NavList:

Well, I was an RN navigator, and they seemed to think that + or - one mile was quite good for everyday work (a bit different for the surveyors!). As an ocean racing navigator (back in the days before GPS) landfall accuracy to + or - a mile was well better than most could manage (yachts lurch about a bit), though if one could get that close, it could be a race winner (once was for me). I suspect that key variables are going to prove to be visibility and the nature of the waters near landfall. In excellent visibility super-accuracy matters less because one get the necessary visual clues to start coastal navigation well outside a + or - 1 mile CPE (I’ve taken a dawn bearing on the high mountains of northern Luzon at something like 100 miles out (very useful)). Equally, if a coast is steep to and without a litter of offshore hazards in the approaches, being accurate to + or - 10 miles is OK because, again, coastal marks will be visible in good time - inbound to HK from the Philippines I’ve picked up the chain of the Lema Islands and the high land of HK and the China coast when 40 miles out (c.25 miles from the Lemas) - a raft of bearings on all the visible peaks and then some tracing paper and getting all the bearings to line up on identifiable peaks had a visual fix (that actually confirmed what had felt like a rather iffy sun-run-sun snatched during some momentary clearances during the forenoon watch).