• Journal of Advanced Navigation Technology
• /
• v.21 no.4
• /
• pp.325-331
• /
• 2017

As a GPS stability problem arises, MLAT system is spotlighted as an alternative technology of ADS-B. MLAT system has a high position accuracy as much as ADS-B. Also, MLAT receives the mode A,C,S, and 1090ES(ADS-B) signals from the mounted aircraft transponder. MLAT receives signals from several receiver units and calculates aircraft positions. MLAT has ADS-B level positioning accurarcy using GPS and can calculate the position information with objects independently. According to global environment changes, Local area multiltilateration(LAM) surveillance system is under development for moving vehicles and aircraft detection in airport. These are still under testing in Tae-an Airfield. In the paper, we analyzed the performance by comparing the calculated position data from MLAT to RTK. In order to confirm the position accuracy of MLAT and the deviation of position data between fixed target and moving target on the ground during the field test in Tae-an Airfield.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.22 no.1
• /
• pp.11-19
• /
• 2004

Such social structures as bridges,, buildings, dams and towers have been transformed by their own load or fundamental ground. They have been behaved by other external causes. These regular or irregular behaviors threaten to do their users safety. Therefore, to monitor the load of the structures or reaction shown by them could help to verify their behaviors. RTK GPS allows the use of a static base station and remote rover unit to allow f3r data collection within several seconds and in real time. It is useful for monitoring the behaviors of massive structures like bridges. In this Study, Among GPS methods, we used RTK GPS to analyze the precision of monitoring and then on the basis of it, we developed a monitoring system using RTK GPS when measured the behavior of main tower of a suspension bridge by using RTK GPS. Comparing a deviation between observation values, X axis was Imm, Y axis was 1mm and Z axis 2.2mm. It turned out that it was possible to monitor and measure structures by RTK GPS.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.26 no.2
• /
• pp.139-147
• /
• 2008

The positioning accuracies tend to deteriorate as the distance between the rover and the reference station increases in the Real-Time Kinematic (RTK) surveys using Global Positioning System (GPS). To solve this problem, the National Geographic Information Institute (NGII) of Korea has installed Virtual Reference System (VRS), which is one of the network-based RTK systems. In this study, we conducted the accuracy tests of the VRS-RTK surveys. We surveyed 50 control points inside the NGII's GPS Continuously Operating Reference Stations (CORS) network using the VRS-RTK system, and compared the results with the published coordinates to verify the positioning accuracies. We also conducted the general RTK surveys at the same control points. The results showed that the positioning accuracy of the VRS-RTK was comparable to that of the general RTK, because the horizontal positioning accuracy was 3.1 cm while that of general RTK was 2.0 cm. Also the vertical positioning accuracy of VRS-RTK was 6.8 cm.

• Journal of the Korean Society for Precision Engineering
• /
• v.33 no.4
• /
• pp.271-277
• /
• 2016

For a stable electric power supply in the space, nuclear batteries have been used as the main power source in a spacecraft owing to their long lifetime and high reliability. In accordance with the plan for lunar mission in Korea, nuclear batteries will supply electricity to the rover that needs to be developed. According to the information about the estimated payload, Korea Atomic Energy Research Institute started with the conceptual design based on the previous studies in USA and Russia. Because a nuclear battery converts the decay heat of the radioisotope into electricity, thermal design, radiation shield, and shock protection need to be considered. In this study, two types of nuclear batteries, radial type and axial type, were designed according to the alignment of the thermoelectric module. Heat transfer analyses were performed to compare their thermoelectric efficiency, and test mockups were fabricated to evaluate their performances.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2012.06a
• /
• pp.78-79
• /
• 2012

To improve moving vehicles' accuracy, one-way Network RTK which guarantees high accuracy and integrity regardless the distance from rovers to Reference Station(RS) is being considered. Correction of one-way Network RTK can be generated only after constructing RS network surrounding the rover, therefore a correction discontinuity is inevitably occurred when the RS set has been changed. The discontinuity is not eliminated by the DD(Double Difference) method, and our simulation shows that it causes 13cm(horizontal) and 48cm(vertical) position error. We suggest three solutions to reduce this discontinuity, which are identification of master RS with neighbor networks, duplication of communication module to receive corrections from other network, and ambiguity levelling between neighbor networks.

• The KIPS Transactions:PartB
• /
• v.15B no.2
• /
• pp.95-102
• /
• 2008

The interactive virtual reality technology has used in scientific inquiry learning since it can overcome the restriction of real world and it draws user's interest and foster active participation. However, prior works are mostly designed for a specific inquiry learning lesson and it is quite difficult to use them for constructing other inquiry learning environments. Hence, we developed the integrated virtual reality system, SASILE (System for Augmenting Scientific Inquiry Learning Environments), that helps ease the development of the scientific inquiry learning environment. In this paper, we first describe the related works on supporting VR scientific inquiry learning systems, followed by the SASILE system architecture and implementation. Then, we illustrate the use of this system to develop a Virtual Moyangsung application for teaching a scientific structure of Korean traditional house by exploring and observing the convection currents as well as a Mars Rover application for estimating the asteroid impacts on Mars by measuring rock properties. Finally, we will discuss the future research directions for this system.

• Journal of KIISE:Computer Systems and Theory
• /
• v.35 no.3
• /
• pp.103-110
• /
• 2008

This paper proposes an effective keyword extraction method for the Web videos. The proposed method classifies the Web video pages in one of 4 types. As such, we analyzed the structure of the Web pages based on the number of videos and the layout of the Web pages. And then we applied the keyword extraction algorithm fit to each page type. The experiment with 1,087 Web pages that have total 2,462 videos showed that the recall of the proposed extraction method is 18% higher than ImagerRover[2]. So, the proposed method could be used to build a powerful video search system for WWW.

• The Journal of the Petrological Society of Korea
• /
• v.19 no.4
• /
• pp.245-254
• /
• 2010

Technology of surface investigation using X-ray is one of widely used technology nowadays. This technique has been numerously used for planetary surface investigations for both orbital and rover scientific instruments. Korea has a plan to send an orbiter and lander to the Moon by the early 2020s. Therefore, the time has come for Korean researchers to develop major scientific instruments and start to do research on basic research for the Moon. Because of this situation, we firstly investigate X-ray technology, which is essential as one of core techniques of planetary remote sensing from the orbit and ground. This paper presents the current status of planetary exploration using X-ray techniques and new development of worldwide X-ray technology which could be adapted for prospective planetary missions.

• Journal of Advanced Navigation Technology
• /
• v.14 no.5
• /
• pp.625-631
• /
• 2010

In this paper, robustness performance of SNUR message is compared with those of existing ones, RTCM(Radio Technical Commission for Maritime Services) v2 MT(Message Type) 18/19 and MT 20/21 under a poor broadcast condition such as temporary data loss or disconnection We defined the temp oral data loss as 2 second delay and reconnection after disconnection as 7 second latency, and then evaluated its robustness for each latency case by double differentiating the observables. Our result shows that SNUR protocol method can reduce the latency error of the existing RTCM messages by 30~60%. Moreover, a rover using SNUR message, whose latency error is bounded within 1/4 L1 wave length, can figure out its own fixed position continuously in spite of 7 second disconnection, while the other using RTCM message, whose error is larger than half wave length, cannot keep its previous fixed solution.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.9 no.3
• /
• pp.638-646
• /
• 2005

In recent wireless communications, direct conversion transceiver or If sampling SDR-based receivers have being designed as an alternative to conventional transceiver topologies. In direct conversion receiver a.chitectu.e, the 1.equency/phase offset between the RF input signal and the local oscillator signal is a major impairment factor even though the conventional AFC/APC compensates the service deterioration due to the offset. To rover the limited tracking range of the conventional method and effectively aid compensation scheme in terms of I/Q channel imbalances, the frequency/phase offset compensation in RF-front end signal stage is proposed in this paper. In RF-front end, the varying phase offset besides the fixed large frequency/phase offset are corrected by using early-late phase compensator. A more simple frequency and phase tacking function in digital signal processing stage of direct conversion receiver is effectively available by an ingenious frequency/phase offset tracking method in RF front-end stage.