Using the Compass in Interaction with a Map (English)

GREEK ORIENTEERING CLUB OF THESSALONIKI

For more information about the sport internationally search the site:  www.orienteering.org  For more information
about the sport in Greece search the site:  www.orienteering.org.gr 

E-mail: compass7@ath.forthnet.gr    Konstantinos
Koukouris, Ph.D

Reference: Kjetil Kjernsmo’s (1997-2000) illustrated
guide on how to use a compass. http://www.learn-orienteering.org/old/fog1.html
kjetikj@astro.uio.no
It’s when you use both compass
and map the compass is really good, and you will be able to navigate safely and
accurately in terrain you’ve never been before without following trails. But it’ll take some training and experience,
though. The most
important steps are summarized below.
1. Align the edge of the compass
with the starting and finishing point.
2. Rotate the compass housing
until the orienting arrow and lines point N on the map.
3. Rotate the map and compass
together until the red end of the compass needle points north.
4. Follow the direction of travel
arrow on the compass, keeping the needle aligned with the orienting arrow on
the housing.
Take a map. In our first example, we look at a
map made for orienteering, and it is very detailed. You want to go from A,
to B. Of course, to use this method successfully, you’ll have
to know you really are at A. What you do, is that you put your compass on the map so that the edge of
the compass is at A. The edge you must be using, is the edge that is parallel
to the direction of travel arrow. And
then, put B somewhere along the same edge. Of course, you could use the direction arrow itself,
or one of the parallel lines, but usually, it’s more convenient to use the
edge. The edge of the compass, or rather the direction
arrow, must point

from A to B! And again, if you do this wrong,
you’ll walk off in the exact opposite direction of what you want. So take a second look. Beginners often make
this mistake as well.

Keep the compass steady on the map. What you
are going to do next is that you are going to align the orienting lines and the
orienting arrow with the meridian lines of the map. The lines on the map going
north, that is while you have the edge of the compass carefully aligned from A
to B, turn the compass housing so that the orienting lines in the compass
housing are aligned with the meridian lines on the map. During this process,
you don’t mind what happens to the compass needle.
There are a number of serious mistakes that can be made here. Let’s take
the problem with going in the opposite direction first. Be absolutely certain that you
know where north is on the map, and be sure that the orienting arrow is
pointing towards the north on the map. Normally, north will be up on the map. The possible mistake is to let the orienteering
arrow point towards the south on the map. And then, keep an eye on the edge of
the compass. If
the edge isn’t going along the line from A to B when you have finished turning
the compass housing, you will have an error in your direction, and it can take
you off your course. When you are sure you have the compass housing right, you
may take the compass away from the map. And now, you can in fact read the
azimuth off the housing, from where the housing meets the direction arrow.
Be sure that the housing
doesn’t turn, before you reach your target B!

Hold the compass in your hand. And
now you’ll have to hold it quite flat, so that the compass needle can turn. Then turn yourself, your hand,
the entire compass, just make sure the compass housing doesn’t turn, and turn
it until the compass needle is aligned with the lines inside the compass
housing.
The
mistake is again to let the compass needle point towards the south. The red
part of the compass needle must point at north in the compass
housing, or you’ll go in the opposite direction.
It’s time to walk off. But to do that with optimal accuracy, you’ll have
to do that in a special way as well. Hold the compass in your hand, with the
needle well aligned with the orienting arrow. Then aim, as carefully as you
can, in the direction of travel-arrow is pointing. Fix your eye on some special
feature in the terrain as far as you can see in the direction. Then go there.
Be sure as you go that the compass housing doesn’t turn. If you’re in a dense
forest, you might need to aim several times. Hopefully, you will reach your
target B when you do this. Unfortunately, sometimes, for some quite often, it
is even more complicated. There is something called magnetic declination.
And then, for hiking, you wouldn’t use orienteering maps.
Using
the compass alone
The first thing you need to
learn, are the directions. North, South, East and West.
North is the most important. There are several kinds of compasses, one kind to
attach to the map, one kind to attach to your thumb. The thumb-compass is used
mostly by orienteers who just want to run fast. I would recommend the third
kind of compass. Let’s take a look at it: You see this red and black arrow? We
call it the compass needle. Well, on some compasses it might be red and
white for instance, but the point is, the red part of it is always pointing
towards the earth’s magnetic north pole.
But if you don’t want to go
north, but a different direction? Hang on and I’ll tell you.
You’ve got this turnable thing on your compass. We call it the Compass
housing
. On the edge of the compass housing, you will probably have a
scale. From 0 to 360 or from 0 to 400. Those are the degrees or the azimuth
(or you may also call it the bearing in some contexts). And you should have the
letters N, S, W and E for North, South, West and East. If you want to go in a
direction between two of these, you would combine them. If you would like to go
in a direction just between North and West, you simply say: “I would
like to go Northwest “
.
Let’s use that as an
example: You want to go northwest. What you do, is that you find out where on
the compass housing northwest is. Then you turn the compass housing so that
northwest on the housing comes exactly there where the large direction of
travel-arrow
meets the housing.

Hold the compass in your hand. And you’ll have to hold it quite flat, so that
the compass needle can turn. Then turn yourself, your hand, the entire compass,
just make sure the compass housing doesn’t turn, and turn it until the compass
needle is aligned with the lines inside the compass housing.

Now, time to be careful!. It is extremely important that the red,
north part of the compass needle points at north in the compass housing. If
south points at north, you would walk off in the exact opposite direction of
what you want! And it’s a very common mistake among beginners. So always take a
second look to make sure you did it right!
A second problem might be local magnetic attractions. If you are carrying
something of iron or something like that, it might disturb the arrow. Even a
staple in your map might be a problem. Make sure there is nothing of the sort
around. There is a possibility for magnetic attractions in the soil as well,
magnetic deviation“, but they are rarely seen. Might occur if
you’re in a mining district.
When you are sure you’ve got
it right, walk off in the direction the direction of travel-arrow is pointing.
To avoid getting off the course, make sure to look at the compass quite
frequently, say every hundred meters at least.
But you shouldn’t stare down on the compass. Once you have the direction, aim
on some point in the distance, and go there. But this gets more important when
you use a map.
There is something you
should look for to avoid going in the opposite direction: The Sun. At noon, the
sun is roughly in South (or in the north on the southern hemisphere), so if you
are heading north and have the sun in your face, it should ring a bell.
When do you need this
technique? If you are out there without a map, and you don’t know where you
are, but you know that there is a road, trail, stream, river or something long
and big you can’t miss if you go in the right direction. And you know in what
direction you must go to get there, at least approximately what direction. Then
all you need to do, is to turn the compass housing, so that the direction you
want to go in, is where the direction of travel-arrow meets the housing. And
follow the above steps. But why isn’t this sufficient? It is not very accurate.
You are going in the right direction, and you won’t go around in circles, but
you’re very lucky if you hit a small spot this way. And that’s why I’m not
talking about declination here. And because that is something connected
with the use of maps. But if you have a mental image of the map and know what
it is, do think about it. But I think you won’t be able to be so accurate so
the declination won’t make a difference. If you are taking a long hike in
unfamiliar terrain, you should always carry a good map that covers the terrain.
Especially if you are leaving the trail. It is in this interaction between the
map and a compass, that the compass becomes really valuable. And that is dealt witKjetil
Kjernsmo’s illustrated guide on
Magnetic
Declination
The
compass is pointing towards the magnetic northpole, and the map is
pointing towards the geographic northpole, and that is not the same
place. To make things even more complicated, there is on most hiking-maps
something (that is very useful) called the UTM-grid. This grid doesn’t
have a real north pole, but in most cases, the lines are not too far away from
the other norths. Since this grid covers the map, it is convenient to use as
meridians.
On most orienteering maps
(newer than the early 70’s), this is corrected, so you won’t have to worry
about it. But on topographic maps, this is a problem. First, you’ll have to
know how large the declination is, in degrees. This depends on where on the
earth you are. So you will have to find out before you leave home. Or somewhere
on the map, it says something about it. One thing you have to remember in some
areas, the declination changes significantly, so you’ll need to know what it is
this year. If you are using a map with a “UTM-grid”, you want to know how this grid differs from the
magnetic pole.
Στους χάρτες προσανατολισμού δεν χρειάζεται να ανησυχούμε για την μαγνητική
απόκλιση. Αλλά στους τοπογραφικούς χάρτες αυτό είναι ένα πρόβλημα. Για να
κάνουμε τα πράγματα ακόμη πιο πολύπλοκα στους περισσότερους πεζοπορικούς χάρτες
υπάρχει κάτι που ονομάζεται UTMgrid. Αυτό το δικτυωτό πλέγμα δεν έχει πραγματικό βόρειο πόλο
αλλά στις περισσότερες περιπτώσεις οι γραμμές δεν απέχουν πολύ μακριά από τον
μαγνητικό βορρά και τον πραγματικό βορρά. Σε μερικές περιοχές η απόκλιση
αλλάζει σημαντικά. Γι’ αυτό χρειάζεται να γνωρίζουμε πόση είναι αυτή τη χρονιά.
You don’t align the orienting lines
with the grid lines pointing west or east, or south for that matter. When you
have taken out a course like you’ve learned, you must add or subract an angle,
and that angle is the angle you found before you left home, the angle between
the grid lines or meridians and the magnetic north. The declination is given as
e.g. “15 degrees east”. When you look at the figure, you can pretend
that plus is to the right, or east, and minus is to the left and west. Like a
curved row of numbers. So when something is more than zero you’ll subtract
to get it back to zero. And if it is less, you’ll add. So in this case
you’ll subtract 15 degrees to the azimuth, by turning the compass housing,
according to the numbers on the housing. Now, finally, the direction of
travel-arrow points in the direction you want to go. Again, be careful to aim
at some distant object and off you go. You may not need to find the declination
before you leave home, actually. There is a fast and pretty good method to find
the declination whereever you are. This method has also the advantage that
corrects for local conditions that may be present This is what you do:
  1. Determine by map inspection the grid azimuth from
    your location to a known, visible, distant point. The further away, the
    more accurate it gets. This means you have to know where you are, and be
    pretty sure about one other feature in the terrain.
  2. Sight on that distant point with the compass and
    note the magnetic azimuth. You do that by turning the compass housing so
    that it is aligned with the needle. You may now read the number from the
    housing where it meets the base of the direction of travel-arrow.
  3. Compare the two azimuths. The difference is the
    declination.
  4. Update as necessary. You shouldn’t need to do
    this very often, unless you travel in a terrain with lots of mineral
    deposits.
If you live in an area where
you don’t go far for it to change between east and west, it is so small you
wouldn’t need to worry about it anyway. So it’s best to just remember whether
you should add or subtract.
Uncertainty
You
can’t always expect to hit exactly what you are looking for. In fact, you must
expect to get a little off course. How much you get off course depends very
often on the things around you. How dense the forest is, fog, visibility
is a keyword. And of course, it depends on how accurate you are. You do
make things better by being careful when you take out a course, and it is
important to aim as far ahead as you can see.
In normal forest conditions
we say that as a rule of thumb, the uncertainty is one tenth of the distance
traveled. So if it is like in the figure, you go 200 meters on course, it
is possible that you end up a little off course, 20 meters or so. If
you’re looking for something smaller than 20 meters across, there
is a chance you’ll miss. If you want to hit that rock in our example you’ll
need to keep the eyes open! In the open mountain areas, things are of course a
lot easier when you can see far ahead of you. The only way to learn this
properly is to try it in the backcountry. Well that is until the fog comes. Fog
can make orienteering in the mountains and in the forest extremely difficult,
and therefore, it can also be dangerous to the unexperienced.
How
to navigate in foggy conditions
Fog makes things difficult,
and in some situations dangerous. When you hike, you will probably some day
experience these difficulties, and you’d better be prepared. The fog can come
creeping very fast. I have myself experienced from clear view to dense fog in
10 seconds. How fast this goes, depends on where you are. In normal summer
conditions without snow, it is often not much of a problem. Unless you are
supposed to find a hut or something. The ground provides normally so much
contrast, you could do the aiming I have written about in lesson 2. Just be very careful and accurate. Perhaps you also
might use some of the advice given later.
Winter conditions can make
things a lot worse, when there is snow on the ground. The fog is white (or
grey), the snow is also white. You may get a condition we call a “white-out”. It’s too late to read the terrain, and then the map
isn’t of much use. You can’t see anything anyway. You have no choice but to put
blind faith in your compass. I hope you knew where you were, because you need
to take out a good compass course, like described in the other lessons. If you
are skiing, you should tie your compass to your arm or something, so you can
look at it for every step you take. A rubberband is good. Check for more or
less every step you take that the compass needle is aligned with the orienting
lines.
But if it is cold, make sure it doesn’t affect circulation of blood
in your arm, because that will make you freeze. If you are going on an
expedition where you expect conditions like this, you should perhaps consider a
arrangement to attach to your chest.
Let’s consider a method to
enhance the accuracy in conditions when you can’t aim at anything. If you are
three persons in a row, like on the figure, and the last one carries a compass
(of course, it is better that all three carry a compass, but the last one has
command), he or she will see if you get off course because one of those in
front of him or her will not be covered by the person in front. On the figure,
the situation to the left is ok. The person on top is heading forward and but
he sees only the person in front of him or her. In the situation to the right,
it’s time to stop. The last person can see the backs of both of them in front,
and they are about to leave their course.
The further apart you go,
the more accurate this method is, but it is also very important to have good
contact. Sometimes the conditions get so bad there is no way to maintain
contact, and then, the method may fail. There is also another method for two
people, where the lead person goes out on a compass azimuth, as far as the
visibility will allow. The person behind stands still and watches the lead
person, telling them if they are in the correct line or not. Once they have
moved correctly into line they then stand still and the back person joins them.
They then have their turn to move out ahead on the azimuth, and the whole cycle
repeats. The problem with this method is when the visibility is very bad, the
lead person can’t go more that a few meters, and it would be dangerous to loose
each other.
Finally, I’d like to comment
on something that is seen in many standard texts on mountaineering navigation:
You are commonly taught to use methods that use terrain features that are
easily recognizable but far away. In my opinion, such methods are of little
use, unless you require surveyor’s accuracy in knowing where you are (hikers
rarely do). As long as the weather is good, navigation is fairly easy and
you’ll naturally use these features as part of a more general approach.
However, when the visibility is poor, you can’t see these far-away-features and
this makes the methods involving them rather useless. Therefore, focus your
training in navigation on using features in your vicinity.
Kjetil Kjernsmo’s (1997-2000) illustrated guide on how to use a compass. http://www.learn-orienteering.org/old/fog1.html kjetikj@astro.uio.no

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