compass

[slimpig]

can I use a watch as a compass

[Buenchico]

It depends on whether you've got an analogue or digital watch and whether the sun's shining or not. Assuming that you've got an analogue watch (or that you've used your digital watch to draw a picture of an analogue watch) and that the sun is visible, then finding north is straightforward. (To do it really accurately, your watch should be set to GMT rather than BST - or your local equivalent if you're not in the UK).

Simply point the hour hand of your watch towards the sun and imagine a line, from the centre of your watch, which bisects the angle between the hour hand and '12' on the watch. This imaginary line will point towards (true) north.

More on this here:
http://www.learn-orienteering.org/old/nocompass1.html

Hoping this helps,

Chris

[Loosehead]

In the northern Hemisphere, the line described by Buenchico will point SOUTH and it will point north in the southern Hemisphere. Just to clarify as I don't know where Buenchico is geographically.

[brachiopod]

For it to work in the southern hemisphere, you need a 'backwards' watch, ie one that travels in an anti-clockwise direction.

[Buenchico]

Oops!
Sorry about the error! Loosehead is right, of course. (Well, it was 4.42a.m.- perhaps I shouldn't have opened that last can!).

I hope that this is the only time that I've got that wrong, otherwise there will be a lot of people I used to prepare for the Duke of Edinburgh's Award Scheme wandering around lost!

(I think I got confused because I was looking for a website with a diagram - the first one I found was based in Australia! As Brachiopod says, things get a little mixed up in the Southern hemisphere!).

Chris

[Tatty Rollox]

In the Northern Hemisphere, hold the watch horizontal and point the hour hand at the sun. Bisect the angle between the hour hand and 12 and this bisection is the North - South line. If you then have trouble deciding which end of the line is North, remember that the sun rises in the East and sets in the West. It is therefore due South at noon, East before noon, and West after noon. If your watch is set on daylight saving time, bisect the angle between the hour hand and 1 to find the North - South line.

[wildwood]

and you don't need a backwards watch in the southern hemisphere. The Earth revolves the same way wherever you are. Due North however is where the sun is at 12noon as opposed to south in the northern H.

[brachiopod]

wildwood, you DO need an anti-clockwise watch in the southern hemisphere. The hour hand needs to track the apparent path of the sun, which in the southern hemisphere is anti-clockwise.

Imagine you are facing due North at 12.00 local noon. The hour hand points at the sun and there is no angle to bisect, so your watch is telling you that you are facing due North. All well and good.

Now, imagine it is 11 am. In the southern hemisphere the sun still rises in the East and sets in the West, so at 11 am the sun will be a little short of the noon position - in other words, slightly East of Due North.
Agree so far?

You point the hour hand (showing 11 o'clock am) of your conventional clockwise watch at the sun. You bisect the angle between 11 and 12 and this should be Due North.
However, this bisector line points a little further East than where the sun is now, when we know that it should be a little further West (the sun hasn't quite reached noon / Due North yet, remember?)

Now repeat with with a 'backwards' watch. (The 11 O'clock position is now where the 1 O'clock position is on a conventional watch.) Point the hour hand at the sun and bisect the angle between it and the 12 position.
Your bisector line now points to a position slightly West of the sun, which is, indeed, the position of Due North.

You will find that at earlier times in the AM and later in the PM the error is very large.

Try it on some paper. If you're still in doubt post back and I'll stick up a diagram !!