Closed TAlonglong closed 4 years ago
Thanks for reporting this. You mention here that the problem appears with long passes, so do I understand correctly that short passes don't exhibit this problem ?
Oh, I forgot to test that. Just a few minutes.
Testing with 3 segments of data gives good results. These are the segments where the feature appear. So the original data must be fine.
[DEBUG: 2019-12-06 10:55:45 : satpy.readers.eps_l1b] Reading /data/pytroll/testdata/AVHR_xxx_1B_M03_20191206071603Z_20191206071903Z_N_O_20191206082758Z
[DEBUG: 2019-12-06 10:55:45 : satpy.readers.eps_l1b] Reading /data/pytroll/testdata/AVHR_xxx_1B_M03_20191206071903Z_20191206072203Z_N_O_20191206082825Z
[DEBUG: 2019-12-06 10:55:46 : satpy.readers.eps_l1b] Reading /data/pytroll/testdata/AVHR_xxx_1B_M03_20191206072203Z_20191206072503Z_N_O_20191206082851Z
Testing now with one more segment closer to the South Pole
4 segments still ok.
[DEBUG: 2019-12-06 11:00:50 : satpy.readers.eps_l1b] Reading /data/pytroll/testdata/AVHR_xxx_1B_M03_20191206071303Z_20191206071603Z_N_O_20191206082728Z
[DEBUG: 2019-12-06 11:00:51 : satpy.readers.eps_l1b] Reading /data/pytroll/testdata/AVHR_xxx_1B_M03_20191206071603Z_20191206071903Z_N_O_20191206082758Z
[DEBUG: 2019-12-06 11:00:51 : satpy.readers.eps_l1b] Reading /data/pytroll/testdata/AVHR_xxx_1B_M03_20191206071903Z_20191206072203Z_N_O_20191206082825Z
[DEBUG: 2019-12-06 11:00:52 : satpy.readers.eps_l1b] Reading /data/pytroll/testdata/AVHR_xxx_1B_M03_20191206072203Z_20191206072503Z_N_O_20191206082851Z
With 5 segments the feature reappeared
[DEBUG: 2019-12-06 11:04:30 : satpy.readers.eps_l1b] Reading /data/pytroll/testdata/AVHR_xxx_1B_M03_20191206071003Z_20191206071303Z_N_O_20191206082627Z
[DEBUG: 2019-12-06 11:04:30 : satpy.readers.eps_l1b] Reading /data/pytroll/testdata/AVHR_xxx_1B_M03_20191206071303Z_20191206071603Z_N_O_20191206082728Z
[DEBUG: 2019-12-06 11:04:31 : satpy.readers.eps_l1b] Reading /data/pytroll/testdata/AVHR_xxx_1B_M03_20191206071603Z_20191206071903Z_N_O_20191206082758Z
[DEBUG: 2019-12-06 11:04:31 : satpy.readers.eps_l1b] Reading /data/pytroll/testdata/AVHR_xxx_1B_M03_20191206071903Z_20191206072203Z_N_O_20191206082825Z
[DEBUG: 2019-12-06 11:04:32 : satpy.readers.eps_l1b] Reading /data/pytroll/testdata/AVHR_xxx_1B_M03_20191206072203Z_20191206072503Z_N_O_20191206082851Z
Thank you for checking this. I got the data locally, I will have a look a it.
Reproduced. I'll look into it.
I've looked a bit, and I'm pretty sure this isn't a satpy/pyresample bug, but something in proj. I got some strange behaviour to show up, and reported the issue to proj, let's see what they say: https://github.com/OSGeo/PROJ/issues/1922
@TAlonglong We got an answer in the issue above, and this can be fixed by setting the ellipsoid of omerc_bb
to sphere
. I'll change the default in satpy.
(the calls you perform in your script are equivalent to using the omerc_bb
area to resample to)
This should be solved with pytroll/pyresample#252
When resampling a long pass of global metop l1b eps data with compute_optimal_bb_area some strange results appear.
The image below is a small capture of the resampled data showing the strange results.
https://drive.google.com/open?id=1jNxMLVe0bXXEfUJ0QBcq4_8HdLNEovCb
When eg. displayed in DIANA, and DIANA itself resample the image to eg. a stere projection results like this shows up ( this time over the Antarctic)
https://drive.google.com/open?id=1pSN-o5ZV-1Z0g7pqVJMmUFgBVSyl_nEM
with a close up:
https://drive.google.com/open?id=1_vVzLUwV2dt7FoxRAcZVJ-F59kvhSLwD
It looks like the feature starts at the south pole
The code uses the simple image writer to save to a png. But the images above is produced with the mitiff writer. The feature exists using both writers.
Environment Info: