Gamma LAT: Reference Manual

ISP offset/processing parameter file: <date_date>.off

(text-file)

NAME
<date_date>.off - contains parameter values used by the Interferometric SAR Processor ISP. The ISP offset/processing parameter file contains the information on the co-registration of the SLC image pair, the image section to be processed, and parameters used or determined during the interferometric processing.

SYNOPSIS
Non-executable. May be created using create_offset.

EXAMPLE


GAMMA Interferometric SAR Processor (ISP) - Parameters associated
with ISP processing and offsets between SLC image pair

title:     Death Valley, 8059_8560, 5-look complex data
initial_range_offset:                  -11
initial_azimuth_offset:                  1
slc1_starting_range_pixel:              12
number_of_slc_range_pixels:           4900
offset_estimation_starting_range:      128
offset_estimation_ending_range:       4784
offset_estimation_range_samples:        32
offset_estimation_range_spacing:       146
offset_estimation_starting_azimuth:    512
offset_estimation_ending_azimuth:     4817
offset_estimation_azimuth_samples:      16
offset_estimation_azimuth_spacing:     270
offset_estimation_window_width:         12
offset_estimation_window_height:        12
offset_estimation_threshhold:         3.00
range_offset_polynomial:     -1.0508e+01  -3.6019e-04   9.8214e-05
azimuth_offset_polynomial:    2.1188e+00  -9.8766e-05  -4.5460e-06
slc1_starting_azimuth_line:            100
interferogram_azimuth_lines:          2520
interferogram_width:                  2450
first_nonzero_range_pixel:               8
number_of_nonzero_range_pixels:       2439
interferogram_range_looks:               2
interferogram_azimuth_looks:             2
interferogram_range_pixel_spacing:       15.81184   m
interferogram_azimuth_pixel_spacing:     39.96044   m
resampled_range_pixel_spacing:            0.00000   m
resampled_azimuth_pixel_spacing:          0.00000   m
resampled_starting_ground_range:          0.00000   m
resampled_pixels_per_line:               0

(Example represents state as it occurs after the co-registration, interferogram generation and removal of the phase trend, but before the derivation of the terrain heights. Therefore, some values at the end of the file are not yet determined (set to zero).

FORMATS AND DEFINITIONS
The formats are defined in ISP type definition file typedef_ISP.h.

char title[128]	ASCII string with title of the interferogram
int initr, initaz	initial slant range and azimuth offset estimates (integer number of complex pixels). With an identical object having the (slant range, azimuth) coordinates (268,1805) in SLC-1 and (250,1930) in SLC-2 the offset estimates are -18 and 125 for range and azimuth, respectively.
int nofstr, npr:	Slant range of first range sample to be used for interferogram, width of interferogram (number of samples in slant range direction) to process.
int rstr, rend, nr:	Sampling for precision co-registration: starting range sample, ending range sample, number of samples in range direction (range values are relative to the selected interferogram, i.e. for an interferogram with a width of 800 pixels starting at range pixel 1035 (relative to SLC-1) the range interval (rstr,rend)=(50,750) is a reasonable choice).
int azstr, azend, naz	Sampling for precision co-registration: starting azimuth sample, ending azimuth sample, number of samples in azimuth direction (azimuth values are relative to SLC-1).
int rwin, azwin	search window size in range, azimuth pixels (centered at initial offset estimate) used to estimate offset at each sample.
double thres	fringe SNR threshold to save offset estimate or discard.
double rpoly[MAR]	range offset as a bi-linear function of range and azimuth. range coordinate is relative to first range pixel of interferogram (nofstr). azimuth coordinate is relative to SLC-1.
double azpoly[MAAZ]	azimuth offset as a bi-linear function of range and azimuth. range coordinate is relative to first range pixel of interferogram (nofstr). azimuth coordinate is relative to SLC-1.
int lbegin, nls	starting azimuth in interferogram (relative to start of SLC-1), number of (multi-look) interferogram lines.
int nr, nrb, nrps	Number of range pixels, range coordinate of first non-zero interferogram pixel (relative to range of first interferogram pixel), number of non-zero interferogram pixels in range direction.
int rlks, azlks	number of interferometric looks in range and azimuth.
double rps_int, azps_int	interferogram sample spacing (meters) in slant range and azimuth direction
double rps_res, azps_res	true ground range and azimuth spacing (meters) in resampled height map
double grg_start	starting ground range relative to satellite footpoint at altitude=0.0m
int ngrg	number of (true ground range) samples in the cross track direction.

DESCRIPTION
<orbit>.off - contains parameter values used by the Interferometric SAR Processor ISP. The ISP offset/processing parameter file contains the information on the co-registration of the SLC image pair, the image section to be processed, and parameters used or determined during the interferometric processing. The size and location of the interferogram are selected in <orbit>.off The number of looks in azimuth and range direction used for the interferometric processing are selected in <orbit>.off The bilinear offset polynomial indicating the offset of SLC-2 relative to SLC-1 is indicated in <orbit>.off (as determined by the co-registration program). <orbit>.off - is generated interactively using the make_offset program. Processing related values are introduced later during the interferometric processing. The formats used in <orbit>.off are defined in the in ISP type definition file typedef_ISP.h. The formats are also described in the interactive parameter selection in the make_offset program.

OPTIONS
The ISP offset/processing parameter file date1_date2.off may be edited manually.