• Journal of Positioning, Navigation, and Timing
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• v.12 no.1
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• pp.83-89
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• 2023

The Korea Augmentation Satellite System (KASS) system is a Satellite Based Augmentation System (SBAS) under development to provide APV-I SBAS service in the Republic of Korea. The KASS ground segment generates correction and integrity information for GPS measurements of KASS users using the accurate positions of KASS Reference Station (KRS) antenna phase centers. For this reason, the accuracy of KRS reference points through geodetic survey campaigns is one of the important factors for providing the KASS service in compliance with the required navigation performance. In order to obtain accurate positions, two geodetic survey campaigns were performed at several reference points, such as Mark, Center of Mast at Ground Level (CMGL), and Center of Hole in Top Plate (CHTP), of each KRS site using three different survey methods, the Virtual Reference Station (VRS), Flächen Korrektur Parameter (FKP), and raw data post-processing methods. By comparing and analyzing the results, the computed coordinates of the reference points were verified and Antenna Phase Center (APC) positions were calculated using KRS Antenna Reference Point (ARP) data, and the first KASS Site Acceptance Test (SAT#1) was performed successfully using the verified APC coordinates. After the first site survey activities, the KASS operators should maintain the coordinates with the required performance such that the overall KASS navigation performance commitment is guaranteed during the lifetime of 15 years. Therefore, the maintenance plan for the KRS antenna coordinates should be developed before the commissioning of KASS operation planned after 2023. Therefore, this paper presents a geodetic survey method selected for the maintenance activities and provides the rationale for using this method.

• Journal of Positioning, Navigation, and Timing
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• v.11 no.4
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• pp.269-277
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• 2022

In this paper, we overview the system development status of the national maritime precise point positioning-real-time kinematic (PPP-RTK) service in Korea, also known as the Precise POsitioning and INTegrity monitoring (POINT) system. The development of the POINT service began in 2020, and the open service is scheduled to start in 2025. The architecture of the POINT system is composed of three provider-side facilities-a reference station, monitoring station, and central control station-and one user-side receiver platform. Here, we propose the detailed functionality of each component considering unidirectional broadcasting of augmentation data. To meet the centimeter-level user positioning accuracy in maritime coverage, new reference stations were installed. Each reference station operates with a dual receiver and dual antenna to reduce the risk of malfunctioning, which can deteriorate the availability of the POINT service. The initial experimental results of a testbed from corrections generated from the testbed network, including newly installed reference stations, are presented. The results show that the horizontal and vertical accuracies satisfy 2.63 cm and 5.77 cm, respectively. For the purpose of (near) real-time broadcasting of POINT correction data, we designed a correction message format including satellite orbit, satellite clock, satellite signal bias, ionospheric delay, tropospheric delay, and coordinate transformation parameters. The (near) real-time experimental setup utilizing (near) real-time processing of testbed network data and the designed message format are proposed for future testing and verification of the system.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.4
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• pp.437-443
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• 2014

Based on the radio wave propagation measurement of DGPS land-based reference stations, the DGPS service coverage and signal quality in the receiving points are analyzed in this paper. The DGPS signal strength and SNR in the receiving point are measured in the winter and summer season, respectively. In case of DGPS reference station that can not provide the designed service coverage, the solution to improve the service coverage is presented in this paper. Almost all DGPS reference station except reference station with low ground conductivity or mountainous terrain provide the DGPS service coverages of 80% or more of the designed service area. The service coverages of DGPS reference stations can be improved to pre-designed service area in case of installation management of DGPS site on the plain terrain and good ground conductivity. It is necessary to get the high efficiency of transmitting antenna to improve the service area.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.6
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• pp.1255-1261
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• 2014

Based on the radio wave measurement of korean ocean-based DGPS by season, in this paper, the service coverages of ocean-based DGPS reference stations were analyzed according to the climate and season. The signal strengths and signal-to-noise ratios in the land service areas that are provided by ocean-based DGPS reference stations were measured. The ocean-based DGPS reference station except reference stations on the mountainous terrain and the low ground conductivity provide more than 68% service area in comparison with the designed land service coverage providing by the ocean-based DGPS reference stations. To provide the designed service area that is unrelated to a season, it is necessary to install and operate the DGPS reference station with good ground conductivity and high efficiency antenna. Also, the poor service regions which is generated by obstacles of electric wave on pathway can be resolved by the double service area providing by land-based DGPS reference stations.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.3
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• pp.163-169
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• 2017

This paper proposed a method of broadband method of dual polarized dipole antenna for 700 MHz band base station. The proposed antenna has a structure that PCB feeder is mounted on the metallic radiator. The design of radiator and feeder is optimized by using 3D EM simulation. The proposed antenna(bandwidth 31.6 %) is broadened over 12.2 % through the lower frequency band than reference antenna(bandwidth 19.4 %), however the size is not increased. Measured results of S-parameters, radiation patterns, and gain have a good agreement with simulation ones.

• Journal of Advanced Navigation Technology
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• v.20 no.5
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• pp.394-400
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• 2016

It is well known that the encrypted ranging signal, such as GPS P(Y) code, is immune to spoofing attack. However, in order for users to use the signal, there needs permission from the operator. And also there are many restrictions for use because of security issues. In this paper, a ground reference station equipped with high-gain directional antenna and a user receiver were simulated. In the reference station, the encrypted code can be demodulated from the high-gain signal. And then the code can be used to detect spoofing attack in the user receiver. This paper proposes the spoofing detection method using the encrypted signal and deals with simulation results.

• Journal of Positioning, Navigation, and Timing
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• v.10 no.2
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• pp.139-144
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• 2021

In this paper, we described configuration and construction of infrastructure for the KASS Reference Station (KRS), subsystem of Korea Augmentation Satellite System (KASS). KASS system consists of three subsystems(KRS, Mission Control Center (MCC), KASS Uplink Station (KUS)). One of these subsystems, KRS receives GNSS data for generating range error and integrity verification and sends to MCC. It is needed to antenna facilities for mounting GNSS antenna and shelter for operating KRS and infra equipment(power and network system, lightning and grounding system, fire extinguish) for operating KRS. For this reason, we have established the requirements for KRS infrastructure and constructed infrastructure for KRS to meet the requirements of KRS infrastructure.

• Journal of Advanced Navigation Technology
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• v.24 no.4
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• pp.273-279
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• 2020

In the Korea's SBAS(KASS), reference site is an important infrastructure facility for the collecting and monitoring GPS/GEO signals. The SBAS reference station has an clear requirements than other regular monitoring stations. It requires constant maintenance during the system operation. The development for KRS site should be prepared for site survey, site construction, antenna geodetic survey, equipment installation and operation. Site survey is initially performed as an important step to predict site availability and system performance. The operation center must provide the reference site, equipment room, and appurtenant to satisfy the site requirements. The position of antennas is very important information, and accuracy must be secured through the geodetic survey. Measurement collected at the from precise antenna are provided to the KASS processing station. The position of antenna should be maintained through continuous position checks and updates during the operation. When the development of the KRS site is completed, it performs tasks for installing and operating the KRS equipment. In this paper, we presented the procedures and some results for the development of the 7 KRS sites.

• Proceedings of the KIEE Conference
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• 1998.07e
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• pp.1656-1658
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• 1998

This paper deals with a measurement system of a distance between lightning strokes and observatory station and spectrum analysis of electric fields radiated from lightning discharges. The distance measurement system, which consists of a loop type magnetic field sensor, a microphone and one chip microprocessor, is connected to a personal computer through RS232 port to acquire and process the data. This system is to use a difference of propagation velocity between an electromagnetic wave and a sonic wave produced by lightning discharge. Also, an electric field waveform and a frequency spectrum were investigated by an electric field measurement system with a hemisphere antenna and a spectrum analyzer with a biconical antenna and a log-periodic antenna, respectively. The results would be used as a basic reference to protect the power systems and electric circuits from lightning overvoltages.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.7
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• pp.1213-1223
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• 1994

VSATs(Very Small Aperture Terminals) have introduced new concepts in satellite business communications and are typically used in a star network configuration to provide information directly to the user`s premise. The characteristics of this system are low earth station costs, easy in stallation, compact, and very high flexibility for a varierty of applications (Credit Checks, Electronic Mail, Video Conferencing, Reservation System, Database Inquires, Order Entry, etc.). So, the requests of VSAT service have considerably enlarged. The link design of a VSAT network using Korea Sat. is discussed in this paper. This paper is intended to collect in a convient way the principle formula and reference data necessary to make overall performance calcurations and to calcurate antenna size. HPA power size and link margin of earth stations for satellite communications systems. Generally, because the antenna size of the Hub station in the VSAT system is bigger than the Remote station, the method of power allocations of inbound and outbound carriers is utilized in this paper. The size of Hub station and Remote station are assumed to be 3.7m and 1.2m. respectively.