If ASAS data are available for a particular area, model inversions can be performed using walthall, which yields images containing the BRDF model parameter information for each pixel. If a TM scene of the same area is available, this can be classified using the spectral information available in each pixel of the ASAS images of the same region (see miniDist(1)). If every pixel of the ASAS images are assigned a separate class, then the model parameters produced by walthall can be directly related to these classes. A control file can be constructed (see getModelParams) with each class containing the model parameter information for a single pixel in the ASAS images. These parameters are then mapped through to the corresponding classes in the TM scene.
# comment, or information about file
CLASS 0 X X X X # class name
CLASS 1 X X X X # class name
CLASS 2 X X X X # class name
CLASS 3 X X X X # class name
CLASS 4 X X X X # class name .br.br . . . . . . .br.br . . . . . . .br.br . . . . . . .br.br
The initial comment line is ignored, and is for the users information only, as are the comments or names following each class. The X's obvioulsy represent the DN value for each class, in each band (4 bands in this case). A null class (CLASS 0) can also be used. Checks are made to ensure that the number of bands specified is the same on each line, and also that the number of separate classes actually present in the image is not greater than the number listed in the control file.