• Korean Journal of Remote Sensing
• /
• v.37 no.5_1
• /
• pp.1071-1081
• /
• 2021

Remote Sensing using unmanned aerial vehicles(UAV) can acquire images with higher time resolution and spatial resolution than aerial and satellite remote sensing. However, UAV images are photographed at low altitude and the area covered by one image isrelatively narrow. Therefore multiple images must be processed to monitor large area. Since UAV images are photographed under different exposure conditions, there is difference in brightness values between adjacent images. When images are mosaicked, unnatural seamlines are generated because of the brightness difference. Therefore, in order to generate seamless mosaic image, a radiometric processing for correcting difference in brightness value between images is essential. This paper proposes a relative radiometric calibration and image blending technique. In order to analyze performance of the proposed method, mosaic images of UAV images in agricultural and mountainous areas were generated. As a result, mosaic images with mean brightness difference of 5 and root mean square difference of 7 were avchieved.

• Korean Journal of Remote Sensing
• /
• v.37 no.5_1
• /
• pp.1177-1186
• /
• 2021

As the Arctic melt ponds play an important role in determining the interannual variation of the sea ice extent and changes in the Arctic environment, it is crucial to monitor the Arctic melt ponds with high accuracy. Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2), which is the NASA's latest altimeter satellite based on the green laser (532 nm), observes the global surface elevation. When compared to the CryoSat-2 altimetry satellite whose along-track resolution is 250 m, ICESat-2 is highly expected to provide much more detailed information about Arctic melt ponds thanks to its high along-track resolution of 70 cm. The basic products of ICESat-2 are the surface height and the number of reflected photons. To aggregate the neighboring information of a specific ICESat-2 photon, the segments of photons with 10 m length were used. The standard deviation of the height and the total number of photons were calculated for each segment. As the melt ponds have the smoother surface than the sea ice, the lower variation of the height over melt ponds can make the melt ponds distinguished from the sea ice. When the melt ponds were extracted, the number of photons per segment was used to classify the melt ponds covered with open-water and specular ice. As photons are much more absorbed in the water-covered melt pondsthan the melt ponds with the specular ice, the number of photons persegment can distinguish the water- and ice-covered ponds. As a result, the suggested melt pond detection method was able to classify the sea ice, water-covered melt ponds, and ice-covered melt ponds. A qualitative analysis was conducted using the Sentinel-2 optical imagery. The suggested method successfully classified the water- and ice-covered ponds which were difficult to distinguish with Sentinel-2 optical images. Lastly, the pros and cons of the melt pond detection using satellite altimetry and optical images were discussed.

• Journal of Astronomy and Space Sciences
• /
• v.26 no.2
• /
• pp.171-186
• /
• 2009

Various Earth-Moon transfer trajectories are designed and analyzed to prepare the future Korea's Lunar missions. Minimum fuel trajectory solutions are obtained for the departure year of 2017, 2020, 2022, and every required mission phases are analyzed from Earth departure to the final lunar mission orbit. N-body equations of motion are formulated which include the gravitational effect of the Sun, Earth and Moon. In addition, accelerations due to geopotential harmonics, Lunar J2 and solar radiation pressures are considered. Impulsive high thrust is assumed as the main thrusting method of spacecraft with launcher capability of KSLV-2 which is planned to be developed. For the method of injecting a spacecraft into a trans Lunar trajectory, both direct shooting from circular parking orbit and shooting from the multiple elliptical intermediate orbits are adapted, and their design results are compared and analyzed. In addition, spacecraft's visibility from Deajeon ground station are constrained to see how they affect the magnitude of TLI(Trans Lunar Injection) maneuver. The results presented in this paper includes launch opportunities, required optimal maneuver characteristics for each mission phase as well as the trajectory characteristics and numerous related parameters. It is confirmed that the final mass of Korean lunar explorer strongly depends onto the initial parking orbit's altitude and launcher's capability, rather than mission start time.

• Journal of the Korean Geophysical Society
• /
• v.3 no.4
• /
• pp.291-310
• /
• 2000

In this study, a series of data processing methods to calculate gravity anomaly from observed marine gravity data by NORI(National Oceanic Research Institute) using RV 'Hayang2000' in 1999 at southern part of the yellow sea were developed. As a results, the RMS difference of Free air anomaly among 264 crossover points is 0.436 mGal. The shipborne gravity data by NORI using RV 'Haeyang2000' will be very useful for gravitational research in and around Korean peninsula.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.13 no.3
• /
• pp.1270-1274
• /
• 2012

The pipe laid underground more than three decades ago are already starting to reveal the problem like corrosion. There have been many studies to design robotic system for a cost-effective revival of old pipes. And the ability to inspect in the pipes, the ability to treat and repaint the pipes and the fault-tolerant robotic system are well known important factors for the robotic system. It's real hard part to manage the underground pipes for companies because it needs high technical and too much money. According to this reasons, in this paper, we had design an in-pipe robotic system having abilities to inspect outworn pipes, to treat and paint old pipes. This new robot system is pressing wall type robot, and it has a good carrying power for working.

• Proceedings of the KSRS Conference
• /
• 2006.03a
• /
• pp.232-235
• /
• 2006

해저 해빈모래가 다량 유실되어 이 지역의 장기관리를 위해 침식구간에 대한 지속적인 모니터링 작업이 필요하다. 그러나 각 구청은 지형변화 분석 작업 없이, 양빈작업에 급급하고 있어 장기효과가 나타나지 않고 있다. 그러므로 본 연구는 수심측량 및 GPS 측량을 통해 해저 해빈지대의 정확한 공간자료를 구축, RS GIS 기법을 도입하여 지형변화를 정량 정성적으로 탐지 분석하였다. 연구 결과, 해운대 해저지형은 과도한 도시개발과 하천복개공사로 지난 25년간, 평균수심 0.40m, 수표면적 $11,028m^2$, 수중체적 $2,207,884m^3$ 가량 침식되었다. 해빈지형은 지난 5년간, 평균고도 0.27m, 총면적 $6,501m^2$, 총체적 $25,667m^3$ 가량 퇴적되었다. 이의 원인은 지오그리드의 설치로 해빈모래가 서측까지 도달하지 못하고, 계절영향으로 사료된다. 본 연구는 해저 해빈지형의 정확한 측량작업으로 해안 및 지형변화에 관한 모니터링 작업을 실시하여 연안침식 현황을 분석하고, 양빈작업 및 안전한 해양레저 활동, 해수욕장 관리에 필요한 정보를 제공할 수 있을 것으로 판단된다.

• Korean Journal of Remote Sensing
• /
• v.30 no.2
• /
• pp.331-339
• /
• 2014

Determination of an ionospheric delay scale factor, which converts ground-based ionospheric delay into low Earth orbit ionospheric delay, using the international reference ionosphere model is proposed. Ionospheric delay from international GNSS service model combined with IRI-derived scale factor is evaluated with NASA GRACE satellite data. At approximately 480km altitude, mean and standard deviation of the scale factor are 0.25 and 0.01 in 2004. The scale factor reaches high in night time and Spring and Fall seasons. Ionospheric delay error by the proposed method has a mean of 3.50 TECU in 2004.

• Proceedings of the KSRS Conference
• /
• 2009.03a
• /
• pp.46-52
• /
• 2009

TerraSAR-X 자료를 이용하여 고해상 X-밴드 SAR 시스템을 이용한 조간대 적용 가능성을 시험하였다 연구대상지역은 강화도 남단과 영종도를 잇는 조간대이며, 단일편파자료와 이중편파자료를 이용하였다. 연구내용은 다음과 같은 세 가지로 분류된다. 첫째, X-밴드 영상에서의 연안의 레이더 반사도 특성 연구 및 waterline 추출 정밀도를 평가하였다. 연안지역의 wateline은 HH 편광자료의 레이더 반사도 특성을 통하여 추출하였을 때 가장 신뢰도가 높았으며, TerraSAR-X 시스템의 짧은 파장과 높은 제도정밀도로 인하여 정밀한 지리좌표로의 변환이 가능하였다 연구지역의 조간대 지형 경사도는 평균적으로 수평방향으로 60m당 20cm의 고도변화를 가지므로, TerraSAR-X HH 편광자료를 이용한 waterline 추출은 정밀한 조간대 DEM 추출로 응용될 수 있다. 둘째, 이중편파자료의 편파특성을 이용한 조간대 염생식물의 산란특성 관측하였다. 조간대에서 수륙의 경계부에서 잘 관측되는 칠면초와 같은 염생식물은 해수면변화에 따른 조간대의 육지화를 모니터링 하는데 좋은 표적이 된다. TerraSAR-X 이중편파자료의 산란특성을 이용한 염생식물 관측결과는 2007년에 현장에서 취득된 실측자료와 비교하여 3dB 이내의 정밀도로 일치하였다 셋째, 단일편파 자료의 레이더 간섭기법을 이용한 조간대 DEM 작성 시도하였다. 조간대 내에서 육지화가 진행된 지역은 표면에 염생식물이 발달하였음에도 불구하고 높은 간섭긴밀도를 나타내었다. 레이더 간섭기법을 통한 DEM의 제작은 일반적인 조간대에서는 적용이 제한적이며, TanDEN-X의 적용이 필요하다.

• Spatial Information Research
• /
• v.14 no.1 s.36
• /
• pp.115-128
• /
• 2006

The aim of the study is to select and verify for development of groundwater resources using Geographic Information System(GIS). The water balance, land cover, forest, soil, elevation, slope, hydrogeology and lineament were analyzed. Using GIS, relationship between the data and groundwater yield data was analyzed and the groundwater resources potential map was made for selecting suitable area for groundwater development. Then groundwater resource potential map was verified using groundwater yield data. The verified result showed the good agreement between the potential map and groundwater yield data. The potential map can be used for groundwater management which is related to groundwater development.

• Korean Journal of Remote Sensing
• /
• v.22 no.2
• /
• pp.131-139
• /
• 2006

IKONOS images have the perspective geometry in CCD sensor line like aerial images with central perspective geometry. So the occlusion by buildings, terrain or other objects exist in the image. It is difficult to detect the occlusion with RPCs(rational polynomial coefficients) for ortho-rectification of image. Therefore, in this study, we detected the occlusion areas in IKONOS images using the nominal collection elevation/azimuth angle and restored the hidden areas using another stereo images, from which the rue ortho image could be produced. The algorithm's validity was evaluated using the geometric accuracy of the generated ortho image.