• 반도체디스플레이기술학회지
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• 제22권2호
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• pp.50-55
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• 2023

Due to the unavailability of global positioning system (GPS) indoors, various indoor pedestrian positioning methods have been designed to estimate the position of the user using received signal strength (RSS) measurements from radio beacons, such as wireless fidelity (WiFi) access points and Bluetooth low energy (BLE) beacons. In indoor environments, radio-frequency (RF) signals are unpredictable and change over space and time because of multipath associated with reflection and refraction, shadow fading caused by obstacles, and interference among different devices using the same frequencies. Therefore, the outliers in the positional information obtained from the indoor positioning method based on RSS measurements occur often. For this reason, the performance of the positioning method can be degraded by the characteristics of the RF signal. To resolve this issue, a map-matching (MM) algorithm based on maximum probability (MP) estimation is applied to the indoor positioning method in this study. The MM algorithm locates the aberrant position of the user estimated by the positioning method within the limits of the adjacent pedestrian passages. Empirical experiments show that the positioning method can achieve higher positioning accuracy by leveraging the MM algorithm.

• 한국태양에너지학회 논문집
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• 제40권3호
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• pp.43-52
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• 2020

By blocking irradiance, shadows cast by high-rise buildings in urban areas can reduce the power generation efficiency of PV panels installed on low-rise buildings. As the conventionally installed PV panel is not suitable for the urban environment, which is unfavorable for power generating, a more radical solution is required. This study aims to help solve this problem by estimating the optimal PV panel angle. Using the proposed method, the optimal PV angle was calculated by considering shadows that could be cast by nearby buildings throughout the year, and the correlation between solar shading and elevation angle was discovered based on the calculated data.

• 국제학술발표논문집
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• The 9th International Conference on Construction Engineering and Project Management
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• pp.912-919
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• 2022

The study is an image-based assessment that uses image processing techniques to determine the condition of concrete with surface cracks. The preparations of the dataset include resizing and image filtering to ensure statistical homogeneity and noise reduction. The image dataset is then segmented, making it more suited for extracting important features and easier to evaluate. The image is transformed into grayscale which removes the hue and saturation but retains the luminance. To create a clean edge map, the edge detection process is utilized to extract the major edge features of the image. The Otsu method is used to minimize intraclass variation between black and white pixels. Additionally, the median filter was employed to reduce noise while keeping the borders of the image. Image processing techniques are used to enhance the significant features of the concrete image, especially the defects. In this study, the tonal zones of the histogram and its properties are used to analyze the condition of the concrete. By examining the histogram, the viewer will be able to determine the information on the image through the number of pixels associated and each tonal characteristic on a graph. The features of the five tonal zones of the histogram which implies the qualities of the concrete image may be evaluated based on the quality of the contrast, brightness, highlights, shadow spikes, or the condition of the shadow region that corresponds to the foreground.

• 한국지리정보학회지
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• 제11권2호
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• pp.121-131
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• 2008

2차원적인 도로설계는 설계기준과 운전자의 반응 사이에는 상이한 점이 많아 위험성을 내포하고 있다. 따라서 2차원 도로설계는 시공전에 예측을 하기가 어려운 실정이다. 그러나, 3차원 도로설계는 요구되는 구성요소의 완성 이후 발생하는 문제를 예측할 수 있다. 본 연구에서는, 실제도로에서 도로설계평가를 위하여 설계를 하였다. 그리고 도로설계는 Inroad를 라는 도로설계프로그램을 사용하였다. 또한, 수치지형도와 포고자료를 이용하여 DTM을 생성하였다. 3차원 도로설계는 도로의 DTM 과 지형자료를 합성하여 설계를 하였다. 3차원적으로 도로설계된 것을 이용하여 설계평가를 수행하였다. 도로선형의 안정성 평가를 위하여 운전자 시뮬레이션과 시거분석을 실시하였다. 그리고, 음영시뮬레이션을 통해 도로노면결빙구간의 불량구간을 추출하였다. 시뮬레이션 결과, 본 연구에서는 도로완공후의 모습을 확인할 수 있었다. 그리고 시거를 시각적으로 산정을 할 수 있었다. 또한 음영 시물레이션을 의해 도로노면결빙구간을 추출하였다.

• Korean Journal of Geomatics
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• 제2권1호
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• pp.37-46
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• 2002

Accurate classification of water area is an preliminary step to accurately analyze the flooded area and damages caused by flood. This step is especially useful for monitoring the region where annually repeating flood is a problem. The accurate estimation of flooded area can ultimately be utilized as a primary source of information for the policy decision. Although SAR (Synthetic Aperture Radar) imagery with its own energy source is sensitive to the water area, its shadow effect similar to the reflectance signature of the water area should be carefully checked before accurate classification. Especially when we want to identify small flood area with mountainous environment, the step for removing shadow effect turns out to be essential in order to accurately classify the water area from the SAR imagery. In this paper, the flood area was classified and monitored using multi-temporal RADARSAT SAR images of Ok-Chun and Bo-Eun located in Chung-Book Province taken in 12th (during the flood) and 19th (after the flood) of August, 1998. We applied several steps of geometric and radiometric calculations to the SAR imagery. First we reduced the speckle noise of two SAR images and then calculated the radar backscattering coefficient $(\sigma^0)$. After that we performed the ortho-rectification via satellite orbit modeling developed in this study using the ephemeris information of the satellite images and ground control points. We also corrected radiometric distortion caused by the terrain relief. Finally, the water area was identified from two images and the flood area is calculated accordingly. The identified flood area is analyzed by overlapping with the existing land use map.

• 한국과학교육학회지
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• 제30권7호
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• pp.901-907
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• 2010

The purpose of this study is to analyze methods for measuring the size of the Earth, put forth in 6 different Korean 8th grade science textbooks. The research questions are as follows: 1) Do they adequately map out the experiments for measuring the size of the earth by using the concept of the sun's altitude? 2) Do they reduce the size of the sun like as the Earth is similarly downsized to the globe? 3) Do they suggest the precise experimental conditions for selecting two equal longitudinal spots for measuring the size of the earth? 4) Do they design adequate experiments for exact measurement? 5) Do they offer a proportional expression for seeking the size of globe which is easily understood by students? 6) Do they develop experiments to measure actual size of the earth? Four graduate students and one researcher took part in this study. All conditions were unanimously agreed upon by the participants. The results are as follows. First, one publishing company must include the concept of the sun's altitude to accurately measure the size of the Earth. However, some textbooks fail to mention this. As such, the concept of the sun's altitude must be introduced to accurately measure the size of the Earth. Second, a reduced size globe is used as the actual earth so; the sun should be factored in with a reduced light value. Third, you have to lay a stress on two points at the same longitude. In other words, a shadow located at the same longitude from two randomly selected points. Most textbooks mention two points at the same longitude but two of them design the experiment with a shadow at the same longitude. Fourth, we need a method to precisely measure the angle between a stick and its shadow. The angle between the stick and the tip of its shadow is the sun's altitude difference. Fifth, we need to present more specific proportional expressions for calculating the size of the globe. Only 3 out of the 6 texts employed a proportional expression. Sixth, we need to calculate the size of the earth by accurately presenting the scale of the globe to attain the goal of the experiment. Two of the texts analyzed, designed the experiment for the purpose of calculating the size of the globe. Three of the texts designed their experiments to calculate the radius of globe which is not even relevant to the purpose of experiment.

• International journal of advanced smart convergence
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• 제12권1호
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• pp.92-100
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• 2023

Wireless communication technology is becoming increasingly prevalent in smart factories, but the rise in the number of wireless devices can lead to interference in the ISM band and obstacles like metal blocks within the factory can weaken communication signals, creating radio shadow areas that impede information exchange. Consequently, accurately determining the radio communication coverage range is crucial. To address this issue, a Radio Environment Map (REM) can be used to provide information about the radio environment in a specific area. In this paper, a technique for estimating an indoor REM usinga mobile robot and machine learning methods is introduced. The mobile robot first collects and processes data, including the Received Signal Strength Indicator (RSSI) and location estimation. This data is then used to implement the REM through machine learning regression algorithms such as Extra Tree Regressor, Random Forest Regressor, and Decision Tree Regressor. Furthermore, the numerical and visual performance of REM for each model can be assessed in terms of R2 and Root Mean Square Error (RMSE).

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume II
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• pp.888-891
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• 2006

SAR image is not dependent on the weather condition and Sun's electromagnetic energy. But geometric distortions exist in almost all radar image, it need to be correction. The Radarsat-1 SAR images are used to monitoring of moisture acquired in May 1/1998 and May 25/1998. Radarsat-1 C band data is sensitive on moisture condition. Study area is located in Non-san site. It is made up almost agricultural area and a little of forest area. In May, Rice-planting is started in the midland of Korea. So moisture condition is undergoing many changes. Forest area need to be terrain effect removal for accurately results because it is included in layover, shadow, and so on. Results of land-cover moisture condition map are useful tool for fields of agriculture, forestry industry, and disaster.

• 로봇학회논문지
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• 제5권3호
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• pp.251-261
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• 2010

In this paper, we introduce an internal pipeline exploration of an in-pipe robot, based on the landmark recognition system. The fittings of pipelines such as elbows and branches are used as the landmarks. The robot recognizes the landmarks with a vision system by using the shadows of the elements, which are generated by the specially designed illuminator on the robot. By using a simple image-processing, the robot can easily detect and distinguish these landmarks while recognizing the direction of the pipeline path. Simultaneously, all information for exploration is continuously recorded and used to reconstruct the map of the pipelines. The effectiveness of the proposed method is verified by real experiments using the in-pipe robot MRINSPECT V for moving inside of the miniature urban 8-inch gas pipeline structure.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2008년도 정보통신설비 학술대회
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• pp.181-185
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• 2008

Recently, location based service(LBS) expended based on personal specialized service, however since commercialized GPS based emergency rescue service comes with shadow zone for GPS signal such as inside building, the accuracy and reliability are not guaranteed. Therefore to improve such problem, we propose an active location detecting algorithm using RFID-TAG and Yagiantenna. To track the location of RFID-TAG where signal is generated, location tracking device in which Yagi-Antenna is installed moves around. Since directed wave and reflected wave co-exist during signal reception, final signal generated location is searched by setting up multiple of locations where signal can be generated on the map and moving location tracking device along minimum length of path. The algorithm proposed in this paper was verified of its technical validity through simulator.