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pix_sigma0 or pix_gamma0, which should be used for geocoding lookup table refinement?
Added by Kang Liang over 2 years ago
Dear GAMMA developers,
According to the manual or the demo, a general geocoding procedure is done by 1). generate lookup table by gc_map2; 2) generate the normalization area which can be treated as a "simulated" SAR intensity image; 3) using offset_pwrm and offset_fitm to refine the lookup table.
My question is, which normalization area generated by pixel_area should be used in the offset_parm?
I found in some of the demos, the pix_sigma0 is used. for example, in line 71 and 78 of README_Gamma_IPTA_demo_PALSAR2_Ticino:
pixel_area 20160903.rmli.par Ticino.dem_par Ticino.dem Ticino.20160903.lt Ticino.20160903.ls_map Ticino.20160903.inc 20160903.pix_sigma0
offset_pwrm 20160903.pix_sigma0 ../rslc2/20160903.rmli 20160903.diff_par 20160903.offs 20160903.ccp 128 128 - 2 32 32 0.1 5 .8 0
However, in the line 434 and 449 of geocoding.py script:
status = pg.pixel_area(MLI_par_name, DEM_out_par_name, DEM_out_name, lt_name, ls_map_name, inc_name, '-', pix_gamma0_name)
status = pg.offset_pwrm(pix_gamma0_filled_name, MLI_name, diff_par_name, offs_name, ccp_name, rwin, azwin, '-', 1, nrstep, nazstep, 0.1)
pix_gamma0 or pix_sigma0, which one I should use?
Thanks for your help!
Kang Liang
Replies (3)
pix_sigma0 or pix_gamma0, which should be used for geocoding lookup table refinement? - Added by Charles Werner over 2 years ago
Hello,
Either pix_gamma0 and pix_sigma0 can be used, but the pix_gamma0 is generally
closer to the radar image and is what I would use. Look at the 2 images using
vispwr.py using the -a option, and you can see the modest differences. You can
also compare these with the original SAR image.
Best regards,
Charles
pix_sigma0 or pix_gamma0, which should be used for geocoding lookup table refinement? - Added by Charles Werner over 2 years ago
Hello,
Either pix_gamma0 and pix_sigma0 can be used, but the pix_gamma0 is generally
closer to the radar image and is what I would use. Look at the 2 images using
vispwr.py using the -a option, and you can see the modest differences. You can
also compare these with the original SAR image.
Best regards,
Charles
RE: pix_sigma0 or pix_gamma0, which should be used for geocoding lookup table refinement? - Added by Kang Liang over 2 years ago
Thanks for your kind and quick reply! I agree with you since pix_gamma0 is the real radar cross-section. I will try to use vispwr.py to check their difference.
Best,
Kang