Youngki Kim

Method of Differential Corrections Using GPS/Galileo Pseudorange Measurement for DGNSS RSIM

In order to prepare for recapitalization of differential GNSS (DGNSS) reference station and integrity monitor (RSIM) due to GNSS diversification, this paper focuses on differential correction algorithm using GPS/Galileo pesudorange. The technical standards on operation and broadcast of DGNSS RSIM are described as operation of differential GPS (DGPS) RSIM for conversion of DGNSS RSIM. Usually, in order to get the differential corrections of GNSS pesudorange, the system must know the real positions of satellites and user. Therefore, for calculating the position of Galileo satellites correctly, using the equation for calculating the SV position in Galileo ICD (Interface Control Document), it estimates the SV position based on Ephemeris data obtained from user receiver, and calculates the clock offset of satellite and user receiver, system time offset between GPS and Galileo, then determines the pseudorange corrections of GPS/Galileo. Based on a platform for performance verification connected with GPS/Galileo integrated signal simulator, it compared the PRC (pseudorange correction) errors of GPS and Galileo, analyzed the position errors of DGPS, DGalileo, and DGPS/DGalileo respectively. The proposed method was evaluated according to PRC errors and position accuracy at the simulation platform. When using the DGPS/DGalileo corrections, this paper could confirm that the results met the performance requirements of the RTCM.

Position Service Integrity Analysis of GPS/DGPS Signals in Port Environment

This paper focuses on integrity analysis on position service of GPS/DGPS signals in port environment in order to support fail-safe navigation of ships. After installation of the developed GPS/DGPS monitoring system at a port, it calculates the quality monitoring and horizontal protection level of navigational signals at port aspect, and also analyzes the integrity using the relation of alert limit and position error. The system can provide the results of reliability level determination based on the quality monitoring and the integrity assessment on Port GPS/DGPS signals to user navigation receiver. This paper presents the comparison results with position accuracy and integrity monitor on the port approach and restricted waters requirement of IMO based on the results of performance assessment using the raw measurement data in a real port environment.

Analysis of Positioning Accuracy Using Multi Differential GNSS in Coast and Port Area of South Korea

ABSTRACT Jang, W.S., Park, H.S., Seo, K.Y., and Kim, Y.K., 2016. Analysis of positioning accuracy using differential GNSS in the coast and port area of South Korea. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 1337 - 1341. Coconut Creek (Florida), ISSN 0749-0208. Obtaining high-accuracy position information in coastal environments is very important. To obtain high-accuracy and high-precision positioning data at low cost, the use of a GPS augmentation system is an appropriate approach. Recently, in addition to GPS, the number of different types of satellite navigation systems is growing; such a system is called a GNSS (Global Navigation Satellite System). The positioning accuracy for every available GNSS is improved compared to the accuracy obtained using only GPS. However, to date, there are no RTCM standards for differential GNSS, except for DGPS. Because the RTCM DGNSS standard and DGNSS receiver did not exist until now, experiments related to GNSS positioning using DGNSS in coastal areas and ports have not been performed. Thus, the creation of GNSS (GPS, GLONASS, BeiDou) correction data is presented in this paper. Moreover, the positioning accuracy was measured using GNSS and its correction data. This experiment was performed for 5 ports in South Korea. The results indicate that the measured positioning accuracy using GNSS correction data should be considered applicable to both coastal and port environments..

A feasibility study of PNT integrity provision for maritime applications

This paper focuses on provision of maritime position, navigation, and timing (PNT) integrity information in order to support safe maritime navigation and application. A simulation system for a feasibility study is used to evaluate the performance of the system according to the requirements set by the International Maritime Organization (IMO) resolution A.915 (22) on accuracy, integrity, and availability. In order to assess the performance requirements and service level of the system, a concept for maritime PNT integrity monitoring is proposed, and the considerations necessary to meet performance requirements are summarized. Related studies are analyzed, and their limitations in monitoring the integrity of the satellite signals are presented. To overcome these limitations, the port PNT information reliability is presented in this work, consisting of the Stanford plot. Finally, this feasibility study determines the reliability level of maritime PNT information, and simulation results are shown.

Detection Method of Radio Frequency Interference Using Raw Measurement of Multi-GNSS Receivers

This paper focuses on the detection method of radio frequency interference (RFI) and the system using multi-GNSS receivers at current DGPS reference station. If the DGPS reference station is affected by radio frequency interference (RFI), it will not be able to perform the functionalities of DGNSS RSIM, as well as affect the quality of the pseudorange because the reference antenna cannot receive the GNSS signals correctly. Therefore, using multi-DGNSS receivers, it proposes the simple method for detecting the RFI at current DGNSS station, and shows the test results. First of all, this paper introduces the configuration and functionalities of DGNSS RSIM, and presents the limitation of integrity monitoring function, when the RFI occurred in the current DGNSS station. With the developed DGNSS software RSIM system interfaced with multi-GNSS receivers, it analyzes the raw measurement output of the receivers, and then proposes the detection method of the RFI, and finally, it summarizes the test results using a RFI simulation system. Based on the test result, it was able to verify the feasibility of RFI detection using the proposed method.

Minimization Method of Measurement Noise for Satellite Clock Anomaly Detection

In order to detect and identify the GPS clock anomaly in the Differential GPS real environment, this paper addresses a method for minimizing the measurement noise of reference receivers. It estimates the real measurement noise that removed the uncommon error source from pseudorange measurement to minimize the measurement noise. Based on the output of two reference receivers, it first removes the uncommon errors, then optimizes the measurement noise by applying the correction data. Finally, it detects and identifies the satellite clock anomaly using the minimized measurement noise. The method will increase the availability of current DGPS reference system.

A study on factors for determination of elevation mask and CNR Mask on DGPS reference station

According to the recommendation of IALA, a 5∼10 degree elevation mask is used in the DGPS reference station. An elevation mask filters out signals from satellites below a certain angle of elevation above the horizon, to prevent them from using noisy signals. A CNR Mask which is used for similar purposes, filters out signals below a certain value of CNR. Using these masks is effective in the production and accuracy of pseudorange correction in the DGPS reference station. In this study we analyze factors to determine of each mask value by measuring the noise and the DGPS position accuracy according to the change of elevation Mask and CNR Mask.

Method for Detection and Identification of Satellite Anomaly Based on Pseudorange

Current differential GPS (DGPS) system consists of reference station (RS), integrity monitor (IM), and control station (CS). The RS computes the pseudorange corrections (PRC) and generates the RTCM messages for broadcasting. The IM receives the corrections from the RS broadcasting and verifies that the information is within tolerance. The CS performs realtime system status monitoring and control of the functional and performance parameters. The primary function of a DGPS integrity monitor is to verify the correction information and transmit feedback messages to the reference station. However, the current algorithms for integrity monitoring have the limitations of integrity monitor functions for satellite outage or anomalies. Therefore, this paper focuses on the detection and identification methods of satellite anomalies for maritime DGPS RSIM. Based on the function analysis of current DGPS RSIM, it first addresses the limitation of integrity monitoring functions for DGPS RSIM, and then proposes the detection and identification method of satellite anomalies. In addition, it simulates an actual GPS clock anomaly case using a GPS simulator to analyze the limitations of the integrity monitoring function. It presents the brief test results using the proposed methods for detection and identification of satellite anomalies.