VIIRS Support in ENVI 5.1
Since support for NPP VIIRS appeared in ENVI (5.0 SP3), I've worked with a number of ENVI users who were confused about VIIRS data support. In this post I'll clarify sources of confusion for folks currently using VIIRS in ENVI, and give an overview of the upgraded VIIRS support that will be available in ENVI 5.1, coming soon.
VIIRS is a highly complex sensor system that collects imagery in 22 separate visible and infrared channels which can be delivered with a number of different ancillary data records. Most of the confusion I've encountered around supported data is related to data access and supported data types.
One source of confusion is data access...There are several different web portals where VIIRS imagery can be found for download,such as from various NASA-sponsored Distributed Active Archive Centers (DAACs). ENVI only supports VIIRS data products accessed via NOAA's Comprehensive Large Array-Data Stewardship System (CLASS). CLASS is the definitive source for VIIRS data, providing data products in HDF5 format. Other files acquired from sources other than CLASS are not supported in ENVI.
Another source of confusion for users of VIIRS imagery in ENVI is related to supported data types. ENVI 5.0 Service Pack 3 currently reads a subset of the total collection of data types available through CLASS,specifically the following:
- All Sensor Data Records (SDRs) including the Day/Night Band (DNB), I-bands (Imagery Bands 01 - 05) and the M-bands (Moderate Resolution Bands 01 - 16)
- The one Application Related Product, VIIRS Active Fires ARP is supported.
A huge upgrade for ENVI is coming soon in ENVI 5.1, when Environmental Data Records (EDRs) will be supported. These are the EDR products that you'll be able to work with directly in ENVI:
- Aerosol Optical Thickness
- Ice Surface Temperature
- Land Surface Temperature
- Ocean Color/Chlorophyll
- Sea Ice Characterization
- Sea Surface Temperature
- Snow Cover Depth Binary Map
- Snow Fraction
- Surface Type
- Suspended Matter – Smoke Concentration
- Vegetation Index
Georeferencing for your VIIRS data is only available if the file you selected has Latitude and Longitude bands. Note that individual VIIRS data granules include geolocation latitude and longitude bands by default, so geolocation shouldn't be an issue unless the option to 'Package Geolocation with NPP Data Products' is deselected via the 'Advanced Options' in the 'Shopping Cart'.
See this tutorial on Data Access from CLASS by NOAA NCDC.