Conference vicki::boats

    
    
    	You are better off saving your money and buying a good set of
    charts for the area that you will be boating.  With the charts you
    have more detail and you can add notes and highlight area that you
    fish etc..   You will need a loran or GPS for navigation and direction
    finding to use with your charts.
    
    		George (JOY III)

Even with an electronic chart/plotter/loran/gps combo you still need the paper charts
For emergency use as well as more defined bottom contour lines for fishing.

If your electronics ever don't work you have the chart and a compass to get you back.

Gordon

The most important thing to remember about electronics at sea is:

	They WILL fail, usually when you most need them.

So, yes, get paper charts, a good compass, a depthsounder, and a
distance log. With them, you can actually navigate quite well with a 
little practice. With a GPS or a loran you'll be able to get whereever
you want to go quite easily. I've been very unimpressed with electronic
charts. Besides the expense and limited resolution, as has been mentioned, 
you can't write notes on or make corrections to electronic charts. 

After all, lorans weren't really affordable until 1982 or later. Before 
then, everyone managed with compass, log, chart, and leadline. 

Alan

    If you have a choice go with GPS.  Loran is good but no one knows how
    much longer it will be supported.
    
    Dennis

    > If you have a choice go with GPS.  Loran is good but no one knows how
    > much longer it will be supported
    
    Just playing devil's advocate; The above is true, however, loran prices
    are reflecting the above fact. You can have loran for significantly 
    less $, and I believe it will not be going away in the immediate
    future. If you are interested in making boating  something less that
    an infinite $ sink, you may want to consider loran. If money is no
    object, I'd probably go with GPS. I think loran gives the most 
    bang for the buck.
    
    Bill
    

And to add further complications: Once you have been to a specific 
location, a loran will give better repeatability in returning to that 
location (maybe as good as 50 to 100 feet) than will a GPS. This is 
because the DoD intentionally degrades the accuracy of GPS position 
fixes for military reasons. 

We bought our loran in 1982 and it has performed reliably and accurately 
ever since. We added a GPS to our inventory last year, partly because of 
its significantly lower electrical power consumption (important when you 
are not using an engine all the time).

Alan

    re .5
    
     You are right Loran is much cheaper. That's why I don't own GPS.  
    
    But if the goverenment stops funding it as threatened in 1998,  your
    still going to want to have something to help you navigate.  The DoD
    can and does shut down GPS, but supposed only if they feel we are being
    threatened.  On the good side we (USPS) just heard that Loran will most
    likely not be shut down because some other countries are now going to
    be using a similar system.
    
    Dennis

    >  But if the goverenment stops funding it as threatened in 1998,  your
    >    still going to want to have something to help you navigate.
    
    Yup, but I'm betting that we'll still be using LORAN-C into the next
    century. And LORAN is cheaper now, and if and when it does go away,
    GPS should be even less expensive than it is now.
    
    My current GPS is a Grey Plastic Sextant that I will be becoming
    more proficient in using prior to the Marion to Bermuda Race 
    which starts on June 16th, and which allows no electronic navigation.
    
    Bill
    

    I just recently bought a GPS.  I got the cheapest I could find, which
    was about $280.  I initially planned to get a LORAN, but found that
    they are getting harder to find.  Many retailers and manufacturers are
    dropping (or severely limiting) their LORAN products in favor of GPS.
    
    That's what pushed me to the GPS.
    
    Mark,
    

Re: .9

Mark, would you please share your GPS experience? 

Did you buy a portable or a fixed unit? Which one? Why?

Have you used it? How good have you found its *repeatable* accuracy to be?

Is it susceptible to outside interference? (Like, my LORAN won't lock on
in my back yard if there's a TV turned on in the house.)

What kind of boat are you using it on? Is it under a cover of any kind?

...

Thanks,

Art 

    
    
     Re:.10
    
     Art,
    
      This year we installed an LMS 350 GPS unit on the charter boat, all
    i can say is that is one darn fine unit, easy to use, many options to
    choose from, and very easy to read.
    
       in the experience i have with using it this year it has done a fine
    job, havent had to deal with blinking numbers yet, and one of the
    waypoints that we have stored is the chanell marker bouy at sodus point
    and that waypoint has not moved since, when the arrival alarm sounds
    you can reach out and touch the bouy. ( the only reason this waypoint
    was entered was for checking returnability) we have absolutly NO
    negative comments about this unit (except cost).
    
    
                                              Lee
    

    Art,  I'll be happy share my experience with the GPS as soon as I
    get a chance to go fishing!
    
    I got the Meridean handheld from Magellan.  It has all the features
    I'll need, even though it is the cheapest available.  I'm using it
    in an open boat.  Even though I got the handheld, I will probalby get
    the mounting bracket and power to go with it.
    
    Mark,
    

re .10:

We have both loran and GPS. Watch the lat/long displayed by a non-moving 
GPS -- they will vary quite a bit over a short time (a few minutes). 
I've seen published plots that show the variation to by on the order of 
a few hundred yards. This says that you shouldn't depend on the 
repeatability of a GPS to find, say, a bouy in dense fog. Our loran, on 
the other hand, is very repeatable, good enough that we have to be 
careful not to hit the bouys. 

Moreover, if GPS positions had excellent repeatability, why would the 
Coast Guard being spending so much money on differential GPS? 

Alan

��              <<< Note 1213.13 by UNIFIX::BERENS "Alan Berens" >>>
��                      -< GPS repeatability not too good >-

��re .10:

��We have both loran and GPS. Watch the lat/long displayed by a non-moving 
��GPS -- they will vary quite a bit over a short time (a few minutes). 
��I've seen published plots that show the variation to by on the order of 

    It's my understanding that the DOD reduced accuracy is
    induced as a 'wobble' about the actual position.  Given
    this, variations of a non-moving GPS are to be expected.

    So, you can either take readings over some period of time,
    (like 24 hours) and average them, or wait for the US to
    invade Iraq again, and have SA turned off.

re .14:

Yes, but the inaccuries (wobble) also affect the lat/long displayed by a
moving GPS receiver, but when the receiver is moving it is much more
difficult to see (if you can see at all) the wobble in position. The
uncertainties in position are, I assume, one reason the speed over
ground given by a GPS is rather inaccurate (about 8% error in some
tests). Besides, iff'n you're looking for a bouy in the fog, you want an
accurate position now, not in 24 hours (or whenever). The uncertainties
in GPS positions is one reason we recently had our 1982 vintage loran
overhauled and realigned. 

Alan

>>                                        <<< Note 1213.15 by UNIFIX::BERENS "Alan Berens" >>>
>>
>>re .14:
>>
>>Yes, but the inaccuries (wobble) also affect the lat/long displayed by a
>>moving GPS receiver, but when the receiver is moving it is much more
>>difficult to see (if you can see at all) the wobble in position. The
>>uncertainties in position are, I assume, one reason the speed over
>>ground given by a GPS is rather inaccurate (about 8% error in some
>>tests). Besides, iff'n you're looking for a bouy in the fog, you want an
>>accurate position now, not in 24 hours (or whenever). The uncertainties

    Back when I was a kid, we didn't have loran or gps.  We'd
    de'd reckon for gongs, whistles and bells, and then use our
    ears.   

    Of course, now, the right tool would be radar.

    We've done about 15,000miles on our boat in the last 2 years, some
    inshore and mostly offshore. With 2 Lorans and the cheapest GPS we
    could get at the time (a Garmin), we've found the Lorans to be
    superfluous and even downright innaccurate much of the time. Many times
    less than 2 miles offshore US, we couldn't get a fix from the Lorans at
    all, but never ever had a problem with the GPS. Let's face it, although
    there may be some slightly improved repeatability over GPS, the Loran
    is old technology whose days are numbered.
    
    Also, many times the Lorans have proven to be a mile off or more, the
    GPS is NEVER wrong. Fixes to within 60 feet are not very useful, most
    of the time anyway, so a few feet more accuracy on a Loran is just a
    technicality that means little when nevigating.
    
    Who's still using RDF these days?
    

Loran may be old technology, but there is still an argument for using 
it. Last night I watched the position given by my GPS while it sat 
motionless in my yard. Over several minutes, the positions it gave
varied by almost 500 feet. Granted, this much variation is obviously
completely unimportant when well offshore or navigating in good
visibility. 

But ...... I've used my 1982 vintage loran along the American east coast 
from Cape Cod to Lunenberg, Nova Scotia. The only time it has failed to 
give good positions was within a few miles of the very high power Navy 
transmitters in Cutler, Maine. 

The absolute accuracy of a loran is perhaps a quarter mile, which is 
worse than that of a GPS. The repeatable accuracy of a loran is 50 to
100 feet. Depending on your use, this greater repeatable accuracy may or
may not be important. 

An example. One morning we left Pulpit Harbor, ME, in good visibility. 
Several miles from the harbor, dense fog quickly closed in. As Pulpit 
was the nearest harbor, we decided to return. The entrance to Pulpit is 
maybe 100 feet wide with rocky shore to either side. Visibility was
maybe 100 feet at most. We had noted the loran TDs at the center of the
entrance. Which would you rather depend upon for finding the entrance, a
loran or a GPS? I'll take the loran. And ours got us back to the center 
of the harbor entrance without any searching for it. 

A simpler example. A prudent mariner will never depend on a single means 
of finding position. It is much easier to find a bouy in dense fog if 
you can get to within a hundred feet of it rather than several hundred 
feet. 

One of the interesting things about boating is that for every problem, 
there is seldom or never just one right answer. I've found that there 
are usually multiple answers, some better than others, some just 
different than others. The appropriate answer for you may not be the 
appropriate answer for someone else. 

Last year we bought a GPS. I intend to to use both GPS and loran for as 
long as loran is available. Besides, if one box fails, the other should 
still work. 

Alan

    Alan,
    
     There was an article on some radio news show in the last week about
    "commercializing" some gv't functions, GPS included. In their
    explanation of the benefits of GPS, i.e. airports now using them for
    autopilot landings, they explained more about how GPS works. Take it
    with a grain of salt - I was in heavy traffic and only half listening
    while the article was on... 
    
    It seems there are two signals from the GPS sat's. One is for military
    only and is dead nuts on. The second was designed for non-military use.
    According to the story, there are minor built in, changing error factors 
    on the non-military GPS signals to prevent an enemy from using it to
    send a missle to a very specific location. 
    
    It seems there are companies that figured that out and do
    "autocorrections". They use stationary units that detect the changes
    induced by the random number generator and send out corrected signals. 
    This is how the airport autopilot systems work. 
    
    Chuck                      

    It is the governmnent who is doing the low powered corrections.
    It is also for marine use. It is called Differential GPS, and is 
    available at numerous harbors, not just at airports.
    I believe the USGC is doing the differential GPS for marine use.
    
    Bill
    

    re Differential GPS - 
    
    In most cases, the differential receiver that you add onto a GPS set
    that is differential ready costs several times what most GPS sets cost.
    
    I'm not aware of any GPS sets with the differential GPS correction
    built in.
    
    Bill
    

Also, the range of the low frequency transmitters used for differential
GPS is rather short. Differential GPS is intended, as I understand it, 
mainly for getting large ships safely into busy ports. There won't be 
general coverage of the coast.

Alan

It was my understanding that the are enough 'differential' sites to provide 
coverage all along the coast as well as across the country. 

It is also my understanding that the 'dithering' that is applied to the GPS 
signal is specifially there to make it infeasable for a 'non-friendly' to try to
use it for weapons guidance since the 'differential' signal will not reach far 
enough off shore.

I spoke to a fellow 'deccie' from the  Springs who had been using a Megellan
5000 GPS for prospecting in the moutains. He claimed he was regularlly able to 
use the 5000 to return to no more than 50ft of a previous way point.


Fred

    Continuing on the built in error theme, with plotting in mind:
    
    I am interested in using GPS for diving.  I will cruise to the rough area
    of a wreck, then execute a search pattern while watching the echo
    sounder until the form of the wreck appears.  The plotter track will
    allow me to execute a decent search pattern.  What I don't understand
    is how the plotter track will jump about over 5-20 minutes of wreck
    hunting, and the effect this will have on my search. Can anyone explain
    please?
    
    Cheers-Ken

    When using LORAN, an abrupt jump in position results from 
    "cycle slip" where the receiver changes it's lock from the 3rd cycle
    of the received pulse to a later  (or earlier) one.
    I don't know if this is also occurs with GPS sognal processing or not.
    
    Bill
    

    If you plot GPS output without differential correction at a stationary
    point you will see the position varying up to about 100 meters.  The
    position will not be jumpy, but will move most of the time with a speed
    less than a knot.