Description of ASCII and Binary Logs with Short Headers

One difference from the standard OEM7 logs is there are two possible headers for the ASCII and binary versions of the INS logs. Which header is used for a given log is described in the log definitions in the SPAN Logs chapter. The reason for the alternate short headers is that the normal OEM7 binary header is quite long at 28 bytes. This is nearly as long as the data portion of many of the INS logs and creates excess storage and baud rate requirements.

These logs are set up in the same way as normal ASCII or binary logs except a normal ASCII or binary header is replaced with a short header (see Table: Short ASCII Message Header Structure and Table: Short Binary Message Header Structure).

Short ASCII Message Header Structure

Field	Field Name	Field Type	Description
1	%	Char	% symbol
2	Message	Char	This is the name of the log
3	Week Number	Ushort	GNSS week number
4	Seconds	GPSec	Seconds from the beginning of the GNSS week (Same byte arrangement as a Float type)

Short Binary Message Header Structure

Field	Field Name	Field Type	Description	Binary Bytes	Binary Offset
1	Synch	Char	Hex 0xAA	1	0
2	Synch	Char	Hex 0x44	1	1
3	Synch	Char	Hex 0x13	1	2
4	Message Length	Uchar	Message length, not including header or CRC	1	3
5	Message ID	Ushort	Message ID number	2	4
6	Week Number	Ushort	GNSS week number	2	6
7	Milliseconds	GPSec	Milliseconds from the beginning of the GNSS week (Same byte arrangement as a Long type)	4	8