NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: USNA Sight Reduction?
From: Stan K
Date: 2015 Oct 20, 15:51 -0400
From: Stan K
Date: 2015 Oct 20, 15:51 -0400
Lu,
From Bowditch 2002:
2000. Computer Sight Reduction
The purely mathematical process of sight reduction is
an ideal candidate for computerization, and a number of
different hand-held calculators and computer programs
have been developed to relieve the tedium of working out
sights by tabular or mathematical methods. The civilian
navigator can choose from a wide variety of hand-held
calculators and computer programs which require only the
entry of the DR position, altitude and azimuth of the body,
and GMT. It is not even necessary to know the name of the
body because the computer can figure out what it must be
based on the entered data. Calculators and computers
provide more accurate solutions than tabular and
mathematical methods because they can be based on actual
values rather than theoretical assumptions and do not have
inherent rounding errors.
U.S. Naval navigators have access to a program called
STELLA (System To Estimate Latitude and Longitude Astronomically;
do not confuse with a commercial astronomy
program with the same name). STELLA was developed by
the Astronomical Applications Department of the U.S. Naval
Observatory based on a Navy requirement. The
algorithms used in STELLA provide an accuracy of one
arc-second on the Earth’s surface, a distance of about 30
meters. While this accuracy is far better than can be obtained
using a sextant, it does support possible naval needs
for automated navigation systems based on celestial objects.
These algorithms take into account the oblateness of
the Earth, movement of the vessel during sight-taking, and
other factors not fully addressed by traditional methods.
STELLA can perform almanac functions, position updating/
DR estimations, celestial body rise/set/transit
calculations, compass error calculations, sight planning,
and sight reduction. On-line help and user’s guide are included,
and it is a component of the Block III NAVSSI.
Because STELLA logs all entered data for future reference,
it is authorized to replace the Navy Navigation Workbook.
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So STELLA just needs a computer. It is not dependent on other "outside" electronics.
Stan
-----Original Message-----
From: Lu Abel <NoReply_LuAbel@fer3.com>
To: slk1000 <slk1000@aol.com>
Sent: Tue, Oct 20, 2015 2:39 pm
Subject: [NavList] Re: USNA Sight Reduction?
From: Lu Abel <NoReply_LuAbel@fer3.com>
To: slk1000 <slk1000@aol.com>
Sent: Tue, Oct 20, 2015 2:39 pm
Subject: [NavList] Re: USNA Sight Reduction?
Stan:
Stella is, I presume, a computer program? Just want to clarify the electronics dependency....
Lu
From: Stan K <NoReply_StanK@fer3.com>
To: luabel{at}ymail.com
Sent: Monday, October 19, 2015 7:57 PM
Subject: [NavList] Re: USNA Sight Reduction?
Lu,
My guess is that they will be using their own STELLA program.
Stan
-----Original Message-----
From: Lu Abel <NoReply_LuAbel@fer3.com>
To: slk1000 <slk1000---.com>
Sent: Mon, Oct 19, 2015 6:42 pm
Subject: [NavList] USNA Sight Reduction?
Okay, the US Naval Academy is resuming teaching of celestial navigation. But has anyone heard what methodology they will teach for sight REDUCTION??
Are they going totally non-electronic by teaching HO229 or HO249 (or maybe even NASR)? Or will they allow the use of calculators (or a fine computer app, like list member Stan Klein's Celestial Tools)?
I guess another way of asking my question is how far back in time are they going? What technologies do they consider "unacceptable" in whatever scenario has caused them to once again teach celestial??
Even more important, what is the scenario? The bad guys knock out all the GPS satellites? Okay, there are other GNSS systems, some owned by countries that logically might be the "bad guys" I suspect they wouldn't shoot down or jam their own systems
Or maybe jamming GPS. I rather strongly suspect that the US has (and has had for a long time) drones that will home in on and destroy a jammer.
Etc, etc, etc. Is there truly a credible scenario, or is the Naval Academy responding to traditionalists but justifying the move by citing some vague and unspecified threat to GPS and friends?
