"Paul J. Adam" wrote in message
...
In message , Kevin Brooks
writes
"Harry Andreas" wrote in message
...
SAR updates to pre-programmed INS settings have been used since the
early 90's to improve the accuracy of GPS aided munitions.

Uhmmm...Harry, what GPS guided munitions were in service during the
"early
90's"?

"In service" or "in development and undergoing testing"?

JDAM did not begin being delivered for testing purposes until 1997, from
what I have read in a couple of sources; the program was not started until
1992. Another poster has noted that the SLAM used GPS prior to that date,
but not independently--it used an optical terminal seeker with a datalink
back to the launch aircraft.


You don't need the SAR update to launch a JDAM, but it dramatically
improves the CEP of the weapon and essentially means that you can use
a smaller weapon to take out a target.

Well, it improves it, but not sure how "dramatically";

Depends how good your maps are. GPS/INS guidance will hit a designated
point, but how well does that relate to the actual location of the
target? SAR radar helps a lot if you know that the target is "fourth
warehouse from the road" but your mapping isn't precisely sure about
exactly where in WGS84 co-ordinates that warehouse, or the road, is (but
you know fairly closely where, and the warehouses and the road both show
on SAR)

Actually, from what I have read the SAR contribution is not so much in terms
of allowing for defective mapping as it is a case of providing both a much
more accurate position of the weapon at release, and a finite
release-to-target distance and altitude. Doubtless in those areas that do
lack good digital mapping affording reliable 10-digit grids it would also be
of significant value.

Brooks