Nowadays, spectrometers are being increasingly used in the remote sensing of the earth system processes and they can be
well conducted field spectral calibrated by using absorption features of atmospheric profile. The spectral calibration
accuracy of an ASD spectrometer in different atmospheric conditions is analyzed in this paper. First of all, set the atsensor
spectral radiance spectrum as the reference spectral curve, which is generated by the MODTRAN5 radiative
transfer model outputs convolved with the spectral response function of each channel. The results can be totally different
when input different water vapor contents. Meanwhile, under the same atmospheric conditions (the same observation
target, the sun elevation angle, azimuth, aerosol distribution, composition and concentration distribution of
atmosphere..etc. ), the diffuser whiteboard is measured by the ASD spectrometer to acquire observed spectral curve. The
best spectral matching algorithm is used to compare the observed spectrum with the reference one. Central wavelength of
the ASD is obtained by calculating the results of matching spectrum shifts within feature spectrum range. Finally,
quantitative analysis and calculation about the effect on the accuracy of instrument spectral calibration with different
water vapor contents is presented.
The hyperspectral imager is able to acquire space and spectral information of ground object
simultaneously. When using a prism splitting mode, different wavelengths of light will disperse nonlinearly in
spectral dimension after going through the slit and the prism. Due to the longer slit and different angles of
incidence, when going through the slit and the prism, the same wavelength of light will curve in space
dimension. For SWIR bands, the maximum shift is more than 1.5 bandwidth. The shift cannot be ignored, for is
alters the pixel spectral and reduces match accuracies between space and spectral information. In this paper, a correction method of non-uniform spectral radiance in hyperspectral image is put forward. First, the
laboratory spectral calibration is performed to acquire center wavelength and full width half maximum (FWHM)
of each band as well as each pixel. Secondly, for each band, the mean of center wavelength which is
calculated according to the results of the spectral calibration is regarded as each pixel's adjusted center
wavelength. For each band and each pixel, calculate the ratio coefficient based on adjacent bands, then
establish a ratio coefficient form of full pixels. At last, correct the image by looking up the form. By using MNF
transformation, a corrected image can be well evaluated, a brightness gradient of the images has been
removed and the phenomenon of image spectral radiance mixing has been reduced greatly, especially at the
edge of the image.
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