This document discusses using IDL to work with Suomi NPP VIIRS data. It presents an overview of VIIRS data and examples of constructing false color composite images and cloud masks from VIIRS imagery files. The examples demonstrate reading VIIRS data from HDF5 files, performing image processing, and displaying results. In summary, HDF5 makes it easy to work with Suomi NPP VIIRS data in IDL.

1. Using IDL with
NPP VIIRS Data
HDF & HDF-EOS Workshop XV
Mark Piper
mark.piper@exelisvis.com
idldatapoint.com
The information contained in this document pertains to software products and
services that are subject to the controls of the Export Administration Regulations
(EAR). The recipient is responsible for ensuring compliance to all applicable U.S.
Export Control laws and regulations.

2. Agenda
> Overview of VIIRS data
> Using IDL with VIIRS data (examples)
> Summary / Q&A
Presentation files:
exelisvis.com/esg/Seminars.aspx
HDF and HDF-EOS Workshop XV
2012-April-19
Riverdale, MD
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3. About Suomi NPP VIIRS
> Overview: http://npp.gsfc.nasa.gov/viirs.html
3

4. VIIRS data overview
> Data from NOAA CLASS site (http://www.class.ngdc.noaa.gov)
> VIIRS I-Band (imaging channel) EDR (level 2); single HDF5 file
I(1,2,3,4,5) and GEO info (Longitude, Latitude, Height, etc.)
> Four granules:
>
375 m
pixel size
along
cross
granule
1541 pixels
(~578 km)
8241 pixels
(~3100 km)
> Band comparison:
HDF and HDF-EOS Workshop XV
2012-April-19
Riverdale, MD
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5. Example #0
> Browse a VIIRS I-Band file with TX_NPP_BROWSER.
> View the domain of the data with IDL or Google Earth / NASA World Wind.
namespace = 'vis_viirs_'
viirs_file
string
display_domain
.kml file
HDF and HDF-EOS Workshop XV
2012-April-19
Riverdale, MD
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6. Example #1
> Construct a VIIRS I-Band (3,2,1) false color composite image.
namespace = 'vis_viirs_'
viirs_file
string
read_dataset
make_rgb
scale_dataset
rgb
bytarr [8241,6164,3]
HDF and HDF-EOS Workshop XV
2012-April-19
Riverdale, MD
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7. Example #1
HDF and HDF-EOS Workshop XV
2012-April-19
Riverdale, MD
7

8. Example #2
> Construct a cloud mask from VIIRS I-Band imagery.
namespace = 'vis_viirs_'
viirs_file
string
read_dataset
make_cloudmask
scale_dataset
mask
bytarr [8241,6164]
HDF and HDF-EOS Workshop XV
2012-April-19
Riverdale, MD
8

9. Example #2
HDF and HDF-EOS Workshop XV
2012-April-19
Riverdale, MD
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10. References
Here are a few references that I found helpful in making this presentation.
> Suomi NPP Science Documents:
http://npp.gsfc.nasa.gov/science/documents.html
> About VIIRS:
http://npp.gsfc.nasa.gov/viirs.html
http://www.nesdis.noaa.gov/jpss/instruments.html
> Landsat 7 Automatic Cloud Cover Assessment:
http://landsathandbook.gsfc.nasa.gov/pdfs/ACCA_SPIE_paper.pdf
HDF and HDF-EOS Workshop XV
2012-April-19
Riverdale, MD
10

11. Summary
HDF5 makes it easy to work with
Suomi NPP VIIRS data in IDL!
HDF and HDF-EOS Workshop XV
2012-April-19
Riverdale, MD
11

12. Using IDL with
NPP VIIRS Data
HDF & HDF-EOS Workshop XV
Mark Piper
mark.piper@exelisvis.com
idldatapoint.com
Presentation files:
exelisvis.com/esg/Seminars.aspx
The information contained in this document pertains to software products and
services that are subject to the controls of the Export Administration Regulations
(EAR). The recipient is responsible for ensuring compliance to all applicable U.S.
Export Control laws and regulations.