NavList:

David,

Let me clarify: First, there is no intercept involved, we're talking about any LOPs, not necessarily ones from St. Hilaire sight reductions. Second, it's not a special case. The position on LOP1 is determined both from that LOP (from whatever source) and along it from the other positional information (which I pointed out is always available, if nothing else from previous DR work). It's called an EP (estimated position) because it's partially determined by less accurate data, such as DR.

Randall,

I'm afraid you've missed the estimation concept. I used no math, only the criterion that we use all available information, make no unwarranted assumptions, and make no contradictions.

In the plots there is a contradiction between DR2 and the traditional fix located at RFIX. Otherwise they'd be at the same location. The estimation question is how best to deal with this contradictory information. Now if your DR across oceans is better than LOPs, you can ignore this discussion and leave your GPS ashore.

Regards,
John
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