Abstract
The wide field of view (WFV) is an optical imaging sensor on-board the Gao Fen 1 (GF-1). The WFV lacks an on-board calibrator, so on-orbit radiometric calibration is required. Zhong et al. proposed a method for cross-calibrating the charge-coupled device on-board the Chinese Huan Jing 1 (HJ-1/CCD) that can be applied to the GF-1/WFV. However, the accuracy is limited because of the wider radiometric dynamic range and the higher spatial resolution of the GF-1/WFV. Therefore, Landsat-8 Operational Land Imager (OLI) imagery with a radiometric resolution similar to that of the GF-1/WFV and DEM extracted from ZY-3 three-line array panchromatic camera (TLC) with a higher spatial resolution were used. A calibration site with uniform surface material and a natural topographic variation was selected, and a model of this site’s bidirectional reflectance distribution function (BRDF) was developed. The model has excellent agreement with the real situation, as shown by the comparison of the simulations to the actual OLI surface reflectance. Then, the model was used to calibrate the WFV. Compared with the TOA reflectance from synchronized Landsat-8/OLI images, all errors calculated with the calibration coefficients retrieved in this paper are less than 5%, much less than the errors calculated with the calibration coefficients given by the China Centre for Resource Satellite Data and Application (CRESDA).
Highlights
The wide field of view (WFV) camera is one of the key instruments operating on the Gao Fen 1 (GF-1)satellite, launched by the China Centre for Resource Satellite Data and Application (CRESDA) on 27 April 2013
3 a fGF ( )d / fOLI ( )d where α is the spectral matching factor; λ is the spectral wavelength; ρλ is the ground-measured spectrum of the desert at the calibration site, which is plotted in Figure 4; fGF (λ) and fGF (λ) are the relative spectral response functions for GF-1/WFV and Landsat-8/Operational Land Imager (OLI), respectively. λ1-λ2 is the spectral range of GF-1/WFV; λ3-λ4 is the spectral range of Landsat-8/OLI
The updated cross-calibration method uses DEM data extracted by the ZY-3/three-line array panchromatic camera (TLC), which has a higher spatial resolution than the ASTER GDEM product, so more accurate cross-calibration results can be obtained with the updated method
Summary
The wide field of view (WFV) camera is one of the key instruments operating on the Gao Fen 1 (GF-1)satellite, (hereafter, the WFV camera on-board the GF-1 satellite is written as GF-1/WFV), launched by the China Centre for Resource Satellite Data and Application (CRESDA) on 27 April 2013. The wide field of view (WFV) camera is one of the key instruments operating on the Gao Fen 1 (GF-1). The GF-1 satellite has four WFV cameras and two panchromatic cameras on-board. For WFV cameras, the nominal spatial resolution is 16 m. The GF-1 has the highest performance of all satellites launched by China up to now due to its perfect combination of higher spatial and spectral resolution. As the HJ-1/CCD does, the GF-1/WFV lacks on-board calibration capabilities, which would limit the applications of the data. To better use the GF-1/WFV data quantitatively, alternative calibration methods need to be developed. The radiometric capability is not always stable for a whole year because the WFV cameras are not the state-of-the-art instruments. The frequency of vicarious calibration needs to be increased as the instruments age
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