I have no first hand experience of this but I have been looking into celestial navigation as an altenative to GPS. It is my understanding that to get the most accurate reading possible you need to have an up-to-date nautical almanac to list all the daily variations in sun and star positions (relative to us) due to semi-eliptical orbits etc.. This information is only published for maritime areas as far as I can tell. With the information in the nautical almanac it is possible to get your position to within 2 nautical miles.. Without it you would be doing well to get to within 10.. Thats pretty good when your at sea and looking for a land mass but not much use on land when, more than likely, you could be reading a map to provide much greater accuracy..
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