| High temperature target refers to all kinds of ground objects whose temperature is significantly higher than normal temperature(above 500K),including spontaneous combustion coal seam,oil well torch,molten magma,forest fire,etc.The Research on high temperature target identification and temperature inversion method has important theoretical significance and practical value for remote sensing resource investigation,environmental monitoring and disaster early warning.Previous studies have shown that the shortwave infrared remote sensing data has good recognition and temperature inversion effect on the high-temperature target,but the surface high-temperature target is affected by many factors such as landform and surface structure state,resulting in a series of problems such as the spectral radiance received by the remote sensor is not the normal spectral radiance of the high-temperature target,which restricts the accuracy of temperature inversion.The purpose of this study is to find the correlation rules between the spectral radiance direction effect of high-temperature targets of different materials and surface roughness and wavelength,so as to improve the accuracy of temperature inversion.In this paper,graphite plate and 304 stainless steel plate are selected as the representatives of high-temperature targets of different materials.The experimental samples with five levels of surface roughness are prepared respectively.The multi angle observation experiment of high-temperature target(500℃)emission spectrum(observation zenith angle 0°-70°)is carried out in the dark room and room temperature.Taking the normal spectral radiance as the reference,the spectral radiance of hightemperature targets with different materials,different surface roughness and different angles is compared and analyzed by analysis of variance,and the correlation model between spectral radiance ratio of high-temperature targets and observation zenith angle is established by least square method.The experimental observation and data results show that the variance analysis results of the spectral radiance ratio of high-temperature targets with different materials and the same surface roughness at the same observation zenith angle are significantly greater than the F-test threshold;The variance analysis results of spectral radiance ratio of high-temperature targets with different surface roughness of the same material under the same observation zenith angle are significantly greater than the F-test threshold;The variance analysis results of the spectral radiance ratio of the same high-temperature target in different bands and the same observation angle are significantly greater than the F-test threshold;Using (6exp((7)+ (8exp((9)form of exponential function,the spectral radiance ratio of high-temperature targets(graphite plate and 304 stainless steel plate)can be fitted with high precision with the observed zenith angle,and the determination coefficients of the fitting curve are greater than 0.9 and 0.85 respectively.The experimental results show that under the same conditions,the directional effect of spectral radiance of 304 stainless steel plate is more significant than that of graphite plate(the spectral radiance ratio has a more significant downward trend with the increase of observed zenith angle);Under the same condition,the directional effect of spectral radiance of high-temperature targets with different surface roughness is significantly different.With the increase of surface roughness,the directional effect of spectral radiance decreases gradually;The directional effect of spectral radiance of the same high-temperature target is also different in different bands.With the increase of wavelength,the directional effect of spectral radiance decreases gradually;In the short wave infrared band,the spectral radiance ratio of graphite plate and 304 stainless steel plate with different surface roughness shows an exponential correlation model with the observed zenith angle.Therefore,the influence of target material,surface roughness and wavelength must be considered in temperature inversion. |
