I have a subscription for MODIS-A images of chlorophyll concentration from ocean color (the L2 product) which I receive by email (and also have retrieved from the http server). The images are extracted for a relatively small area (Massachusetts Bay).
The images are useful, but I would like to be able to access the L2 data values (and ideally the quality flags for them) underlying what is shown in each image.
I have many past years of images, and would like to access the underlying data for all of them. So I need to be able to do this via scripting-- an image browsing tool does not seem like a suitable solution.
Any suggestions for viable ways to accomplish this goal would be appreciated.
I understand that I could set up my subscription for images to also include data files. But this is only possible for images from now onward. And I would like the data from images of many past years.
Ideally I could access the data using OpenDAP or ERDDAP, in order to easily subset it to the small domain I am interested in. But so far I have been unable to find L2 data available in that way. (I see some L3 products are available via OpenDAP, but they don’t have the high resolution I need.) Is it correct that this is not possible for L2 data? Are there any plans to make L2 data available via OpenDAP/ERDDAP or equivalent? If so is there any anticipated timeline for them?
Barring access by OpenDAP/ERDDAP or equivalent as an option, I understand that I could use SeaDAS. But is SeaDAS really the only possibility?
And a final question, about using SeaDAS, if I pursue that: is there any anticipated timeline for when the “science data processing code” will be included in the Windows version?
Advice on accessing extracted data: many years of L2 MODIS-A chlorophyll
Advice on accessing extracted data: many years of L2 MODIS-A chlorophyll
Have you considered CoastWatch data like that shown in this Massachusetts Bay (image)? There are NetCDF and HDF files, but you may not agree with NOAA's choice of flags to mask.
The OCSSW processing software can be installed in a WSL instance in Windows 10 for batch processing, but processing will be significantly slower than for native linux on the same hardware. The OCSSW software runs well under linux on low-end hardware, so you might consider recycling an old, unloved and unwanted, computer.
The OCSSW processing software can be installed in a WSL instance in Windows 10 for batch processing, but processing will be significantly slower than for native linux on the same hardware. The OCSSW software runs well under linux on low-end hardware, so you might consider recycling an old, unloved and unwanted, computer.
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OB.DAAC - SeanBailey
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Advice on accessing extracted data: many years of L2 MODIS-A chlorophyll
No, we do not offer our L2 data via OPeNDAP, but you can easily obtain subsetted L2 data from us. The L1/L2 browser allows you to select a region of interest as well as a time period of interest to create an extracted data order. You can think of that as a hindcast equivalent to a forward stream extracted data subscription :grin:
The tools provided with SeaDAS can accomplish what you need to do - and as George points out - SeaDAS does now offer a client/server model that provides processing support under the Windows OS, either via a virtual machine or via the Windows Subsystem for Linux (WSL) that comes with Windows 10.
Sean
The tools provided with SeaDAS can accomplish what you need to do - and as George points out - SeaDAS does now offer a client/server model that provides processing support under the Windows OS, either via a virtual machine or via the Windows Subsystem for Linux (WSL) that comes with Windows 10.
Sean
Advice on accessing extracted data: many years of L2 MODIS-A chlorophyll
Thank you for the suggestions. Quite helpful.
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The CoastWatch products look interesting. I like that they provide an application ("CDAT") enabling various manipulations of the data.
I did a spot check and it seemed like their algorithm (NOAA OC3 NIR-SWIR algorithm) can give quite different results from what I get here-- I'm not knowledgeable enough about the algorithms to know which would be 'better' in Mass Bay. If you have any guidance on that it would be great to hear.
I believe their products only go back to 2014 (or 2010 by special request) though.
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SeaDAS seems like it would be the most powerful choice but also has a steep learning curve (and as I'm limited to windows, the VM or WSL approaches represent somewhat of an additional hurdle).
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So, I'll probably start with data requests from the L1/L2 browser and see how far I can get with that. I like that it should allow me to go back farther to early years, and that it apparently will let me get SeaWiFS and VIIRS as well as MODIS. In addition to newer higher resolution and/or quality products (VIIRS), conditions before 2000 (SeaWiFS) are of interest to us.
--
The CoastWatch products look interesting. I like that they provide an application ("CDAT") enabling various manipulations of the data.
I did a spot check and it seemed like their algorithm (NOAA OC3 NIR-SWIR algorithm) can give quite different results from what I get here-- I'm not knowledgeable enough about the algorithms to know which would be 'better' in Mass Bay. If you have any guidance on that it would be great to hear.
I believe their products only go back to 2014 (or 2010 by special request) though.
--
SeaDAS seems like it would be the most powerful choice but also has a steep learning curve (and as I'm limited to windows, the VM or WSL approaches represent somewhat of an additional hurdle).
--
So, I'll probably start with data requests from the L1/L2 browser and see how far I can get with that. I like that it should allow me to go back farther to early years, and that it apparently will let me get SeaWiFS and VIIRS as well as MODIS. In addition to newer higher resolution and/or quality products (VIIRS), conditions before 2000 (SeaWiFS) are of interest to us.