NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Andrés Ruiz
Date: 2009 Jan 9, 09:01 +0100
Sincerely is the first
time I have heard the name of Sinellius. But the described method is very
common in Coastal Navigation:
Fix by 3 simultaneous bearings or
Fix by two simultaneous horizontal angles
THE METHOD
is one of my favorites
for its simplicity and precision.
D: Bearing
AH: Horizontal Angle
-Ref: [NavList 2504] Re: Coastal Plotting Sheets. 28/03/2007-
AH = ANG_H( visual1,
visual2 ). From the sea, there are tree cases:
·
AH = 90º
·
AH <
90º a = 90-AH
towards sea
·
AH >
90º a = AH-90
towards land
Is independent of total
correction = variation + deviation, (supposing deviation is the same for the
two bearings: AH = Dv2-Dv1 = Da1+dm+Des1 - (Da2+dm+Des2) = Da2-Da1 . v:true,
a:compass)
You can use it in tree
different ways:
1.
three bearings directly
2.
two horizontal angles directly
3.
two horizontal angles by three bearings:
AH1 = D2-D1 AH2 = D3-D2
THE INSTRUMENTS
I usually use a sextant,
or a hand- bearing compass, (HOCKEY PUCK – Celestaire)
Aboard an
THE PLOT on a nautical
chart
I use tree methods for
plotting.
1.
The direct is to use a stationer pointer
2.
The plotting tools like rules and
compass, more complicated
3.
The plot on fig 2. (s/v is the fix)
IN PRACTICE
For practice, when I go
sailing near the coast, I usually check my position with this method against
the GPS, and the results always are very good.
Once I use a Perolus
Compass aboard a cargo and compare the bearings with the hockey puck; they were
the same. Also I have compared the hockey puck with other hand-bearing
compasses and its superiority is clear, up to 3 degrees of error in the same
conditions.
REFERENCES
My spanish bibliography
has lot of references to this method. (a book is available off list by request,
because “this is illegal”, like “The Black Crowes” song
says)
Andrés Ruiz
Navigational Algorithms
http://www.geocities.com/andresruizgonzalez
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