Idepix tool does not recognize input files

snap
#1

Good Morning. I am struggling with input sources for SNAP Idepix processing: when I try to feed gpt Idepix command with a proper valid input, SNAP reacts saying something like: the input is not recognized, the sensor should be one of : “Supported sensors are: MERIS, SPOT VGT, MODIS, Landsat-8, SeaWiFS, Sentinel-2 MSI, Sentinel-3 OLCI, PROBA-V, VIIRS”. We deal with multiple sensors and at the moment struggle with recognition of two sensors: VIIRS SNPP and SeaWiFS. Sinse r2022, VIIRS changed file naming system: instead of V2023188234800.L1A_SNPP.nc, they use now SNPP_VIIRS.20230707T234800.L1A.nc. After you convert (with NASA seadas l2gen) an L1A file into L1C, with the same (new) prefix SNPP*, Idepix rejects it saying: wrong input, does not belonge to the valid sensor list. If you rename the new L1C file to the old style, it still does not work, the same way. The workaround is to set old style output to l2gen. Apparently, Idepix takes filename for sensor detection from metadata, not the filename itself. Easy to check: rename the file and open in SNAP browser - you will still see the inital name before renaming. Similar problem with SeaWiFS: we have produced lots of *.L1C files, but Idepix wants files with different extension: *L1C_LAC/GAC, and re-naming the input does not help. Thus I have two questions:

  1. Can you please list proper/valid names for Idepix inputs for the following sensors: SeaWiFS, MODISA, MERIS, VIIRS, OLCI? I am sure this information should be relatively easy to exctract from source codes of SNAP readers;
  2. How to make Idepix to believe (to cheat?) that this is a right/valid input, despite the formally wrong (now) name stored somewhere in metadata?

Thank you

#2

I have found a better workaround for SeaWiFS (rather than modifying output name for the l2gen processing): you need to modify global attribute of L1C file (input for Idepix):
ncatted -O -h -a product_name,global,m,c,“S1999364071336.L1C” S1999364071336.L1C_GAC
which makes Idepix to accept and recognize the source as SeaWiFS file. But we cannot create just S1999364071336.L1C file because SeaWiFS files often come in pairs: GAC and (M)LAC, with the prefix part the same. Thus, one needs to create two different files: S1999364071336.L1C_GAC and S1999364071336.L1C_LAC but change the global attrinute ‘product_name’ to same for both: ‘S1999364071336.L1C’. Looks like this works, but, I believe, this is not a proper way but a workaround. Is there a better way to handle SeaWiFS files? The same problem arises (unless SNAP updated in future) with Idepix processing of VIIRS r2022 files.

#3

Maybe @TomBlock could help you.