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

atm_mod_pt

ANSI-C program: atm_mod_pt.c

NAME
atm_mod_pt - Perform linear regression of atmospheric phase with respect to height

SYNOPSIS
atm_mod_pt <plist> <pmask> <patm> <phgt> <pmod> [rec_num]

<plist>	(input) point list (int)
<pmask>	(input) point data stack of mask values (uchar, set to - to accept all points)
<patm>	(input) unwrapped phase point data stack (float)
<phgt>	(input) heights at the points (float)
<pmod>	(output) modelled phase values from the regression of phase with respect to height (float)
[rec_num]	record number in pdata to process (default -: all records)

EXAMPLE
atm_mod_pt plist pmsk1 pres1 phgt pmod -

determines the linear regression coefficients of the residual phase with respect to height for all layers in the pres1 stack

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

DESCRIPTION
This program is used to determine the height dependence of the residual phase during interferometric point target analysis. Depending on atmospheric conditions there is an altitude dependence of the path delay with respect to altitude caused by changes in the atmospheric water vapor and preassure profiles between the acquisitions of the interferometric image pair. For each interferogram in the stack, atm_mod_pt estimates the parameters of a linear model of the residual phase with respect to the altitude values in the input height stack phgt. The model consists of a phase constant a0 in radians and phase slope a1 in unitis of radians per meter.

It is important that only phase due to atmosphere is present in the points used to estimate the regression coefficients. For this reason the point mask should be used to exclude points with deformation from consideration in the regression. If there are insuffient points to perform the regression, then the coefficients are set 0.0.

The output stack pmod has the height dependent unwrapped phase as determined from the regression: pmod [i] = a0 + a1*hgt[i]. The program sub_phase_pt can then be used to remove the modelled phase from all the points in the stack. The phase model is calculated for all points where valid height values are available not just those in the mask. Valid heights are defined as non-zero values in the set of point heights.

SEE ALSO
sub_phase_pt