It's just a tad bit more complicated than that

Really? Don't misunderstand, I am not doubting you; but I am curious as to what those complications would be. IANARS.

With GPS the missile will always know exactly where it is, and exactly where it needs to go. Too far South? Just fire a small maneuvering jet and aim it a bit more North.

What am I missing here?

tanstaafl.
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"There Ain't No Such Thing As A Free Lunch"