Over the years there has been a great deal of speculation and debate about
whether the approach to the advanced LOP employed what is known as an “offset.”
When trying to find an island using only a Line of Position, it makes sense
to deliberately “offset” your approach to one side or the other.
This deliberate error removes the doubt about which way you should turn
when you get to the line.
However, in Earhart’s case, the intention was never to use only
the advanced LOP to find the island. Radio Direction Finding was supposed
to provide guidance for the final approach and the phrase “We must be on
a straight-in approach to a specific spot where the island was expected
to be. Of course, no one can say for sure, but we see nothing to indicate
that an offset was used and some evidence that an offset was not employed.
See map at LOP Map and
discussion of LOP navigation at Navigation FAQ.