Period Navigation...?

[Patrick Hand]

From what I understand about period navigation, they could find thier laditude (shooting the sun at noon), but had no accurate way to tell thier longitude (and did they have a concept of longitude, but just no accurate way to measure it at the time)

If they were trying to find a specific island, did they sail in the general direction, untill they got to the right laditude and then sail East or West untill they found it? Using known locations (other Islands) to correct thier course?

Currents and the wind must have realy messed with thier "guess" of where they were.....

I can find information about how to figure where a ship is now (modern) ... but not much info on how they did it then........

[oderlesseye]

and did they have a concept of longitude, but just no accurate way to measure it at the time

Ealy maps sugeest longitude was already a concept.

link

More specifically the time line I found says:

1760's was when the lunar tables became available and some guy named John Harrison invented the chronometer. Twas only then was we able to find longitude wit any accuracy.

Eyes : just read all this in the lasty chapter of me book " Under the Black Flag" by David Cordingly pgs. 82-83.////86-87 has a few more facts too

but ya got to look at the book. I don't wanna plagerize David.

Otherwise eyes thinks ya answered yer own question already. East-West

direction (longitude) was fer the most part an educated guess; fer maps of the tyme were'nt all that accurate.

[Capn_Enigma]

The "sail to the correct latitude, then east or west" trick sometimes yielded quite disastrous results:

On March 7, 1741, Admiral Anson navigated an already scurvy- ridden Man- O- War, the "Centurion" through the Le- Maire Straits. Upon reaching Cape Horn, he was met by a westerly storm, which lasted for 58 days. Anson tacked on a westerly course, generally following the 60th parallel. He relied on Dead Reckoning to chart his course, as the storm didn't allow to shoot the sun.

After the storm, Anson laid a North course for the island of Juan Fernandez, where he hoped he would find fresh water and supplies for his dying crew.

But then land ahead was sighted, which turned out to be Cape Noir, on the western coast of Tierra del Fuego. It dawned upon Anson that although he sailed West for almost two months, he had hardly made any way over ground due to adverse currents.

He had no choice but to lay a westerly tack again before sailing north in order to reach the island.

On May 24, 1741, the ship's log book noted 35 degrees southern latitude. All Anson had to do now was sailing east or west to reach the island. But which way was the right one?

Anson opted for the westerly course. Four desperate days later, he became insecure and reversed the direction, now following the 35th parallel in easterly direction.

48 hours later, land was sighted, but it was not Juan Fernandez, but the inaccessible western coast of Chile. Anson was forced to concede that he had been merely hours away of the island, when he had chosen to sail the easterly course.

So, they again sailed in westerly direction, and dropped anchor at Juan Fernandez on June 9, 1741, after having lost more than half of the 500 soul complement to scurvy.

[MadMike]

Anson's fiasco had more to do with scurvy, lack of proper provisions, and bad luck rather than "sailing the latitude" (since it was rather difficult to locate in a storm lasting 58 days).

Yours, &c.

Mike

[Capn_Enigma]

It was a matter of proper navigation, or rather, lack thereof.

[oderlesseye]

Where be this story you share from?

[Skull pyrate Carter]

by what I know, Longitude was done by setting a "clock" on the time of their departing port. Then when they sailed they kept time via the sun. This would give them a time difference which would translate to how far out they were.

[Capn_Enigma]

Where be this story you share from?

It's the history, oderlesseye.

[Patrick Hand]

Skull pyrate Carter, but that wasn't untill after the GAoP (mid 1700's) untill they could make a clock that was accurate and stable at sea.......

[Coastie04]

It was a matter of proper navigation, or rather, lack thereof.

Before completely writing it off as poor navigation, I suggest you try to get an accurate celestial fix, even with a modern timepiece, after 58 days of dead reckoning. I can tell you from experience, that even with the newest sextant and a perfectly accurate watch, it is still hard to get a good position. An error of 1-2 miles is pretty good for this navigation. The only problem, is that celestial navigation relies on having an idea of where you are. Thus, the 58 days of dead reckoning, which is estimating your ship's position based on speed and course over a period of time, definitely affected any celestial fix (besides, there's many errors that can affect the dead reckoning position, including unknown current, ship's leeway which has to be estimated based on conditions and sail plan, and the fact that speed was probably taken ever half hour in stormy seas with a chip log). Plus, if the ship's chronometer (if equipped) could have been affected by the stormy seas as well. Therefore, the mistake made was not necessarily poor navigation, given the equipment and knowledge of the time. It was just a decision that proved to be wrong in the end.

Coastie

[Ship's Gunner]

Anson was one of the best officers in the Royal Navy at the time. I think that the difficulties he encountered were much more of a testament to the incredible difficulty of accurate navigation during the mid-18th century than to any shortcomings on his part. That he was able to complete the circumnavigation at all was proof of his navigational skill.

I believe my shipmate Coastie is correct...Navigating by dead reckoning for 58 days in bad weather, without any way to determine longitude, would be unbelievably difficult.

It's amazing that he did as well as he did.

Just further testimony of what a hard life those fellows led.

Tough men, indeed.

Respectfully,

Chad Teasley

Ship's Gunner

[oderlesseye]

EYEs found this site to be of some interest link

[hitman]

Navigation by means of Lattitude sailing and dead reckoning was common practise among navigators from at least the time of the Vikings and although I don't have sources for this I'd lay odds the Phoenicians and the Chinese had simmilar techniques. It was for a long time the only means of navigation at sea. longitude was "invented" for lack of a better word at the same time as Lattitude. They have always been a team just like pb&j. The problem with determing Longitude without a chronometer is that it requires a clear veiw of the moon and before the relase of works like The Practical American Navigator very well developed skills in trig. Pirates and the navies that chased them were in many ways quessing when out of sight of land. Now as for skill of the navigators quite frankley the fact that these men were able to get any where safley is damned amazing. Hell Galileo tried to devise a way to determine longitude at sea and failed. The seriousness of this is proven by the fact that parliment offered a prize for anyone who solved the problem. A great site about this and Mr. Harrison (who invented the chronometer) is

http://www.nmm.ac.uk/server/show/conWebDoc....355/viewPage/1

From Colunbus "discovering" the New World to the Spanish Armada crashing onto the rocks of England's west coast lattitude only navigation could easily be said to have been quite succesful and quite dangerous. Most pirates were by nature coastal hence these concerns ment less to them than say a good working knowledge of the reefs and bays in their given area of operations. The History channels Tales of the Sea series has an excellent program on navigation through the years you can buy it from them on vhs or wait for it to come on History International. On the subject of Jhon Harrison his chronometer and the trials of his winning the parlimentry prize check out the book Longitude or the A&E movie by the same name. I used to have a link to a sight with 14 chapters of the 1995 edition American Practical Navigator on it but I can no longer find the link. Hope this helps

[Patrick Hand]

I read a book about Mr. Harrison ("The Man who discoverd longitude" .... or something like that.....) I just remember that it told how difficult it was to sail before the chronometer or celestrail tables were finished..... The link that oderlesseye posted was helpfull..... (interestingly enough.... I've never read HOW a backstaff worked, I just guessed at it.... and I was right.... cool....)

I just figure that there were so many varribles, that to get anywhere took a lot of luck..... wind, currents, a basic idea of where you were by the sun, and stars, and kinda which way was North......(did they know about the magnetic varreations at the time?)

Kinda like a Moon shot...... they have the rocket ready, now to figure where the moon is going to be....... and you can see the moon.....

[William Blydes]

Having been a Navigator and taught Nav at our fleetschool, I’ve seen kids get lost after 12minutes (that’s 2 Dead Reckonings) let along 58 days.

[hitman]

I used to know when the magnetic deviation was discovered pretty early on actually and certanly before the GAoP. I'll try and look up the time frame if you want it.

[Patrick Hand]

hitman.... thanks that would be cool (OK interesting) if you could find that...... I'm courous about "when" they figured that sorta thing out..........

I'll be looking fer your next post....... (but no pressure... or anything like that..... )

[hitman]

still digging through some of my papers for a better refrence but I did run across this little tid bit "charts showing magnetic devation were readly availble by 1701 for diffrent parts of the world." and that the first compasses were used only when the sun/stars were not visable because when they were out of familliar waters they couldn't trust the reading and didn't know why.

[Fox]

William, those kids weren't lost, they were exploring...

The question of longitude is an interesting one. It is generally accepted that Harrison solved the problem in about 1760 (after decades of trying), but mostly overlooked is an interesting earlier attempt to use watches to overcome the problem of latitude.

Almost a century before Harrison's success a scientist and mathemetician named Christiaan Huygens approached Prince Rupert, a former pirate and now English Admiral with two watches which he believed could keep reliable time at sea. Rupert sent the two watches to sea with his former piratical comrade Sir Robert Holmes. On October 21st 1663 Holmes' report ("An Account of the Going of Two Watches at Sea from 28th April to 4th September 1663") was presented to the Royal Society by Sir Robert Moray. Details suggest that the results were encouraging and that the watches were more reliable at sea than any previously tried. A second experiment was arranged.

In 1664 Holmes again took the watches to sea. He possibly trusted the watches too much, for on more than one occasion he used them to correct his own navigational calculations, and those of his officers - despite the fact that the watches had been up to half an hour wrong on the first voyage. However, after about 6 weeks spent crossing the Atlantic, Holmes' reliance on the watches brought him up to his correct landfall.

On Holmes' return to England he praised the watches greatly and Huygens was delighted. The members of the Royal Society were informed of Holmes' success and... well, no mention of the first useable (if not perfect) sea-chronometer seems to have ben made again. For some reason or another the experiments were dropped and it wasn't until Sir Cloudesly Shovell's navigational disaster in 1707 that the Royal Navy again began to seriously think about longitudinal navigation.

IMHO, the tragedy of Anson's voyage could probably have been avoided by better supplies, but it is doubtful whether the few days lost because of Anson's navigational errors (which were a sign of the times, not the man) would have made much difference to the health of the crews when compared to the many many days lost because of contrary winds and currents. Better navigation (which was not available) would not have saved many lives, but better supplies (which were available) would have made a huge difference.

Nonetheless, the story of Anson's voyage does illustrate very neatly some of the potential pitfalls of pre-Harrison navigation.

[Patrick Hand]

OK.... now I'm slightly confused........

Who was the man that was working to make an accurate cronographer (watch...... that I can spell) so they could tell how far away from Grennich they were (for longitude.....)

Can't remember his name.... but from what I remember ("the Man who inventer/discovered Longitude" or some books title very close) was trying to make a clock that would work at sea.... the motion of a ship... kinda messed a clock up..... he worked at it.... got it to work... sorta kinda..... but the board that awarded the "prize" had thier "golden boy"... astral navigation...... so there was some political junk going on as well.......

But that IS all after the GAoP...........

So back to what they would have known before ..... 1730.... or thereabouts.....

(not that I don't want to know who the man was that was working on an accurate cronogr....... watch......... and the navigational stuff that is outta period also.....)

[Capn_Enigma]

Who was the man that was working to make an accurate cronographer (watch...... that I can spell)  so they could tell how far away from Grennich they were (for longitude.....) 

That was John Harrison (1693 - 1776).

("the Man who inventer/discovered Longitude" or some books title very close)

Probably "Longitude" by Dava Sobel.

the motion of a ship... kinda messed a clock up..... he worked at it.... got it to work... sorta kinda.....

Even the H1, Harrison's first model, exceeded the necessary requirements in accuracy, but Harrison was not satisfied with the size and believed that the clock could be made even smaller and more accurate, hence he started to work on the H2, H3 and H4 subsequently.

but the board that awarded the "prize" had thier "golden boy"... astral navigation......

The board under Nevil Maskelyne favored the Method of Lunar Distances.

But that IS all after the GAoP........... 

The H1 was finished in 1735, the H4 in 1761.

So back to what they would have known before ..... 1730.... or thereabouts.....

That would be the "Follow the Latitude" or the "Sail the Rhumb Line" practice, sometimes with the known disastrous results.

The Caribbean is generally too small a sea to get really lost. Coasts are too close to each other that steering in a general direction would not get you at least near your point of destination after a few days.

What makes the Caribbean really dangerous are the treacherous shoals everywhere.