From: roy@mchip00.med.nyu.edu (Roy Smith)
Newsgroups: rec.boats
Subject: Re: Celestial vs. GPS (was Re: Bermuda Trip - 7/'93)
Date: 29 Dec 92 21:44:17 GMT
Organization: New York University, School of Medicine
NNTP-Posting-Host: mchip00.med.nyu.edu

bartley@spss.com (Dennis Bartley) writes:
> You really don't have to be a rocket scientist to use Loran or GPS,
> and with just a little thought you can tell the position it's giving
> is in error.

	I think part of the problem is that most people don't understand the
difference between precision and accuracy, and assume that just because a
Loran shows you your position to 1/10th (or even 1/100th) of a minute it
must be correct.

	Case in point: last year I was on a boat with Loran in the Around
Long Island Race (that's not saying much; I doubt there was a boat that
didn't have it).  The "navigator" had brought his own Loran with him; a
snazzy unit with a nice dot-matrix LCD display, course plotter function, 99
waypoints, etc, etc.  On the last morning of the race, I was doing my own
navigation (good old visual bearings and pencil plots on a chart) when I
noticed the Loran coordinates didn't make any sense.  It took a lot of
convincing to get the Loran owner to believe me that something was wrong.
It wasn't until I dragged him to the chart and showed him where his box said
we were, then dragged him up on deck and pointed to an object and said,
essentially, "Look over there; that's Stratford Shoals Light, about a mile
or so to the north of us.  Your box says it's to the south of us.  Either
your box is wrong, or somebody moved the light since this chart was
printed".

	Maybe the problem is that it *doesn't* take a rocket scientist to
push buttons on a Loran.  Any dummy can do it, which means there are lots of
people who are fooling themselves that they know how to navigate when all
they really know is how to hit the "on" button and read numbers, a skill
which isn't much harder than telling time from a digital clock (and if
telling time is so easy, why is there an entire usenet newsgroup devoted to
it?).

	I remember reading a neat letter in Ocean Navigator a year to two
back about two boats, both with mis-functioning Lorans, who managed to
navigate jointly.  Apparantly, each could get a single reliable TD out of
their units (I think there was some chain-wide problem causing the
flakyness), but each boat got a different line (i.e. one boat had the 9960-X
TD while the other had the 9960-Y TD, or something like that).  They spent
the whole passage in VHF contact with each other exchanging their TD data,
and doing essentialy running fixes.  That says to me these people really
understood navigation and the tools they had.  It wasn't the tools that made
them navigators, but the knowledge.  My guess is that most people who own
Lorans wouldn't know a TD if it bit them on their waypoint.

> For those who sail offshore, it should be an essential tool to back
> up sometimes tempermental electronics.

	I've only got a single offshore trip (i.e. out of sight of land for
a whole day or more) under my belt, so I'm not much of an expert, but it
seems to me that celestial is more than just an essential backup.  If you
don't spend several hours a day taking, reducing, and plotting sights, what
else are you going to do to keep from going stir-crazy in the middle of the
ocean?
-- 
Roy Smith <roy@nyu.edu>
Hippocrates Project, Department of Microbiology, Coles 202
NYU School of Medicine, 550 First Avenue, New York, NY 10016
"This never happened to Bart Simpson."
Newsgroups: rec.boats