• Title, Summary, Keyword: Radiance

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Extraction of the atmospheric path radiance in relation to retrieval of ocean color information from the TM and SeaWiFS imageries

  • Ahn, Yu-Hwan;Shanmugam, P.
    • Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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    • pp.241-246
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    • 2004
  • The ocean signal that reaches the detector of an imaging system after multiple interactions with the atmospheric molecules and aerosols was retrieved from the total signal recorded at the top of the atmosphere (TOA). A simple method referred to as 'Path Extraction' applied to the Landsat-TM ocean imagery of turbid coastal water was compared with the conventional dark-pixel subtraction technique. The shape of the path-extracted water-leaving radiance spectrum resembled the radiance spectrum measured in-situ. The path-extraction was also extended to the SeaWiFS ocean color imagery and compared with the standard SeaWiFS atmospheric correction algorithm, which relays on the assumption of zero water leaving radiance at the two NIR wavebands (765 and 865nm). The path-extracted water-leaving radiance was good agreement with the measured radiance spectrum. In contrast, the standard SeaWiFS atmospheric correction algorithm led to essential underestimation of the water-leaving radiance in the blue-green part of the spectrum. The reason is that the assumption of zero water-leaving radiance at 755 and 865nm fails due to backscattering by suspended mineral particles. Therefore, the near infrared channels 765 and 865nm used fur deriving the aerosol information are no longer valid for turbid coastal waters. The path-extraction is identified as a simple and efficient method of extracting the path radiance largely introduced due to light interaction through the complex atmosphere carried several aerosol and gaseous components and at the air-sea interface.interface.

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Analysis of Spectral Response Specification for the Infrared Channels of Meteorological Imager (기상 영상기의 적외선 채널 분광 응답 규격에 대한 분석)

  • Cho, Young-Min
    • Aerospace Engineering and Technology
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    • v.6 no.2
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    • pp.104-110
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    • 2007
  • Analyzed is the spectral response profile specification used for the infrared (IR) channels of the meteorological imagers of GOES series geostationary satellites. The variation characteristics of effective wavelength and effective input radiance due to the change of the spectral response function profile within the imager performance specification are analyzed in order to propose how to understand the spectral response specification. As an analysis approach, at first a center symmetrical spectral response function and 4 worst case spectral response functions are selected within the spectral response specification, and then effective wavelength and effective input radiance are calculated for each spectral response function. As a result, the maximum allowable ranges of effective wavelength and effective input radiance are provided per the spectral response specification.

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Study on the Seasonal IR Signature Characteristics of a Naval Ship with Plume Gas Effect (배기가스를 고려한 함정의 계절별 적외선 신호 특성에 대한 연구)

  • Han, Kuk-Il;Kim, Dong-Geon;Choi, Jun-Hyuk;Kim, Tae-Kuk
    • Journal of the Korea Institute of Military Science and Technology
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    • v.16 no.4
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    • pp.545-552
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    • 2013
  • This paper is a part of developing a computer code that can be used to generate IR images of a naval ship by considering the emitted and reflected infrared signals. The spectral radiance received by an IR sensor is consisted of the self-emitted component from the ship surface, the reflected component of the solar/sky irradiance at the ship surface, the emitted radiance from the ship surface and the exhaust plume gas, and the scattered radiance by the atmosphere. The plume gas radiance occupies a large part of the emitted radiance from a naval ship in operation. Therefore plume gas radiance must be taken into account when calculating the radiance from a naval ship for reliable IR images. In this paper, IR images of a naval ship with the exhaust gas effect in various environmental conditions are generated by using an exhaust gas prediction model called the JPL model. The contrast radiance (CR) values of the IR images are calculated to analyze the effect of the exhaust gas radiance quantitatively. The results obtained by quantitative analysis show that the IR signatures with the exhaust plume gas are 2.26 times larger than those neglecting the plume gas effect. The effect of the exhaust plume gas is shown to be more eminent in winter than in summer in the daytime.

POST-LAUNCH RADIOMETRIC CALIBRATION OF KOMPSAT2 HIGH RESOLUTION IMAGE

  • Yoon, Jong-Suk;Lee, Kyu-Sung;Chi, Jun-Hwa;Lee, Dong-Han
    • Proceedings of the KSRS Conference
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    • v.1
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    • pp.402-405
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    • 2006
  • Radiometric calibration of optical image data is necessary to convert raw digital number (DN) value of each pixel into a physically meaningful measurement (radiance). To extract rather quantitative information regarding biophysical characteristics of the earth surface materials, radiometric calibration is often essential procedure. A sensor detects the radiation of sunlight interacted atmospheric constituents. Therefore, the amount of the energy reaching at the sensor is quite different from the initial amount reflected from the surface. To achieve the target reflectance after atmospheric correct, an initial step is to convert DN value to at-sensor radiance. A linear model, the simplest radiometric model, is applied to averaged spectral radiance for this conversion. This study purposes to analyze the sensitivity of several factors affecting on radiance for carrying out absolute radiometric calibration of panchromatic images from KOMPSAT2 launched at July, 2006. MODTRAN is used to calculate radiance at sensor and reflectance of target is measured by a portable spectro-radiometer at the same time the satellite is passing the target for the radiometric calibration. As using different contents of materials composing of atmosphere, the differences of radiance are investigated. Because the spectral sensitivity of panchromatic images of KOMPSAT2 ranges from 500 to 900 nm, the materials causing scattering in visible range are mainly considered to analyze the sensitivity. According to the verified sensitivity, direct measurement can be recommenced for absolute radiometric calibration.

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Calculation of At-sensor radiance for KOMPSAT-2 image collection planning (KOMPSAT-2 촬영계획을 위한 At-sensor radiance 계산)

  • Lee, Dong-Han;Seo, Doo-Chun;Song, Jeong-Heon;Choi, Myung-Jin;Yang, Ji-Yeon;Jung, Ho-Ryung;Lim, Hyo-Suk
    • Proceedings of the KSRS Conference
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    • pp.18-21
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    • 2009
  • 2006년 발사되어 현재 운영 중인 아리랑위성 2호의 활용도를 높이기 위해서는 촬영 지역의 radiance 값에 따라 아리랑위성 2호의 TDI와 Vp gain 값을 조절해야만, 10bit인 radiometric resolution을 넓게 사용할 수가 있다. 촬영하고자 하는 지역의 radiance 값을 미리 예측하기 위해서, 한 픽셀이 $250km\times250km$인 월별 전 세계 radiance 평균값을 기본으로 촬영 날짜, 촬영 시각, 촬영 지역의 기후 조건 및 아리랑위성 2호의 ON-to-Radiance 변화 계수 값들을 사용하여서 최종 At-sensor radiance 값을 계산하는 알고리즘을 개발하였다. 실제 아리랑위성 2호의 자료수집계획 작성 시에 참고 값으로 사용 중이고, 80%이상의 정확도가 있음을 확인하였다.

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Assessment of BIN Method to Predict Energy Saving in Office Building Using the RADIANCE Program (RADIANCE 프로그램을 이용한 오피스 건축물에서의 에너지 절감율 예측을 위한 BIN Method 검토)

  • Hong, Seong-Kwan;Park, Byoung-Chul;Choi, An-Seop;Lee, Jeong-Ho
    • 한국태양에너지학회:학술대회논문집
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    • pp.154-159
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    • 2008
  • Daylight is an important component for human and energy saving. Also, available daylight in inside provides positive influence on psychological and physiological aspects as well as good visual environment. It is important to lighting design for office building not only designing for artificial lighting but also using daylight for energy savings. Therefore, lighting designers and architectures must consider the effects of the daylight for human environment and energy savings. The BIN Method is one of the methods to predict energy savings using computer simulation but it spends more time than expectation. So, this study performs to simulate a simple space using the RADIANCE for examination and simplification of the BIN Method.

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Method of Integrating Landsat-5 and Landsat-7 Data to Retrieve Sea Surface Temperature in Coastal Waters on the Basis of Local Empirical Algorithm

  • Xing, Qianguo;Chen, Chu-Qun;Shi, Ping
    • Ocean Science Journal
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    • v.41 no.2
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    • pp.97-104
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    • 2006
  • A useful radiance-converting method was developed to convert the Landsat-7 ETM+thermal-infrared (TIR) band's radiance ($L_{{\lambda},L7/ETM+}$) to that of Landsat-5 TM TIR ($L_{{\lambda},L5/TM+})$ as: $L_{{\lambda},L5/TM}=0.9699{\times}L_{{\lambda},L7/ETM+}+0.1074\;(R^2=1)$. In addition, based on the radiance-converting equation and the linear relation between digital number (DN) and at-satellite radiance, a DN-converting equation can be established to convert DN value of the TIR band between Landsat-5 and Landsat-7. Via this method, it is easy to integrate Landsat-5 and Landsat-7 TIR data to retrieve the sea surface temperature (SST) in coastal waters on the basis of local empirical algorithms in which the radiance or DN of Lansat-5 and 7 TIR band is usually the only input independent variable. The method was employed in a local empirical algorithm in Daya Bay, China, to detect the thermal pollution of cooling water discharge from the Daya Bay nuclear power station (DNPS). This work demonstrates that radiance conversion is an effective approach to integration of Landsat-5 and Landsat-7 data in the process of a SST retrieval which is based on local empirical algorithms.

Radiometric Characteristics of Geostationary Ocean Color Imager (GOCI) for Land Applications

  • Lee, Kyu-Sung;Park, Sung-Min;Kim, Sun-Hwa;Lee, Hwa-Seon;Shin, Jung-Il
    • Korean Journal of Remote Sensing
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    • v.28 no.3
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    • pp.277-285
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    • 2012
  • The GOCI imagery can be an effective alternative to monitor short-term changes over terrestrial environments. This study aimed to assess the radiometric characteristics of the GOCI multispectral imagery for land applications. As an initial approach, we compared GOCI at-sensor radiance with MODIS data obtained simultaneously. Dynamic range of GOCI radiance was larger than MODIS over land area. Further, the at-sensor radiance over various land surface targets were tested by vicarious calibration. Surface reflectance were directly measured in field using a portable spectrometer and indirectly derived from the atmospherically corrected MODIS product over relatively homogeneous sites of desert, tidal flat, bare soil, and fallow crop fields. The GOCI radiance values were then simulated by radiative transfer model (6S). In overall, simulated radiance were very similar to the actual radiance extracted from GOCI data. Normalized difference vegetation index (NDVI) calculated from the GOCI bands 5 and 8 shows very close relationship with MODIS NDVI. In this study, the GOCI imagery has shown appropriate radiometric quality to be used for various land applications. Further works are needed to derive surface reflectance over land area after atmospheric correction.

Examining a Vicarious Calibration Method for the TOA Radiance Initialization of KOMPSAT OSMI

  • Sohn, Byung-Ju;Yoo, Sin-Jae;Kim, Yong-Seung;Kim, Do-hyeong
    • Korean Journal of Remote Sensing
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    • v.16 no.4
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    • pp.305-313
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    • 2000
  • A vicarious calibration method was developed for the OSMI sensor calibration. Employing measured aerosol optical thickness by a sunphotometer and a sky radiometer and water leaving radiance by ship measurements as inputs, TOA (top of the atmosphere) radiance at each OSMI band was simulated in conjunction with a radiative transfer model (Rstar5b) by Nakajima and Tanaka (1988). As a case of examining the accuracy of this method, we simulated TOA radiance based on water leaving radiance measured at NASA/MOBY site and aerosol optical thickness estimated nearby at Lanai, and compared simulated results with SeaWiFS-estimated TOA radiances. The difference falls within about $\pm$5%, suggesting that OMSI sensor can be calibrated with the suggested accuracy. In order to apply this method for the OSMI sensor calibration, ground-based sun photometry and ship measurements were carried out off the east coast of Korean peninsula on May 31, 2000. Simulations of TOA radiance by using these measured data as input to the radiative transfer model show that there are substantial differences between simulated and OSMI-estimated radiances. Such a discrepancy appears to be mainly due to the cloud contamination because satellite image indicates optically thin clouds over the experimental area. Nevertheless results suggest that sensor calibration can be achieved within 5% uncertainty range if there are ground-based measurements of aerosol optical thickness, and water leaving radiances under clear-sky and optically thin atmospheric conditions.

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Analysis of Window Transmittance Using Horizontal Blind by RADIANCE Program (RADIANCE 프로그램에 의한 창문 블라인드의 투과율 분석 연구)

  • 정근영;최안섭
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.17 no.6
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    • pp.7-15
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    • 2003
  • The purpose of this simulation study is to determine the window transmittance by RADIANCE lighting simulation tool where the horizontal blind is installed. Parameters such as sky types, seasonal changes, altitude, azimuth, and horizontal blind angle at a 0$^{\circ}$, 45$^{\circ}$, 90$^{\circ}$ were considered. The simulation results present that measured directional transmittances have different values according to each directional property of the horizontal blind. In addition, methodology was described to apply window transmittance data to DayDim program which is a lighting calculation and analysis tool especially for the performance of daylight responsive dimming systems.