• Journal of information and communication convergence engineering
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• v.9 no.4
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• pp.363-368
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• 2011

The DGPS transmits the enhancement signal to GPS using the medium frequency band. The NDGPS service that covers the Korean peninsula has been started since 2009. The service area of ocean-based DGPS(maritime-DGPS) reference stations covers the 100NM, but land-based DGPS(land-DGPS) covers 80km service area less than that of maritime DGPS. The DGPS's antenna has the top-loaded monopole antenna type. Top-loaded monopoles are the logical antennas to be used in order to get a low profile antenna and a performance according to the broadcaster and communication needs. The antenna needs to get the ground plane with good conductivity characteristics and flat ground plane without obstacle near to the transmitting antenna. In this paper, the radiation characteristics of an equivalent MF antenna are analyzed in view points of the ground conductivity and the ground plane with obstacle near to the antenna.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.4
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• pp.797-804
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• 2014

The experimental design method based-on the measured data in the several LF monopole antenna was used in MF monopole antenna design. The design technique is also utilized in MF DGPS antenna design. It is not possible to predict the antenna performance of the MF short-monopole antenna because of simple experimental antenna design. Furthermore, it is difficult to design and analyze the various wired short-monopole antenna. The antenna models for performance analysis of the DGPS antenna with the various wired short-monopole structure are proposed in this paper. Based on the proposed antenna models, also, the antenna performance and design data of the wired short-monopole antennas are presented. To evaluate the validity of the analyzed antenna models, the wired short-monopole antenna for 100 kHz are modeled and analyzed. The antenna performance of the wired short-monopole antenna are compared with those of the previously presented LF antenna performance. Based on the evaluation for proposed antenna analyzing models, the DGPS wired short-monopole antennas are modeled and analyzed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.2
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• pp.231-236
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• 2016

The stability of DGPS signal in the DGPS service area was measured and the service availability according to the receiving signal strength was analyzed in this paper. Based on the effects of radio wave propagation in the seasons of winter and summer, daytime and night, the method to provide the DGPS service coverage was presented in this paper. The signal's strength of DGPS radio wave were measured at a constant distance from the DGPS reference station during a constant period. The propagation of DGPS radio wave is affected by status of ground conductivity, so the DGPS service area is dependant on the ground conductivity. To provide the stable service coverage, it is necessary to apply the adaptive power control for receiving signal's variations and the antenna design for alleviation of high elevation's radiation.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2011.06a
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• pp.310-311
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• 2011

In this paper, refer to necessity about independent navigation system for back up of GPS by LORAN-C and suggest a solution of Co-location modeling of LORAN-C with DGPS and analysing for the interference.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.12
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• pp.1086-1092
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• 2012

It has been studied for DGPS/INS(Differential Global Positioning System/Inertial Navigation System) to offer the more precise and reliable navigation data with the aviation industry development. The flight performance evaluation of navigation system is very significant because the reliability of navigation data directly affect the safety of aircraft. Especially, the high-level navigation system, as DGPS/INS, need more precise flight performance evaluation method. The performance analysis is performed by comparing between the DGPS/INS navigation data and reference trajectory which is more precise than DGPS/INS. The GPS receiver, which is capable of post-processed CDGPS(Carrier-phase DGPS) method, can be used as reference system. Generally, the DGPS/INS is estimated the CG(Center of Gravity) point of aircraft while the reference system is output the position of GPS antenna which is mounted on the outside of aircraft. For this reason, estimated error between DGPS/INS and reference system will include the error due to lever arm. In order to more precise performance evaluation, it is needed to compensate the lever arm. This paper presents procedure and result of flight test which includes lever arm compensation in order to verify reliability and performance of DGPS/INS more precisely.

• Journal of Navigation and Port Research
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• v.26 no.1
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• pp.15-21
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• 2002

Re Ministry of Maritime Affairs and Fisheries in Korea completed the installation of 8 maritime DGPS station mfd is to going install 3 additional Maritime DGPS station for the enhancement of dual coverage in Korean coasts until Oct. 2002. Moreover, Korean government decided to provide the NDGPS service over the whole Korean inland area, which will be schedule to complete until June. 2004. On this paper to evaluate the propagation characteristics of using maritime DGPS site as un element of NDGPS ann to evaluate the required number of additional NDGPS sites, the propagation characteristics of the radio waves of 300kHz bands on sea and land nth are studied With the result of study, the conceptional design of Korean NDGPS System is proposed, which consists of 5 NDGPS sites with modified antenna and tかee coverage monitoring sites.

• Journal of Advanced Navigation Technology
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• v.3 no.2
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• pp.108-119
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• 1999

In recent, there has been remarkable progress in the field of GPS applications. In a few years, an appreciable number of aircraft will adopt GPS as a landing guidance system because GPS is more economic, more reliable and more accurate than any other aviation systems. In this respect, we have performed several helicopter landing flight tests based on the real-time DGPS system made in SNUGL (Seoul National University GPS Laboratory). From the experimental results, we found several problems Which should be fixed to adopt DGPS as a aircraft landing guidance system. In this paper, we will introduce the problems found in tests and also suggest modifications to solve the problems. Our modifications can be classified into three parts. The first is about the attitude determination with single GPS antenna. The second deals with the cockpit display module. The display was devised to integrate the Instrument Landing System(ILS) with tunnel-the-sky using virtual reality. With the display, pilot can achieve more safe landings. The last part is the digital map. We inserted digital map into our system and put direction indicator on the map using position information from GPS. It is very useful for pilot to find airports even in bad weather. Using the newly designed DGPS landing system, we conducted flight test at Kimhae International Airport, Pusan, Korea. It was successful! Our system can also satisfy Category-I criterion for aircraft landing approach and determine attitude angle with a high level of reliability. It is supported by video materials.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.23 no.2
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• pp.101-108
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• 2005

Inertial Navigation System has been used extensively to determine the position, velocity and attitude of the body. An INS is very expensive, however, heavy, power intensive, requires long setting times and the accuracy of the system is degraded as time passed due to the accumulated error. Global Positioning System(GPS) receivers can compensate for the Inertial Navigation System with the ability to provide both absolute position and attitude. This study describes a method to improve both the accuracy of a body positioning and the precision of an attitude determination using GPS antenna array. Existing attitude determination methods using low-cost GPS receivers focused on the relative vectors between the master and the slave antennas. Then the positioning of the master antenna is determined in meter-level because the single point positioning with pseudorange measurements is used. To obtain a better positioning accuracy of the body in this research, a wireless internet is used as an alternative data link for the real-time differential corrections and dual-frequency GPS receivers which is expected to be inexpensive was used. The numerical results show that this system has the centimeter level accuracy in positioning and the degree level accuracy in attitude.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.16 no.3
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• pp.162-170
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• 2004

On the basis of the radiotracer technology and the related equipments which have been developed for its industrial application through the nuclear long-term research project, a radiotracer study on sediment transport was carried out as a part of the development of the radiotracer technology for a coastal environment. The crystalline material doped with iridium having a similar composition and specific gravity as those of the bedload sand collected from the research area was produced by the oxide-route method. A radioisotope container was specially designed to inject the radiotracer from 1 m above the sea bedload without radioactive contamination during the transport from the nuclear reactor at KAERI. The position data from the DGPS and the radiation measurement data were collected concurrently and stored by means of the application software programmed with the LabVIEW of the National Instrument. The position data was reprocessed to represent the real position of the radiation probe under water and not that of the DGPS antenna on board. The time dependency of the spatial distribution of the sediment was studied in the area through three tracking measurements after the iridium glass was injected. This trial application showed the potential of the radiotracer technology as an important role for maintaining and developing the coastal environment in the future.

• Journal of Korean Society for Geospatial Information Science
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• v.22 no.1
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• pp.47-54
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• 2014

Precise Point Positioning (PPP) algorithms using GPS code pseudo-range measurements were developed and their accuracy was validated for the purpose of implementing them on a portable device. The group delay, relativistic effect, and satellite-antenna phase center offset models were applied as fundamental corrections for PPP. GPS satellite orbit and clock offsets were taken from the International GNSS Service official products which were interpolated using the best available algorithms. Tropospheric and ionospheric delays were obtained by applying mapping functions to the outputs from scientific GPS data processing software and Global Ionosphere Maps, respectively. When the developed algorithms were tested for four days of data, the horizontal and vertical positioning accuracies were 0.8-1.6 and 1.6-2.2 meters, respectively. This level of performance is comparable to that of Differential GPS, and further improvements and fine-tuning of this suite of PPP algorithms and its implementation at a portable device should be utilized in a variety of surveying and Location-Based Service applications.