Gamma LAT: Reference Manual

gamma_map

ANSI-C program: gamma_map.c

NAME
gamma_map - Gamma MAP filter for power files of type float (Lopes et al. 1990).

SYNOPSIS
gamma_map <input_data> <output_data> <width> <nlooks> <bx> [by]

<input_data>	input data (file of type float)
<output_data>	output data (file of type float)
<width>	number of samples/row
<nlooks>	number of looks
<bx>	filter size in x direction (number of cols)
[by]	filter size in y direction (number of rows)(default=bx)

EXAMPLE
gamma_map 1352_1610.pwr1 1352_1610.pwr1_gamma_map 2500 4 11 11

INSTALLATION
Source code gamma_map.c in ./src. For compilation adjust and use Makefile: Executable version gamma_map in ../bin

AVAILABILITY
Uses type definition file typedef_ISP.h.

DESCRIPTION
The gamma_map filter performs gamma map filtering. Gamma filtering is primarily used to remove speckle while preserving edges. The Gamma MAP filter was first proposed by Kuan (1987). Lopes (1993) modified the Kuan filter by assuming a gamma distributed scene and setting up two thresholds. Input parameters are the filter box size and number of looks. Different filter sizes will greatly affect the quality of the processed image. If the box size is to small, the noise filtering is not effective. If the filter is too large, fine structures will be lost. The nlooks parameter refers to the number of looks of the radar image. It is used to compute the noise variance.

OPTIONS
Number of looks of input image and userdefined filter window size (odd numbers).

SEE ALSO
typedef_ISP.h, frost frost .

DIAGNOSTICS
All messages are generally self-explanatory.

NOTES
None.