MISR Level 1B2 and AGP Conversion to ASCII Routines

The MISR Level 1B2 to ASCII and MISR AGP to ASCII conversion routines
	l1b2_to_ascii
and
	agp_to_ascii

read parameters from MISR Level 1B2 or AGP data files and write those parameters 
to a set of ASCII formatted files, with one output file for each MISR block for 
each parameter.  

These routines are written in Exelis Visual Information Solutions IDL programming language. 
They can be run either with a licensed version of the IDL software package or 
by using the IDL Virtual Machine application. The IDL Virtual Machine is a free 
runtime version of IDL available from Exelis Visual Information Solutions at
 
http://www.exelisvis.com/Downloads/ProductDownloads.aspx

The IDL VM software may be downloaded from this site or ordered from Exelis VIS on 
CD at no cost. The site provides installation instructions. These code was 
developed and tested with IDL and IDL VM version 6.1 and if using IDL VM, 
should be run with IDL VM 6.1 or higher.

Installation
To install this software, put all of the files into a single directory. The 
files include
	For L1B2 to ASCII conversion:
		l1b2_to_ascii.pro
		l1b2_to_ascii.sav
		read_global_attr.pro
		read_grid_field.pro
		l1b2_to_ascii.prj
	For AGP to ASCII conversion:
		agp_to_ascii.pro
		agp_to_ascii.sav
		read_grid_field.pro
		agp_to_ascii.prj

Execution
To run the programs:

If you have a licensed version of IDL, start the IDL development environment 
and, from the idlde File menu, open the appropriate .prj (IDL project) file.  
From the idlde Project menu, choose Build and then choose Run. 

Using the IDL Virtual Machine, 
a.  on a Unix system at the Unix command prompt, type idl -vm
b.  on a PC, double click on the IDL VM desktop icon or invoke IDL VM from the 
    Start>Programs menu

The IDL VM splash screen will be displayed. Click anywhere on the splash screen 
and then use the dialog box that appears to navigate to and select the 
appropriate .sav (IDL pre-compiled) file.  Or, on a PC you can drag the 
appropriate .sav file from a Windows Explorer window onto the IDL VM desktop 
icon and then click on the splash screen and the program will start directly.

Input:

The program will display a file selection graphical user interface box for 
choosing a list file.  This list file should contain the file name with full 
path of each of the MISR Level 1B2 or AGP files to be converted to ASCII, one 
file name per line.  The default location for this file is the directory where 
the code for these routines resides.

Output:

One file is written for each block containing good (non-fill) data** for each 
parameter, in ASCII text format. The files are written to the directory that 
contains the MISR file being converted, and the files are named using the 
original file name with the parameter and block number appended and a .txt 
suffix, e.g., for the Level 1B2 routine 

MISR_AM1_GRP_ELLIPSOID_GM_P016_O029945_AF_F03_0024_BlueBand_Block19.txt

and for the AGP routine

MISR_AM1_AGP_P016_F01_24_GeoLatitude_Block10.txt

A MISR block is dimensioned with m samples or pixels by n lines, 
e.g. 512 samples by 128 lines or 2048 samples by 512 lines, depending on the 
parameter, and that format is used in the output file.  That is, there are 128 
lines of data, each containing 512 values, or 512 lines of data, each 
containing 2048 values.

**NOTE:  MISR makes measurements in the daylit portion of each orbit.  There 
are 180 blocks defined to cover full extent of the daylit orbit range, but only 
about 144 of those 180 blocks fall within the daylit portion for any given 
orbit.  The range of blocks containing good Level 1B2 data for a particular 
orbit varies depending on the time of year.  The remaining blocks contain only 
fill values and are not written out by the Level 1B2 conversion routine. For 
the AGP, all 180 blocks contain latitude and longitude values for the orbit 
path, so files are created for all 180 blocks.

Updated: 
August 03, 2010  - changed link to IDL VM from RSI to ITT VIS
January 24, 2012 - changed link from ITT VIS to Exelis VIS