Out&About with Dayv at the Lambert Centre, near Finke, Northern Territory

Three Norths – and Why Have them – the travel compass

Knowing where you are, where you’re going and where you’ve been is a very important element of camping and travel in all its forms. That is unless you really want to go where the breeze takes you and what the throw of the dice dictates – but there’s always others to consider and the possibility of needing to get out of a problem quickly.

A basic Map

If you pick up a basic map from the tourist centre or petrol station there’s a chance that somewhere on the map there’ll be an arrow that points north. The purpose of this North Point (once highly decorated) is to simply allow you to orientate the map with the customary top of the map being north – then with some confidence you’ll be able ‘get your bearings’* on where you are, where you want to go and where you’ve been.

Note: You can see now where this expression has its origins – with bearings referring to the compass directions.

The three norths

However, true navigation and finding your way around in the bush (or elsewhere) requires a bit more information – and accuracy.

For this blog, we’ll start with the ‘Three Norths’ (that you’ll find on more serious maps) and step our way further into some basic navigation.

True North – Santa’s Home

True North refers to direction that you would need to travel if you wanted to get to the Earth’s Geographic North Pole. And, as we all know, that’s where Santa, his Mrs and all the  helpers live. That’s why I recon it’s referred to as True North.

The only trouble with True North is that there is no real way to point to it and the only real time we see it is when you look at a globe of the world and peer down on it from the top.

If you were to hang a beach ball (representing the Earth) by a string tied to the valve (where you blew it up), the top could be considered as the North Pole. Looking further at this beach ball you’d see panels of colour that reach down the ball to converge at the bottom. 

North Pole
North Pole – True North

South Pole

The bottom of the beach ball would represent the South Pole, and the lines between these panels of colour would represent the lines of longitude that vertically divide the globe and its 360 degree circumference.

So, standing now on the real Earth and looking along one of these lines of longitude, you would be looking towards the North or South Pole – to the north is True North.

Hopefully not going too fast, but… when you are standing in Australia and looking towards True North – to your left the lines of Longitude reduce in value until you get to zero (the Meridian Line that travels through Greenwich, London UK) and to your right the lines increase until you get to 180 degrees (near where the International Date Line is and every new day begins).

The Australian mainland itself straddles between approximately 113 deg East of Greenwich at Point Steep, WA and 153 deg east of Greenwich at Cape Byron, NSW. That’s a spread of about 40 degrees – or about 1/10th of the Earth’s total circumference.

Australia
Australia’s place on earth

Magnetic North

Now, this North you can ‘see’.

Just pick up a magnetic compass and the usually red arrow will point to the Magnetic North. BUT, only for where you are standing.

It’s important to understand that the magnetic field of the Earth weaves and wavers all about its surface – as does the extent of this wavering as time goes by.

Navigation compass for camping
Compass Pointing to Magnetic North
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Metal Objects – watch out

Just be careful to keep away from metal objects (like cars and fences) and electromagnetic fields (such as powerlines) that can affect the compasses ability to point to Magnetic North.

So, what’s Magnetic North to you is not the same Magnetic North as that for someone else some distance away. But, it does provide a good starting point if you have a good map and you’re not wanting to travel a long way using the one compass bearing.

Now, I guess your next question may be “What’s the difference between the direction of True North and Magnetic North”. Well, for a particular point (usually the centre of the map your using), the cartographer will have provided an angle (in degrees, minutes and seconds) from True North to the Magnetic North that is east or west of True North. This is referred to as the Magnetic Declination at that point.

The three north poles
Simplistic Representation of Magnetic North and True North. Source: RACQ Gold Coast – Northern Rivers Tourist Map 1:420,000

Magnetic North and True North

On top of this, the cartographer may have provided you with a bit more information that tells you how much this angle has changed every so many years since the datum date that that figure was valid for. So, knowing the date that the angle (Magnetic Declination) was correct; and the number of years since that date to today; and the increment over that time, you are now able to calculate the current angle between Magnetic North and True North.

East is Least

Note: Don’t be surprised if, after doing these sums, the declination has probably changed less than you could read by eye on the compass anyway.

If you’ve come this far, you need to know that where the Magnetic North on the map is pointing east of True North, you need to take the declination away (subtract) from the magnetic bearing to find True North. This is usually the case on the east coast of Australia. Remember “East is Least”.

If you are in Western Australia, the chances are that the Magnetic North will point west of True North and you will need to add that declination to the compass reading to get to True North. Remember “West is Best”.

Grid North

You may be somewhat upset with me now when I say that all that has been written above is all well and good, but not much use when you’re trying to find your way around in the bush or outside street maps.

This situation can perhaps be best summed up by the words in the Introduction (clause 1.1.2) of the The Australian Map Grid – Technical Manual (Australian Government, 1972) where it says:

Geodetic coordinates are usually computed in latitude and longitude. For many purposes, including mapping, a system of rectangular grid coordinates – eastings and northings – is more convenient.

Note: The Forward to this manual was written by the then Chairman of the National Mapping Council, B.P. Lambert. If you travel near Finke in the Northern Territory, you may like to duck into the Lambert Centre – the geographical centre of Australia named in his honour.

Grid Mapping

This is where grid mapping comes in and the third North becomes valuable – Grid North.

Without going into too much detail, the Australian Map Grid divides Australia up by grid lines that don’t have any direct relationship with the Earth’s lines of longitude or latitude.

With the grid’s origins somewhere in the Southern Indian Ocean (South-West of Australia) the vertical lines (Eastings – which tell you how far east you are) incrementally increase as you travel east and the horizontal lines (Northings – which tell you how far north you are) increase as you travel north.

Grid Referencing

For grid referencing and navigational purposes, these grids can then be broken down further into tenths and then tenths again to give you four, six and eight figure grid referencing. I can write more on this later.

For now though, it’s important to know that, at this level of mapping (usually what we call Army Topographical Maps), the cartographer gives you the Grid-Magnetic Angle for the centre of the map – and just like the Magnetic Declination above, you can calculate the Grid North bearing from your location by applying the variation to your compass bearing.

Camping with a map reference
Magnetic Variations Shown in Detail. Source: Spring Mountain, Queensland Topographic Map 1:25 000 (9442-12)

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The cartographer may also give you the Grid North-True North variation (Grid Convergence) to allow you to find all three Norths in one go. Otherwise, take out a pencil and calculator and do the sums yourself – but don’t rely on the diagram on the map as it’s just that, a diagram.

Summary

There is perhaps so much more to be said, and perhaps quite a lot has been said here already. But, at least (for now) I hope you have a better understanding of the Three Norths and how (and why) you can find them.

Good luck and don’t get lost.

Until next time.

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