Celestial Navigation explained.

[Farmer John]

I bought a book called "The Boatman's Manual" some time ago, and it got put on one side till later. Later has arrived, and I would like to share a quote that is given at the beginning of the Chapter headed " The Instruments of Piloting".

Celestial Navigation for the small-boat man defined by Alfred Loomis "The ability to distinguish sunrise from sunset, then to steer towards the sunset until a large continent looms in sight." then the comment "On the Pacific coast it would be as well to steer for the sunrise".

You really can't go wrong!

I should point out that this leads to the explanation that when you find the continent, then you need piloting, by which is meant coastal navigation.

This comes close to my favourite quote, when an admiral of little sea experience went on board a ship and was heard to mutter "Jehosophat, it's hollow"

Well, that's explained that.

[Richard]

Originally Posted by Farmer John

I bought a book called "The Boatman's Manual" some time ago, and it got put on one side till later. Later has arrived, and I would like to share a quote that is given at the beginning of the Chapter headed " The Instruments of Piloting".

Celestial Navigation for the small-boat man defined by Alfred Loomis "The ability to distinguish sunrise from sunset, then to steer towards the sunset until a large continent looms in sight." then the comment "On the Pacific coast it would be as well to steer for the sunrise".

You really can't go wrong!

I should point out that this leads to the explanation that when you find the continent, then you need piloting, by which is meant coastal navigation.

This comes close to my favourite quote, when an admiral of little sea experience went on board a ship and was heard to mutter "Jehosophat, it's hollow"

Well, that's explained that.

I knew there was nothing to this navigation lark. Simple isn't it.
Basically, head for the sunset, or sunrise and when the boat stops, you're there!

[Varley]

Ah. Richard the optimist. I am afraid there are enough rocks between Sun (at any azimuth and elevation) to bring about a stop prior and more abrupt to the one intended.

[BobClay]

Reminds me of Captain Jack Sparrow stepping ashore off the top of the mast as the boat went under .... and was then asked for a berthing fee !!

https://youtu.be/dvdrCPr3gDQ

[Dartskipper]

The art of piloting is knowing where the rocks are, or perhaps where they aren't.

[Farmer John]

Originally Posted by Dartskipper

The art of piloting is knowing where the rocks are, or perhaps where they aren't.

Well make up your mind, do you want to hit them or not?

[BobClay]

I think that's called Heisenberg's Uncertainty Principle. The more you know about position, the less you know about momentum, ... and Vicky Verka.

[Dartskipper]

Originally Posted by Farmer John

Well make up your mind, do you want to hit them or not?

Preferably, not like this;


http://n7.alamy.com/zooms/dc4ab84a10...910-e7wbfa.jpg

[Farmer John]

Originally Posted by Dartskipper

Preferably, not like this;


http://n7.alamy.com/zooms/dc4ab84a10...910-e7wbfa.jpg

It looks like it was snuck up on from below, sunrise or sunset wouldn't make much difference. That land must have been on it's tiptoes.

[Engine Serang]

Perhaps the Master was having relationships with a Moldovan entertainer.

[Naytikos]

When the Transit system first came out I heard something like this, which applies equally to GPS:

The satellite navigator never knows where it is, but always knows where it isn't. To determine where it might be, in a format useful to a third party, it subtracts where it was yesterday from where it hopes to be tomorrow and applies correction factors based upon what it thinks the wind, tide, current and auto-pilot are doing at any given moment. The result should never be relied upon for navigation purposes when out of sight of land.

[Dartskipper]

Originally Posted by Naytikos

When the Transit system first came out I heard something like this, which applies equally to GPS:

The satellite navigator never knows where it is, but always knows where it isn't. To determine where it might be, in a format useful to a third party, it subtracts where it was yesterday from where it hopes to be tomorrow and applies correction factors based upon what it thinks the wind, tide, current and auto-pilot are doing at any given moment. The result should never be relied upon for navigation purposes when out of sight of land.

Was that instruction manual written by Sub Lieutenant Phillips of HMS Troutbridge by any chance?

[BobClay]

I'm currently reading a book by top physicist Kip Thorne called 'The Science of Interstellar.' He was the science advisor for the film 'Interstellar.'

In order to explain some of the weird stuff in the film with regard to the black hole featured therein he puts forward some mind boggling concepts.

In order to do this he gives an introduction to Einstein's General Theory of Relativity with regard to time dilation in gravitational fields, and our old friend the GPS comes in for quite a lot of the explanation.

Here's a typical sentence: "Time at a 20,000 kilometre height flows more rapidly on Earth by forty microseconds each day, and the satellites must correct for this. They measure time with their own clocks, then slow that time down to the rate of time flow on Earth before transmitting it to our phones."

You have to wonder what planet Albert Einstein came from ?

[Dartskipper]

I don't know what planet, but it's probably in the Samsung Galaxy.......

[Varley]

Originally Posted by Dartskipper

Was that instruction manual written by Sub Lieutenant Phillips of HMS Troutbridge by any chance?

I love both of those. Isn't it truer to say that Transit knew where it was at a particular time which cannot be precisely now? With several fixes per day but no continuous updating it was, I suppose, fair game to allow them to have a DR function. That might also be just true of GPS whilst the constellation was completed. Why on earth was this permitted (for type approved sets anyway) after GPS had universal cover. It invited Royal Majesty's woe (or more properly, rather late to woe). The set is either working and getting virtually instant position information or it is not. If it is not then one might proceed by DR but why would one trust a defective piece of kit to do the computation?

Has the 'fudge' (requiring indication of mode and alarm on mode change) been to keep the yachty market engaged?

[BobClay]

Surely the art of good navigation is that you don't put all your eggs in one basket ? From the Mark One eyeball through sextants, radars right up to GPS (and beyond ?)

I carry a Satmap GPS (and my phone) on mountain walks. But I still have a map and compass in the rucksack, and (vaguely ) still know how to use them.

[Naytikos]

On Sunday I attended the funeral of a chap who had been to sea on schooners before and during the 2nd World War. He had no formal training or qualifications, started out as a dogsbody but rose to be Mate. That doesn't quite have the connotations it would on a more modern small cargo ship, but for the purposes of local trade within the Caribbean he was accepted as being entitled to the position he held.

Example: Leave the island on a turtling trip to the Serrannas Keys (Columbia possession these days); set sail due South until sighting Man-O'-Wars (large birds) and follow them as the sun sets.
Next morning, look-out for discoloured waters indicating shoals; if the colour changes rapidly but no land is in sight, then turn either East or West until the shoals are passed; head South again.
Follow the same procedure until actual land, in the form of rocks sticking up above the sea, is seen.

From the shape and size of the rocks he would know what and where they were; if not the intended destination, then again head East or West until safely around the rocks and continue the voyage.

Not very efficient, but when it didn't matter if the ship arrived today, tomorrow, or next month, it worked and it was cheap.

Who needs either a sextant or GPS just follow the birds!

[BobClay]

I often wondered when watching those albatross birds wheeling back and forth following the ship as we chugged across the Pacific (and demonstrating flying abilities far beyond anything we've come up with,) was it a co-incidence the ship was going where they wanted to go ? ... or were they just hitching a lift so to speak with no particular destination in mind.

Someone told me the albatross will spend months in the air, then return to the island where they were born to breed. If that's true, and given the size of the Pacific Ocean, that's pretty impressive navigation.