GAMMA Interferometric Point Target Analysis Software (IPTA): Reference Manual

ph_offset

ANSI-C program: ph_offset.c

NAME
ph_offset - determine phase bias of an interferogram by averaging a rectangular region and subtract (float or fcomplex format)

SYNOPSISusage: ph_offset <f1> <f2> <width> <dtype> <roff> <loff> [nr] [nl] [offset]

<f1>	`(input) input data file (float or fcomplex format)`
<f2>	`(output) average of input data files (float or fcomplex format)`
<width>	`number of samples/line`
<dtype>	`data type (0:fcomplex 2:float(unwrapped)`
<roff>	`range pixel offset to center of reference region (enter - for none)`
<loff>	`line offset to center of reference region (enter - for none)`
<nr>	`number of range pixels to average in the reference region (default = 16)`
<nl>	`number of lines average in the reference region (default= 16)`
<offset>	`additional phase offset (radians, default = 0.0)`

<>EXAMPLE
ph_offset f1 f2 2456 0 1000 1500 32 32
Evalate average of complex interferogram at location 1000,1500 with a 32x32 rectangle. Subtract the phase of this average from the
complex interferogram f1 to produce f2.

INSTALLATION
Source code ph_offset.c in ./IPTA/src, executable version ph_offset in ./IPTA/bin

DESCRIPTION
ph_offset is a program program that is used to estimate and subtract a phase offset for an interferogram. The average phase value is estimated from samples within a rectangular window with center specified by command line parameters roff and loff. The size of the window is specified to nr pixels wide and nl lines centered about (roff,loff). The phase of this average is subtracted from the entire image. In the case of float data, the image values are assumed to be unwrapped phase, while for fcomplex, data the phase is obtained by taking atan(imag, real).

This program is used to create a common phase reference for a stack of differential interferograms. The program is run with the same reference point location for each interferogram in the stack. In this way the processed interferograms will have a common reference point and zero reference phase.

The user can also specify a constant phase offset on the command line for the entire image.

OPTIONS
none.

SEE ALSO
ipta.h.