Navigation the Rite Way.. or Is GPS Reliable???

[starcrest]

ITS TOO EASY THESE DAYS TO GO TO A LOCAL SHOPPING MALL TO BUY A GPS.IF THOSE WERE AVAILABLE 20 YEARS AGO THE WAY THEY ARE TODAY IT WOULDNT BE THE SAME.SEXTANTS, NAUTICAL ALMANACS,PLOTTING SHEETS,SIGHT REDUCTION TABLES ARE PROBABLY UNHEARD OF BY MANY BOATERS TODAY.BASICALLY CELESTIAL NAV PRACTICES,ONCE ACHIEVED ALLOWS THE NAVIGATOR TO TAKE A PLAIN BLANK PIECE OF PAPER,AND WITH JUST A FEW SIMPLE TOOLS A LATTITUDE AND LONGITUDE GRID CAN BE DRAWN UP FOR ANY LOCATION.(THAT IS TO SAY THE LONGITUDE LINES WILL BE PROPERLY SPACED FOR ANY GIVEN LATTITUDE)TOO MANY PEOPLE ARE OUT ON THE WATER IN MULTI-MEGABUCKS BOATS AND EVEN WITH ALL THE ELECTRONC GADGETRY STILL CANT DECIPHER A NAUTICAL CHART.I WILL AGREE THAT LEARNING CELESTIAL NAV IS LIKE LEARNING LATIN....IT IS A LOST OR DYING ART.BUT BEFORE I GO ACROSS THE OCEAN I WILLGET A GOOD METAL BODY SEXTENT AND ALL THE ASSOCIATED TOOLS AND PUBLICATIONS NEEDED TO USE IT.ON MY SECOND RETURN TRIP FROM HAWAII TO CALIFORNIA I WAS GETTING ERRONOIUS READOUTS FROM A VECTOR TWO LORAN RECEIVER.IT TOLD ME THAT I WAS TRAVELLING IN A ZIG ZAG PATTERN FROM DAY TO NITE.I ACTUALLY HAD TO REVERT TO USING A WW2 ERA SEXTANT TO GET A PROPOER POSITION AND I KNOW FROM EXPERIENCE YOU CAN NEVER DOUBT THE POLARIS SIGHT.THAT ZIG ZIG READOUT  THAT I GOT FROM DAY TO NITE PROBABLY WAS CAUSED BY RADIO WAVES TRAVELLING DIFFERENTLY FROM DAY TO NITE.ANYWAY MY SUGGESTION TO ANYONE VENTURING BEYOND THE HORIZON IS JUST BE SURE YOU ARE READY FOR ANYTHING.BECAUSE NO NATER HOW MANY THOUSANDS OF MILES OFFSHORE YOU ARE,YOU ARE NEVER MORE THAN ONLY FIVE MILES FROM........DAVY JONES LOCKER.AND THOSE THINGS DONT JUST HAPPEN IN THE MOVIES OR ON TV...THERE ARE MANY WELL FOUND STRONGLY BUILT SEAWORTHY BOATS ON THE BOTTOM.

[s/v Faith]

Good point Eric,

In the area where I sail, we experience something called a 'SRA' from time to time.  They are usually announced in the paper and local radio stations. The military can induce an error, a liner offset (I was moving 9 knots, at the dock) or just eliminate the signals from the GPS all together.

  Imagine you are 75 miles from Bermuda, and something bad happens ('bad' in a homeland security sense of the word). 

Hum....  How much food and water DO you have onboard?....


 

[starcrest]

BEFORE I VENTURE BEYOND I WILL HAVE ENOUGH TO LAST NO LESS THAN NINE MONTHS HOWEVER THE VOYAGE I WANT TO DO WILL ONLY BE 5 OR 6 MONTHS.AND THAT IS TAKING MY TIME.IF I GO INTO A HURRY UP MODE I CAN ACCOMPLISH THIS NEXT TRIP IN LESS THAN 5.THERE IS STILL MUCH STUDYING TO DO AND PREPARATION.HOWEVER  I  WILL IN FACT "KEEP IT SIMPLE......."

[Captain Smollett]

I will go so far as to carry a slide rule for doing site reductions without site reduction tables.  If I lose my slide rule, I can compute my table of sines, if need be.

Math is fun, and Celestial is very, very cool.    :D

(my personal best fix, though from a beach rather than a pitching boat, is 2 nm from actual position.  That was with a Davis Mark 15).

[starcrest]

well I used one of those tamaya 3/8 size mini sextants,and came up with 3 lines  that cross in an area the size of a match head.that was on a replica of an 1800's era clippership half way to nowhere.

[The Edge]

KISS,

     I have been know to navigate in pea soup with a compass, leadline, chart and watch in Casco Bay, Maine.  Does it get simpler than that :o?

[hearsejr]

I thinking about getting one...a cheap one for training and learning on...and was wondering if anyone in N.C. I might could get up with and learn.
I figure I could use the training and I can atleast start useing it before I go out to sea.

Bill

[starcrest]

my advice to you is to get a good metal one.the index error (or to say by how much it is innacurate) varies greately with any plastic bodied sextant.you can be this accurate tho...place a half dollar coin on a plotting sheet...you will be anywhere with in the diameter of a half dollar coin at best. its because plastic compared to metal is very unstable... in the sun its micro dimensions can change minute to minute and this becomes very apparent when you read the arc. even with a metal body one....when you take it out of the box and place it in the sun....you must let it set for a few minutes to let the index error stabilize.with  any metal bodied one you....well atleast I....have come up with 3 lines that cross ....on a plotting sheet....in the area the size of a match head....just a few square miles.depending upon your lattitude a standard vp-os plotting sheet(if you are unfamiliar witht that term look it up on any search engine) covers about 250,000 square miles.as far as learning celestial there are various aspects of it.... but  simple sun lines can be accuratly and intensively learned in one day.....but you have to do nothing but sun lines all day.if you do get into doing this dont let the mathematics scare you.its nothin more than simple addition and subtraction in groups of 60...that  is to say 35 minutes + 35 minutes does not= 70 minutes.its" 1hr 10 min." its also as easy as figuring your taxes but theres no cheating.very simply  put ,numbers are retrieved from various publications and applied to a formula.even so before you can take algeobre 2 you must take algeobra 1.before you do celestial it is a must that you can proficiently do basic navigation.....you shoud be able to plot  courses,figure speed time distance, (you know that 60d=st thing)you should be able to proficiently read a nautical chart

[Iceman]

A fellow in New Bern named Tad Michel tought us celestial nav
We also bought an Astra 3 from him them as well

He had great lessons

Not sure if hes still teaching it but tell him I sent you

Send me a personal message and Ill give yoy my email and phone number

Iceman

[hearsejr]

I would be happy to learn sun lines now and once
I have figured out how to do that, maybe try to learn the rest of it. I want to beable to have a back up for a G.P.S., so as not to end up in Detroit while looking for Bahama.
thanks.
Bill

[Captain Smollett]

There are a couple of web sites that provide various calculators useful for practice.  I do my site reductions "by hand' with a calculator or slide rule.  This eliminates needing the site reduction tables and errors introduced in interpolating the table data.  Most folks will want to use the site reduction tables, so it's a matter of choice.

Also, I don't like buying an almanac each year.  When I do buy one, I buy Reeds; it contains a LOT more than just the ephermerides of the celestial bodies, such as ABC tables (an alternative to using the standard site reduction tables) tide charts and chartlets for major ports. In addition, Reeds has good info on how to do CN that is easy to follow, no matter what method you use to reduce sites.  In other words, Reeds is a good stand-alone book - you don't NEED any other books or tables to do CN, and it CAN be used for TWO years if you want to do some extra calculations.

When land bound and practicing, I use online resources, such as:

1. Cel Nav Data

On this one, you input your assumed position, date and time and get essentially an almanac page.  Includes stars, planets and moon.  This is essentially an online epheremerides, or your online almanac.

2. Transit Times

Tables of transit time and declinations of five major planets.  Also includes equations and links to download the entire tables.

3. USNO List of Data Services

Links to many helpful and informative pages from the US Naval Observatory (including the two linked above).

4. Cel Nav Resources

Also from the USNO, links, addresses, etc useful for Celestial Navigation.

(These USNO links in turn contain links to where you can download site reduction tables if you don't use an online or calculator based method).

Also, Henning Umland provides some free javascript based site reduction calculators (a really good way to check your site reductions as you learn) and almanacs..visit these web sites and save the pages (you don't have to be ONLINE to use them, the calculator is actually stored on your computer, so you can put them on your shipboard laptop and not even fool with manual site reductions:

Site Reduction Calculators and Almanacs

And finally, FYI, Bowditch, a must read for those serious about navigation and pilotage, is available online for either full or chapter by chapter download:

Nathaniel Bowditch, the American Practical Navigator  This is the 2002 edition.

[hearsejr]

 kewl thanks for the links. I'm going to stick to the sun readings first. I have a very limited understanding of how to do that. maybe in 5-6 years I'll understand this stuff. lol
thanks,
Bill

[s/v Faith]

I like Reeds also, and have the companion, the 2006 almanac.

  Sadly they elected to remove the sight reduction tables from the almanac (last year? Two years ago?)

http://www.reedsalmanac.com/

  You can purchase a separate book 'Reeds 2006 Astro Navigation Tables'

  I have all three right here next to me at the moment.  ;D

[Captain Smollett]

kewl thanks for the links. I'm going to stick to the sun readings first.

Bill,

Those links and calculators, etc, are useful for doing sun sites.  I use them for that as well.

Sadly they elected to remove the sight reduction tables from the almanac (last year? Two years ago?)

I did not know that!   :(

I do not use reduction tables anyway.  I can crunch the numbers with a regular calculator (the equations are simple) just as fast, and do the same with a slide rule almost so.  It elminates the need for the extra books (SRTs), but is not approach for everybody.

[hearsejr]

thanks, I got a couple of good higher quality calculators, both with solar cells and they work great. ofcourse I've never  even seen a slide rule  :o LOL

[starcrest]

if you really want to get a good idea of the celestial nav process,once you learn basic sun lines then get all your toys together and go for a long ride up and down the coast in your car.take sunlines along the way at various stops.for wwv time I brought the short wave receiver with me.take as many lines as possible and  record the info on paper(tme and arc reading)then go home and worke out all the sights and see how well you tracked the motion of your car.moving at that speed the lines will show drastic changes.

[Captain Smollett]

if you really want to get a good idea of the celestial nav process... go for a long ride up and down the coast in your car.

That's a really good idea.  You don't HAVE to be on the coast, if you use an artificial horizon (essentially a pan of water on the ground). This adds one extra conversion (since Hs will be off by a factor of two), but is excellent for sextant practice away from big water.

[hearsejr]

kkkkkkkkeeeeewwwwllll!!!!!!! I gotta try that! maybe I can start early in the morning, and shoot down the outer banks and try it. it'll give me a reason...eeerrr excuse to run down the beach. lol.
thanks for the idea.
Bill

[Amorous]

I like ghosting along close in to shore just as the sun is coming up and the water is like a mirror.  But this leads to some tricky navigational problems.  I am always amazed at just how many things can be used to navigate a boat.  Dogs barking, the sound of doors slamming as someone lets their dog out for it's morning romp, cars starting or driving down the road, the morning train, fishing boats or simply the sound of fishing boats returning to port after a night of working the coast.  When all these things are recognized as tools you are able to constantly refine and reduce your position to a point that you are no longer making an educated guess as to where you are on that chart, you KNOW.

[starcrest]

staying to close to a shore line can lead to trouble.next thing ya know yore walkin home