Gamma ISP: Reference Manual

rascc_mask

ANSI-C program: rascc_mask.c

NAME
rascc_mask - Generate phase unwrapping validity mask using correlation and intensity

SYNOPSIS
rascc_mask <cc> <pwr> <width> [start_cc] [start_pwr] [nlines] [pixavr] [pixavaz] [cc_thres] [pwr_thres] [cc_min] [cc_max] [scale] [exp] [LR] [rasf]

<cc>	(input)coherence image (float)
<pwr>	(input)intensity image (float, enter - if not available)
<width>	number of samples/row
[start_cc]	starting line of coherence image (default=1)
[start_pwr]	starting line of intensity image (default=1)
[nlines]	number of lines to display (default=0: to end of file)
[pixavr]	number of pixels to average in range (default=1)
[pixavaz]	number of pixels to average in azimuth (default=1)
[cc_thres]	coherence threshold for masking, all pixels with coherence below cc_thres are set to (0,0,0)
[pwr_thres]	intensity threshold, pixels with relative intensity below pwr_thres are set to 0 (default: 0.)
[cc_min]	minimum coherence value used for color display (default=.1)
[cc_max]	maximum coherence value used for color display (default=.9)
[scale]	intensity image display scale factor (default=1.)
[exp]	intensity display exponent (default=.35)
[LR]	left/right flipping flag, (default=1: normal, -1: mirror image)
[rasf]	(output)validity mask (default=.ras: SUN raster format, .bmp: BMP format)

EXAMPLES

rascc_mask 01608_02109.cc 01608_02109.pwr1 2456 1 1 0 1 1 .3

Generates an (8-bit) SUN rasterfile to be used as validity mask for phase unwrapping. The coherence threshold has been set at 0.3. The output validity mask is a combined coherence and intensity display with all samples of the image with coherence below the threshold set to 0.

rascc_mask 01608_02109.cc 01608_02109.pwr1 2456 1 1 0 1 1 .3 .1

Generates an (8-bit) SUN rasterfile to be used as validity mask for phase unwrapping. The coherence threshold has been set at 0.3 and the relative power threshold to 0.0. The output validity mask is a combined coherence and intensity display with all samples of the image with coherence below the threshold or relative intensity below the threshold set to 0.

DESCRIPTION
rascc_mask generates an (8-bit) SUN rasterfile to be used as validity mask for phase unwrapping. The output validity mask is a combined coherence and intensity display with all samples of the image with coherence below the thresholds set to 0. The user can select thresholds for both correlation and relative intensity.

The validity mask is used for phase unwrapping with the program mcf, which allows to avoid regions of high phase noise in the phase unwrapping.
The hue of the output image is determined by the coherence level. If the user specifies an intensity image, this image is used for the image intensity, otherwise, the output image has a constant intensity except for masked regions. All pixels corresponding to pixels with a coherence or intensity below the threshold values are set to black, i.e. (0,0,0). The intensity threshold is useful to eliminate regions of very low signal that may contain coherent interferance. If the interference is coherent, then the correlation is high and these unwanted points would be within the unwrapping mask unless there is a theshold for minimum signal intensity.

For the normal use of the program, i.e. to generate a validity mask for phase unwrapping the starting lines need to be set to 1 (start at first line), the number of lines needs to be set to the total number of lines (the default=0 can be used for this), the range and azimuth averaging (pixavr, pixavaz) need to be set to 1, and no left/right flipping needs to be selected (i.e. LR=1). Setting these values differently results in a modification of the image geometry which will then no longer correspond to the one of the interferogram to be unwrapped.

OPTIONS
One reason for data masking is to reduce the number of samples considered in the global optimization step of the Minimum Cost Flow (MCF) phase unwrapping technique. Additional, reduction of the number of samples can be achieved using adaptive thinning of the sampling, i.e. by reducing the sampling in areas with little phase variation, as supported by the program rascc_mask_thinning.

SEE ALSO
mcf, rascc_mask_thinning, interp_ad