측량학회 2011 한국측량학회 학술대회자료집 Vol.2011 No.4

본 논문은 시간지연에 강건한 compact RTK와 GPS의 공간이격 오차 감소에 효과적인 기준국 networking의 결합 형태인 Compact Network RTK를 제시한다. MAC, FKP, VRS 등 모든 network RTK 방식에 대해 RTCM의 후보 메시지인 Compact RTK 프로토콜의 호환성을 검증하고, 저장된 1시간 미국 CORS rinex data를 이용하여 실측 데이터에도 효과적임을 확인하였다. 모든 network RTK 방식에 대하여 10-40초 사이에 미지정수를 검출하였으며, 가로세로 100km 지역에서 수평정확도 6~7cm, 수직정확도 7~8cm (95%) 가 확보됨을 확인하였다. 뿐만 아니라, 기존 9600bps 전송속도에서 구현되고 있는 network RTK 시스템의 전송속도를 500~700 bps 수준으로 낮출 수 있을 것으로 기대된다. This paper suggests a method combining Compact RTK (Real Time Kinematic) and Reference Station (RS) networking technique, and shows this method can reduce both temporal and spatial decorrelation error. Compact RTK"s compatibility with all the conventional Network RTK methods, i.e. Master-Auxiliary concept (MAC), Virtual Reference Stations (VRS), and Flachen-korrektur-parameter (FKP), is examined theoretically in this paper. To prove that the Compact RTK is not only valid, but also helpful to the Network RTK system, we construct a field test using 1 hour rinex data logged every second from CORS RS. No matter which network RTK method may be applied, Compact Network RTK resolves the ambiguity of the carrier phase in 10-40 seconds and determines the position with 6~7cm horizontal and 7~8cm vertical error (95%) in the 100 by 100 km region. Moreover, the Compact Network RTK enables Network RTK service providers to reduce a datalink bandwidth for correction message to 5~700bps from several thousand bps, currently 9600bps of GPRS/GSM, without a severe degradation of accuracy.

The Compact Network RTK Method: An Effective Solution to Reduce GNSS Temporal and Spatial Decorrelation Error

Park, Byungwoon,Kee, Changdon Cambridge University Press 2010 The Journal of navigation Vol.63 No.2

<P>This paper proposes a method that combines compact real-time kinematic (RTK) and reference station (RS) networking techniques, and shows that this approach can reduce both the temporal and spatial decorrelation error. The compact RTK method compatibility with all the conventional network RTK systems, i.e., Master-Auxiliary Concept (MAC), Virtual Reference Stations (VRS), and <I>Flächen-Korrektur</I> Parameter (FKP), is examined theoretically in this paper. To prove that the compact RTK approach is not only valid, but also helpful to the network RTK system, a field test was held using one hour of Receiver Independent Exchange Format (RINEX) data logged every second from Continuously Operating Reference Stations (CORS). No matter which network RTK method is applied, the Compact Network RTK approach resolves the ambiguity of the carrier phase in 10-40 s and determines position with 6-7 cm horizontal and 7-8 cm vertical error (95%) in a 100 by 100 km region. Moreover, the Compact Network RTK approach enables network RTK service providers to reduce the data-link bandwidth for correction messages to 5-700 bps (bit/s) down from several thousand bps, currently 9600 bps of GPRS/GSM, without a severe degradation of accuracy.</P>

DGPS Enhancement to GPS NMEA Output Data: DGPS by Correction Projection to Position-Domain

Park, Byungwoon,Lee, Jeongkeun,Kim, Younsil,Yun, Ho,Kee, Changdon Cambridge University Press 2013 The Journal of navigation Vol.66 No.2

<P>Most Differential Global Positioning System (DGPS) correction formats are based on range information, and thus typical DGPS systems can be implemented only on correction message-readable or raw observable-providing devices. There is no other way to improve an already-calculated position than a ‘block shift technique’, which has a very limited applicability. This paper suggests an algorithm to project measurement correction directly to position domain data without requiring raw pseudorange data. By post-processing methodology, we evaluated the performance of our new algorithm compared to conventional DGPS, which requires raw pseudorange data; the observed difference between them was only 0·1 mm . The proposed correction projection algorithm can be used with commercial off-the-shelf receivers that provide National Marine Electronics Association (NMEA) format data. Our testing with a U-blox LEA-5H receiver resulted in a drastic reduction of horizontal Root Mean Square (RMS) error from 4·75 m to 1·09 m.</P>

LNSS 미래우주항법 시스템 및 요소기술 소개

박병운(Byungwoon Park),김성익(Sungik Kim),윤정현(Jeonghyeon Yun),주현진(Hyun-jin, Joo) 한국항공우주학회 2023 한국항공우주학회 학술발표회 논문집 Vol.2023 No.6

Feasibility Study on Integration of SSR Correction into Network RTK to Provide More Robust Service

Lim, Cheol-Soon,Park, Byungwoon,Kim, Dong-Uk,Kee, Chang-Don,Park, Kwan-Dong,Seo, Seungwoo,So, Hyoungmin,Park, Junpyo The Institute of Positioning 2018 Journal of Positioning, Navigation, and Timing Vol.7 No.4

Network RTK is a highly practical technology that can provide high positioning accuracy at levels between cm~dm regardless of user location in the network by extending the available range of RTK using reference station network. In particular, unlike other carrier-based positioning techniques such as PPP, users are able to acquire high-accuracy positions within a short initialization time of a few or tens of seconds, which increases its value as a future navigation system. However, corrections must be continuously received to maintain a high level of positioning accuracy, and when a time delay of more than 30 seconds occurs, the accuracy may be reduced to the code-based positioning level of meters. In case of SSR, which is currently in the process of standardization for PPP service, the corrections by each error source are transmitted in different transmission intervals, and the rate of change of each correction is transmitted together to compensate the time delay. Using these features of SSR correction is expected to reduce the performance degradation even if users do not receive the network RTK corrections for more than 30 seconds. In this paper, the simulation data were generated from 5 domestic reference stations in Gunwi, Yeongdoek, Daegu, Gimcheon, and Yecheon, and the network RTK and SSR corrections were generated for the corresponding data and applied to the simulation data from Cheongsong reference station, assumed as the user. As a result of the experiment assuming 30 seconds of missing data, the positioning performance compensating for time delay by SSR was analyzed to be horizontal RMS (about 5 cm) and vertical RMS (about 8 cm), and the 95% error was 8.7 cm horizontal and 1cm vertical. This is a significant amount when compared to the horizontal and vertical RMS of 0.3 cm and 0.6 cm, respectively, for Network RTK without time delay for the same data, but is considerably smaller compared to the 0.5 ~ 1 m accuracy level of DGPS or SBAS. Therefore, maintaining Network RTK mode using SSR rather than switching to code-based DGPS or SBAS mode due to failure to receive the network RTK corrections for 30 seconds is considered to be favorable in terms of maintaining position accuracy and recovering performance by quickly resolving the integer ambiguity when the communication channel is recovered.

Monitoring QZSS CLAS-based VRS-RTK Positioning Performance

Cheolsoon Lim,Yebin Lee,Yunho Cha,Byungwoon Park,Sul-Gee Park,Sanghyun Park 사단법인 항법시스템학회 2022 Journal of Positioning, Navigation, and Timing Vol.11 No.4

The Centimeter Level Augmentation Service (CLAS) is the Precise Point Positioning (PPP) – Real Time Kinematic (RTK) correction service utilizing the Quasi-Zenith Satellite System (QZSS) L6 (1278.65 MHz) signal to broadcast the Global Navigation Satellite System (GNSS) error corrections. Compact State-Space Representation (CSSR) corrections for mitigating GNSS measurement error sources such as satellite orbit, clock, code and phase biases, tropospheric error, ionospheric error are estimated from the ground segment of QZSS CLAS using the code and carrier-phase measurements collected in the Japan’s GNSS Earth Observation Network (GEONET). Since the CLAS service begun on November 1, 2018, users with dedicated receivers can perform cm-level precise positioning using CSSR corrections. In this paper, CLAS-based VRS-RTK performance evaluation was performed using Global Positioning System (GPS) observables collected from the refence station, TSK2, located in Japan. As a result of performing GPS-only RTK positioning using the open-source software CLASLIB and RTKLIB, it took about 15 minutes to resolve the carrier-phase ambiguities, and the RTK fix rate was only about 41%. Also, the Root Mean Squares (RMS) values of position errors (fixed only) are about 4cm horizontally and 7 cm vertically.

Performance Analysis of GNSS Residual Error Bounding for QZSS CLAS

Yebin Lee,Cheolsoon Lim,Yunho Cha,Byungwoon Park,Sul-Gee Park,Sanghyun Park 사단법인 항법시스템학회 2023 Journal of Positioning, Navigation, and Timing Vol.12 No.3

The State Space Representation (SSR) method provides individual corrections for each Global Navigation Satellite System (GNSS) error components. This method can lead to less bandwidth for transmission and allows selective use of each correction. Precise Point Positioning (PPP) - Real-Time Kinematic (RTK) is one of the carrier-based precise positioning techniques using SSR correction. This technique enables high-precision positioning with a fast convergence time by providing atmospheric correction as well as satellite orbit and clock correction. Currently, the positioning service that supports PPPRTK technology is the Quazi-Zenith Satellite System Centimeter Level Augmentation System (QZSS CLAS) in Japan. A system that provides correction for each GNSS error component, such as QZSS CLAS, requires monitoring of each error component to provide reliable correction and integrity information to the user. In this study, we conducted an analysis of the performance of residual error bounding for each error component. To assess this performance, we utilized the correction and quality indicators provided by QZSS CLAS. Performance analyses included the range domain, dispersive part, non-dispersive part, and satellite orbit/clock part. The residual root mean square (RMS) of CLAS correction for the range domain approximated 0.0369 m, and the residual RMS for both dispersive and non-dispersive components is around 0.0363 m. It has also been confirmed that the residual errors are properly bounded by the integrity parameters. However, the satellite orbit and clock part have a larger residual of about 0.6508 m, and it was confirmed that this residual was not bounded by the integrity parameters. Users who rely solely on satellite orbit and clock correction, particularly maritime users, thus should exercise caution when utilizing QZSS CLAS.

Multiband antenna using a half-wavelength loaded line structure for mobile handheld systems

Jung, Byungwoon,Shin, Hoo,Harackiewicz, Frances J.,Park, Myun-Joo,Lee, Byungje Wiley Subscription Services, Inc., A Wiley Company 2006 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS Vol.48 No.9

<P>A novel multiband internal antenna is proposed, which can be applied for GSM(880–960 MHz), GPS(1575.42 MHz), DCS(1710–1880 MHz), PCS(1850–1990 MHz), and WCDMA(1920–2170 MHz) band mobile handheld systems, by using a half-wavelength loaded line structure (HWLLS). The proposed antenna is a combined structure of HWLLS and a shorted monopole. A gap is cut between the antenna shorting pad and the PCB ground plane of system. Then this gap is connected by a chip inductor in order to easily control the upper frequency bands, DCS, PCS, and WCDMA without degradation of resonant characteristics in the lower bands, GSM and GPS. Simulation and experimental results show that the proposed antenna provides enough effective bandwidth (VSWR <2.5) to cover all five bands with the peak gain variation of less than 0.53 dB with varying the chip inductance of less than 3.3 nH. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1683–1687, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21803</P>

Design concept of multiband antennas under the influence of the human body

Jung, Byungwoon,Lee, Hyunkyu,Byun, Joonho,Won Jung, Chang,Park, Myun-Joo,Chung, Young-Seek,Lee, Byungje Wiley Subscription Services, Inc., A Wiley Company 2009 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS Vol.51 No.2

<P>A novel wideband antenna, consisting of a double T-shaped element and a coaxial cable, is proposed for multiband applications including AMPS, GSM, DCS, PCS, UMTS, and WiBro bands. The proposed antenna also mitigates the degradation of an antenna performance due to the human body. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 513–515, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24086</P>