The ancient navigators

originally posted by: anonentity
a reply to: Hanslune

I bet that the way that the Royal Observatory wanted it was a perfct line of Longitude. I bet if you didn't cross all the T"s and dot all the I's you could get a quick fix that placed you on the vessel's horizon.

While chronometers could deal with the conditions of a ship at sea, they could be vulnerable to the harsher conditions of land-based exploration and surveying, for example in the American North-West, and lunar distances were the main method used by surveyors such as David Thompson. Between January and May 1793 he took 34 observations at Cumberland House, Saskatchewan, obtaining a mean value of 102° 12' W, about 2' (2.2 km) east of the modern value. Each of the 34 observations would have required about 3 hours of calculation. These lunar distance calculations became substantially simpler in 1805, with the publication of tables using the Haversine method by Josef de Mendoza y Ríos. 1&it=r&sid=AONE&asid=7874bcb9. en.wikipedia.org...

a reply to: Hanslune

Thanks that was interesting.Then again not bad fixes.

originally posted by: anonentity
a reply to: Hanslune

Thanks that was interesting.Then again not bad fixes.

Here is a detailed explanation of 'Lunars'. Once upon a time before GPS. I use to teach land navigation. I had learned this method but it was completely impractical at the time due to the instruments and books needed to do it for anyone who didn't have the knowledge and those items.

www.starpath.com...

a reply to: anonentity

Here is a Powerful Thought Provoking Video of Descriptions of Mankind's Ancient Past in Atlantis and Lemuria , Two Civilizations thought by Most as just Wishful Mythical Places .





www.youtube.com...

originally posted by: Zanti Misfit
a reply to: anonentity

Here is a Powerful Thought Provoking Video of Descriptions of Mankind's Ancient Past in Atlantis and Lemuria , Two Civilizations thought by Most as just Wishful Mythical Places .


www.youtube.com...

Tripura means three cities not three walls

en.wikipedia.org...(mythology)

Then into conspiratorial paranoia....

Tin-Hinan is said to be from the 4th BC, nope 4th century AD. Tin Hinan was a 4th- 5th century Tuareg queen.
en.wikipedia.org...

Tin-Hinan and aliens - well I cannot find any such legend or myth. Do you have link to that?

So three errors in less than 3 minutes..........TTFL failure.

a reply to: Hanslune

That was a good read. But you can see that you have to be lucky to get the meteorological conditions right to get a reasonable fix. But just as an example on the day of the equinox if you were on the equator. The moment the tip of the sun's upper limb just goes above your horizon, you know that ninety degrees off it gives you true north or south. If you take the reading on a compass and log the reading. then you know that ninety degrees off the reading are the compass deviation. I'm just using the equinox as an example so you haven't got to do any adjustments. so placing the big chart on the flat surface you orientate it North and south. Geographical north-south. Then you know where the geographical north pole is on your chart, you know the deviation from the magnetic north pole, and where it is on your chart. The angle between the two is totally unique to your position so with a protractor set at that angle. Where the open ends touch the geo north and the magnetic pole should be your position on the ocean, by triangulation. Surely you have at least a rough idea of your position.

originally posted by: anonentity
a reply to: Hanslune

That was a good read. But you can see that you have to be lucky to get the meteorological conditions right to get a reasonable fix. But just as an example on the day of the equinox if you were on the equator. The moment the tip of the sun's upper limb just goes above your horizon, you know that ninety degrees off it gives you true north or south. If you take the reading on a compass and log the reading. then you know that ninety degrees off the reading are the compass deviation. I'm just using the equinox as an example so you haven't got to do any adjustments. so placing the big chart on the flat surface you orientate it North and south. Geographical north-south. Then you know where the geographical north pole is on your chart, you know the deviation from the magnetic north pole, and where it is on your chart. The angle between the two is totally unique to your position so with a protractor set at that angle. Where the open ends touch the geo north and the magnetic pole should be your position on the ocean, by triangulation. Surely you have at least a rough idea of your position.

Yeah, but I was wondering (I'll have to look it up later) if the position of the sun at different points on the horizon due to the movement between the Equinox and Solstice would distort that 90 degrees? astrocoffeehut.files.wordpress.com...

a reply to: Hanslune

I Agree . His Facts are a Little Off the Mark , but his Attempt at Explaining Myths were Admirable .

a reply to: Hanslune

What I am suggesting is simply that if you know the position of the true geographical north, Like shove a little pin at that point on the chart and you know the present position of the Magnetic north, shove a pin in the chart. and you know the angle of deviation, the angle between the two at your local position is unique, you have to be there. The example given was to find true north at sea that's the key, You could have a small gyro compass, but i was suggesting you use the sun read its deviation from what the compass says, set that angle on a protractor, and where the end of the protractor touches the two pins, at the protractors pivot point is where you are on the chart. If you didn't have a chart you could use a globe , with some attachments to get the pivot point.
I mean in simplistic terms , the usual way is to know the suns ground position when you take a sextant reading and draw a circle around it, then wait an hour or two and do the same again, you know from the two points that the circles cross where you are most likely to be, but you still need that clock. Where the angle of deviation does not.