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Old 02-21-2007, 03:17 AM   #21
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fyi, there are now 3 GPS type systems.

Russian (GLONASS), European(Galileo), and American (GPS). Galileo will come online next year. Hopefully we'll see some receivers capable of using all 3 systems.
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Old 03-01-2007, 12:34 PM   #22
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I know this tread is a bit old, but it is seemed to be a good first post as i now a few things about it...

At the moment the only satellite system that provides accurate positions is GPS. GLONASS is 'semi' operational, not all planned satellites are in orbit and some are broken. Receivers are hard to get (never seen one). Even Russian ships use GPS, GLONASS only has a advantage in very high lattitude due to the angle of the sat's orbits (so if you own a Nuclear Icebreaker and want to visit the north pole it might be wise to use it ). Galileo is not going to be operational for a few years as the sat's still have to be build, but the receivers should be GPS compatible.

Although asto navigation is still part of the STCW requirements and teached on nautical academy(?) the use of it on a yacht will not add much safety, you will need to practise it often to be able to produce a good position and I gues from a small and fast moving platform (like a yacht) its a lott harder than from the bridge of a 15000GT cargo vessel.

Apart from this: sextants are expensive kit and nautical almenacs aren't cheap either (and need replacement every year). So it might be wiser to invest this money (and the time) into something else that has a bigger added (safety-) value, like updated charts or better knowledge of the COLregs.

A last remark: if you see astro navigation as a hobby, its another story; the kick you get when you calculate a position without any electronics and are within 2 miles of the GPS is priceless

NB: i'm 2nd mate on oceangoing cargoships at the moment (with litle exp on small boats), but like to get a yacht and visit all those beautifull places I sailed past at 18kn the last years. This forum seems like a good start...
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Old 03-01-2007, 12:56 PM   #23
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Welcome aboard Bertje. Thanks for the interesting information.

Enjoy your stay here.
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Old 03-01-2007, 01:46 PM   #24
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Indeed, welcome aboard. It is good to have another big ship sailor in the forum. I think we have a lot to offer this site, but a lot to learn too. This is a great forum where people willingly share their knowledge. Enjoy yourself here.

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Old 07-15-2009, 10:57 AM   #25
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GPS is the primary means of navigation, and in the next few years we will see the whole area of GNSS expand with the addition of a revived GLONASS system (20 of the requisite 26 satellites currently operational, with another 6 going up later this year), as well as the European Galileo. In time we will see GNSS receivers that will use satellites from any and all of these systems together to provide a more reliable and accurate fix.

For coastal navigation, commercial vessels use radar as their secondary means of navigation.

Also, eLoran is slowly being rolled out in Europe (not sure what the status is in the USA), as Loran on steroids.

But using a sextant has a great feeling of achievement to it. If you want to avoid the need for almanacs and arithmetic, you could use a software package like WinAstro with it.
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Old 07-15-2009, 02:25 PM   #26
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I would have to agree that there are too many sailors (sail and power) out there who have no idea of "where they are" and "where the closest safe harbor/landfall" is located. They just follow the chart plotter into oblivion or rocks sometimes. The real value of electronic navigation is "telling you where your are now." But a prudent navigator must write down or somehow remember this information AND it must agree with common sense/logic. If for some weird reason your GPS or plotter tells you that you have moved 150 nm from your last position in minutes or hours - there is something wrong and you need to find out what it is. Always having in your mind or on paper your basic route and ticking off your position now and then is essential. Also knowing what direction to point the boat should an emergency arise can save lives and money.

Most likely you will loose GPS positions because of power failure or GPS mechanical failure - I have had both even with relatively new GPS units. So be prepared to continue on using tried and true basic navigation techniques which really are not difficult or onerous to learn. Christopher Columbus made it across - without a sextant - using "constant latitude" sailing - keeping the sun angle above the horizon constant based on a "noon site" or something similar. Longitude had to wait for the invention of a good portable clock. Having a sextant in a life raft or even a boat requires either copious tables and an electronic calculator or just a dedicated navigation pocket calculator with an astro database. "Electronic" means it is also relying on batteries and subject to being wiped by solar flare or "EMP" effects just like a GPS.

Most sailing folks don't realize that 90% of all those airline flights from here to there around the world are using GPS as primary navigation. The US Air Force, nobody, is allowed to mess with the GPS system, turn it off, or anything - by Presidential decree and law or thousands of people could die from air crashes which would not be good for your re-election prospects. That does not mean that "natural events" - solar flares, etc. cannot take down or partially affect the GPS system, after all it was invented and managed by bureaucrats. So like old Chris Columbus, you had better know some basic navigation techniques.
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Old 07-17-2009, 01:01 PM   #27
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my 5 cents:

I know of very litle people who still do astro navigation, GPS has taken over. 2 GPS'es are cheaper than one good sextant.

but I do not agree with their arguments:

if you're sailing, then the argument of "the modern world we live in" makes no sense. In a modern world, people go by motorvessel and navigate electronically.

In the old fashioned world people go by wind force, and navigate with what the stars provide. For me, sailing is a way to keep old knowledge alive. If you were able and willing to learn to sail, then you should be able and willing to do astronavigation.

Of course you can have a manual GPS as backup, just like you have an engine to enter harbour.

Astro navigation is easy enough and is fun ! ( Just like using morse on the radio is ;-) )
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Old 07-17-2009, 01:07 PM   #28
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Quote:
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Christopher Columbus made it across - without a sextant - using "constant latitude" sailing.
I understand from my reading that this method resulted in many near blind helmsman as they looked through a stick to keep the sun at the correct angle without the benefit of modern filters!
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Old 07-17-2009, 02:11 PM   #29
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I just did a little web search on Columbus - "The Great Navigator" and found he really wasn't. He used a "Quadrant" which was a metal device in shape of a quarter of a circle with a weight (plumb bob) on a string and a sighting fixture on on top. He would take a night sighting of the North Star and look at the string to get a angle between the gravity center of the earth and the star. From this he could calculate his latitude. Try to imagine trying to hold the quadrant steady and read the string while a ship is rolling or pitching?

His other instrument was as an "Astrolabe" which also supposedly calculated the star's altitude (degrees), It was a full circle instrument without the string and weight and used a free swinging internal pointer which also relied on gravity to determine up and down. Columbus could never get any results from the Astrolabe so reportedly never used it.

Both methods were reported by him to be very unreliable, once he tried getting a sight and latitude while anchored in Cuba and came up with a result of 42 degrees North instead of 20 degrees, the actual latitude. So he ended up not using either instrument and used tried and true (with a lot of luck) Dead Reckoning Navigation steering West by South heading and hoped for the best. Maybe that is why he managed landfalls stretching from the Bahamas to Trinidad some 600 nm apart in latitude.
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Old 07-17-2009, 10:59 PM   #30
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Thanks very much for the WinAstro link. Here in South East Asia during the South West Monsoon - the GPS has turned out to be a real boon - many days and nights no ways can one get a decent fix.

Coming back to the software - had a quiet chuckle at their description of the price reduction :-

"WinAstro Price Cut - Cheaper then ever before!

With the reduction of VAT in the UK, the retail price of WinAstro has been reduced from £24.95 to £24.42."
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Old 07-19-2009, 08:40 PM   #31
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How about both GPS and Sextant? That's the way to go, IMHO.

"Speed is an important factor in accurate navigation, and, since the sixteenth century, sailors had determined a vessel’s speed using a log. This device was basically a rope with knots tied at intervals along its length. With a board attached to one end to create drag, the log-line would be heaved overboard and allowed to run out for a short period of time. The number of knots counted off indicated the speed. (The unit of speed at sea is therefore the knot, one knot being equal to one nautical mile per hour.) Logs were susceptible to a variety of errors, so instrument makers developed mechanical logs to improve the recording of speed and distance." reference

Assuming that one wishes to have a non-electrical navigation system, then if one wishes to use a sextant for navigation, one also might be interested in obtaining a taft-rail log like the Walker Log.

We were fortunate in that recently an elderly couple who are former cruisers and former schooner owners gave us their Walker Log (Excelsior) for use on our newly re-launched schooner This type of log uses a torpedo-shaped bronze spinner a few inches long towed behind the boat on a length of braided line. As it moves through the water, spiral fins on the torpedo make it spin, twisting the line. The on-board end of the line is hooked on to the back of the log instrument, where it turns a shaft connected to a reduction gear box. This in turn moves the hands on a series of dials, rather like those of an old fashioned gas meter, to give Direct reading of the distance the spinner has moved through the water.

And, there you are--if you know the distance traveled since your last siting...you might know where you are!
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Old 07-20-2009, 01:37 AM   #32
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Walker Log (Excelsior) for use on our newly re-launched schooner This type of log uses a torpedo-shaped bronze spinner a few inches long towed behind the boat on a length of braided line. As it moves through the water, spiral fins on the torpedo make it spin, twisting the line.
Having lost one to a large denizen of the sea - suggest paint it black or chemically treat it so it has a dark flat patina.
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Old 07-20-2009, 12:17 PM   #33
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Ditto on the "make it invisible" to sharks, etc. The companies that make "towable" water generators first came out with an outboard motor prop attached to a long line then to the generator fixed to the aft rail. It did not take long before a lot of complaints about the disappearance of the propeller came back. They finally fixed - sort of - the problem by putting a meter long steel rod attached to the prop and then the line. Ended up with a whole line of sharks waiting for the shark Orthodontist to fix broken teeth after trying to bite through the steel rod.

- - As far as having a sextant on board for navigational purposes - don't bother. It is not an easy device to both use and to resolve a fix. It takes constant practice, skill, and patience - and - cooperation from Mother Nature. Then to use it without any electrical power or electronics, you have to have massive tables, a chronometer, and tons of paper and pencils and significant knowledge of spherical trigonometry . If you use the dedicated calculators - which are rather expensive - and are now not very available (dead market after GPS came on line), then you might as well just have several hand held GPS or the newest thing - a GPS wristwatch. It has been out a couple of years and only costs about US$200 +/- which is cheaper than the dedicated calculator. Also portable VHF radios now come with GPS built in.

- - If you are seriously proficient and expert with a sextant and resolving a fix, then the best you can get has an error probability of 3 nm with occasionally down to 2 nm. Normal amateur fix accuracy is more in the line of - "we are in the Atlantic (or Pacific) Ocean, north (or south) of the Equator." That is why even Columbus gave up on them and used the old DR plot system. However for historical fun endeavors, learning to use a sextant fills the bill just as much as learning to read, write and speak Latin.

- - But using DR navigation is also tricky. You need to know what the current set and drift are, what your leeway is at different speeds and wind angles, and your boat speed through the water. Errors in accounting for these factors can add up to 100%. IMHO, for 1 or 2 day passages these can be accounted for reasonably in your head and still be close enough to be in sight of your destination. Weeks or Months at sea using DR can add up to 600nm errors - just like Columbus had. Ever wonder why there are so many treasure hunters? There are a lot of ancient galleons, etc. with not so good navigators and an over abundance of rocks and reefs around.
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Old 07-20-2009, 02:11 PM   #34
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Yes, our Walker Log has an extra spinner, but we've been advised by some other folks to paint it flat black.

Just as there are different types of boats, sails, engines....all of which get you well on your way quite nicely, there are also different ways of performing navigation for one's voyages. Having and using multiple systems with redundancy or systems with different underlying technology (satellite GPS vs trig-based celestial nav, for example) can help make sure that a cruiser completes a difficult passage with success.

Using a sextant isn't that hard--my on my, folks, please don't make it seem insurmountable. Osiris, you are correct that one needs the tables, etc, if one doesn't have a program on the computer, on their Palm, programmable calculator, etc. However, developing the ability to use a sextant proficiently is entirely within the reach of common man... as well as DR navigation...both are worthwhile things to do IMHO. The world is not black-and-white (GPS vs DR/CNav) and one would think that even if one's electrical system failed, one might have a useful handheld calculator onboard to perform required calcs, anyway. It's not costly--there are freeware as well as inexpensive programs with the tables as well as some nav calculators available for use on PDA's (like the Palm OS).

Since I have only limited experience (but positive) using a sextant, and hubby has most of his sextant experience from when he was in the Navy (aviators were required to know how to use a sextant, and encouraged to practice, btw), we can't speak from personal experience of crossing oceans or long offshore passages using DR and a sextant. When coastal cruising, we exclusively use DR with success--while we have two GPS we never bother turning them on unless we want the entertainment value of charting our course. I imagine if we found ourselves in a fog bank or in a tricky situation we'd have the GPS on as well as any other electronic aids we have aboard, of course--but that wouldn't stop us from continuing our DR plotting. And, yes, for offshore work especially, one must be aware of currents and set as well as the leeway performance to expect from one's vessel, too. Lucky us, when coastal cruising thus far, seldom is there a time that we can't take bearings from landmarks to verify our situation. While bluewater miles may be many, most passages that most cruisers will undertake are by-and-large done close to sight of land, thus DR is an easy to use technique in those situations.

We are surrounded by folks who cruised in the 1950's, 60's, 70's, and 80's w/o fancy electronics. By and large, these folks had a sextant aboard and sometimes a taft rail log to go with their mag compass and cronograph and that was it.

I love the story a friend tells of his passage on a 30 footer back to Canada from HI around 1990. It was an El Nino year and everything was off--winds keeping him headed to Japan for far too long before the turn eastward. Overcast skies from the 3rd day onwards meant that he got one good fix with the sextant at about day 10 or so. It ended up being a 6 week passage, stormy and amazingly difficult. The radio died at about week 3. However, he kept up his DR plot thinking it was entirely worthless--but he was in the habit, so what the heck...when he saw land, it didn't look quite right, so they spent the night about 15 miles out and then in the morning, he rowed over to some fishing boats he saw and asked them "where are we?" and learned he was only about 70 miles north of his DR plot. He was amazed. One fix, and within 70 miles of his goal, wow.

Given the influence of many similar stories from these older, successful, cruisers, and our own experiences of DR while coastal cruising...seems to me that celestial nav/use of a sextant and DR aren't rocket science and should be skills readily picked up by today's voyagers interested in adding a navigation skill.

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Old 07-20-2009, 04:24 PM   #35
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Interesting to note that this topic has been around (and alive) for some years now! :-)

I and my wife intend to share tasks when we finally buy our own boat (she´ll take diesel mechanics and electrical, I´ll navigate... or so I hope), but we will both strive to learn navigation in the samel level, and astronomical navigation will be an essential part of our learning - both for the undeniable fun of it AND as a backup. Sailing IMHO is in a good part about being self-sufficient, and if you put your life entirely at the mercy of solar flares or some whacko who could scramble the GPS system in Uzbekistan or something... you know, we´d better be prepared!

A great week and safe waters,

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Old 08-10-2009, 10:29 AM   #36
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fyi, there are now 3 GPS type systems.

Russian (GLONASS), European(Galileo), and American (GPS). Galileo will come online next year. Hopefully we'll see some receivers capable of using all 3 systems.
Actually Galileo won't be working till 2012/13, assuming no further delays in the program.

GLONASS is being upgraded and, although still a few satellites short, gives pretty good coverage. Surveyor grade GPS units have been augmenting GPS with GLONASS for many years now, to get better accuracy, but this hasn't percolated down to the leisure marine sector receivers yet. It probably will as the new generation GLONASS satellites transmit signals more compatable with GPS than at present, making receiver design simpler.

A big risk of GPS (and any GNSS system) is that orf interference or jamming. You are only receiving a signal of milliWatts, and tests show that a 4W transmitter will jam signals over a 100 mile radius. This may not be intentional - for example active TV receivers often cause problems. This is the case for keeping LORAN going and upgrading the system to eLORAN, which will give about 20 metrs accuracy.

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Old 08-10-2009, 03:25 PM   #37
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- - I would suggest the "Primary Navigation" is done with the eyeball, compass, and a nautical chart. "Secondary Navigation" is done by GPS. GPS is incredibly accurate - you can locate items inside your boat with the modern GPS's maximum accuracy of +/- 7 feet (2 meters). BUT - and a rather large - BUT - transferring lat/longs (positions) from or to a nautical chart from a GPS lat/long can get you in "deep trouble" (pun intended.) Most nautical charts in the world were geographically last updated 40+ years ago to as much as 200 years ago in some places in the world. And there is a thing called a "Datum" - which is the mathematical model of the earth that the local chart was built on. The earth is not a sphere, but actually more like a pear with a rather rough skin. There are 140+ datums in use around the world which when using a GPS lat/long, can give locations with up to 10 nm difference in location. Bottom line, the GPS is very accurate - the nautical charts are not when it comes to Latitude & Longitude.

- - So GPS and charts get you to the vicinity of your destination, but it is your eyeballs and your brain that get you safely into harbor. If you are using computer based GPS ENC navigation you can record and store past "tracks" or actual paths your boat took to get into and out of a harbor, etc. When returning to that location if you do follow your "past track" - and did not hit anything the first time you went in/out - then GPS ENC navigation will safely get you back to your past location. Of course this does not apply if you are going somewhere for the first time. And, still you had better have your eyes looking around outside to see if anything has changed since the last time you were there.

- - It is very convenient to use GPS for taking down intermediate fix/locations enroute and recording them on something non-electric. That way if the power fails you have a good location to initiate your DR navigation. But again use your brain, if the GPS gives you a location far too many miles away from last location - i.e., it doesn't make logical sense that you traveled 160 nm in 2 hours, then find out what is wrong with your equipment. This is where the 2nd and 3rd handheld GPS units come in handy - comparing them to your primary to see is if there is a non-logical difference. I have had GPS's freeze up or "spike" out on me and having an independent alternate GPS running maintains the integrity of my navigaton.

- - As to Solar Flares, etc., I would hope that "the powers that be" have long since worked out how to deal with it as ALL of the world's major oceanic airlines use GPS as primary navigation and the separation between individual aircraft is based on GPS. If GPS goes down, there will be a major crisis or many disasters in the airways of the world. GPS is even being used for "blind flying" or zero-zero visibility approaches and landing at major airports. Governments would fall if that many airliners started falling from the skies (metaphorically speaking). The are no ends to the number of "chicken-little" individuals who gain publicity by such doom and gloom predictions. But I applaud their efforts as a necessary nuisance to keep the politicians and "bean counters" on their toes about possible problems. "Never say never" but I doubt the solar flare issue will be a problem primarily because there is just too much money invested in the GPS systems and world transportation. And if there is one thing politicians pays attention to, it is money.

- - Sextants, nice, fun, historical, great hobby, but we are in the 21st century and "learning Latin is not going to enable you to understand "California Valleygirl talk"." In other words, IMHO, navigation by sextant is not safe or prudent in our congested seaways. Even Christopher Columbus gave up on his versions back then as when he tried the devices while in Havana harbor it plotted out that he was in Chesapeake Bay. So he gave up and used old fashioned and reliable DR navigation. His DR accuracy was plus/minus 250nm which was good enough to find the Caribbean - somewhere.
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Old 08-11-2009, 02:47 AM   #38
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- - Sextants, nice, fun, historical, great hobby, but we are in the 21st century and "learning Latin is not going to enable you to understand "California Valleygirl talk"." In other words, IMHO, navigation by sextant is not safe or prudent in our congested seaways.
Strong statement, Osirissailing. You could substitute "sails and sailing in your assessent--let's see, this is what power boaters might say:

[sails and sailing], nice, fun, historical, great hobby, but we are in the 21st century.... [travel by sailboat] is not safe or prudent in our congested seaways.



"learning Latin is not going to enable you to understand "California Valleygirl talk"...that is soo true! But learning Latin will assist you in understanding French, Catalan, Spanish, Portuguese, Italian, English....oh...so many languages. Where as understanding CVGT will only help you with the ah hem.....

Moving right along...Learning celestial navigation can help anyone wishing to become a more proficient navigator. There's nothing imprudent about learning and using centuries old nav skills that do work. It IS totally imprudent to voyage as many people do today--dependent upon an electronic chart plotter w/o any ability to navigate if one's GPS fails. Even if one doesn't have the ability or desire to learn celestial navigation...Loran, Radio Direction Finders (RDF), NDB (non-directional beacons) are all available to assist voyagers. But, there aren't very many cruisers these days who have a RDF to pick up radio stations or NDB. Folks are entirely too reliant upon the single tool of GPS.

Multiple nav tools are great to have...for example, with RDF aboard, if you hear a mayday call, you might be able to get a vector on the radio signal, for example. Or, if you're looking for a particular port, you can get a vector on a commercial radio station or a NDB in the area or both! Celestial nav is also a useful tool for those who choose to learn it and use it.

About that CVGT, on the other hand...
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Old 08-11-2009, 04:35 AM   #39
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Moving right along...Learning celestial navigation can help anyone wishing to become a more proficient navigator. There's nothing imprudent about learning and using centuries old nav skills that do work. It IS totally imprudent to voyage as many people do today--dependent upon an electronic chart plotter w/o any ability to navigate if one's GPS fails. Even if one doesn't have the ability or desire to learn celestial navigation...
I could not agree more. If you head out into the great ocean you should have a sextant and know how to use it. Also, any other tool you have can be useful. GPS are great but you do need redundancy and not rely only in a single method i.e. satellites.
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Old 08-11-2009, 02:19 PM   #40
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- - To keep things lively and interesting - By "sails and sailing" I assume you mean sailboats without engines. How often have you encountered a cruising sailor on a boat without an engine? And especially, in the Caribbean? It would be quicker to walk and swim eastward than rely solely on pure sailing. So yes, I would agree that "purely sailing, no engine" should be included in the statement. In point of fact, there are many commercial harbors and ports, especially in the USA, where if you attempt to enter without an engine you will be arrested and fined as a "deliberate hazard to navigation." Even if you have a sailboat with a disabled engine you had better get towed in.

* * Side note: Anybody wishing to enter the USA on a sailboat should first sign up with one of the "towing services" such as BoatUS/TowboatUS or Seatow - before - entering USA waters. It could and will most probably save you some serious money.

- - There was a point I was trying to make that "Primary Navigation" is the old fashioned visual plotting, chart work and DR. GPS and even Celestial come after (or are subsets) of primary navigation. The main problems with Celestal are practical and valid - you need a DR position, reasonably steady boat, a clear sky, a very accurate clock, a quality (expensive) Sextant and lots of books and paper and pencils. I exclude anything electronic or electric as they can shut down, fail, go dead and you are back to the "old ways." Celestial computers/calculators that do the "math" cost more than spare GPS's by an order of magnitude.

- - But I did not say that GPS, etc. are "secondary navigation" (Well, the etc. really doesn't work anymore since governments have abandoned Loran, RDF, and all of the other "old ways"). Which in itself is incredibly stupid on their part, but we all know "intelligent politician" is an oxymoron. And being "not intelligent" is not limited to politicians, too many people take off in a vessel with no knowledge or skill in basic navigation and put their lives at risk depending upon one or maybe two little electronic navigation devices that they do not even know how to operate correctly. I think we agreeing on that point. I am ignoring the "not intelligent" people in the discussion as there is no helping them - they are determined to gain fame trying for the "Darwin Awards" each year.

- - I have navigated the skies with RDF - and my life has depended upon how well I did it - and it is not easy. Which is why the equipment has disappeared. As not surprisingly, Sextants fall in that same category/situation, they are not easy to use and master and the results are only marginally accurate at best and normally horrific for a new or unpracticed navigator. That is why Christopher Columbus gave up and simply used DR navigation.

- - I must apologize to anyone offended if their "sacred turf" is the target. I like baiting Sextant folks as much as I like baiting Learning Latin folks - it's easy and only done in the spirit of good natured debate and fun. Learning any "classic" form of navigation is worthwhile and valuable, if only to make the sailor aware of where we came from and the importance of knowing how to navigate with the most accurate techniques available. And to make them aware of how to stay alive should it get down to just you and the ocean. There are dozens of "really" basic techniques from "thumbnail" navigation, "1 in 60", and contrail navigation to others that all work reasonably well enough to find land.
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