IDL HDF-EOS Data Access Utility Routines for use with MISR Data Files

A set of callable IDL routines has been written to simplify accessing data 
stored in MISR files.  Additional "wrapper" routines are also available to 
provide examples of calling these routines. This code was developed using IDL 
version 6.2.

The utility routines can be used with MISR Level 1B2, Level 2, and Level 3 data 
files, which are all written using the HDF-EOS grid format. The utilities are 
not for use with the Level 1A or Level 1B1 MISR data products since these are 
written using the HDF-EOS swath format.

The MISR Data Products Specifications (DPS) documents, available at
       http://eosweb.larc.nasa.gov/PRODOCS/misr/DPS/
are a source of detailed information for MISR data files. These documents 
contain descriptions of the contents and structures of each MISR file type.  
Use these documents to find information that will be passed as parameters to 
these utility routines, such as the names of the data fields, grids, and 
attributes. A good overview of MISR file layout is contained in section 3 of 
the DPS. The DPS document has been revised as MISR file formats have evolved. 
Be sure to use the version of the DPS that matches the version 
of the data file you want to access. The MISR Data Versioning web pages, 
       http://eosweb.larc.nasa.gov/PRODOCS/misr/Version/
describe the data file versions with links to the appropriate DPS version.

The four utility routines are:

read_grid_field.pro - reads a data field (MISR parameter) from the specified file

read_grid_attribute.pro - reads a grid attribute (grid metadata) from the specified file

read_global_attribute.pro - reads a global attribute (file metadata) from the specified file

read_vdata.pro - reads the records in an HDF vdata table. The vdata records are 
returned in an array of IDL structures, where the structure contains one record 
from the vdata and the structure tag names are the names of the fields in the 
vdata. MISR uses vdata structures to store orbit per-block metadata and other 
information as described in the DPS.

Documentation of the input and output parameters and a usage example are 
provided in the header comments of each utility routine. In addition, sample 
"wrapper" routines are provided to show the use of these utilities in the 
context of reading information from MISR data products. The routines provided are:

l1b2_wrapper.pro - reads data fields, global attributes, grid attributes, 
including a radiance scale factor, and the per-block metadata vdata from a MISR 
Level 1B2 data file

l2aerosol_wrapper.pro - reads a data field, global attributes, and grid 
attributes from a MISR Level 2 aerosol data file

l2land_wrapper.pro - demonstrates reading values from a MISR Level 2 land 
surface file, including a data field (LandBRF), global attributes, and grid 
attributes related to LandBRF

l3_wrapper.pro - reads a data field and two file metadata vdata structures 
from a MISR Level 3 global aerosol file

Questions concerning the use of these routines may be addressed to User and 
Data Services at the Atmospheric Science Data Center:

e-mail:  support-asdc@earthdata.nasa.gov
phone :  757-864-8656
fax :    757-864-8807
mailing address:
User and Data Services
Atmospheric Science Data Center
NASA Langley Research Center
MS 157D
Hampton, VA  23681-2199  USA