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GVAR Image Index Files

GVAR Index File Naming Convention

The naming convention is: signal_type.ccyy.ddd.hhmmss.INDX

Where:

signal_type	is the satellite signal type, e.g., gvar
cc	is the century when the image started
yy	is the year when the image started
ddd	is the julian day the image started
hh	is the UTC hour the image started
mm	is the minute the image started
ss	is the second the image started

As an example, the index file name for a 1996 GVAR image, whose nominal image date and time are 228 and 12:20:00, respectively, has the name gvar.1996.228.122000.INDX . This date and time is the "priority frame start time" from the satellite.

GVAR Index File Format

Each GVAR index file text entry has the following six fields GVAR

*Field Name*	*Description*
SDF name	name of the Stretched Data Format file containing the block
Word Offset	a four-byte word offset into the SDF file that locates the word containing the starting bit of this block.
Bit Offset	a bit offset into the word pointed to by the Word Offset to locate the block's starting bit
Length	the length of the block in bits
Block Type	the data block type identified; values are 0 to 10 (see Appendix A, GVAR Signal Characteristics)
Image Line	the image line this block is associated with (GVAR block 0's only)

Sync errors and bit-slip errors are also logged in the GVAR Image index files.

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