• Korean Journal of Remote Sensing
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• v.29 no.1
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• pp.81-94
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• 2013

The Radar altimeter transmits radio signals to the surface, receives the backscattered signals and measures the distance between the airplane and the nadir surface. The measurements of radar altimeter are affected by various factors on the surface below the aircraft. This study performed flight campaigns in June 2012 and acquired raw data from radar altimeter, LiDAR and other sensors. Based on the LiDAR DSM (Digital Surface Model) as a reference data, the characteristics of radar altimeter were analyzed in the respect of range and surface area affecting on the receiving power of the radar altimeter. Consequently, the radar altimeter was strongly affected by the surface area within beam width and reflectivity related to RCS (Radar Cross Section) rather than range.

• Journal of Korean Society for Geospatial Information Science
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• v.20 no.2
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• pp.101-107
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• 2012

With the foot-and-mouth disease problems emerging as a serious social issue, this study set out to analyze the problems with the current setting of preventive zones against epidemics and find ways to minimize damage through preventive measures. For those purposes, the study analyzed the outbreaks of the foot-and-mouth disease and assumed that the disease would be transmitted via vehicles along the roads based on the network map of national roads and boundaries among administrative districts to conduct network analysis. The analysis results were then used to estimate spread time, whose results were then categorized according to lineal road distance and actual road distance. Then lineal moving speed and actual moving speed on the road were obtained according to the national roads and administrative districts to analyze the problems with the current method of setting preventive zones against the foot-and-mouth disease. As for spread speed around the areas where the foot-and-mouth disease broke out, the average lineal spread speed was 53.9km/day, and the average spread speed on the road was 71.1km/day, which indicates there are problems with the current method of setting preventive zones against epidemics.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.16 no.5
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• pp.265-271
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• 2023

Recently, location information services are gradually expanding due to the development of information and communication technology. RSSI is widely used to extract indoor and outdoor locations. The indoor and outdoor location estimation methods using RSSI are less accurate due to the influence of radio wave paths, interference, and surrounding wireless devices. In order to improve this problem, a distance estimation method that takes into account the wireless propagation environment is necessary. Therefore, in this study, we propose a distance estimation algorithm that takes into account the radio wave environment. The proposed method estimates the distance by learning RSSI input and output considering the RBF neural network and the propagation environment. To evaluate the performance of the proposed method, the performance of estimating the location of the receiver within a range of up to 55[m] using a BLE beacon transmitter and receiver was compared with the average filter and Kalman filter. As a result, the distance estimation accuracy of the proposed method was 6.7 times higher than that of the average filter and Kalman filter. As shown in the results of this performance evaluation, if the method of this study is applied to location services, more accurate location estimation will be possible.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.10
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• pp.2256-2271
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• 1997

In this paper, we analyze the multipath fading and the inter-satellite interference considering the satellite mobility in the LEO mobile satellite communication networks and evaluate the link perfodrmance for various wave propagation environments and reliabilities of communiation system. Multipath fading is estimated by analyzing the variation of fading margin for the satellite motion in rural, urban and suburban environments. The inter-satellite interferences are classified into 8 bypes with respect to interference path. The interferences evaluated in the paper are as follows:intra-LEO satellite interference, inter-LEO satellite interference, and GEO satellite to LEO satellite interference. As a conclusion, this apaper analyzes the change of elevation anagle and propagation distance with respect to time in the LEO satellite netwoek and prosents the variation of link margin continuously.

• Journal of IKEEE
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• v.24 no.4
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• pp.1064-1068
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• 2020

For LW-TLM antenna of 65 kHz, Near-field propagation characteristics due to wave propagation obstacle are analyzed in this paper. The simulation modeling for propagation effects are based on the model of actual LW-TLM antenna which utilizes the frequency of 65 kHz, and the model expressed as propagation obstacle at a mountain height and a proximity of antenna and mountain. The near-field performance are analyzed based on the parameters of simulation model. In case of a normal mountain height and distance between the adjacent mountain and antenna site, a field strength change of about 1.7 dB has occurred. Above the constant distance of propagation obstacle and antenna, the wave propagation characteristics of disregarding the effects of propagation obstacle are shown. The results of this paper can be used to design and build a transmitting antenna site with 65 kHz operating frequency.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2007.12a
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• pp.98-99
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• 2007

It is necessary to use satellite radio navigation system as well as satellite radio navigation augmentation system such as differential Global Positioning System to achieve the positioning accuracy and reliability requested by International Maritime Organization in port and coastal area. Especially, position accuracy of DGPS user is effected by accuracy of pseudorange correction broadcasted from DGPS reference station. This paper shows pseudorange correction calculation algorithm adopting a non-common error estimation filter in order to improve accuracy of pseudorange correction. Finally, this paper verifies that the pseudorange correction calculated by adopting a non-common error estimation filter satisfies performance specifications of RTCM.

• The Magazine of Kiice
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• v.5 no.1
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• pp.33-37
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• 2004

최근 M/W 주파수 대역은 3∼30 ㎓까지 이용되고 있으나 주로 3∼11 ㎓에 밀집되어 운용 중에 있다. 향후 새로운 이동통신 주파수 대역으로 전파전파 특성상 6 ㎓ 이하 대역이 부각되고 있어 이동통신용 주파수 대역을 확보하기 위해서는 기존의 서비스 채널을 재배치하는 것이 필수적인 사항이다. 즉, 일반적으로 3∼10㎓ 대역은 전송거리가 15∼60km 정도까지 M/W 통신로를 구성할 수 있으며, 10∼20㎓ 주파수 대역은 전송거리가 15km 이하인 전송로 구성으로 이용되고 있다. 그러나 갈수록 전송용량이 기하급수로 증가하고 있어 장거리용으로 사용되고 있는 주파수 대역의 부족현상이 나타나는 추세이다. (중략)

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2016.05a
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• pp.40-41
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• 2016

위성전파항법시스템은 이용의 편리성으로 인해 다양한 분야에서 측위, 항법 및 시각동기 정보를 획득하기 위한 목적으로 널리 활용되고 있다. 그러나 위성전파항법시스템은 낮은 신호전력특성 때문에 전파간섭에 매우 취약하다. 전파간섭으로 인한 위성전파항법시스템의 가용성 저하 사례가 빈번해짐에 따라 백업 시스템에 대한 필요성과 국제적 공조를 통한 백업 시스템 마련에 대한 기술 협력의 공감대가 높아지고 있다. R-Mode는 현재 해상에서 활용되고 있는 전파신호를 이용하여 거리측정을 하는 방법으로써 신규 전파항법 인프라 구축에 따른 큰 투자 없이 적은 비용으로 위성전파항법시스템의 백업 시스템을 구현한다는 장점을 갖는다. 본 논문에서는 R-Mode의 기술 현황과 국제 표준화 동향에 대해 살펴본다. 그리고 R-Mode를 국내에 적용하기 위해 고려해야 할 사항들을 설명한다.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06c
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• pp.495-498
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• 1998

수중폭발성음원인 SUS(signal underwater sound)는 수중에서의 폭발과 동시에 충격파와 기포파들이 연속적으로 발생한다. 이러한 신호는 광범위한 주파수대역을 가지고 전파거리가 길어지면서 굴절과 반사등의 다중경로 전파효과에 의한 신호의 변형까지 생긴다. (1,2,3). 본 연구에서는 deconvolution 방법을 이용하여 수신신호중에서 기포파효과를 최소화시켜 충격파의 수신기 도달시간을 파악하고, 각 충격파들의 전파경로를 추정하여 이 중 직접경로와 해저면 반사경로의 신호를 이용하여 해저면 반사계수를 계산하였다.

• Journal of Astronomy and Space Sciences
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• v.15 no.2
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• pp.307-320
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• 1998

We investigate the propagation of Coronal Mass Ejections(CMEs) near the earth with multi-satellite observations. Among the CMEs observed in the near-earth between Nov. 1994 and Nov. 1997, we select two events of Jan. 6-11,1997 and Nov. 4-7, 1997 which were observed by more than 3 satellites when these satellites were located apart with a sufficient distance from each other. We determine the speed and propagation of the two CMEs by calculating the position of each satellite in various coordinates and the onset time of each event. The results show that the speed of CMEs becomes significantly reduced when the perturbation arrives in the magnetosphere. It is also suggested that the propagation of the CMEs is approximated as the -x direction in GSE coordinates in the near-earth space.