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Processing of L1A_LAC.x.hdf files

Posted: Thu Nov 30, 2017 1:15 pm America/New_York
by jcfischer
Dear colleagues,
I have the following problem: I want to create L3 files of the parameter Kd_490 out of L1 files (MODIS data). I can´t use the provided L3 Kd_490 product because the resolution (4 and 9 km) is too coarse. Even a 1 km resolution is too coarse. That´s why I process the L1 files in SeaDAS to get a res. of 250 m and don´t use a L2 file. The processing works nicely if I use a L1A_LAC file (which is available for direct download). But I have to process a large number of files and the creation of L2 files (created from this big L1A file) takes very long. Therefore, the order data function is very handy as it allows to order more files at once and I can order already cropped files. But those files come in this format: L1A_LAC.x.hdf. And the whole processing doesn’t work with that format/these files.

Can anybody tell me how to convert L1A_LAC.x.hdf to L1A_LAC files? Or does anybody know how the processing of L1A_LAC.x.hdf files to L3 files can be done?

This would help me a lot. Thank you in advance! Greetings, JC

Processing of L1A_LAC.x.hdf files

Posted: Thu Nov 30, 2017 9:12 pm America/New_York
by OB.DAAC - SeanBailey
Rename them. :grin: If there is something in the processing stream that isn't happy with the .x.hdf, lop it off.  The files are the same format and our code does process them.

Now, as for processing Kd490 at 250m - sure the number of pixels will be higher and you may convince yourself that the data are at a higher resolution, but it a fallacy.
The bands used for the Kd algorithm are the (native, thus nominally) 1km bands.  All the code is doing when you ask for 250m resolution is outputting replicated data.
Only the visible band at 250m resolution is the 645nm band.  If you output that band, yes, it will be at 250m.


Processing of L1A_LAC.x.hdf files

Posted: Tue Dec 12, 2017 11:35 am America/New_York
by jcfischer
Dear Sean,
thanks for the answer! With renamed files it all works well.
Regarding the resolution, I will stick to the 1 km resolution images.