SeaWiFS Level 2 Global Area Coverage (GAC), Local Area Coverage (LAC), and Merged LAC (MLAC) Data ProductsEntry ID: SEAWIFS_LEVEL_2
Abstract: This data set consists of global satellite measurements by the Sea-viewing Wide
Field-of-view Sensor (SeaWiFS), in orbit on the OrbView-2 (formerly SeaStar)
platform. SeaWiFS acquires approximately 15 pole-to-pole orbital swaths of
data per day, and approximately 90% of the ocean surface is scanned every two
days. SeaWiFS products are processed and distributed by the Ocean Biology
Processing ... Group (OBPG). Processing details can be found at
The Level 2 data products consists of geophysical values that are generated
from Level 1A data by applying sensor calibration, atmospheric correction, and
bio-optical algorithms. The resolution is the same as the corresponding level
1A Local Area Coverage (LAC, 1 km resolution), and Global Area Coverage (GAC, 4
km resolution) products. Unusual conditions may be flagged on a pixel-by-pixel
basis. Before computing Level 2 data, pixels are eliminated if they contain
clouds, sun glint, or other abnormalities. For pixels that pass these screens,
an atmospheric correction is applied to subtract the atmospheric scattering
components from the total radiance to obtain the water-leaving radiances for
bands 1-5 (see http://oceancolor.gsfc.nasa.gov/VALIDATION/atm.html). See
http://gcmd.nasa.gov/getdif.htm?SEAWIFS_LEVEL_1A for additional information
about Level 1A data.
SeaWiFS Standard Level 2 Products:
-Normalized water-leaving radiances at 412, 443, 490, 510, 555, and 670 nm.
-Aerosol optical thickness at 865 nm (for atmospheric correction).
-Epsilon of aerosol correction at 765 and 865 nm (for atmospheric correction).
-Diffuse attenuation coefficient at 490 nm (measure of optical clarity)
-Angstrom coefficient, 510-865 nm
Level-2 processing is performed using the Multi-Sensor Level-1 to Level-2
(MSl12) code, which is developed and maintained by the OBPG. MSL12 is used for
the standard processing of all ocean products distributed through the web
browsers and FTP sites. This software is capable of retrieving oceanic optical
properties and various derived products from the observed top-of-atmosphere
(TOA) radiances collected by a variety of ocean remote sensing radiometers.
Full documentation, updated code source, sensor files, and output product
descriptions can be found at http://oceancolor.gsfc.nasa.gov/DOCS/MSL12/.
Ancillary meteorological data (U and V winds, surface pressure, water vapor)
and Ozone data (O3) are used for atmospheric correction in Level 2 processing.
EPTOMS Ozone is the primary source for ozone used within OBPG. The Ancillary
Data is Quality Controlled and made available to the public by FTP from the
Ocean Color Web Site. Other Level 2 processing steps include data navigation so
that land mask may be correctly placed, computational steps to derive the
geophysical products, and tests for anomalous conditions in the data (masks and
More detailed information on the Level-2 format specifications can be found at
Browse Level 2 (GAC, LAC and MLAC) data at
ISO Topic Category
Distribution Media: Online
Fees: No fees
Role: TECHNICAL CONTACT
Email: h2osoft at usgs.gov
U.S.G.S. Hydrologic Analysis Software Support Program 437 National Center
Province or State: VA
Postal Code: 20192
Role: SERF AUTHOR
Phone: (301) 614-6898
Email: Tyler.B.Stevens at nasa.gov
NASA Goddard Space Flight Center Global Change Master Directory
Province or State: MD
Postal Code: 20771
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Creation and Review Dates