Calibration of remote sensing image using BRDF model

Abstract

A new bidirectional reflectance distribution function (BRDF) model of earth objects is established for the calibration of remote sensing image by the national metrology equipment. This model colligates the solar radiance, the atmosphere status, the object type, and the space camera parameter, etc. The output data of this model is the enter radiance data for the space camera. The remote sensing image can be appeared more “true” through this calibration. A kind of ground glass for architecture is measured and the correspond remote sensing image is simulated. After calibrated, the chromatism of this image is improved by 2 and the luminance contrast of that is improved by 3. OCIS codes: 120.0120, 280.0280, 290.0290. doi: 10.3788/COL201210.S11201. The aero camera receives different radiance and emit different wavelength light at the same time for the generation of the remote sensing image. Bidirectional reflectance distribution function (BRDF) combine these incident light, reflect light, and scatter light in one variable and it is the best variable to describe the space radiance performance of objects. The complex BRDF model for remote sensing image is based on the BRDF fundament equation, and colligates the solar radiance, the atmosphere status, the object type, and the space camera parameter, etc. In this model, the solar radiance and it’s change through atmosphere are considered in the incident variable of BRDF, and the proximity effect of atmosphere and the parameters of aero camera are considered for the reflect variable of BRDF, for example, the BRDF performance of aerosol [1] . Then the BRDF value of some typical objects are measured and calibrated. The absolute BRDF value are achieved and simulated using the complex BRDF model. Thus the remote sensing image which is calibrated is achieved. The whole procedure is shown in Fig.1. The basement equation of the complex BRDF model is established by the definition of BRDF as shown in Eq.(1) which defined as the ration of the reflect radiance and the incident irradiance on the appearance of the objects [2] . In Eq.(1), �i represents the incident zenith angle, 'i represents the incident azimuth angle, �r represents the incident zenith angle, 'r represents the incident azimuth angle, � the represents wavelength, Lr(�i,'i,�r,'r,�) represents the reflect radiance at specified angles and wavelength, Ei(�i,'i,�) represents the incident irradiance at specified angles and wavelength. Equation (1) is true in the controllable incident solid angle d i, which is shown in Fig.2. Under this condition, Lr(�i,'i,�r,'r,�) can be simplified to Lr(�r,'r,�). fr(�i,'i,�r,'r,�) = dLr(�i,'i,�r,'r,�) dEi(�i,'i,�) = Lr(�r,'r,�) Ei(�i,'i,�) .