A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: John Karl
Date: 2015 Apr 29, 18:32 -0700
This discussion of advancing LOPs suffers from several of us having a different understanding of what’s known at the start of the running fix.
I’m considering starting from an estimated position determined by a relative accurate LOP1 but an estimate of position along LOP1. This EP1 has a far superior accuracy perpendicular to it (of say 1 or 2 miles like CN) with an accuracy along the LOP that’s far less (determined by dead reckoning from previous knowledge, hours before acquiring LOP1). LOP1 greatly improves the accuracy perpendicular to itself, but leaves the accuracy along itself unchanged.
Frank in Post (g11185) assumes the traditional running fix (RFIX) is completely accurate (say within CN tolerances) and that the DR estimated from LOP1 to LOP2 is completely accurate. But, as the attached figure shows, this is an additional conformation of my observation that this tradition considers the distance perpendicular to LOP1 to be accurate and completely ignores any knowledge of distance along LOP1. In fact you can easily visualize from the figure that any DR track with the same LOP1 perpendicular as the ones shown will yield the identical RFIX. Its orientation can be anything.
This assumption means that the accuracy of our dead reckoning from LOP1 to LOP2 is determined by the orientation of LOP1 !!!
Hence my old question: How can the orientation of a previously acquired LOP have anything do with the accuracy of our latest dead reckoning??
(The estimated position technique doesn’t present this conundrum.)
Nothing “fixes” the mind like tradition,