PROBLEM 1: For us, we had a problem initially with this processing. Warning signs often come up and may not necessarily mean problems, but sometimes they are valid. We ran into this problem:
WARNING: Autofocus range offset greater than threshold: 2.00
WARNING: Rejecting autofocus, check number of doppler ambiguities
The source of the error was in this output line:
correlation peak column, row, SNR: 0.743 -2.765 72.613
If either of the first two numbers (in this case 0.743 and -2.765) is above |2|, the process quits.
SOLUTION: The suggestion to check doppler ambiguities can be done by opening ERS_PROC in jot and turning on the program dop_mlcc by erasing the # ‘s.
PROBLEM 2: Our MSP Processing failed another time at another spot:
ERROR: subroutine pos_int, interpolation outside of range at time(s): 52133.82473
SOLUTION: The subroutine pos_int is within az_proc. I checked the size of the .slc and it was just over a gigabyte (the typical size) which shows that most of the data wasn’t affected. I then went ahead with the next sub program in the ERS_PROC sequence, which is multi_SLC. Everything went fine, and there seemed to be no problems with the .slc.
PROBLEM: It has happened that the offset estimate for range was in the hundreds, which is way too much. Offset estimate for azimuth is typically in the hundreds and is not a problem.
SOLUTION: To remedy this, you must resize the window used to estimate offset. Often times, offset is at a minimum at the top of the images, and increases to a maximum at the bottom. Therefore, change the coordinates of your window to be near the top of the images. Open a raster file of your .mli image and click on a spot near the top. You cannot use the coordinates directly, as the .mli image has been sampled according to 1 5 or 2 10, so multiply the raster coordinates by these numbers and input the true coordinates into the init_offset command line. So if you get (1600, 200) in the black xv coordinate box, and you sampled at 1 5, then the true coordinates are 1600, 2000. You must run all three init_offsets again with this new window location.