You can't always believe what you read or see!!!

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Orla

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You can\'t always believe what you read or see!!!

I aquired a 1995 edition of the MacMillan & Silk Cut Yachtsman's Handbook for sail and power with my boat and have recently started to read it, lots of great information.
Until I came to this bit of text, can any body spot the error.

DodgyText.jpg


Here's one of the map

WholeMap.jpg


The first edition was published in 1985 so this must have been in since then, Amazing that this could get into a book of this calibre without being spotted.
Anybody got a more recent edition?
Is the error still in it?
/forums/images/graemlins/grin.gif
 
Re: You can\'t always believe what you read or see!!!

Arse about face. Well spotted by the way. It is amazing it was not corrected earlier.
Nicki
 
Re: You can\'t always believe what you read or see!!!

Eh? Looks right to me, and (I've just checked) agrees with both my astro-nav books.

What some find confusing is that the actual clock time is ahead of GMT in the eastern hemisphere, so that, for example, 1200hrs (Z) occurs at the same moment as 1300hrs (Z-1).

Something every cross-channel sailor who has just missed the restaurant opening in Cherbourg because his watch is still on English time will be aware.
 
Re: You can\'t always believe what you read or see!!!

[ QUOTE ]
So using the information from the map East coast Canada is about 5 hours ahead of us (+5)?

[/ QUOTE ]

No, capn666 is right. Add 5 to the Canada time to get Greenwich. If it's 0500 in Canada then it's 1000 in London. That's the way that time zones are specified. Look at the tide tables for any French port; you'll see that the time zone is specified as -0100. That means subtract 1 hour from the French standard time to get GMT.

Obviously Andrew can type faster than I can.
 
Re: You can\'t always believe what you read or see!!!

Ahem. It is absolutely correct and the recognised convention.

Lets say you are in East Med, somewhere. Your local noon (i.e. the Sun is Top Dead Centre) is 3 hours before it is at the same point at good old Greenwich. That 3 hours before then becomes -3.
Now lets say you are having a noon rum in Antigua. Yer local noon is 4 hours after it was at, yup, good old Greenwich, therefore plus 4.
Before any pedantic tw@ts drip, sorry chums, but this is the true fact of how it is measured. Any drips, see a plummmer.
PS, I love the fact that the Sun moves around the World at 15 degrees an hour of longtitude and the person who eventually made even me understand it deserves 10 medals!!
 
Re: You can\'t always believe what you read or see!!!

[ QUOTE ]
The first edition was published in 1985

[/ QUOTE ] Actually first published in 1980 as part of the almanac before being published as a separate volume from '85 onwards.

The early editions did not contain the time zone map but careful reading of the explanation of the +/- time zone figures made it clear. I do remember reading it over several times before getting to grips with it though.
 
Re: You can\'t always believe what you read or see!!!

Aha thank you.... I had a feeling that this type of publication would probebly be correct (and i would be wrong)
All the Time zone maps I have seen in the past show -hrs West of Greenwich and +hrs East of Greenwich.
Clear as mud really, once explained.
Thanks for the support Nicki I dont feel as daft knowing you seen it the way I did....
Im away to hit something with a hammer.
/forums/images/graemlins/blush.gif
 
Re: You can\'t always believe what you read or see!!!

Pleasure. No need to feel daft. we both learnt summat. It's not like we thought that New York, for example, was ahead of us time wise. Now that would have been ignorant.
Nicki
 
Re: You can\'t always believe what you read or see!!!

Your local noon (i.e. the Sun is Top Dead Centre) is 3 hours before it is at the same point at good old Greenwich. That 3 hours before then becomes -3.
------------------------------------------------------------------------

Correct.

Your local Noon, lets say 1203 hrs, is the same time all around the world on that day (based on your local mean time - LMT).

However, this LMT, must be corrected for longitude (+W/-E) in order to correct it to UT (GMT), then entered into tables (Nautical Almanac) to obtain Declination if working out a noon sight for Latitude.
As your longitude changes, the LMT corrected back to UT will change.
 
Re: You can\'t always believe what you read or see!!!

[ QUOTE ]
PS, I love the fact that the Sun moves around the World at 15 degrees an hour of longtitude and the person who eventually made even me understand it deserves 10 medals!!

[/ QUOTE ]I think you will find that it works the other way round. This was established several hundred years ago, if not longer. /forums/images/graemlins/grin.gif
 
Re: You can\'t always believe what you read or see!!!

What, why was I not told. I suppose you'll be claiming a round earth next!
 
Re: You can\'t always believe what you read or see!!!

It probably is just the case that in the context of almanacs they do it differently than it is done else where. All the other maps I have seen always have the time zones east of GMT as + and the west as -

The international standard for formatting dates and times (ISO 8601) also uses this convention and for things like emails the date time in the email follows this. e.g. an email I sent today at 10:26(BST) has the time recorded as Fri, 4 Apr 2008 10:26:25 +0100

Jonathan
 
Re: You can\'t always believe what you read or see!!!

[quoteI think you will find that it works the other way round. This was established several hundred years ago, if not longer. /forums/images/graemlins/grin.gif

[/ QUOTE ]

You've never studied navigation, then. It's a fundamental premise that the earth is stationary, and all the celestial clutter whizzes round us in a predictable manner.
You'll find it all a lot easier to handle once you grasp this. Navigational concepts like hour angle and declination will make your brain spin if you believe the mad notions of the deluded non-sailors Copernicus and Galileo.

Work it out for yourself. If the earth was spinning, we'd all fly off it. We haven't, so it isn't. There's no life on nearby planets or systems, so they are spinning.

This knowledge of how the universe is structured has served the ship's navigator well for a very long time.
 
Re: You can\'t always believe what you read or see!!!

[ QUOTE ]

Work it out for yourself. If the earth was spinning, we'd all fly off it. We haven't, so it isn't.

[/ QUOTE ]

And by the same token, the earth is flat. If it was curved, we'd all slide down the slope. We don't, so it isn't.....
And that's how the map-makers depict it - and they should know!

/forums/images/graemlins/smirk.gif
 
Re: You can\'t always believe what you read or see!!!

If it was curved, we'd all slide down the slope. We don't, so it isn't.....
And that's how the map-makers depict it - and they should know!
------------------------------------------------------------------------

Doesn't the angle of the slope have something to do with which chart projection is being used?

Some being blue, some red & some black runs.
Some, you slide in a straight line & others in a curve.:p
 
Re: You can\'t always believe what you read or see!!!

[ QUOTE ]
And by the same token, the earth is flat. If it was curved, we'd all slide down the slope. We don't, so it isn't.....
And that's how the map-makers depict it - and they should know!

[/ QUOTE ]

Well, for most yachting purposes, it is, isn't it? That's why the simplest form of navigational calculation (anything up to about 600nm) is called Plane Sailing. This term has entered the language as "Plain Sailing," but in fact it refers to calculations where the earth is assumed to be a plane, and you can use school-kid trig to do all the sums. We used to spend hours doing "Day's Work" calculations using Traverse Tables, but it's quicker with a calculator now.
 
Re: You can\'t always believe what you read or see!!!

There are at least three ways of naming time zones.

In the conventional nautical system, used in most technical publications, including those produced by the UK Admiralty, the US Naval Observatory, and Reeds Nautical Almanac:
zones that are ahead of UT (generally those to the east) are designated as negative
zones that are behind UT (generally those to the west) are designated as positive

The International Standards Organisation -- being run by bureaucrats -- has adopted a system that is the exact opposite of the established nautical system:
zones that are ahead of UT (generally those to the east) are designated as positive
zones that are behind UT (generally those to the west) are designated as negative

And the military system uses letters, rather than numbers
UT is designated "Z" or "Zulu"
zones that are ahead of UT are designated from A to M (omitting J) zones that are behind UT are designated from N to Y

If you can't believe everything you read in books or magazines, where the writers at least have to take personal responsibility for what they write, why on earth do you trust *anything* you read on a web forum?
All the best
 
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