• Title/Summary/Keyword: cross-calibration

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OSMI ocean color products with updated cross-calibration coefficients

  • Lee S. G.;Kim Y. S.
    • Proceedings of the KSRS Conference
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    • pp.494-497
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    • 2004
  • To date the KOMPSAT OSMI(Ocean Scanning Multi-spectral Imager) data have been widely used in natural disaster monitoring such as Typhoon, Asian Dust, Red Tide, and Forest Fire. Quantitative analyses related to the marine ecosystem have been delayed because they require good quality of data through Cal/Val activities. To resolve such problem, KARI performed the OSMI crosscalibration study with SeaWiFS team. In this study, we will demonstrate the OSMI ocean color products with updated cross-calibration coefficients and compare them to the previous cross-calibration results.

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The Assessment of Cross Calibration/Validation Accuracy for KOMPSAT-3 Using Landsat 8 and 6S

  • Jin, Cheonggil;Choi, Chuluong
    • Korean Journal of Remote Sensing
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    • v.37 no.1
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    • pp.123-137
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    • 2021
  • In this study, we performed cross calibration of KOMPSAT-3 AEISS imaging sensor with reference to normalized pixels in the Landsat 8 OLI scenes of homogenous ROI recorded by both sensors between January 2014 and December 2019 at the Libya 4 PICS. Cross calibration is using images from a stable and well-calibrated satellite sensor as references to harmonize measurements from other sensors and/or characterize other sensors. But cross calibration has two problems; RSR and temporal difference. The RSR of KOMPSAT-3 and Landsat 8 are similar at the blue and green bands. But the red and NIR bands have a large difference. So we calculate SBAF of each sensor. We compared the SBAF estimated from the TOA Radiance simulation with KOMPSAT-3 and Landsat 8, the results displayed a difference of about 2.07~2.92% and 0.96~1.21% in the VIS and NIR bands. Before SBAF, Reflectance and Radiance difference was 0.42~23.23%. Case of difference temporal, we simulated by 6S and Landsat 8 for alignment the same acquisition time. The SBAF-corrected cross calibration coefficients using KOMPSAT-3, 6S and simulated Landsat 8 compared to the initial cross calibration without correction demonstrated a percentage difference in the spectral bands of about 0.866~1.192%. KOMPSAT-3 maximum uncertainty was estimated at 3.26~3.89%; errors due to atmospheric condition minimized to less than 1% (via 6S); Maximum deviation of KOMPSAT-3 DN was less than 1%. As the result, the results affirm that SBAF and 6s simulation enhanced cross-calibration accuracy.

Automatic Cross-calibration of Multispectral Imagery with Airborne Hyperspectral Imagery Using Spectral Mixture Analysis

  • Yeji, Kim;Jaewan, Choi;Anjin, Chang;Yongil, Kim
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.33 no.3
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    • pp.211-218
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    • 2015
  • The analysis of remote sensing data depends on sensor specifications that provide accurate and consistent measurements. However, it is not easy to establish confidence and consistency in data that are analyzed by different sensors using various radiometric scales. For this reason, the cross-calibration method is used to calibrate remote sensing data with reference image data. In this study, we used an airborne hyperspectral image in order to calibrate a multispectral image. We presented an automatic cross-calibration method to calibrate a multispectral image using hyperspectral data and spectral mixture analysis. The spectral characteristics of the multispectral image were adjusted by linear regression analysis. Optimal endmember sets between two images were estimated by spectral mixture analysis for the linear regression analysis, and bands of hyperspectral image were aggregated based on the spectral response function of the two images. The results were evaluated by comparing the Root Mean Square Error (RMSE), the Spectral Angle Mapper (SAM), and average percentage differences. The results of this study showed that the proposed method corrected the spectral information in the multispectral data by using hyperspectral data, and its performance was similar to the manual cross-calibration. The proposed method demonstrated the possibility of automatic cross-calibration based on spectral mixture analysis.

Development of a Web-Based Program for Cross-Calibration and Record Management of Radiation Measuring Equipment

  • Park, So Hyun;Lee, Rena;Kim, Kyubo;Ahn, Sohyun;Lim, Sangwook;Cho, Samju
    • Progress in Medical Physics
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    • v.30 no.2
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    • pp.59-63
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    • 2019
  • Purpose: To manage radiation measurement equipment, a web-based management program has been developed in this study. Materials and Methods: This program is based on a web service and Java Server Pages (JSP) and employs compatibility and accessibility. Results: The first step in the workflow has been designed to create accounts for each user or organization and to log in. The program consists of two parts: fields for listed instruments, and measurement information. The instruments for measuring radiation listed in this program are as follows: ionization chambers, survey meters, thermometers, barometers, electrometers, and phantoms. Instrument properties can be put in the recording fields and browsing for associated instruments can be performed. The main part of the program is the cross-calibration for each ion chamber. For instance, the ionization chamber to be used as a relative dosimeter can be registered by cross-calibration data with a reference chamber calibrated by an accredited laboratory. This program supports methods using the central axis transfer theory for cross-calibration for the ionization chambers. The reference and field ionization chambers were placed in a solid water phantom along the beam central axis at two different depths, and then the positions were switched. Each measured value was used for calculating the cross-calibration factor. Conclusions: Because many instruments are used and managed in radiation oncology departments, systematic, traceable recording is very important. The web-based program developed in this study is expected to be used effectively in the maintenance of radiation measurement instruments.

Absolute Radiometric Calibration for KOMPSAT-3 AEISS and Cross Calibration Using Landsat-8 OLI

  • Ahn, Hoyong;Shin, Dongyoon;Lee, Sungu;Choi, Chuluong
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.35 no.4
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    • pp.291-302
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    • 2017
  • Radiometric calibration is a prerequisite to quantitative remote sensing, and its accuracy has a direct impact on the reliability and accuracy of the quantitative application of remotely sensed data. This paper presents absolute radiometric calibration of the KOMPSAT-3 (KOrea Multi Purpose SATellite-3) and cross calibration using the Landsat-8 OLI (Operational Land Imager). Absolute radiometric calibration was performed using a reflectance-based method. Correlations between TOA (Top Of Atmosphere) radiances and the spectral band responses of the KOMPSAT-3 sensors in Goheung, South Korea, were significant for multispectral bands. A cross calibration method based on the Landsat-8 OLI was also used to assess the two sensors using near simultaneous image pairs over the Libya-4 PICS (Pseudo Invariant Calibration Sites). The spectral profile of the target was obtained from EO-1 (Earth Observing-1) Hyperion data over the Libya-4 PICS to derive the SBAF (Spectral Band Adjustment Factor). The results revealed that the TOA radiance of the KOMPSAT-3 agree with Landsat-8 within 5.14% for all bands after applying the SBAF. The radiometric coefficient presented here appears to be a good standard for maintaining the optical quality of the KOMPSAT-3.

Examination of Cross-calibration Between OSMI and SeaWiFS: Comparison of Ocean Color Products

  • Lee, Sun-Gu;Kim, Yong-Seung
    • Proceedings of the KSRS Conference
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    • pp.209-215
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    • 2002
  • Much effort has been made in the radiometric calibration of the ocean scanning multispectral imager (OSMI) since after the successful launch of KOMPSAT-1 in 1999. A series of calibration coefficients for OSMI detectors were obtained in collaboration with the NASA Sensor Intercomparison and Merger for Biological and Interdisciplinary (SIMBIOS) project office. In this study, we compare the OSMI level-2 products (e.g., chlorophyll-a concentration) calculated from the NASA cross-calibration coefficients with the SeaWiFS counterparts. Sample study areas are some of diagonostic data sites recommended by the SIMBIOS working group. We will present the preliminary results of this comparative study.

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Examination of Cross-calibration Between OSMI and SeaWiFS: Comparison of Ocean Color Products

  • Kim, Yong-Seung;Lee, Sun-Gu
    • Korean Journal of Remote Sensing
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    • v.19 no.3
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    • pp.201-208
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    • 2003
  • Much effort has been made in the radiometric calibration of the ocean scanning multispectral imager (OSMI) since after the successful launch of KOMPSAT-1 in 1999. A series of calibration coefficients for OSMI detectors were obtained in collaboration with the NASA Sensor Intercomparison and Merger for Biological and Interdisciplinary (SIMBIOS) project office. In this study, we ompare the OSMI level-2 products (e.g., chorophyll-a concentration) calculated from the NASA cross-calibration coefficients with the SeaWiFS counterparts. Sample study areas are some of diagonostic data sites recommended by the SIMBIOS working group. Results of this study show that the OSMl-derived chlorophyll-a concentration agrees well with the SeaWiFS counterpart in Case 1 water; however, differences become larger in Case 2 water.

Cross-calibration of Bone Mineral Density between Two Different Dual X-ray Absorptiometry Systems: Hologic QDR 4500-A and Lunar EXPERT-XL (서로 다른 이중에너지 방사선흡수기계 기종(Hologic QDR 4500-A와 Lunar EXPERT-XL) 간의 골밀도 교차 보정)

  • Jo, Jin-Man;Kim, Jae-Seung;Kim, Ghi-Su;Kim, Sang-Wook;Shin, Jung-Woo;Moon, Dae-Hyuk;Lee, Hee-Kyung
    • The Korean Journal of Nuclear Medicine
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    • v.33 no.3
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    • pp.282-288
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    • 1999
  • Purpose: A cross-calibration equation is needed to compare bone mineral density measured by different dual X-ray absoptiometry systems. We performed this study to establish appropriate cross-calibration equations between two different dual X-ray absorptiometry systems. Materials and Methods: Bone mineral density of anterior-posterior lumbar spine (L2-4 level) and femoral neck were measured in 109 women ($55{\pm}11yr$) using two different dual X-ray absorptiometry systems (Lunar EXPERT-XL and Hologic QDR 4500-A). Bone mineral density values measured by two systems, including area, bone mass content, bone mineral density and percentile of young normals were compared and cross-calibration equations between two systems derived. Results: The bone mineral density values of 109 women measured by Lunar system were $0.958{\pm}0.17g/cm^2$ at L2-4 and $0.768{\pm}0.131g/cm^2$ at femur neck, which were significantly higher ($13{\pm}6%$ at L2-4 and $19{\pm}7%$ at femur neck, p<0.001) than those ($0.851{\pm}0.144 g/cm^2$ at L2-4 and $0.649{\pm}0.108 g/cm^2$ at femur neck) by Hologic system. Bone mineral content and percentile of young normals measured by Lunar system were also significantly higher than those by Hologic system (p<0.001), whereas there was no difference in area (p>0.05). There was a high correlation between bone mineral density values of L2-4 and femoral neck obtained with both dual X-ray absortiometry systems (r=0.96 and 0.95, respectively). Cross-calibration equations relating the bone mineral density were Lunar= 1.1287${\times}$Hologic -0.0027 for L2-4 and Lunar= 1.1556${\times}$Hologic+0.0182 for femoral neck. Conclusion: We obtained cross-calibration equations of bone mineral density between Lunar EXPERT-XL and Hologic QDR 4500-A. These equations can be useful in comparing bone mineral density obtained by different dual X-ray absorptiometry systems.

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Modified parity space averaging approaches for online cross-calibration of redundant sensors in nuclear reactors

  • Kassim, Moath;Heo, Gyunyoung
    • Nuclear Engineering and Technology
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    • v.50 no.4
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    • pp.589-598
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    • 2018
  • To maintain safety and reliability of reactors, redundant sensors are usually used to measure critical variables and estimate their averaged time-dependency. Nonhealthy sensors can badly influence the estimation result of the process variable. Since online condition monitoring was introduced, the online cross-calibration method has been widely used to detect any anomaly of sensor readings among the redundant group. The cross-calibration method has four main averaging techniques: simple averaging, band averaging, weighted averaging, and parity space averaging (PSA). PSA is used to weigh redundant signals based on their error bounds and their band consistency. Using the consistency weighting factor (C), PSA assigns more weight to consistent signals that have shared bands, based on how many bands they share, and gives inconsistent signals of very low weight. In this article, three approaches are introduced for improving the PSA technique: the first is to add another consistency factor, so called trend consistency (TC), to include a consideration of the preserving of any characteristic edge that reflects the behavior of equipment/component measured by the process parameter; the second approach proposes replacing the error bound/accuracy based weighting factor ($W^a$) with a weighting factor based on the Euclidean distance ($W^d$), and the third approach proposes applying $W^d$, TC, and C, all together. Cold neutron source data sets of four redundant hydrogen pressure transmitters from a research reactor were used to perform the validation and verification. Results showed that the second and third modified approaches lead to reasonable improvement of the PSA technique. All approaches implemented in this study were similar in that they have the capability to (1) identify and isolate a drifted sensor that should undergo calibration, (2) identify a faulty sensor/s due to long and continuous missing data range, and (3) identify a healthy sensor.

Radiometric Cross Calibration of KOMPSAT-3 and Lnadsat-8 for Time-Series Harmonization (KOMPSAT-3와 Landsat-8의 시계열 융합활용을 위한 교차검보정)

  • Ahn, Ho-yong;Na, Sang-il;Park, Chan-won;Hong, Suk-young;So, Kyu-ho;Lee, Kyung-do
    • Korean Journal of Remote Sensing
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    • v.36 no.6_2
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    • pp.1523-1535
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    • 2020
  • In order to produce crop information using remote sensing, we use classification and growth monitoring based on crop phenology. Therefore, time-series satellite images with a short period are required. However, there are limitations to acquiring time-series satellite data, so it is necessary to use fusion with other earth observation satellites. Before fusion of various satellite image data, it is necessary to overcome the inherent difference in radiometric characteristics of satellites. This study performed Korea Multi-Purpose Satellite-3 (KOMPSAT-3) cross calibration with Landsat-8 as the first step for fusion. Top of Atmosphere (TOA) Reflectance was compared by applying Spectral Band Adjustment Factor (SBAF) to each satellite using hyperspectral sensor band aggregation. As a result of cross calibration, KOMPSAT-3 and Landsat-8 satellites showed a difference in reflectance of less than 4% in Blue, Green, and Red bands, and 6% in NIR bands. KOMPSAT-3, without on-board calibrator, idicate lower radiometric stability compared to ladnsat-8. In the future, efforts are needed to produce normalized reflectance data through BRDF (Bidirectional reflectance distribution function) correction and SBAF application for spectral characteristics of agricultural land.