Is this how the ancients navigated?

I was thinking if Eratosthenes Knew the Earth was a globe , as the keeper of the Library of Alexandria.Then he went out and did a calculation that was accurate to about 1%. regarding the Earths circumference. Was he just checking what was already written in the Library, like the original Piri Ries map?

Then I thought the next problem would time keeping with regards to practical navigation. Like if you were blown off course by a storm how would you regain your bearings. How would you know how far from land you were etc. Chronometers were not invented until the 17th century. Then the other day on a show about the Vikings ,I saw that they used a sun compass. IE. Point it north and the sun dials shadow, lined up with a mark on the circular disk , which gave you your approximate latitude. But this could have done more.

Knowing the next problem would be longitude, and knowing the Prime longitude on the Piri Ries Map was probably the tip of the Great Pyramid, at Giza. Why not have a sun compass that had marks about its dial, that correctly defined the latitude at noon along the lines of latitude. So if you were halfway across the Atlantic in a Phoenician type boat, and you used the sun compass at local noon. Wouldn't you know by the markings how far noon was ahead of Giza, and therefore the amount of time and distance you were away from this place. Plus your approx. longitude depending on the time of the year with regards to the Suns declination?

a reply to: anonentity

So if you were halfway across the Atlantic in a Phoenician type boat, and you used the sun compass at local noon. Wouldn't you know by the markings how far noon was ahead of Giza, and therefore the amount of time and distance you were away from this place.

No, you wouldn't. You don't know the time of local noon (it isn't at 12:00 very often) without a clock so you don't know how far you are from the prime meridian. Latitude is easy, longitude is a real problem without an accurate timepiece. www.pbs.org...


The best ancient navigators were the Polynesians, crossing thousands of miles of open water more than 1,000 years ago. They used a combination of celestial navigation, ocean currents, wave patterns and weather for their wayfinding.

A circumnavigation of the world, using these techniques recently got under way.
www.hokulea.com...

a reply to: anonentity

The Piri Reis map is fascinating.
I think phage is right.

originally posted by: Phage
a reply to: anonentity

So if you were halfway across the Atlantic in a Phoenician type boat, and you used the sun compass at local noon. Wouldn't you know by the markings how far noon was ahead of Giza, and therefore the amount of time and distance you were away from this place.

No, you wouldn't. You don't know the time of local noon (it isn't at 12:00 very often) without a clock so you don't know how far you are from the prime meridian. Latitude is easy, longitude is a real problem without an accurate timepiece. www.pbs.org...


The best ancient navigators were the Polynesians, crossing thousands of miles of open water more than 1,000 years ago. They used a combination of celestial navigation, ocean currents, wave patterns and weather for their wayfinding.

A circumnavigation of the world, using these techniques recently got under way.
www.hokulea.com...


If I was on the equator heading west. As per Eratosthenes, I would know that whatever time local noon was, then noon over the G.P. had to be x number of hours before that, because the suns ground position travels at a constant rate. Since I know the circumference of the Earth because of Eratosthenes calculation. Then I know when its noon where I am, then I also know it had to be x number of hours ago at Giza. Then I know how far west I would be. They might have used sunrise, instead of noon.? Like you said latitude was easy the great circle you were on would have changed the calculation of the circumference, but in the example the equator is easier to imagine.

a reply to: anonentity

Since I know the circumference of the Earth because of Eratosthenes calculation. Then I know when its noon where I am, then I also know it had to be x number of hours ago at Giza. Then I know how far west I would be.

Circular logic. You don't know what time local noon is because you don't know where you are. You are trying to determine the time based on your longitude then use that time to determine your longitude. You can do either one but you can't do both.

Do you really think that it would have taken until the development of accurate timepieces for seafarers to determine longitude if it were such a simple matter as you describe?

a reply to: Phage

Your argument is that because they didn't have accurate clocks to lock the time at the prime meridian, is probably correct. But they had everything else, and like you said the Polynesians did it by the Stars. The Antikithera mechanism, plots the position of just about all observable heavenly bodies. It looks a bit too precise for an astrological mojo.
All they needed was an accurate time piece .How they did the Piri Reis map without one , just makes me think they had something.

originally posted by: anonentity
Was he just checking what was already written in the Library, like the original Piri Ries map?

No original Piri Reis map it was put together from contemporary source find a non fringe source and read the margin notes written on the map they tell you how it was made and from what sources

Knowing the next problem would be longitude, and knowing the Prime longitude on the Piri Ries Map was probably the tip of the Great Pyramid, at Giza.

Not even probable nor indicated on the map, I suggest you read McIntosh's detailed book on the map, 'The Piri Reis map of 1513'

As for the nav info ...listen to Phage, Phage are you a graduate of the US navy's navigation school?

Oops duplicate post deleted

a reply to: anonentity

But they had everything else, and like you said the Polynesians did it by the Stars.

Everything but the one thing required to determine longitude. The Polynesians did not determine longitude by stars, they determined latitude. They would sail until a particular star was overhead then turn east or west and sail until they could see land or clouds that indicated land. pvs.kcc.hawaii.edu...

How they did the Piri Reis map without one

By the use of dead reckoning navigation. It's not really a very accurate map.

a reply to: Hanslune

Phage are you a graduate of the US navy's navigation school?

No. But I've fiddled with shooting the Sun a bit. No good at it but I know how it's supposed to work.

originally posted by: Phage
a reply to: Hanslune

Phage are you a graduate of the US navy's navigation school?

No. But I've fiddled with shooting the Sun a bit. No good at it but I know how it's supposed to work.

Ah, I though you might be a devotee of Saint Brendan

Not to interrupt or derail OP
here is how the ancients navigated and proof that they did:
the working celtic cross as navigational instrument
www.viewzone.com...

and a whole lot of connected stuff:
www.abovetopsecret.com...

and this is who was navigating
archive.org...

so much for the cargo cult of ya way
and the monotheistic religions

have a nice day, and we now return you to the regularly scheduled thread now in progress

a reply to: Phage

the ancients who travelled world wide 7000 years ago have been ridiculed as sun worshippers...
but they were shooting the sun - using solar and lunar navigation..
to travel and for construction alignments - henges pyramids, etc and the astrological animals saved by the Arc
( lunar nav for finding longitude without a chronometer)...
lol...by the Aryan goths who came out of Anatolia after the seas rose up over the continental shelves and recivilized sumeria ...then all over the place etc
for example:
note the root word of MITHRA is the same as the root word for Miter, and the RAys coming out of his head in the artistic depictions are geometric rays

"our lord amen" was the first ruler of both Upper and lower Egypt and was an admiral...Sargon the great's sun ( son)
so ha ha, realize that if you are one to say the "our father" or similar.

a big fat LOL that is eh Phage?
I hope you check my citations and get the joke...
Its a good one,
on us...
yours
dan

ps
this is why the antikythyra device...you need something like that or at least tables, and a cross to shoot with
its why we say "to cross an ocean"

a reply to: Danbones

The AM wouldn't have helped you - you would have needed an accurate sea capable time piece associated with a set time and tables to really determine where you were - that is if you had a map that could tell you that.

What a truly interesting thread, thank you all for my increase in knowledge. (so that's how the red haired giants got to New Zealnd before the Mouris!)

originally posted by: pikestaff
What a truly interesting thread, thank you all for my increase in knowledge. (so that's how the red haired giants got to New Zealnd before the Mouris!)

Simple - they didn't as they are a creation of great imagination and misinterpretation of data by people like Martin Doutre.

originally posted by: Hanslune
a reply to: Danbones

The AM wouldn't have helped you - you would have needed an accurate sea capable time piece associated with a set time and tables to really determine where you were - that is if you had a map that could tell you that.

not so: the use of the moon and astrological signs will give longditude without a chronometer

originally posted by: Danbones

originally posted by: Hanslune
a reply to: Danbones

The AM wouldn't have helped you - you would have needed an accurate sea capable time piece associated with a set time and tables to really determine where you were - that is if you had a map that could tell you that.

not so: the use of the moon and astrological signs will give longditude without a chronometer

While you can use a number of methods, like lunar distance, to determine your position if you have an almanac with the correct tables but I'm unsure of why you would believe why the AM would be of any value to you?

originally posted by: Hanslune

originally posted by: pikestaff
What a truly interesting thread, thank you all for my increase in knowledge. (so that's how the red haired giants got to New Zealnd before the Mouris!)

Simple - they didn't as they are a creation of great imagination and misinterpretation of data by people like Martin Doutre.

You know, Hans, if they were giants, they could have waded there.

Harte

originally posted by: Harte

originally posted by: Hanslune

originally posted by: pikestaff
What a truly interesting thread, thank you all for my increase in knowledge. (so that's how the red haired giants got to New Zealnd before the Mouris!)

Simple - they didn't as they are a creation of great imagination and misinterpretation of data by people like Martin Doutre.

You know, Hans, if they were giants, they could have waded there.

Harte

.....or tied scores of geese to their bodies and flown there, remember one name of the far flung Irish was the wild geese.

lol