차량 간 GPS 공통 가시위성 검색을 통한 상대위치 추정 정확도 향상에 대한 연구

본 논문은 저가의 GPS 수신기와 MEMS급 IMU, B-CDMA 무선 통신 모듈을 이용한 다수 차량의 상대위치 추 정에 관한 연구이다. 차량의 상대위치를 추정함에 있어서, 각 차량의 가시 위성 조합이 불일치 할 경우 오차가 급증하는 현상이 발생한다. 본 논문에서는, 이를 개선하기 위하여 측정치 기반으로 상대위치를 계산하는 RGPS 알고리즘을 제안한다. 동시에 GPS/INS 통합 항법 알고리즘을 적용하여 각 차량의 방향각과 속도를 추정한다. 최종적으로 RGPS 알고리즘과 각 차량의 GPS/INS 통합항법 알고리즘 결과를 사용한 Position Integration Filter 알고리즘으로부터 최종적인 상대위치와 상대속도를 추정한다. 이와 같은 연구 결과를 증명하기 위하여 실제 실 험을 통하여 추정 결과를 확인하였다. 실시간 프로그램과 실험용 모형 차량을 제작하여 상대위치, 상대속도 추 정 실험을 실시, 실제 환경에서의 알고리즘의 성능을 검증하였다.In this paper, we present relative positioning algorithm for moving land vehicle using GPS, MEMS IMU and B-CDMA module. This algorithm does not calculate precise absolute position but calculates relative position directly, so additional infrastructure and I2V communication device are not required. Proposed algorithm has several steps. Firstly, unbiased relative position is calculated using pseudorange difference between two vehicles. Simultaneously, the algorithm estimates position of each vehicle using GPS/INS integration. Secondly, proposed algorithm performs filtering and finally estimates relative position and relative velocity. Using proposed algorithm, we can obtain more precise relative position for moving land vehicles with short time interval as IMU sensor has. The simulation is performed to evaluate this algorithm and the several field tests are performed with real time program and miniature vehicles for verifying performance of proposed algorithm.OAIID:oai:osos.snu.ac.kr:snu2012-01/102/0000003405/9SEQ:9PERF_CD:SNU2012-01EVAL_ITEM_CD:102USER_ID:0000003405ADJUST_YN:NEMP_ID:A000360DEPT_CD:446CITE_RATE:0FILENAME:05 한영민(927~934).pdfDEPT_NM:기계항공공학부EMAIL:[email protected]_YN:NCONFIRM:

A Study on Improving Performance of Network RTK through Tropospheric Modeling for Land Vehicle Applications

학위논문 (박사)-- 서울대학교 대학원 : 기계항공공학부, 2016. 2. 기창돈.Network Real-Time Kinematic (RTK) has been developed in the late 2000s to overcome the limitation of the conventional single baseline RTK. It is capable of achieving cm-level positioning accuracy while reducing the number of reference stations required to cover the same amount of area compared to that of the RTK. However, Network RTK has been widely used for mostly static applications such as surveying and geodesy. Recently, many researchers have been studying on application of the Network RTK for dynamic purposes and users, especially for land vehicles, such as automatic vehicles, smart car systems, traffic control and monitoring vehicles carrying hazardous material, due to the increasing demands for user convenience and safety. This thesis focuses on improving the performance of Network RTK through modeling tropospheric delay for land vehicle applications. The post-processing Network RTK system was developed by the GNSS laboratory at Seoul National University in 2008. This thesis further strives to generate robust and accurate corrections by improving the estimation performance of the integer ambiguities between reference stations that constitute a network by estimating tropospheric wet vertical delay and multipath errors for medium-baselines. In addition, the technique for adjusting integer ambiguity levels among networks is proposed to enable dynamic users to continuously achieve high-accuracy positioning regardless of network switching. Furthermore, a new multiple corrections modeling method is proposed to improve user accuracy. According to how it generates corrections, Network RTK is classified into three techniques: VRS, MAC and FKP. This thesis generates the MAC-based Network RTK corrections since the other methods are known to be deduced from the MAC approach. In order to generate MAC correction, precisely estimated integer ambiguities between reference stations are necessary. The baseline length of the two reference stations in a network is typically 50 to 70km. Therefore the conventional single baseline RTK cannot be used to estimate those ambiguities. This thesis utilizes Kalman filters to estimate tropospheric wet zenith delay and multipath errors for accurate estimation of such integer ambiguities. The dynamic users can receive different corrections from different networks because they are in constant motion and therefore the network from which users receive correction can be switched. Regardless of network change, the user should be able to continuously calculate accurate positions at any location. In order to fulfill this requirement for the land vehicles, the integer level adjustment technique is proposed. Lastly, users should be able to combine the multiple corrections received from reference stations in a network for their location to eliminate their GPS errors. Although many researchers have developed various correction modeling methods, the method that this thesis proposes is considered to be new as it considers the physical characteristics of tropospheric delay over height. In order to evaluate the performances of the implemented and proposed algorithms, the following tests are conducted: First, the estimation performance of the medium-baseline tropospheric wet zenith delay, multipath errors and integer ambiguities are evaluated using both simulation and real GPS measurements. Second, the ambiguity level adjustment technique is proposed and verified through simulation for Networks distributed all over the South Korea. In addition, dynamic tests are conducted to evaluate the performance of the generated corrections of the MAC-based Network RTK and user positioning accuracy before and after the ambiguity level adjustment. Lastly, the performance of the proposed correction modeling method is evaluated using both the simulated and real GPS measurements for Networks in the USA.I. Introduction 1 1. Motivation and Objective of Research 1 2. Former Research 3 3. Methodology and Outline of Research 6 3.1 Methodology of Research 6 3.2 Outline of Research 8 4. Contribution of Research 10 II. GNSS Measurement, Error sources and Augmentation System 13 1. GNSS Measurements 14 1.1 Pseudorange 15 1.2 Carrier Phase 16 2. GNSS Error Sources 18 2.1 Satellite orbit error and clock bias 18 2.2 Ionospheric delay 21 2.3 Tropospheric delay 28 2.4 Multipath 35 2.5 Receiver error 37 2.6 Antenna related errors 38 2.7 Overall GNSS Error Sources 41 3. GNSS Augmentation System 42 3.1 Local Differential GNSS (DGNSS) 42 3.2 Wide Area DGNSS (WADGNSS) 44 3.3 Real-Time Kinematic, RTK 46 III. Preprocessing for Generating Carrier Phase Corrections 49 1. Cycle Slip Detection using Linear Combination of the L1/L2 Measurements 49 1.1 Cycle slip detection using ionosphere and Melbourne-Wbbena linear combination 50 1.2 Cycle slip insensitive pairs of the ionosphere and Melbourne-Wbbena combinations 53 1.3 The general form of cycle slip insensitive pairs of the ionosphere combination and analysis on detectability 56 2. Verification of the Algorithm using Simulation 61 2.1 Simulation environments 61 2.2 Simulation results 63 IV. Medium Baseline Integer Ambiguity Estimation for Network RTK Correction Generation 67 1. The Necessity of Estimating Correct Integer Ambiguities between Stations in a Network 67 1.1 Former research 67 1.2 The residual errors of the medium-baseline measurements 69 2. Analysis on Error Characteristics of Linear Combinations for L1 and L2 Integer Ambiguity Estimation 72 3. Filter Design for Estimating Integer Ambiguities through Modeling of Tropospheric Delay and Multipath Error 76 3.1 Designing a filter for estimating of widelane ambiguity using Melbourne-Wbbena combination 76 3.2 Designing a filter for the L2 integer ambiguity estimation using ionosphere-free combination 80 4. Search and Resolution of Integer Ambiguity using Estimates from the Designed Filter 90 5. Verification and Evaluati 91 5.1 Simulation environment 91 5.2 Simulation results 92 6. Verification and Evaluation of the algorithm using real GPS data 102 6.1 Performance evaluation for static user 102 6.2 Performance evaluation for dynamic user 114 V. Correction Generation Method of Network RTK for Land Vehicle Users 129 1. Requirements of the Land Vehicle Users 129 2. Study on Generating Network RTK Corrections 132 2.1 Introduction of the Network RTK system 132 2.2 Methods for generating Network RTK corrections 134 3. Integer Ambiguity Level Adjustment between Networks for Consistent Positioning Accuracy of the Land Vehicles 146 3.1 Comparison of the corrections generated from difference networks 147 3.2 Ambiguity Level Adjustment Algorithm 149 4. Verification of the Adjustment Algorithm through Simulation 153 4.1 Verification of the ambiguity adjustment algorithm for two networks 153 4.2 Verification of the ambiguity adjustment algorithm for networks over the whole country 155 5. Verification of the Adjustment Algorithm through Simulation 157 5.1 Performance evaluation of Network RTK for land vehicle users 157 5.2 Performance evaluation of user ambiguity resolution for MAC-based Network RTK 163 5.3 The real-time performance evaluation using developed Network RTK software 177 VI. Improvements of the Performance of the Modeling Network RTK Corrections 189 1. Conventional Network RTK Correction Model 189 1.1 Distance-Based Linear Interpolation Method (DIM) 189 1.2 Linear Combination Method (LCM) 190 1.3 Linear Interpolation Method (LIM) 191 1.4 Low-order Surface Model (LSM) 192 2. The Modified LSM using the Characteristics of Tropospheric Delay over Height 195 2.1 The characteristics of tropospheric delay over height 195 2.2 The modified LSM considering the physical characteristics of tropospheric delay over height 200 3. Verification of the Modified LSM using Simulation 200 3.1 Simulation environments 200 3.2 Simulation results 202 4. Verification of the Modified LSM using Real GPS data 206 4.1 Test environments 206 4.2 Test results 210 VII. Conclusions and Future Work 219 1. Conclusions 219 2. Future Work 222 Reference 225 초 록 235Docto

Study on the Ambiguity Difference Adjustment between Reference Station Cells for the Improvement in Rovers Continuous Network-RTK Positioning

단방향 Network RTK 방식은 최근 높아진 항체의 요구 정확도와 이동성을 동시에 충족할 수 있는 방식으로 고려되고 있다. 항체에 단방향 Network RTK 방식의 보정정보를 적용할 경우, 광역에서의 연속 항법을 위하여 다중 셀 기반의 Network RTK 방식이 필수적이다. 이 경우, 사용자가 셀 간 이동시 보정정보 생성에 사용되는 기준국 조합이 바뀌므로 보정정보의 불연속 값이 발생하는데, RTK 위치 결정을 위한 이중차분으로도 제거되지 않아 수평 13cm, 수직 48cm 수준의 오차가 야기됨을 확인하였다. 이러한 불연속 점을 해소하기 위하여 본 논문에서는 이종 셀 간 동일한 주(Master) 기준국을 사용하는 방안, 복수의 보정정보 수신 모듈을 설치하여 기존 위치를 기준으로 새로운 보정정보를 조정하는 방안, 이종 네트워크 간 미지정수 차이를 조정하는 세 가지 방법을 제시하였다. 세 방법 모두 셀 간 이동으로 인한 불연속 값을 효과적으로 제거되어 측정치의 1/4파장, 3cm 수준으로 위치 오차가 감소함이 확인되었으나, 기준국 셀의 확장성, 사용자 장비 부담 경감 등을 고려할 때 셀 간 미지정수를 조정하는 방식이 가장 바람직하다.N

Study on the Ambiguity Difference Adjustment between Reference Station Cells for the Improvement in Rovers Continuous Network-RTK Positioning

단방향 Network RTK 방식은 최근 높아진 항체의 요구 정확도와 이동성을 동시에 충족할 수 있는 방식으로 고려되고 있다. 항체에 단방향 Network RTK 방식의 보정정보를 적용할 경우, 광역에서의 연속 항법을 위하여 다중 셀 기반의 Network RTK 방식이 필수적이다. 이 경우, 사용자가 셀 간 이동시 보정정보 생성에 사용되는 기준국 조합이 바뀌므로 보정정보의 불연속 값이 발생하는데, RTK 위치 결정을 위한 이중차분으로도 제거되지 않아 수평 13cm, 수직 48cm 수준의 오차가 야기됨을 확인하였다. 이러한 불연속 점을 해소하기 위하여 본 논문에서는 이종 셀 간 동일한 주(Master) 기준국을 사용하는 방안, 복수의 보정정보 수신 모듈을 설치하여 기존 위치를 기준으로 새로운 보정정보를 조정하는 방안, 이종 네트워크 간 미지정수 차이를 조정하는 세 가지 방법을 제시하였다. 세 방법 모두 셀 간 이동으로 인한 불연속 값을 효과적으로 제거되어 측정치의 1/4파장, 3cm 수준으로 위치 오차가 감소함이 확인되었으나, 기준국 셀의 확장성, 사용자 장비 부담 경감 등을 고려할 때 셀 간 미지정수를 조정하는 방식이 가장 바람직하다.OAIID:oai:osos.snu.ac.kr:snu2012-01/102/0000003405/2SEQ:2PERF_CD:SNU2012-01EVAL_ITEM_CD:102USER_ID:0000003405ADJUST_YN:YEMP_ID:A000360DEPT_CD:446CITE_RATE:0FILENAME:항행학회_박병운_최종.hwpDEPT_NM:기계항공공학부EMAIL:[email protected]_YN:NCONFIRM:

Improvement of Relative Positioning Accuracy by Searching GPS Common Satellite between the Vehicles

본 논문은 저가의 GPS 수신기와 MEMS급 IMU, B-CDMA 무선 통신 모듈을 이용한 다수 차량의 상대위치 추정에 관한 연구이다. 차량의 상대위치를 추정함에 있어서, 각 차량의 가시 위성 조합이 불일치 할 경우 오차가 급증하는 현상이 발생한다. 본 논문에서는, 이를 개선하기 위하여 측정치 기반으로 상대위치를 계산하는 RGPS 알고리즘을 제안한다. 동시에 GPS/INS 통합 항법 알고리즘을 적용하여 각 차량의 방향각과 속도를 추정한다. 최종적으로 RGPS 알고리즘과 각 차량의 GPS/INS 통합항법 알고리즘 결과를 사용한 Position Integration Filter 알고리즘으로부터 최종적인 상대위치와 상대속도를 추정한다. 이와 같은 연구 결과를 증명하기 위하여 실제 실험을 통하여 추정 결과를 확인하였다. 실시간 프로그램과 실험용 모형 차량을 제작하여 상대위치, 상대속도 추정 실험을 실시, 실제 환경에서의 알고리즘의 성능을 검증하였다.N