.. _brdf_rahman: Rahman ====== This is a semi-empirical model with 3 parameters, designed to model the reflectance of arbitrary natural surfaces in the visible and near-infrared bands. This is one of eight BRDF kernels listed by Spurr in his 2002 paper. Equation A.18 from Spurr is implemented with the following changes: * cos(phi) is replaced with -cos(phi) * the reflectance is divided by pi Example ------- :: import sasktranif.sasktranif as skif import math brdf = skif.ISKBrdf('RAHMAN') mjd = 52393.3792987115; location = [0.0, 0.0, 25000.0, mjd]; [ok,brdfvalue] = brdf.BRDF( 600.0, location, 0.6, 0.7, -0.8) Properties ----------- .. py:module:: BRDF_RAHMAN BRDFParameters ^^^^^^^^^^^^^^ .. py:function:: BRDFParameters( array param) A 3 element array containing the 3 parameters of the Rahman distribution. ================ ======================================================== n Setting ================ ======================================================== parameters[0] :math:`\rho` parameters[1] :math:`\theta` parameters[2] :math:`k` ================ ======================================================== References ----------- **Rahman H**, Pinty B, Verstraete M. "Coupled surface atmosphere reflectance (CSAR) model: 2. Semi-empirical surface model usable with NOAA AVHRR data.", *J Geophys Res* 1993; 98:20,791–801. **Robert J. D. Spurr**, "A new approach to the retrieval of surface properties from earthshine measurements", *Journal of Quantitative Spectroscopy & Radiative Transfer*, vol. 83, pp. 15-46, Oct. 9, 2002. doi:10.1016/S0022-4073(02)00283-2 url: `http://www.sciencedirect.com/science/article/pii/S0022407302002832 `_