Use this procedure to synthesize an AIRSAR image from a compressed stokes matrix.

Syntax

ENVI_DOIT, 'AIRSAR_SYNTH_DOIT', COMBO=array, DIMS=array, /DO_SQRT, FNAME=string array, FNL=integer, FNS=integer, GENFAC=array, /IN_MEMORY [, MAX_VAL=value], OFFSET=array, OUT_NAME=string, OUT_DT={1 | 4}, R_FID=variable, /SIGMA_ZERO, /STDMULT, TOTAL_POWER=array, XFAC=value, YFAC=value

Keywords

COMBO

Use this keyword to specify a 5 x n array of ellipticity and orientation angles for each image synthesized. The format for the array is:

  • [0, i]: Transmit ellipticity for ith image
  • [1, i]: Transmit orientation for ith image
  • [2, i]: Receive ellipticity for ith image
  • [3, i]: Receive orientation for ith image
  • [4, i]: Stokes band number (0=C, 1=L, 2=P)

DIMS

The “dimensions” keyword is a five-element array of long integers that defines the spatial subset (of a file or array) to use for processing. Nearly every time you specify the keyword FID, you must also specify the spatial subset of the corresponding file (even if the entire file, with no spatial subsetting, is to be processed).

  • DIMS[0]: A pointer to an open ROI; use only in cases where ROIs define the spatial subset. Otherwise, set to -1L.
  • DIMS[1]: The starting sample number. The first x pixel is 0.
  • DIMS[2]: The ending sample number
  • DIMS[3]: The starting line number. The first y pixel is 0.
  • DIMS[4]: The ending line number

To process an entire file (with no spatial subsetting), define DIMS as shown in the following code example. This example assumes you have already opened a file using ENVI_SELECT or ENVI_PICKFILE:

  envi_file_query, fid, dims=dims

DO_SQRT

Set this keyword to calculate the square root of the data before converting to byte. Use this keyword when OUT_DT=1 (byte).

FNAME

Use this keyword to specify a three-element string array of compressed stokes matrix file names for C, L, and P bands, respectively. If you do not use a file, set the array element to ' '.

FNL

Use this keyword to specify the number of lines in the AIRSAR image.

FNS

Use this keyword to specify the number of samples per line in the AIRSAR image.

GENFAC

Use this keyword to specify an array of COMP SCALE FACTORS for each of the files specified by FNAME.

IN_MEMORY

Set this keyword to specify that output should be stored in memory. If you do not set IN_MEMORY, output will be stored on disk and you must specify OUT_NAME (see below).

MAX_VAL (optional)

Use this keyword to set a maximum value for output data.

OFFSET

Use this keyword to specify an array of long integers representing header offsets for each of the files specified by FNAME.

OUT_DT

This keyword indicates the IDL data type of the output data. Set the keyword to one of the following integer values:

  • 1: Byte (8 bits)
  • 4: Floating-point (32 bits)

OUT_NAME

Use this keyword to specify a string with the output filename for the resulting data. If you set the keyword IN_MEMORY, you do not need to specify OUT_NAME.

R_FID

Use this keyword to specify a named variable that contains the file ID for the processed data. You can use this file ID to access the processed data.

SIGMA_ZERO

Set this keyword to convert the output values to sigma zero, 10*log10(data).

STDMULT

Set this keyword to specify the standard deviation multiplier for byte output data types. Plus and minus the STDMULT determines the output minimum and maximum.

TOTAL_POWER

Use this keyword to specify a three-element array of ones and zeros indicating whether the total power should be computed for the C, L, and P bands. A value of 1 causes the synthesis of the total power image.

XFAC

Use this keyword to specify an x subsampling factor used to compute image data statistics prior to the conversion to byte. Use this keyword when OUT_DT=1 (byte).

YFAC

Use this keyword to specify a y subsampling factor used to compute image data statistics prior to the conversion to byte. Use this keyword when OUT_DT=1 (byte).

API Version

4.2