This is an old topic for more than ten years to retrieve land surface temperature (LST) from satellite data, but it has not been solved yet. At first, people tried to transplant traditional split window method of sea ...This is an old topic for more than ten years to retrieve land surface temperature (LST) from satellite data, but it has not been solved yet. At first, people tried to transplant traditional split window method of sea surface temperature (SST) to the retrieval of LST, but it was found that the emissivities of land surface (εi) must be involved in atmospheric correction. Then many different formulas appeared with assumption of emissivities known. In fact, emissivities of land surface with pixel size cannot be known beforehand because of various reasons, so in recent years the focus of attention has been transferred to retrieving emissivities (εi) and LST at the same time. Therefore, we have to solve missing equations problem. For this some people try to introduce middle infrared information, but new problems will be brought in which means that it is very difficult to describe middle infrared BRDF of targets with high accuracy and the scattering of atmospheric aerosol cannot be ignored. Therefore a different way is offered to solve this problem only using two thermo-infrared bands data based on three assumptions, constant emissivities in two measurements, and the same atmospheric parameters for neighbouring pixels and the difference of emissivity (Δε) of two channels can be known beforehand. Results of digital simulations show that it is possible to retrieve LST with its root mean square (RMS) of errors less than 1 K and RMS of relative error of ground radiance at 7% if the error of atmospheric temperature at ± 2°C and the relative error of atmospheric water vapor at ± 10% can be satisfied. Results have been confirmed by initial field test.展开更多
The Large Field of View Airborne Infrared Scanner is a newly developed multi-spectral instrument that collects images from the near-infrared to long-wave infrared channels.Its data can be used for land surface tempera...The Large Field of View Airborne Infrared Scanner is a newly developed multi-spectral instrument that collects images from the near-infrared to long-wave infrared channels.Its data can be used for land surface temperature(LST)retrieval and environmental monitoring.Before data application,quality assessment is an essential procedure for a new instrument.In this paper,based on the data collected by the scanner near the Yellow River in Henan Province,the geometric and radiometric qualities of the images are first evaluated.The absolute geolocation accuracy of the ten bands of the scanner is approximately 5.1 m.The ground sampling distance is found to be varied with the whisk angles of the scanner and the spatial resolution of the images.The band-to-band registration accuracy between band one and the other nine bands is approximately 0.25 m.The length and angle deformations of the ten bands are approximately 0.67%and 0.3°,respectively.The signal-to-noise ratio(SNR)and relative radiometric calibration accuracy of bands 4,9,and 10 are relatively better than those of the other bands.Secondly,the radiative transfer equation(RTE)method is used to retrieve the LST from the data of the scanner.Measurements of in situ samples are collected to evaluate the retrieved LST.Neglecting the samples with unreasonable retrieved LST,the bias and RMSE between in situ LST measured by CE312 radiometer and retrieved LST are−0.22 K and 0.94 K,and the bias and RMSE are 0.27 K and 1.59 K for the InfReC R500-D thermal imager,respectively.Overall,the images of the Large Field of View Airborne Infrared Scanner yield a relatively satisfactory accuracy for both LST retrieval and geometric and radiometric qualities.展开更多
Deriving LST from satellite radiative measurements is desirable, but the accurate determination of LST is very difficult, whcih is related to the atmospheric effect, the nonuniformity of land surface and the coupling ...Deriving LST from satellite radiative measurements is desirable, but the accurate determination of LST is very difficult, whcih is related to the atmospheric effect, the nonuniformity of land surface and the coupling between surface temperature and emissivity. In particular, the coupling between the land surface temperature and emissivity constructs a severe obstacle for the accurate determination of LST, because at present, the knowledge about global and surface emissivity is still very deficient. Based on the assumption that the change of emissivity is normally negligible in a short period of time a two_channel method is proposed to determine LSTs and emissivities, simultaneously, in which a set of measurement data of two channels made at two different time, day and night or two continuous days or nights, are used. If there are emissivity variations in two time measurements, with the relative changes of emissivities for different channels being the same, then a three_channel method can be used to determine land surface temperautre and emssivity simultaneously.展开更多
文摘This is an old topic for more than ten years to retrieve land surface temperature (LST) from satellite data, but it has not been solved yet. At first, people tried to transplant traditional split window method of sea surface temperature (SST) to the retrieval of LST, but it was found that the emissivities of land surface (εi) must be involved in atmospheric correction. Then many different formulas appeared with assumption of emissivities known. In fact, emissivities of land surface with pixel size cannot be known beforehand because of various reasons, so in recent years the focus of attention has been transferred to retrieving emissivities (εi) and LST at the same time. Therefore, we have to solve missing equations problem. For this some people try to introduce middle infrared information, but new problems will be brought in which means that it is very difficult to describe middle infrared BRDF of targets with high accuracy and the scattering of atmospheric aerosol cannot be ignored. Therefore a different way is offered to solve this problem only using two thermo-infrared bands data based on three assumptions, constant emissivities in two measurements, and the same atmospheric parameters for neighbouring pixels and the difference of emissivity (Δε) of two channels can be known beforehand. Results of digital simulations show that it is possible to retrieve LST with its root mean square (RMS) of errors less than 1 K and RMS of relative error of ground radiance at 7% if the error of atmospheric temperature at ± 2°C and the relative error of atmospheric water vapor at ± 10% can be satisfied. Results have been confirmed by initial field test.
基金supported by the National Natural Science Foundation of China(Grant Nos.42171363,41804166,and 41971299)High-Resolution Earth Observation Major Special Aviation Observation System(No.30-H30C01-9004-19/21)+1 种基金the Shanghai Municipal Science and Technology Major Project(No.2021SHZDZX0100)the Shanghai Municipal Commission of Science and Technology Project(No.19511132101).
文摘The Large Field of View Airborne Infrared Scanner is a newly developed multi-spectral instrument that collects images from the near-infrared to long-wave infrared channels.Its data can be used for land surface temperature(LST)retrieval and environmental monitoring.Before data application,quality assessment is an essential procedure for a new instrument.In this paper,based on the data collected by the scanner near the Yellow River in Henan Province,the geometric and radiometric qualities of the images are first evaluated.The absolute geolocation accuracy of the ten bands of the scanner is approximately 5.1 m.The ground sampling distance is found to be varied with the whisk angles of the scanner and the spatial resolution of the images.The band-to-band registration accuracy between band one and the other nine bands is approximately 0.25 m.The length and angle deformations of the ten bands are approximately 0.67%and 0.3°,respectively.The signal-to-noise ratio(SNR)and relative radiometric calibration accuracy of bands 4,9,and 10 are relatively better than those of the other bands.Secondly,the radiative transfer equation(RTE)method is used to retrieve the LST from the data of the scanner.Measurements of in situ samples are collected to evaluate the retrieved LST.Neglecting the samples with unreasonable retrieved LST,the bias and RMSE between in situ LST measured by CE312 radiometer and retrieved LST are−0.22 K and 0.94 K,and the bias and RMSE are 0.27 K and 1.59 K for the InfReC R500-D thermal imager,respectively.Overall,the images of the Large Field of View Airborne Infrared Scanner yield a relatively satisfactory accuracy for both LST retrieval and geometric and radiometric qualities.
文摘Deriving LST from satellite radiative measurements is desirable, but the accurate determination of LST is very difficult, whcih is related to the atmospheric effect, the nonuniformity of land surface and the coupling between surface temperature and emissivity. In particular, the coupling between the land surface temperature and emissivity constructs a severe obstacle for the accurate determination of LST, because at present, the knowledge about global and surface emissivity is still very deficient. Based on the assumption that the change of emissivity is normally negligible in a short period of time a two_channel method is proposed to determine LSTs and emissivities, simultaneously, in which a set of measurement data of two channels made at two different time, day and night or two continuous days or nights, are used. If there are emissivity variations in two time measurements, with the relative changes of emissivities for different channels being the same, then a three_channel method can be used to determine land surface temperautre and emssivity simultaneously.
