• Korean Journal of Remote Sensing
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• v.33 no.6_3
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• pp.1197-1213
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• 2017

This study was carried out to correct shadow area in urban area on KOMPSAT-3 satellite image. For this study, we analyzed characteristics of the shadow area represented by artificial structures in urban area. The proposed shadow correction method divides shadow area into umbra and penumbra areas according to intensity of darkness. The umbra area was detected through the histogram analysis and the statistical method of the NIR image, and then penumbra area and the sunlit area were detected from around the detected umbra area. The correction of the detected umbra and penumbra area were performed by applying the linear correlation correction method. As a result, it was confirmed that the proposed shadow correction method was visually performed well. Quantitative analysis was performed through profile analysis. It is proved that proposed method is useful for shadow area correction.

• Journal of Korea Game Society
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• v.14 no.2
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• pp.77-84
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• 2014

Presence of soft shadow effects from an area light makes virtual scenes look more realistic. However, since computation of soft shadow effects takes a long time, acceleration methods are required to apply it to real-time 3D applications. Many researches assumed that area lights are white rectangles. We suggest a new method which renders soft shadows under the area light source having arbitrary shape and color. In order to approximate visibility test, we use a shadow mapping result near a pixel. Complexity of shadow near a pixel is used to determine degree of precision of our visibility estimation. Finally, our method can present more realistic soft shadows for the area light that have more general shape and color in real-time.

• Journal of Environmental Impact Assessment
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• v.19 no.3
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• pp.297-305
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• 2010

This study has intended to analyze the nature of the errors that occur as a result of shadows during the process of NDVI calculation using high-resolution satellite images of Cheongju City, in order to calibrate such errors, and to verify the results. This study has calibrated the shadow errors by utilizing the relationship between the Greenness above Bare Soil (GRABS) calculated through Tasseled-Cap transformation and the original NDVI. To verify the accuracy of the results, this study has compared the shadow area extracted by the difference between before and after calibration of NDVI, with the original shadow area. The NDVI value converged on the value of -1.0, representing water, because shadow areas could not accept the reflection value from each band. However, after performing Tasseled-Cap transformation, the NDVI of shadow areas that had converged on -1.0 prior to calibration had increased to a level similar to the NDVI of neighboring areas. In addition, the average NDVI in general had increased from -0.08 to -0.01. Finally, the shadow area drawn out was almost matched to the original one, meaning that the NDVI calibration method employed turned out to be highly accurate in extracting shadow areas.

• Journal of Internet Computing and Services
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• v.21 no.5
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• pp.49-56
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• 2020

Detecting shadows in images and restoring or removing them was a very challenging task in computer vision. Traditional researches used color information, edges, and thresholds to detect shadows, but there were errors such as not considering the penumbra area of shadow or even detecting a black area that is not a shadow. Deep learning has been successful in various fields of computer vision, and research on applying deep learning has started in the field of shadow detection and removal. However, it was very difficult and time-consuming to collect data for network learning, and there were many limited conditions for shooting. In particular, it was more difficult to obtain shadow data from buildings and satellite images, which hindered the progress of the research. In this paper, we propose a method for generating shadow data from buildings and satellites using Unity3D. In the virtual Unity space, 3D objects existing in the real world were placed, and shadows were generated using lights effects to shoot. Through this, it is possible to get all three types of images (shadow-free, shadow image, shadow mask) necessary for shadow detection and removal when training deep learning networks. The method proposed in this paper contributes to helping the progress of the research by providing big data in the field of building or satellite shadow detection and removal research, which is difficult for learning deep learning networks due to the absence of data. And this can be a suboptimal method. We believe that we have contributed in that we can apply virtual data to test deep learning networks before applying real data.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.12
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• pp.1352-1370
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• 2010

In this paper, we investigated the shadow area of radio programs which are currently being broadcast via FM 102.5 MHz in Jeollabuk-do consisting of 6 cities and 8-guns. The field strength data of FM 102.5 MHz was used with criterion of shadow area. As a result, the field strength of the eastern mountainous area in Jeollabuk-do was very low. We also measured, compared and analyzed the field strength of 102.5 MHz(TBN-Jeonju), 100.7 MHz(KBS) and 99.1 MHz (MBC) in Jeollabuk-do. Based on the field strength data, we tried to find what correlation exists and how much influence is between difference of antenna output power and solution of shadow area. In result, enhancement of antenna output power is not solution in terms of reducing the shadow Area of 102.5 MHz(TBN-Jeonju). In addition, we measured, compared and analyzed the field strength of 102.5 MHz(TBN-Jeonju) and 106.9 MHz(EBS). In fact, the relay stations with 104.1 MHz, 104.9 MHz, 105.3 MHz and 107.5 MHz of EBS FM has a number of FM relay stations in the eastern mountainous area of Jeollabuk-do. As a result, we confirmed that EBS almost did not have shadow area in the eastern mountainous area of Jeollabuk-do based on the field strength data. As in the case of EBS and KBS, we suggest installing TBN-Jeonju FM relay station with the best solution to reducing the shadow area to extend the audible range of TBN-Jeonju.

• Journal of the Korean housing association
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• v.14 no.5
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• pp.11-17
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• 2003

This study is aimed at analyzing on the sunshine according to the blocks direction by location type of apartment complex in Busan, to propose a planning on the decision of blocks direction and the improvement of architectural law in sunshine environment. The results of this study were as follows; On the basis of winter solstice in "□ block type", the average of ratio of shadow area in flat site is 51 % in apartment with a southern exposure, 39% in apartment with a south-eastern exposure. The average of ratio of shadow area in the descended site toward the north is 49% in apartment with a southern exposure, 34% in apartment with a south-eastern exposure. The average of ratio of shadow area in the descended site toward the south is 66% in apartment with a southern exposure, 53% in apartment with a south-eastern exposure.

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.394-397
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• 2008

Recently WiBro network is installed for high speed wireless internet service by telecommunication service provider, however WiBro service is not provided in the region of mountain or difficult region to install network infra. Fixed repeater is used to resolve those shadow area problem in current WiBro network. This paper study introducing Ad-hoc based multi-hop relay instead of using fixed repeater in order to resolve those shadow area problem. Cost down of fixed repeater and active network expansion is possible to resolve shadow area problem by introducing multi-hop relay technology.

• Journal of Korea Society of Industrial Information Systems
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• v.19 no.4
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• pp.1-8
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• 2014

In order to cope with shadow areas and to extend cell coverage, relay-assisted wireless communication systems have been widely studied. In this paper, we propose a space-frequency(SF) block coded orthogonal frequency division multiple access(OFDMA) transmission system in a relaying multi-path shadow area. The receiving performance of mobile station in a shadow area can be improved by applying SF block code to the recovered signals of multiple relays before re-transmitting them. The simulation result shows that the proposed SF block coded OFDMA transmission system considerably outperforms the conventional single-path OFDMA transmission system.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2003.04a
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• pp.187-190
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• 2003

Due to complexity of diverse features in urban area, accurate feature extraction is laborious task in aerial and satellite imagery. Especially occlusion by buildings, and image distortion of shadow effects make processing more difficult work. In this study, algorithm was presented to correct of shadow effects in aerial color images. This algorithm enables user to accurately interpretate urban information by correction of shadow effects in aerial color images

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2007.04a
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• pp.169-173
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• 2007

Nowadays the aerial photos is using to get the information around our spatial environment and it increases by geometric progression in many fields. The aerial photos need in a simple object such as cartography and ground covey classification and also in a social objects such as the city plan, environment, disaster, transportation etc. However, the shadow, which includes when taking the aerial photos, makes a trouble to interpret the ground information, and also users, who need the photos in their field tasks, have restriction. This study, for removing the shadow, uses the single image and the image without the source of image and taking situation. Also, this study present clustering algorism based on HIS color model that use Hue, Saturation and Intensity, especially this study used I(intensity) to extract shadow area from image. And finally by filtering in Fourier frequency domain creates the intrinsic image which recovers the 3-D color information and removes the shadow.