Introduction
MOD43B1 BRDF/Albedo Model Parameters Product
MOD43B3 Albedo Product
MOD43B4 NBAR Product
MOD43B Validation
MOD43C1 Albedo CMG
MOD43C2 BRDF CMG
MOD43C3 NBAR CMG
BRDF/Albedo Data
MODIS User Tools
Publications
Related Links
BRDF/Albedo@BU
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Tools For MODIS BRDF/Albedo Products
General Tools for MODIS L3 Data
Level-3 one-kilometer MODIS Land (MODLAND) products are archived
in equal area tiles of 1200 by 1200 pixels in a Sinusoidal
projection (SIN). These products are released in Hierarchical Data Format
- Earth Observing System (HDF-EOS) for
each of the 317 land tiles on the globe (see HDF-EOS
FAQ).
While most commericial GIS packages can handle HDF files, there
still seem to be limitations in many of the package's ability to handle
HDF-EOS. Frequently they have difficulty ingesting the four
dimensional arrays that some of our products are produced in (MOD43B1
MODIS BRDF Model Parameters and MOD43B3 MODIS Albedo for
example). However there are two free
tools that have been made available by the EROS Data Center (EDC) DAAC that are
specifically designed to make MODIS data more readily accessible.
These include:
The MODIS Reprojection Tool (MRT)
allows you to reproject the MODIS Level-3 tiles and mosaic
them together. You can also use the MRT to convert the data to
binary.
The LDOPE Tools
allow you to manipulate the MODIS product files and are
particularly useful in allowing you to unpack the QA bits
associated with each product. These tools can also be used to
convert the data to binary.
Note: In addition many users have found that the free HDFLook
software from the Laboratoire d'Optique Atmosphrique at the University
of Lille works well with MODIS Products in HDF-EOS.
Specific Tools for MODIS BRDF/Albedo MODEL Parameters (MOD43B1)
While some users are content to use the MODIS black-sky albedo at
local solar noon and the white-sky albedo measures as provided in
MOD43B3, most researchers want to make use of the BRDF model
parameters (MOD43B1) to obtain black-sky albedos at other solar
illumination angles through the use of a simple polynomial or to
combine the black-sky and white-sky albedos as a function of
optical depth to calculate "actual" or blue-sky albedos for
validation studies. Many others wish to model directional
surface reflectances at a
common geometry. Therefore we make the following code packages available
(these codes accept either binary or HDF-EOS inputs and thus
assume that either the user has converted the
data products to binary or the user has installed the SDPT
Toolkit -- note that a readme file is included in each tar package ):
Actual
(Blue-Sky) Albedo Computation
BRDF
Forward Model
The simple polynomial is part of the actual code or if you
just want an example of the polynomial you can
look at:
Simple
Polynomial Example
Specific Tools for QA Flags (MOD43B and MOD43C)
The MODIS BRDF/Albedo Products provide a wealth of information as
bit-packed flags. Unfortunately, users have experienced
difficulties in unpacking these flags. The LDOPE Tools
mentioned
above will work with the archived HDF-EOS files. Users who have
obtained binary CMG data from this Science Computing Facility (or
who have already converted the data to binary) may wish to prefer
some simple C-code to unpack the bits.
Unpack
Binary Bit Flags
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Author:Crystal Schaaf
Last Updated:5 July 2006
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