UMass Boston

MODIS User Tools

General Tools for MODIS L3 Data

Level-3 500m MODIS Land (MODLAND) products are archived in equal area tiles of 2400 by 2400 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 commercial 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 (MCD43A1 MODIS BRDF Model Parameters and MCD43A3 MODIS Albedo for example). However there are two free tools that have been made available by the Land Process Distributed Active Archive Center (LP DAAC) that are specifically designed to make MODIS data more readily accessible.

These include:


  • 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 Atmosphérique at the University of Lille works well with MODIS Products in HDF-EOS.

Specific Tools for MODIS BRDF/Albedo MODEL Parameters (MCD43A1)

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 MCD43A3, most researchers want to make use of the BRDF model parameters (MCD43A1) 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):
 


The simple polynomial is part of the actual code or if you just want an example of the polynomial you can look at:

Specific Tools for V005 QA Flags (MCD43A and MCD43C)

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.

Professor Crystal Schaaf’s Lab

School for the Environment
University of Massachusetts Boston
100 Morrissey Blvd.
Boston, MA 02125