magnetic deviation to compass bearing

In message <[email hidden]>,
Dundonald <[email hidden]> writes

Quoted message said:

I've been reading up on navigation, being a relatively new mountain
walker, and as I read about using a compass it was explained to add a 4
degree to a compass bearing to accomodate magnetic deviation. What's
that all about then?

http://www.scoutingresources.org.uk/compass_magvar.html

Regards
--
Neil Pugh

In article <[email hidden]>,
Dundonald <[email hidden]> writes

Quoted message said:

I've been reading up on navigation, being a relatively new mountain
walker, and as I read about using a compass it was explained to add a 4
degree to a compass bearing to accomodate magnetic deviation. What's
that all about then?

There are three norths.

True north is the line to the north pole but is not much use
when dealing with OS maps.

Grid north is the alignment of the NS lines of the grid. It
varies around the grid.

Magnetic north is the north direction of the local magnetic
field and points roughly towards the magnetic north pole.

If you take a bearing from an OS map the bearing will be relative to
grid north so to get the magnetic bearing to follow you have to correct
for the difference between the two.

The 4 degrees is a red herring as it isn't the same all over the UK. You
need to refer to the map where it will tell you the difference between
grid and magnetic. It will also tell you the date and the direction and
rate of change.

Currently magnetic is west of grid throughout the UK. Therefore a
magnetic bearing will be greater than the grid bearing. If the deviation
was 4 degrees where you were and you pointed the compass directly grid
north it would read 4 degrees.

To remember which way to correct I use.

Grid to mag add, mag to grid get rid.

--

Dominic Sexton

"Dundonald" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

I've been reading up on navigation, being a relatively new mountain
walker, and as I read about using a compass it was explained to add a 4
degree to a compass bearing to accomodate magnetic deviation. What's
that all about then?

I've just been teaching this tonight at a D of E meeting...........

You are at A. You want to go to B.

1. Line the edge of the compass up along A-B ensuring the direction of
travel arrow is pointing in the direction you want to go.
2. Turn the housing until the parallel lines and the red housing arrow are
parallel with the grid lines on the map and the housing arrow is pointing
grid north.
3.Take the compass off the map and read the bearing at the white line (or
arrow). This is a grid bearing. Add 4 degrees, ie if the grid bearing was 50
deg make it read 54 deg by moving the housing anticlockwise. Most compasses
have 2 degree divisions.
4. Hold the compass in your midriff and turn your whole body round until the
magnetic needle and the red housing arrow align. The direction of travel
arrow now points the way!

Note that i've split it into 4 operations. You do two with the map and two
without it.

In this country we're lucky that grid north (the parallel lines running
south-north on the map) is very close to magnetic north (the direction the
magnetic needle in your compass points to). If you didn't make the
correction, you could still follow a bearing and probably get out of
trouble. However, in other countries the variation could be 20 degrees or
more and would make a vast difference if not taken into account.

Graham

Dundonald said:

I've been reading up on navigation, being a relatively new mountain
walker, and as I read about using a compass it was explained to add a
4 degree to a compass bearing to accomodate magnetic deviation.
What's that all about then?

You don't want to bother with that new fangled map and compass stuff. First
you need to navigate by cairns alone. Once you've mastered that you then
need to learn to navigate by moss on trees and rocks, and use sticks to cast
shadows on the ground. After that you need to study the stars. You'll need
all of those skills as a backup before you risk your life to a piece of
paper and a spinning needle.

;-)

Paul

Dominic Sexton said:

To remember which way to correct I use.

Grid to mag add, mag to grid get rid.

Add for mag, subtract for map.

Paul

"Paul Saunders" <[email hidden]> wrote

Quoted message said:

You don't want to bother with that new fangled map and compass stuff.
First you need to navigate by cairns alone. Once you've mastered that you
then need to learn to navigate by moss on trees and rocks, and use sticks
to cast shadows on the ground. After that you need to study the stars.
You'll need all of those skills as a backup before you risk your life to a
piece of paper and a spinning needle.

;-)

Paul

Horse'n'cartnophobe!

Graham

Graham Seed said:

"Dundonald" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

I've been reading up on navigation, being a relatively new mountain
walker, and as I read about using a compass it was explained to add a 4
degree to a compass bearing to accomodate magnetic deviation. What's
that all about then?

I've just been teaching this tonight at a D of E meeting...........

You are at A. You want to go to B.

1. Line the edge of the compass up along A-B ensuring the direction of
travel arrow is pointing in the direction you want to go.
2. Turn the housing until the parallel lines and the red housing arrow are
parallel with the grid lines on the map and the housing arrow is pointing
grid north.
3.Take the compass off the map and read the bearing at the white line (or
arrow). This is a grid bearing. Add 4 degrees, ie if the grid bearing was 50
deg make it read 54 deg by moving the housing anticlockwise. Most compasses
have 2 degree divisions.
4. Hold the compass in your midriff and turn your whole body round until the
magnetic needle and the red housing arrow align. The direction of travel
arrow now points the way!

Note that i've split it into 4 operations. You do two with the map and two
without it.

In this country we're lucky that grid north (the parallel lines running
south-north on the map) is very close to magnetic north (the direction the
magnetic needle in your compass points to). If you didn't make the
correction, you could still follow a bearing and probably get out of
trouble. However, in other countries the variation could be 20 degrees or
more and would make a vast difference if not taken into account.

Thanks Graham.

Paul Saunders said:

Dundonald said:

I've been reading up on navigation, being a relatively new mountain
walker, and as I read about using a compass it was explained to add a
4 degree to a compass bearing to accomodate magnetic deviation.
What's that all about then?

You don't want to bother with that new fangled map and compass stuff. First
you need to navigate by cairns alone. Once you've mastered that you then
need to learn to navigate by moss on trees and rocks, and use sticks to cast
shadows on the ground. After that you need to study the stars.

On a serious note, I'd like to learn that stuff, I'm eager!

Quoted message said:

You'll need
all of those skills as a backup before you risk your life to a piece of
paper and a spinning needle.

;-)

Or GPS for the purists?

On Wed, 25 Jan 2006 00:11:47 -0000, "Paul Saunders"
<[email hidden]> wrote:

|Dundonald wrote:
|
|> I've been reading up on navigation, being a relatively new mountain
|> walker, and as I read about using a compass it was explained to add a
|> 4 degree to a compass bearing to accomodate magnetic deviation.
|> What's that all about then?
|
|You don't want to bother with that new fangled map and compass stuff. First
|you need to navigate by cairns alone.

Cairns only take you where other people think you *aught* to go, I prefer
to avoid cairned and waymarked routes.
With the new Right to Roam legislation and using map, compass and possibly
GPS one can get off the standard routes.

|Once you've mastered that you then
|need to learn to navigate by moss on trees and rocks, and use sticks to cast
|shadows on the ground. After that you need to study the stars. You'll need
|all of those skills as a backup before you risk your life to a piece of
|paper and a spinning needle.
|
|;-)

LOL
--
Dave Fawthrop <dave hyphenologist co uk>
17,000 free e-books at Project Gutenberg! http://www.gutenberg.net
For Yorkshire Dialect go to www.hyphenologist.co.uk/songs/

"Paul Saunders" <[email hidden]> wrote

Quoted message said:

You don't want to bother with that new fangled map and compass stuff.

First

Quoted message said:

you need to navigate by cairns alone. Once you've mastered that you then
need to learn to navigate by moss on trees and rocks, and use sticks to

cast

Quoted message said:

shadows on the ground. After that you need to study the stars. You'll

need

Quoted message said:

all of those skills as a backup before you risk your life to a piece of
paper and a spinning needle.

And if you doubt your own navigation skills you can always find a sheep and
follow that. Sheep know all the best routes.

AndyP said:

"Paul Saunders" <[email hidden]> wrote

Quoted message said:

You don't want to bother with that new fangled map and compass stuff.

First

Quoted message said:

you need to navigate by cairns alone. Once you've mastered that you then
need to learn to navigate by moss on trees and rocks, and use sticks to

cast

Quoted message said:

shadows on the ground. After that you need to study the stars. You'll

need

Quoted message said:

all of those skills as a backup before you risk your life to a piece of
paper and a spinning needle.

And if you doubt your own navigation skills you can always find a sheep and
follow that. Sheep know all the best routes.

And they're very cuddly if you end up lost and alone.

--
Nobby

In message <[email hidden]>, Nobody
Here <[email hidden]> writes

Quoted message said:

And they're very cuddly if you end up lost and alone.

But only if it's a pretty one, surely.

The way this thread is going should 'magnetic' and 'to compass bearing'
be removed from the subject line?

Regards
--
Neil Pugh

"Graham Seed" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

"Paul Saunders" <[email hidden]> wrote

Quoted message said:

You don't want to bother with that new fangled map and compass stuff.
First you need to navigate by cairns alone. Once you've mastered that
you then need to learn to navigate by moss on trees and rocks, and use
sticks to cast shadows on the ground. After that you need to study the
stars. You'll need all of those skills as a backup before you risk your
life to a piece of paper and a spinning needle.

;-)

Paul

Horse'n'cartnophobe!

Graham

Strictly speaking, what we are talking about here is magnetic VARIATION -
being generally the angular difference between magnetic north and true
north.

DEVIATION is really the angular difference between magnetic north and
compass north. This difference can occur when the compass is influenced by
other magnetic field in its immediate vicinity. This occurs when the compass
is mounted or carried in a vehicle such as a ship, aircraft or land vehicle.
DEVIATION doesn't strictly affect walkers but VARIATION does.

Forget the moss and stars stuff, just follow the used tissues.

Forget the moss and stars stuff, just follow the used tissues.

Neil Pugh said:

In message <[email hidden]>, Nobody
Here <[email hidden]> writes

Quoted message said:

And they're very cuddly if you end up lost and alone.

But only if it's a pretty one, surely.

Depends how lost and alone you are, I guess.

Quoted message said:

The way this thread is going should 'magnetic' and 'to compass bearing'
be removed from the subject line?

LOL

--
Nobby

Dave Fawthrop said:

On Wed, 25 Jan 2006 00:11:47 -0000, "Paul Saunders"
<[email hidden]> wrote:

Quoted message said:

|Dundonald wrote:
|
|> I've been reading up on navigation, being a relatively new mountain
|> walker, and as I read about using a compass it was explained to add a
|> 4 degree to a compass bearing to accomodate magnetic deviation.
|> What's that all about then?
|
|You don't want to bother with that new fangled map and compass stuff. First
|you need to navigate by cairns alone.

Quoted message said:

Cairns only take you where other people think you *aught* to go,

It's not as simple as that. Some cairns mark places where you ought
not to go. Usually these are distinguished by having the stones facing
the other way.

--
Chris Malcolm [email hidden] +44 (0)131 651 3445 DoD #205
IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK
[http://www.dai.ed.ac.uk/homes/cam/]

On Wed, 25 Jan 2006 13:04:12 +0000 (UTC), Chris Malcolm
<[email hidden]> wrote:

|Dave Fawthrop <[email hidden]> wrote:
|> On Wed, 25 Jan 2006 00:11:47 -0000, "Paul Saunders"
|> <[email hidden]> wrote:
|
|> |Dundonald wrote:
|> |
|> |> I've been reading up on navigation, being a relatively new mountain
|> |> walker, and as I read about using a compass it was explained to adda
|> |> 4 degree to a compass bearing to accomodate magnetic deviation.
|> |> What's that all about then?
|> |
|> |You don't want to bother with that new fangled map and compass stuff.First
|> |you need to navigate by cairns alone.
|
|> Cairns only take you where other people think you *aught* to go,
|
|It's not as simple as that. Some cairns mark places where you ought
|not to go. Usually these are distinguished by having the stones facing
|the other way.

Qui?
How can stones face any way?
--
Dave Fawthrop <dave hyphenologist co uk>
17,000 free e-books at Project Gutenberg! http://www.gutenberg.net
For Yorkshire Dialect go to www.hyphenologist.co.uk/songs/

Buy this book by Peter Cliff.
http://www.amazon.co.uk/exec/obidos/ASIN/1871890551/202-7139698-3815062