In article , nafod40
wrote:

Mike Kanze wrote:
Of course it helps mightily if you have a reasonably accurate fix from the
ship before you launch - unlike the pre-launch (and pre-GPS) 40 nm-in-error
"fix" that the CORAL MARU gave a VA-95 crew during its 1975 cruise. (Sea
story previously shared in this NG.) If you don't know from where you
started, DR by itself isn't going to get you home. Worse if you THINK you
know from where you started - like the VA-95 crew, but are wrong and don't
know it.

We were doing blue water ops, and launched on an alert. I was a nugget
null-P in the E-2. The CAPC makes a big deal about grabbing an accurate
chart that's up to date before we going flying. We get airborne and he
opens the chart up...and it's all blue. Top to bottom, left to right. He
looks at it for a second, closes it back up and sticks it in the navbag
and says, "I guess we're there!"

The INS on the ICAP II Prowler was actually pretty good, aligned well,
rarely lost it's platform or ran away too badly (except when really
needed of course). But when getting a CV alignment you often found the
ship had given you the wrong position. The problem here is that you
need an accurate INS position to the real geography to steer the
jammers and give valid steering data to the HARM. So....... launch,
manually degrade the INS and get an accurate update off of something,
apply manual mag var and winds to keep the system as tight as possible,
then when it's time to go home to an EMCOM mom, upgrade to INS mode
again and even though it's not accurate to the real world, point 0 is
still reasonably close to where you left and then apply the recovery
PIM and hopefully the auto dawg machine was where you thought it was.
And when it's not, fess up and call the Hummer or look for the nastiest
thunderstorm around and the boats under it.......

Pugs