Learning how to use a compass with a map is one of the most important skills
you'll learn for the outdoors and will ensure that you know where you are and
what direction to go in to get to your destination. In this video we'll learn
how to: Orient a map using a compass, take a bearing, the difference between
True North and Magnetic North and adjusting for declination. Correctly orienting your
map helps you orient yourself to your surroundings. A useful time to do this is
at track junctions to check where you are on the map or at lookouts and open
areas to identify any landmarks you can see. Firstly find a flat surface to
put your map and compass on. Can you read the words? If not, flip the map until
you're reading it like a book. Line up the orienting lines of the compass with
the grid lines on the map. Make sure that North on the bezel is lined up with the
index marker. Next, turn your map until the needle points to the angle of
declination. For this map it's 23.5 degrees but so long as the needle
points around the 20 degree mark you'll be close enough. Now the map is facing
North so have a look at your surroundings and see if you can identify
any prominent features on the map. Another great skill you can use your
compass for is to take a bearing. This is especially useful if you can't figure
out where the track is heading which can often happen above the bush line or in
open terrain. Take the straight edge of your compass and line the bottom of the
ruler up with your current position. Now perfect the compass so that the top of
the ruler lines up with your destination. You now have a straight line between you
and your destination. Rotate the bezel so that the orienting lines align with the
map's grid lines. Now read the number on the index marker, in this case it's 50 degrees.
Now the Angle of Declination might sound complicated but it's
actually quite simple. It's all to do with the difference between True North
and Magnetic North.
If this ball is Earth then True North is the
direct line from where you are to the top of the Earth aka the North Pole.
This line is represented on the Topo map by north/south grid lines and is referred
to on the map as Grid North however the needle on our compass points
to Magnetic North which isn't actually the North Pole.
In fact it's slightly off in the Arctic Ocean just north of Canada. This means
that our compass points in a different direction. Therefore we need to
compensate for this difference between the two poles in order to find our bearings.
This difference is our angle of declination. To calculate this there are
three points to work off.
1. Our position
2. The position of True North
3. The position of Magnetic North
If we draw a line from our position to True North and another from our position to Magnetic North
then the angle between the lines is the declination. As you move around the earth the declination changes.
In New Zealand the value is somewhere between 18 and 24 degrees east.
Luckily our Topo map has a handy guide at the bottom that lets you
know the declination for the area that we're in. A general rule of thumb is to
add the declination when adding a bearing to the map and taking away the
declination when taking a bearing from the map. As we are taking a bearing from
the map this means I need to take away 23.5 degrees from the
bearing I have of 50 degrees. So I just need to locate 26.5 degrees
on the bezel and rotate it until it lines up with the index marker.
Now pick up your compass and turn your whole body until the needle is over the
orienting arrow.
Now just follow the direction of travel arrow at the top of the compass.
You don't want to be wandering around with a compass in hand the whole time so here's
a quick tip. Find a landmark in the distance that the direction of travel
arrow is pointing, put your compass away and walk to that point. Use your compass
again when you get there to find another landmark to head towards it's a lot to
take in but a compass is an extremely useful tool to have in the outdoors so
take the time to understand how it works and practice