Eccentric angle between IMU and the collimation axis of airborne sensor is one of main reasons causing geometric correction error. Currently, the application of the hyperspectral and LIDAR integrated system are greatly affected by lack of universal calibration methods which can calibrate the hyperspectral data and LiDAR data simultaneously. An eccentric angle calibration model for hyperspectral and LiDAR integrated system is proposed, meanwhile a self-calibration method using “#” shaped flight strip is designed to validate the new calibration model. Firstly, the homogeneous points are searched from all geometrically corrected flight strips by automatic matching methods. Secondly, control points obtained by averaging the coordinates of the homogeneous points are applied to solve the calibration model to get the eccentric angle. Finally, the point clouds are corrected geometrically with the solved eccentric angle, then the above steps are repeated until the solved eccentric angles are stable. An experiment was carried to testify the new calibration model and resolving method, which shows that the proposed model is of high-precision, validity and the resolving method is of fast convergence. The airborne sensors can acquire a plane precision of 0.807 m (about 1.2 pixels) without any ground control points, and the LiDAR can acquire a plane precision of 0.437 m and elevation precision of 0.15m.
The inherent optical property is a significant bridge between the hyperspectral remote sensing data and water color and water quality parameters. Based on the water optical radiation transfer process and existing quasi-analytical algorithm (QAA), this study provides an improved algorithm, namely a linear spectral backscattering coefficient constraint quasianalytical algorithm (LSBCC-QAA), suitable for the retrieval of inherent optical properties for turbid inland waters to address the deficiency of the QAA on the retrieval of inherent optical properties for turbid inland waters. LSBCC-QAA uses the water-leaving reflectance of the bands between 1600 and 1700 nm to estimate the water surface reflectance of the bands between 400 and 900 nm and selects 700~850 nm as the reference wavelengths to estimate the water backscattering coefficients, taking full advantage of the continuity of the backscattering coefficient spectrum. The preliminary validated results show that the particle absorption coefficient, particle backscattering coefficient and phytoplankton absorption coefficient retrieved by LSBCC-QAA are more consistent with the actual situation than those retrieved by the common QAA_v6 algorithm or QAA-Turbid algorithm. Compared with the measured particle diffuse attenuation coefficient, the error of the LSBCC-QAA retrieved particle diffuse attenuation coefficient ranges from 16.0% to 22.9%, and the average error is 18.4%.
Accurate radiometric calibration for thermal infrared hyperspectral data is the precondition for further quantitative applications. A thermal infrared hyperspectral field calibration method which is based on non-uniformity repair had been proposed in this paper. Firstly correct global non-uniformity phenomenon caused by detector response difference, with moment matching algorithm; Secondly correct local non-uniformity phenomenon caused by the environment changes, with department moment matching algorithm; thirdly design an aviation experimental, use outfield target to calculate every band’s calibration coefficient. The thermal infrared hyperspectral field experiments show that this method can effectively eliminate the phenomenon of non-uniformity of thermal infrared hyperspectral images, and get high accuracy radiometric calibration results.
Majority of pixels, in the nature, are non-isothermal in three dimensions, especially for the pixels in meter-scale, tens- meter-scale or hundreds-meter-scale which are paid extensive attention by the researchers in geoscience field. The three-dimensional non-isothermal phenomenon even exists in some pixels in centimeter-scale. For the geosciencific researches, it is significant to determine the component temperatures of a pixel precisely. The airborne WSIS (Wide Spectrum Imaging Spectrometer) data with VNIR (visible-near infrared), SWIR (short-wave infrared) and TIR (thermal infrared) bands were used in the study. First, the components of all the pixels in the image were determined by the linear mixing method. Second, each component emissivity of each pixel was calculated based on an emissivity priori knowledge base. Last, a temperature and emissivity separation algorithm was used to inverse the mean temperature of each pixel, regarded as initial value, the Planck function was linearized to construct a multi-band equation set, and the component temperatures of every pixel were inversed by the Bayesian retrieval technique. The results suggest that the inversion precision of the pixel component temperatures is improved effectively by the Bayesian retrieval technique with the assistance of the VNIR and SWIR hyperspectral remote sensing data.
The cooling water discharged from the coastal plants flow into the sea continuously, whose temperature is higher than original sea surface temperature (SST). The fact will have non-negligible influence on the marine environment in and around where the plants site. Hence, it’s significant to monitor the temporal and spatial variation of the warm-water discharge for the assessment of the effect of the plant on its surrounding marine environment. The paper describes an approach for the dynamic monitoring of the warm-water discharge of coastal plants based on the airborne high-resolution thermal infrared remote sensing technology. Firstly, the geometric correction was carried out for the thermal infrared remote sensing images acquired on the aircraft. Secondly, the atmospheric correction method was used to retrieve the sea surface temperature of the images. Thirdly, the temperature-rising districts caused by the warm-water discharge were extracted. Lastly, the temporal and spatial variations of the warm-water discharge were analyzed through the geographic information system (GIS) technology. The approach was applied to Qinshan nuclear power plant (NPP), in Zhejiang Province, China. In considering with the tide states, the diffusion, distribution and temperature-rising values of the warm-water discharged from the plant were calculated and analyzed, which are useful to the marine environment assessment.
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