Australian_Geographic_Outdoor_2016_07_08_

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70 | AG Outdoor

Theabilitytouseacompassquicklyandaccuratelyis

a specialised skill that can prove invaluable in

numerous competitive outdoor pursuits, ranging

from rogaining and orienteering, through to

expedition-style adventure racing. Australia has

produced some international class athletes who owe

theirsuccesstothecompass-wieldingskillsthey

learnt as youngsters, including Adrian ‘AJ’ Jackson, a

four-time World Champion Mountain Bike Orienteer

(MTBO).

“My parents were foot orienteering way before I

wasborn,soIwastakenalongtofootOfromaearly

age,” explains AJ. “Once MTBO began in Australia our

familywasinvolvedfromthestart.Ikeptmyfocuson

footOwhenIwasajunior,goingtotwoJuniorWorld

Orienteering Championships, but my first year out of

juniors was 2004 when the MTB World Orienteering

Championship was in Australia and it was no looking

back from then on!”

SKILLS | MAP READING

then again at regular intervals throughout the

rest of the trip.

GETTING YOUR BEARINGS

One of the most basic compass-reading skills

commonly employed by bushwalkers and orien-

teers is to take and follow a bearing. This can be

done in three easy steps:

1) On the map, set your compass in a straight

line between your current location and the place

you want to travel to (e.g. a peak) – making sure

the Direction of Travel Arrow is pointing towards

your intended destination.

2) Keeping the compass baseplate still, rotate the

bezel so the orienting lines on the compass align

with the North-South gridlines on your map. The

number indicated by the Dash is your bearing.

3) Take the compass off the map, hold it flat in

front of your stomach with the direction of travel

arrow pointing away from you, and turn until the

red end of the floating needle settles exactly in

the red orienting arrow on the base of the hous-

ing. You are now facing in the direction you want

to go in.

MAGNETIC NUMBERS

So far, so simple, right? Well, here’s where it gets a

little complicated.

Inconveniently, the Earth’s Magnetic North

Pole (which your compass needle is attracted to)

is not the same as ‘true north’ (the direction of a

meridian of longitude which converges on the

North Pole), or Grid North (the direction of a grid

line which is parallel to the central meridian on

the National Grid).

As a result, to accurately plot a course using a

compass, especially over a long distance, you

have to apply something called ‘Magnetic

Variation’, or ‘Declination’. This angle is stated in

the key of all good topographical maps. Simply

put, if the map specifies a declination of 10° W,

you subtract 10° from your bearing by turning

the bezel clockwise; if specifies 10° E, you add 10°

to your bearing by turning the bezel anti-clock-

wise (on good compasses, guides to these mea-

surements can be seen in red on either side of

the Orienting Arrow).

Even more annoyingly, the Magnetic North

Pole doesn’t stay still – it hops around as the

Earth’s magnetic field changes. During the last

100 years, scientists say it has shifted over 1000km

towards Siberia, so the more up-to-date your map

is, the more accurate the information about Mag-

netic Variation given will be. The per annum

increase should be stated alongside the date of

publication and specified declination on a map, so

you can figure it out.

Lastly, because the pull direction of Earth’s mag-

netic field varies according to where you are on

the planet (it pulls vertically at the poles, but more

horizontally towards the equator), most magnetic

compasses are balanced according to the part of

the world they are designed to be used in. So, a

magnetic compass bought in Australia will not

work optimally in the UK.

For years the world has been divided into five

balancing zones, with Australia and New Zealand

in Zone 5. In recent years, Suunto has reduced this

to two zones for its compasses, and you can also

get a universal magnetic compass that works well

anywhere in the world.

MAPS

In Australia, folding paper topographical maps

used by bushwalkers are typically A0 size and

come scaled at either 1:25,000 (1cm on the map

represents 250m on the ground), 1:50,000 (1cm =

500m) or 1:100,000 (1cm = 1km).

Depending on what you’re trying to do, it’s

best to get the biggest scale you can, showing

the most detail. However, the wild nature of

Australia’s remoter corners means that not all of

the country has been mapped to the same

precise degree as somewhere like the UK, where

Ordnance Survey mapping is generally regarded

by experts as the best in the world.

Cartography is improving all the time, how-

ever, and a proper topographical bushwalking

map should clearly show structures, roads, paths,

bridleways, farms and natural features including

forests, rivers, lakes, hills and mountains, repre-

sented by concentric contour lines revealing

specified gains in elevation until you reach the

highest point.

Maps in Australia are produced using the

Geocentric Datum of Australia (GDA) coordinate

system, which uses the Map Grid of Australia

1994 (MGA94), a transverse Mercator projection

that conforms to the internationally accepted

Universal Transverse Mercator Grid system.

Got that? Good.

This basically describes how the grid system is

calculated – older maps may use a superseded

system, which only becomes really important if

you’re quoting grid references to someone else

(they’ll need to know if it’s a different system).

For this and other reasons (including topo-

graphical changes and increases in declination),

its best to use the newest map you can source.

It’s worth stopping regularly to

‘set’ your map, so north on the

map correlates to north on the

ground and you know which way

you’re heading.

The protractor-style

compass with a baseplate,

invented by the Swedish

brothers behind the

company Silva, is the most

popular kind of magnetic

compass on the market.