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John Karl continues to lay down the law about the worthlessness of a running
fix.

I will suggest a plausible scenario, and perhaps John will explain why a
navigator should not learn how to cope with it.

============================

As navigator, John has been travelling toward a coast under overcast skies
for several days. He has little notion of his position.

On a black night, with a bit of haze, a distant lighthouse is seen on the
starboard bow, and identified by its pattern. Because of the haze, the light
isn't at "dipping
distance", but somewhat closer. It's impossible to know how much closer. A
bearing is taken, and a line drawn on the chart. This is just a LOP. There's
no reason to choose any one point in preference to any other, on that LOP,
and mark it as an "estimated position". Any position, up to the dipping
distance, is as possible as any other.

John continues on the same course, and some time later, another bearing is
taken of the same light, after there has been an appreciable change in its
bearing.

No other information is available.

Will John discard the information provided by those bearings, because of
some purist objection-on-principle to the notion of a running fix? Or will
he estimate the course-and-direction travelled in the interim, allowing for
any tidal stream as best he can, offset the first LOP correspondingly, and
cross it with the second bearing?

It doesn't bother me what name is given to that procedure; whether it's a
"fix" or "not a fix". Under those circumstances, it provides the best
position that can be obtained. Why should a student not learn it?

George.

contact George Huxtable, at  george@hux.me.uk
or at +44 1865 820222 (from UK, 01865 820222)
or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.

===================

John Karl wrote-
| My argument against running fixes has nothing to do with how they're
| taught, but it does challenge why they're taught -- at all.
|
| It has nothing to do with how the location DR2 was estimated.  As long
| as DR2 is found by combining relatively inaccurate data, and not by
| forming a fix of a third LOP with LOP2, it is irrelevant what (or
| which) estimates are included in DR2: speed, time, logged distance,
| drift, current, averaged headings, the flight of birds, etc.  I'm
| talking about arriving at DR2 without a bona fide fix.
|
| I pointed out that the concept behind the traditional running fix is
| based on two ridiculous assumptions: the assumption that the estimated
| DR track perpendicular to LOP1 is completely accurate while the DR
| component parallel to LOP1 is completely without value.
|
| I ask again, can anyone on the List refute these these two
| assumptions??  Can anyone justify them??
|
| Ah, the traditions of the sea.
|
| JK
|
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| Or post by email to: NavList@fer3.com
| To , email NavList+@fer3.com

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