ANSI-C program: ph_slope_base.c
NAME
ph_slope_base - Subtract/add interferogram flat-Earth phase trend
as estimated from initial baseline.
SYNOPSIS
ph_slope_base <int_in> <SLC-1.par>
<OFF_par> <base> <int_out> [int_type]
[inverse]
| <int_in> | (input) interferogram (FCOMPLEX) or unwrapped phase (FLOAT) (unflattened) |
| <SLC_par> | (input) ISP parameter file for the reference SLC |
| <OFF_par> | (input) ISP offset/interferogram parameter file |
| <base> | (input) baseline file |
| <int_out> | (output) interferogram (fcomplex) or unwrapped interferogram (float) with phase trend subtracted/added |
| <int_type> | interferogram type: 0=unwrapped phase, 1=complex interf. (default=1) |
| <inverse> | subtract/add inversion flag (0=subtract phase ramp, 1=add phase ramp (default=0) |
EXAMPLE
ph_slope_base 1352_1610.int 1352.par 1352_1610.off
1352_1610.base 1352_1610.flt 1 0
ph_slope_base 1352_1610.flt.unw 1352.par 1352_1610.off 1352_1610.base 1352_1610.int.unw 0 1
DESCRIPTION
ph_slope_base reads the input complex (or real valued
unwrapped) interferogram and subtracts/adds the flat-Earth phase
trend calculated from the initial baseline (first two lines of
provided \ baseline file).
The most common use is to remove the flat-Earth phase ramp of a complex valued interferogram (*.int), a process often named interferogram "flattening", and write out the flattened complex valued interferogram (*flt).
The subtracted/added phase ramp is calculated by determining the component of the baseline parallel to the look vector for each point across the range swath.
Removal of the phase ramp is necessary for accurate estimation of the correlation function, and phase unwrapping. This is especially true for larger interferometric baselines with a large range phase trend. This is because high fringe rates violate the assumption that the phase is constant over the region used to estimate the correlation.
For the baseline a time offset (in seconds) can be specified. The time of a specific image time corresponds to the time as specified by the SLC and ISP/offset interferogram parameter files\ plus the indicated time offset.
OPTIONS
ph_slope_base can also be used for unwrapped
interferograms in float format.
Furthermore, instead of subtracting the flat-Earth phase trend it can be added, allowing to invert the interferogram flattening.
SEE ALSO
typedef_ISP.h, SLC_par, OFF_par.
© Copyrights for Documentation, Users Guide and Reference Manual by Gamma Remote Sensing 2003.
UW, CW, last change 21-Aug-2003.