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Up Topic Special Topics / HICO / HICO level 2 processing
- By lerebourg Date 2014-01-21 17:26
Dear Sean,

from what I understand of previous posts, HICO wavebands are intergrated to MERIS bands for level2 processing.
I assume this is performed upstream (prior atmospheric corrections).

Can you specify which procedure you use to perform spectral integration?

Best regards

- By seanbailey Date 2014-01-21 17:51

There is no band integration involved.  Currently, the HICO reader in our processing code
simply selects the HICO bands nearest to the MERIS bands.  Yes, this is done prior to
atmospheric correction.

We are not currently processing HICO beyond L1 browse imagery and have made no attempt
yet at calibrating the instrument for doing so.  On our exceptionally long list of things to do is
to modify our processing code to be able to handle hyperspectral instruments like HICO.

If you want to see how we're currently handling HICO, the reader code is available in the
source package for SeaDAS (or just for web browsing, here)

- By dshea Date 2014-01-21 18:02
The L1B HICO reader selects the band closest to the center wavelength of each of the 15 MERIS bands.  This is done prior to the atmosphere correction as you suspected.  We started out VERY simple to get started.  I am in the process of modifying l2gen to be able to accept 128 (probably not 384 though) bands.  That might take a while...
- By bryanfranz Date 2014-01-21 18:12
I'd add that the HICO bands are at 6-nm intervals and spectral smoothing is performed with a gaussian filter in the calibration process such that the band widths are nominally overlapping 10-nm FWHM gaussians (much like MERIS bands).  

-- bryan
- By lerebourg Date 2014-01-22 17:39
Thank you very much for these detailed answers.

Best regards

- By robin Date 2014-06-10 02:54
Hi Sean,
I am processing HICO L1b data using Seadas 7, and an IDL code as a wrapper from L1 to L3. I understand that HICO processing "simulates" the MERIS bands. However, I would wish to clarify the following:

1. Is the HICO processing set up under SEADAS 7 meant to generate exactly the same products list like MERIS.
2. I have noted that requesting for processing of some OC products with the HICO bands fails (actually Seadas 7 halts), e.g. tsm_clark, chl_gsm; is it possible to generate such products from HICO bands?

- By seanbailey Date 2014-06-11 12:28
HICO has 128 bands (or 384, but we'll not go there...), but our processing code currently only supports multispectral instruments.
SO, we only read in the bands that match the MERIS band set.  This means that we can produce the same products with HICO
that we can produce with MERIS - although there may be some products that are not "HICO" aware and may not work (although
technically they could - e.g. par).

tsm_clark was removed as a product with 7.0.1 (although seems not completely enough, as it's selectable, but not produceable)
chl_gsm works for me...

- By robin Date 2014-06-11 15:15
Hi Sean,
Thanks, thats great info, I wish would actually go ahead and explain the 384, I am keen to understand a little bit more about HICO. Let me know what you would suggest as a thorough read on this.

Well, nice to meet you the other day at Cornell.
- By seanbailey Date 2014-06-11 15:39
It's nothing super secret :grin:

HICO can be commanded into a special calibration mode where it will record 384 spectral bands.  There are only a few scenes like this.
I don't think the version of the code in the current SeaDAS release will handle these files, although our current development code does.
When we modify our code to be able to deal with hyperspectral data, we are likely to only handle the 128 band files.

- By jasmine Date 2014-06-11 16:58
To add to Sean's reply ...

The HICO sensor collects data from 350 to 1080 nm at 1.91 nm spectral resolution (384 bands).

In normal operating mode, these bands are binned spectrally by three at read-out, yielding the final 128 bands (at 5.7 nm spectral resolution) that are found in the data files.  Binning the bands increases the signal-to-noise ratio.

As Sean mentioned, a high-resolution mode is used periodically for calibration purposes. This mode retains the original 1.91 nm resolution.

Further details about the HICO sensor are available from the HICO website:
You may particularly be interested in this page:

- By robin Date 2014-06-11 17:32
Thank you Jasmine,

Are you aware of any SEADAS chlor-a algorithm that would be "best" suited for retrieving the product from HICO data in inland waters, e.g. a lake, or is all this at experimental stages?

- By jasmine Date 2014-06-11 17:51

I'm not familiar enough with inland waters to recommend a specific seadas chl routine (and it likely depends on your lake).  However, there are numerous HICO projects underway that are specific to inland water bodies (mostly focusing on water quality).  You will find that they all take different approaches, trying to take advantage of the hyperspectral nature of HICO.  A list of known projects can be found on the HICO website projects page.  Some of the projects have provided annual reports (found at the links labelled 2012_AR or 2014_AR) which may have helpful details of implementation and publications.

- By lerebourg Date 2014-07-21 17:14
Does the level2 processing chain implement a vicarious calibration on HICO scenes?

- By seanbailey Date 2014-07-21 22:33

No, not yet anyway.  We do not produce L2 files from HICO operationally, in part because we've not had time to assess the calibration.
Eventually, we will, but for now the gains are set to unity.

- By lerebourg Date 2015-05-26 13:16
Dear Sean,

is SeaDAS processor now able to handle hyperspectral atmospheric correction and therefore generate hyperspectral marine reflectances?


- By seanbailey Date 2015-05-26 16:48

Almost.  The code released with SeaDAS v7.2 can process HICO with the full spectral resolution.  The hicohs data tree needs to be put in place of the hico data tree for this to work.
It's still a work in progress, so no guarantees on the products it produces.  Little things (like, oh say, water vapor corrections) are not quite up to snuff.  No attempt at calibrating
the bands has been made, so caveat emptor.

Up Topic Special Topics / HICO / HICO level 2 processing

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