Roujean

The BRDF object that implements the algorithm developed by Roujean et al. 1992. The algorithm is suitable for surface reflectance from a variety of terrains and is based upon three parameters, k0, k1 and k2 which the user must know a-priori or derive from measurements. The reader is referred to their paper for complete details.

Example

import sasktranif.sasktranif as skif
import math

brdf = skif.ISKBrdf('Roujean')
brdf.SetProperty('SetPredefinedParameters', 8);
mjd            = 52393.3792987115;
location       = [0.0, 0.0, 25000.0, mjd];
mu_in          = math.cos( math.radians( 30.0 ) )
mu_out         = math.cos( math.radians( 60.0 ) )
cosdphi        = math.cos( mat.radians( 150.0 ) )
[ok,brdfvalue] = brdf.BRDF( 600.0, location, 0.6, 0.7, -0.8)

Properties

BRDFParameters( param:array)

A 3 element array containing the 3 parameters of the Roujean distribution. For examples see Table 1 of Roujean et al. 1992.

n	Setting
parameters[0]	k0
parameters[1]	k1
parameters[2]	k2

SetPredefinedParameters( code: int )

An integer value that loads the Roujean BRDF parameters from an internal table of values. The table replicates the values published in Table 1 of Roujean et al. 1992. The table provides a visible setting (580 nm to 680 nm) and a near infra-red (NIR) setting (730 nm to 1100 nm). Pass in the appropriate code from the table below to select the appropriate BRDF setting

Terrain	Visible Code	NIR Code
PLOWED FIELD	1	21
ANNUAL GRASS	2	22
HARD WHEAT	3	23
STEPPE	4	24
CORN	5	25
ORCHARD GRASS	6	26
IRRIGATED WHEAT	7	27
PINEFOREST	8	28
DECIDUOUS FOREST	9	29
SOYBEAN	10	30
GRASS LAWN	11	31

References

Roujean, J.L., M. Leroy, and P.Y. Deschamps, “A bidirectional reflectance model of the Earth’s surface for the correction of remote sensing data”, J. Geophys. Res., 97, D18, 20455-20468, (1992), doi:10.1029/92JD01411.