Ancient navigation

[marujo.sortudo]

I think we underestimate just how successful the ancients were at navigation. I think the stunt that Marvin Creamer did was interesting in that regard:

http://rowanmagazine.com/classnotes/...files/creamer/

[captain58sailin]

I wouldn't regard that voyage as a stunt. Jumping off of a 5 story building is a stunt. He and his crew were on an adventure as well as study in ancient migration theory.

[marujo.sortudo]

Fair enough. I didn't mean to apply anything negative by describing their voyage as a "stunt." Probably the wrong word to use. I find their voyage inspiring.

[captain58sailin]

It is probably me, in my mind, I equate the word stunt with an act performed without due regard for the consequences. Anyway, I thought it was a terrific voyage. I'm a little jealous, I was thinking about doing something similar, I wasn't aiming at a circumnavigation, I was looking for something easier, like from Alaska to Hawaii. Come out of the bay and turn south and follow the jet trails, easy.

[SaltyMonkey]

Originally Posted by captain58sailin

Come out of the bay and turn south and follow the jet trails, easy.

FOUL!!

[captain58sailin]

Yeah, but there are no referees out there. And the man said he studied cloud formations.

[SaltyMonkey]

Originally Posted by captain58sailin

Yeah, but there are no referees out there. And the man said he studied cloud formations.

[Hud3]

Originally Posted by captain58sailin

...Come out of the bay and turn south and follow the jet trails, easy.

Yes, I always thought that if I lost my electronic equipment on the way to Bermuda, I could follow the jet contrails during the day and the glow of the cruise ship lights at night.

[captain58sailin]

Years ago, there was a man who sailed from SF to Hawaii that used the contrails to find his way. Good thing he didn't follow the ones going to Tokyo.

[selkirksghost]

Nice clear night, looking at stars. Who couldn't find their way! Frank Worsley got only two star LOPs, not fixes, between Elephant Island and South Georgia, otherwise DRing Shackleton's boat to landfall... one hundred years ago.
Polynesian, or any other "primitive" navigation, has as much to do with reading the weather and the waves as looking at the pretty white dots in the sky.

[SaltyMonkey]

Reminds me of an old story

Old geezer would go into the head, do his duty and come outside on deck,lick his finger and hold it into the wind. Then he'd look at the waves and check the wind direction, then speak a few pagan words before telling us where we were at.

He always came close to a mile.

Amaising.

Oh this was when the first handheld GPS first came out.

Nice trick.

[gjordan]

Dr David Lewis, wrote WE THE NAVIGATORS, about Polynesian voyaging. He wrote at least one other book on the same subject. Facinating reading!!! I believe he was aboard the Hokulea on the trip from Hawaii to Tahiti. I was in the Tuamotus when the voyage was nearing Tahiti, and the locals were glued to the radio, for any information about the canoe. It was celebrated in Ahe when the canoe reached Tahiti. My uncle gave me a copy of" We The Navigators" the next Christmas, and I didnt get any sleep that night. I could not put the book down. _______Grant.

[captain58sailin]

Me too, wonderful book.

[tomfl]

Originally Posted by marujo.sortudo

I think we underestimate just how successful the ancients were at navigation. I think the stunt that Marvin Creamer did was interesting in that regard:

Marvin Creamer

They did have a sextant on their boat. Columbus carried what was basically a souped up protractor. He also had an ephemeris. One thing this book notes is how often, according to his log, Columbus would stop and anchor at a location that gave a clean sight of a lunar planetary conjunction.

Columbus

I feel a lot better about possible issues with my electronics after taking this class.

[atomj]

Just registered to add to this thread, even if it's a few months old. Recently had the privilege of sailing on part of Hokulea's worldwide voyage via her sister canoe Hikianalia. I wanted to second the recommendation of David Lewis' We, the Navigators, as well as Will Kyselka's An Ocean in Mind for background on ancient and now "modern" non instrument Polynesian Voyaging. (David Lewis also describes Micronesian methods.) Hokulea has a flashy new website documenting the voyage, but the older site Hawaiian Voyaging Traditions is a wealth of knowledge on some of the ancient and recreated methods.

If you are math-inclined, you can get a lot of these methods yourself by using spherical trigonometry applied to the same navigator's triangle that the celestial (sextant) navigation method uses.

sin(D) = sin(L)*sin(H) + cos(L)*cos(H)*cos(Z). D is declination of celestial object, L is your latitude, H is height of object above the horizon, and Z is azimuth of object measured from north "clockwise looking-down" as in NESW.

For example, Hokulea is the Hawaiian name for Arcturus, whose declination of 19.5º is about the same as the latitude of the southern part of the Big Island of Hawaii. So once a sidereal day there (or at another place with the same latitude, like Mexico, Cuba, Saudi Arabia, etc.) Hokulea passes directly overhead. Mathwise, if H = 90º (overhead), that fat equation simplifies down to sin(D) = sin(L), so if a star or the sun is directly overhead, its declination is your latitude.

But you can get direction info also: if Hokulea (Arcturus) is on the horizon, H = 0º, then the equation becomes sin(D) = cos(L)*cos(Z). If you are close to the equator, and most of Polynesia is, then cos(L) ~ 1 so sin(D) ~ cos(Z), so Z = 90º - D or 270º + D. So for Hokulea, Z = 70.5º (when it's on the horizon, rising, which is a bit harder to anticipate), or Z = 289.5º (when it's on the horizon, setting).

So you can use lots of stars, not just Polaris, to get not only heading but also latitude information. The heading info, along with the speed of your vessel and time on course can enable you to mental dead reckon your position, and the latitude info can act as a double-check. And there are a bunch of other less obvious techniques, such as how certain pairs of stars rise together at the same time, or form a vertical line over due north or due south, etc.

Then there's a wealth of info to be had by looking at swell periods and directions (and less reliably, wind) when the sky is overcast. And finally, methods to detect islands, especially high volcanic islands, 100 miles or more away.

The open ocean navigation might not be very accurate, even compared to celestial (sextant) navigation, but the land finding helps narrow things down at the end. And anyway, having also had the privilege of sailing aboard the USS San Francisco, charts aren't always entirely accurate anyway.

Enjoy!