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Alex wrote:-
   >Some books consider finding a fix from 3 lines
   >of position. This case also popped up in our infinite
   >discussion of the Averaging.
   >Can anyone explain, under what circumstances one could
   >possibly want to determine her position from 3 LOP's?
   >It is hard to imagine (for me) such circumstances.
   >(Hard but possible).
   >Alex.

It is only with 3 LOP's that you can create a cocked hat :)

Seriously though, 4 LOP's, with azimuths approximately 90 degrees apart, are
better than two.

The 4 LOP's would create two sets of "tram lines" at right
angles to each other. The 4 LOP's are reduced to two by bisecting each set
of tramlines. Your position is now uniquely defined by the intersection of
these two LOP's.

The advantage of this procedure is a reduction, if not complete elimination,
of errors in dip or index error.

Geoffrey Kolbe

   

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