From: jfh@cs.brown.edu (John F. Hughes)
Subject: Re: GPS
Keywords: Happy
Organization: Brown University Department of Computer Science
Distribution: na
Date: Thu, 8 Oct 1992 14:21:19 GMT

In article <eBs0RB2w165w@gtm-inc.com> terry@gtm-inc.com (Terry Gerritsen) writes:
>gerard@progress.COM (Gerard Bras) writes:
>> keith@iscp.Bellcore.COM (Keith Hawkins) writes:
>> >
>> >Would you recommend GPS over Loran.

>> >I don't plan to sail around the world, but sailing up
>> >to Block Island, Martha's Vineyard, Cape Cod, etc
>> >would be nice.

>> You didn't ask me but you did ask publicly so I'll just
>> jump in.  IMO, for what you want LORAN will work to 100%
>> satisfaction at a fraction of the price.  

>I have to disagree with you Gerard, LORAN will not work to 100% 
>satisfaction, if you sail, or power through any magnetic fields, it 
>will not give you accuracy, you do not encounter this with the GPS
>so what is more important a Loran that works part of the time, but
>costs a lot less, and could endager your life because magnetic fields
>interfer with its signal, or a GPS that is accurate to one foot, but cost
>three times as much. 

I have to disagree with you, Terry. It all depends on your notion 
of satisfaction. The original poster asked about sailing in the NY area, up 
to Cape Cod, etc. The nearest significant magnetic disturbance I know of (and 
I've sailed around here a good deal) happens to be at Seguin I., Maine, about 
160 miles away. Not a big threat. How well does Loran work in this area? 
Pretty well. As well as GPS? Nope. Well enough for a properly handled yacht 
to have all that she needs to stay away from the rocks? Sure. 

If your notion of satsifaction includes protection against magnetic
disturbances that you *might* encounter someday, and accuracy beyond that of
your charts (especially if you don't notice that the chart's got a different
datum than your GPS!), and does *not* involve having a well-stocked bank 
account, then GPS is the way to go. Frankly, I'd take the $600 I might save by
buying a Loran instead of a GPS and get a stormsail, of which one can never
have too many...

What would *I* do? I'd buy a $200 Loran, figuring I'd throw it away in 3 or 4
years, when I can buy a GPS for $250, which will probably last another 5-7
years.  

By the way, there are two other things worth considering: If you are unaware 
that you are sailing through magnetic disturbances, you have more troubles 
than just that your LORAN is acting up. For example, if your LORAN dies, your
*compass* will be acting up, which is a far more serious problem. The same is
true for GPS. This suggests that the most important thing is to know something
about the waters you're sailing in, and to maintain a good DR plot. 

And just as the Notice to Mariners advises something like "the prudent mariner
never bases his navigation on any single floating aid," it might be wise
to add that the prudent mariner also never bases his navigation on any single
piece of electronics.  *All* electronic equipment should be regarded as 
working "only part of the time." GPS may work during a bigger part of the time,
but ....

By the way, my in-laws were nearly killed just off the tip of Long Island this
summer. They were in moderate fog, moving at a couple of knots, about 6 miles
from shore. A very large fishing boat came out of the fog at them. It had not
heard their foghorn---its engines were far too loud---and was barelling along
at about 20 knots. No one was at the helm. One of the passengers (it was a
sportfishing boat) happened to see their boat and alert the captain, who
jumped up, disengaged the autopilot, and spun the wheel, missing my in-laws' 
boat by about 20 feet (still going 20 knots!).  Before the turn, he was headed
just about midships. This all happened in the course of just a few
seconds...hardly time for my father-in-law to alter course enough to do any
good. The best navigation/autopilot equipment in the world won't help you
without common sense. 

-John
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