GAMMA Questions

Hello,
What is the error message?

thanks,
Charles

Hi Charles,

thanks for coming back to me. There is no error message. The program is running until the entire end. However, the result does not look correct. If I try to write it to a tif file, I get nans for average and scaling (see below) and the image itself is empty. I had attached the entire log of SLC_cat_S1_TOPS to my previous post, so you can have a look for yourself. Thank you!

rasSLC 20150323_iw1.slc 21672 1 0 1 1 1. 0.35 1 0 0 20150323_iw1.slc.tif
*** DISP Program rasSLC ***
*** Copyright 2016, Gamma Remote Sensing, v2.8 6-Sep-2016 clw ***
*** Generate 8-bit raster graphics image of intensity of complex (SLC) data using power law scaling ***
OPENMP maximum available threads : 8
OPENMP: setting number of theads: 4
input image: 20150323_iw1.slc
image format: FCOMPLEX
input image width: 21672   height: 26964
range looks: 1   azimuth looks: 1
output image width: 21672   height: 26964
relative scale factor:    1.000   exponent:    0.350
average:          nan   scale factor:          nan
line 26000
lines: 26964  width: 21672
output image: 20150323_iw1.slc.tif

Hi Charles,

as I am trying to solve that issue, I also found that the range samples of the swathes to be concatenated are differing by one pixel:

title:     s1a-iw1-slc-vv-20150323t011258-20150323t011323-005152-0067ee-001.tiff S1A-IW-IW1-VV-5152 (software: Sentinel-1 IPF 002.43)
sensor:    S1A IW IW1 VV
date:      2015 3 23 1 12 58.6229
start_time:              4378.622867   s
center_time:             4391.195677   s
end_time:                4403.768487   s
azimuth_line_time:     2.0555563e-03   s
line_header_size:                  0
range_samples:                 21673
azimuth_lines:                 13482

title:     s1a-iw1-slc-vv-20150323t011233-20150323t011258-005152-0067ee-001.tiff S1A-IW-IW1-VV-5152 (software: Sentinel-1 IPF 002.72)
sensor:    S1A IW IW1 VV
date:      2015 3 23 1 12 33.8015
start_time:              4353.801485   s
center_time:             4366.372240   s
end_time:                4378.942994   s
azimuth_line_time:     2.0555563e-03   s
line_header_size:                  0
range_samples:                 21672
azimuth_lines:                 13482

I have attached the par files of both iw1 swathes, in case that may help you. Please let me know, if I can provide any more information that may help you to find a solution for that problem. Thank you.

Best, Julia

Hello,
the number of range samples should not be an issue, the program extracts the
appropriate number of samples if they differ.
Where is the error message?

Well, in this case, try using the program replace_values to see if you can
replace the nans with 0.
And see if the data are ok..., then it could be a memory error of some kind.

• DISP Program replace_values.c ***
• Copyright 2008, Gamma Remote Sensing, v1.4 6-May-2008 uw/clw/ts ***

• Replace value(s) of input data file with specified value or values extracted
  from a second input data file ***
  usage: replace_values <f_in> <value> <new_value> <f_out> <width> [rpl_flg]
  [type] [zero_flag]

input parameters:
f_in (input) input data file
value threshold value or nan
new_value new value to use or second input data file (float)
f_out (output) output data file
width number of samples/row
rpl_flg replacement option flag (default = 0)
0: replace all points == value with new_value
1: replace all points >= value with new_value
2: replace all points <= value with new_value
type data type
2: float or fcomplex (default)
4: short int
zero_flag interpretation of 0.0 values:
0: interpreted as missing value (default)
1: 0.0 is a valid data value

Best regards,
Charles

If I replace the nans with zero the concatenated image looks like this screenshot.

Hello,

There was an error in SLC_cat_S1_TOPS the prevented correct concatenation of
Sentinel-1 SLCs when there is a change in the number of range samples from one
frame to the next. This happens infrequently, and may not affect your data. The
error manifests itself as total corruption of the bursts in the second appended
frame. There is an update available for this program by request. Send an email
to me (cw@gamma-rs.ch) or Christophe Magnard (magnard@gamma-rs.ch) and we will
send you the binary executable of the updated program.

Regards,
Charles Werner

Dear Charles and Christophe,

thank you again for your quick help and effort to find the source of the problem!
Everything is working now as expected.

Best,
Julia