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PART 5: Navigation
 Travelling
through wild countryside is achieved by the use of a map and a
compass.
The
map conveys a detailed picture of the landscape and terrain we are
travelling across and the compass provides us with a tool that will
steer us in the correct direction. The secret of good navigation is
a good knowledge of map reading and interpretation. The compass
although important is secondary to good map reading skills.
Understanding your map
The map is a representation of the landscape. It is produced from satellite
pictures and on the ground surveying. The map however is
only two dimensional therefore it must employ a method known as
contouring in order to show the rises and dents of the landscape. A
number of symbols are also used to establish such features such as
forests, churches, boggy ground, fences, train tracks etc. Roads and
tracks are marked on the map using a number of different coloured
lines and such methods as broken lines and chequered lines. Rivers
and lakes are marked in blue.
Scale
In order to draw a map of manageable size we use a process of
scaling to insure the correct miniaturisation of the landscape on the
map. Typical scales used are half inch to the mile, one inch to the
mile. In such a scaling system one inch on the map represents one
mile on the ground. Therefore the bigger the scale the more
information it is possible to draw onto the map. For walking
purposes you will be using the Discovery Series of maps which have a
scale of 1 : 50,000 or 2 centimetres to a kilometre ( one and a
quarter inches to a mile)
Grid
lines
Overlaying all maps there is drawn a grid of light lines running
from top to bottom and side to side on the map. The purpose of this
grid is to allow us to identify every part of the map with a unique
number system ( grid reference). These grid lines which correspond
with the lines of longitude and latitude also enable us to identify
the north of the map and aid with compass alignment. You will notice
that each line is given a number, this will enable us to create the
grid reference number.
Grid Reference
A grid reference is a series of numbers (co-ordinates) which
gives us the exact location on a map. It is created by using the
grid lines which appear on all ordinance survey maps using the
following steps.
1. Find your location on the map. If possible choose a
recognisable feature rather than a point in the middle of nowhere.
2. Find the grid letter on the national grid by looking at your
map. These are printed in blue and are large in size. Quote the
letter of the sector your position is in.
3.Start at the bottom left hand side of the map and move across
the grid lines till you arrive at the grid line nearest your
location. The number of the line is the first two numbers of your
reference.
4. You should then divide up the grid square into tenths. Half
way is .5, three quarter the way is .8 etc. State the location of
your position as a decimal. This number is the third number of the
reference.
5. Repeat the same steps for the grid lines that cross the map
and this will give you the 3 figure reference for you location.
6. You now have your six figure reference for your position.
A simple rule of thumb is the phrase that states - 'go in the
door and up the stairs'
Which means that if you visualise a door at the left hand side of
the map - then you go in the door (give the bottom line first) then
go up the stairs (give the side numbers next)
Aligning a map
In order to read a map correctly you must first align the map. This
is done by moving the map around until the map and the landscape
correspond. This is usually done by selecting a landmark or feature,
finding that landmark or feature on the map, then aligning the map
so that when you look at the map and then at the landmark their is
an imaginary line drawn between the two points. When your map is
correctly aligned you will be able to identify other features from
map to ground. The mountain peak on your left or the stream junction
on your right. If this exercise is done correctly by aligning your
map with two or three features rather than just one you can now
travel by using the map alone provided you establish correctly where
you are standing in relation to these features. As each feature or
new feature appears on the trail identify it on the map and
re-establish your position.
Contours
Contours are the method used to convey the shape of the terrain you
are crossing. They are created by an imaginary line along which
every point is the same distance above sea level. These lines are
drawn at 10 metre intervals and allow us to see a representation of
the shape of a hill or mountain. By looking at your map you can
determine whether the mountain has a steep slope (contour lines
close together) or a gentle slope ( contour lines spread apart).
Contour lines are never or rarely circular in shape, because they
are plotting a set ground level they allow us to see the gentle
curves of a mountain as well as deep gullies. Practice on the ground
with your map will provide you with hands on experience, and over a
period of time you will get to know what variations of contour lines
mean and what they translate to in reality on the ground.
 
The north's
A compass points to one north, your map is drawn with grid north,
and the stars point to true north. 
What is the difference and how can you come to grips with then.
True North
True North is determined by sun readings and from the stars and is
the point we would call the north pole or very top of the earth
where all the lines of longitude converge.
Grid north
Map makers create a grid system around every country called the
National Grid. Each box on this grid has a letter. It is this letter
which we use to identify by means of a grid reference our position
on the grid. These grid lines are shown on our map and are numbered
thus allowing a grid reference to be created. As the position of
these grid lines are only slightly out of line with true north we
use them as our method of setting our compasses. So for our purposes
in Ireland and the British Isles Grid north and True north are the
same
Magnetic north
This is the north that is indicated on our compass. Magnetic north
is the location of a part of the earth which is magnetic and
attracts the needle of the compass. This north is located
approximately north of Canada. (8 degrees west of grid north)
How is each used
If you get lost or do not have a compass then you will relay on the
sun, stars and nature signs to show you the direction to follow. The
direction you will seek is true or celestial north. It is only a
general indicator and no fine navigation will be done by this
method. e.g. If you are lost and you know that from the last time
you looked at a map that a road was to the east of you. What you
would do is determine where north was by using the stars or sun and
create a compass in effect. If you are facing north then east is to
your right west is your left and south is to your back.
Grid north
Grid north as we have said is the map makers north. Therefore every
map is created with the top of the map being north, bottom south. If
you have your map folded up and you can read the writing on the map
( it is not upside down) it is turned in the right direction. This
is an important point to remember when it comes to taking a compass
bearing from your map (explained later)
Magnetic
Bearing
The magnetic north is the north that your compass needle will always
point to. This magnetic field is constantly moving so in Ireland it
moves by a number of degrees every couple of years. In Ireland the
current variation is 7 degrees west (1994) See the side panel of you
map to see what the current variation is. This means that your map
and your compass or out of line with each other. So in order to take
a directional bearing from the map and translate that to the compass
for you to follow you have to add on the variation of 7 degrees (
for convenience we use 8 degrees - 4 marks on the compass ). This
variation is different in every country so always check the side
panel of your map for variation particular to that location.
The
Compass
The compass is an instrument that tells us where north is. This is
done by way of a magnetised needle that is allowed to float freely
within the instrument housing. Around the edge of the compass is
plotted a circle on which marking similar to that on a ruler are
inscribed. Each marking determines the number of degrees it is from
north to this point.
There are many compasses on sale from the simple floating needle
type to the more expensive plotting compasses. We will only be
concerning ourselves with one compass and that is the Silva Compass.
This is the best compass and only compass you should use for
navigational purposes on land.
The Silva Compass is made up of three parts - the needle, the
compass housing and the base plate. The needle is coloured red and
white and the red end points to north the white to the south. The
compass housing revolves and determines any desired bearing or
direction of travel. The base plate is used to indicate line of
travel.
How to use your compass
Your compass is a tool that is used in conjunction with your map. By
using the compass it is possible to navigate very precisely between
points on a map. Your compass can also be used to check your
position on the map and check the correctness of your line of
travel.
Taking a bearing
Place the compass on the map with the edge of the base plate along
the desired line of travel. The direction arrow on the compass
should point to the place you wish to go.
Move the compass housing until the north - south lines on the
transparent base of the compass housing are parallel with the grid
lines on the map. The north arrow on the compass housing should be
pointing north. You should be as accurate as possible when lining up
these lines as a movement each way will add or subtract degrees from
your final bearing and result in bad navigation and missing your
destination by hundreds of yards.
 Lift
up the compass from the map and read the bearing indicated on the
compass dial. Say this number to yourself then add on the magnetic
variation (e.g. bearing is 92 degrees add on variation 8 degrees
result 100 degrees) now move the compass housing to this setting. It
is a good practice to do bearings this way rather than adding on by
moving the compass housing immediately so that you do not make a
mistake. It is better to confirm in your mind what the bearing is
before you move the compass.
Your compass is now set. Hold the compass in your hand and move your
body around until the needle of the compass is correctly aligned
with the north - south markings on the housing. The direction of
travel arrow on the compass now points in the direction you need to
travel to your next destination.
This exercise is repeated from point to point as you travel on your
journey.
 Following
a bearing
You travel on a bearing by sighting a recognisable landmark along
its path and then travelling to that point and repeat until you
reach your destination. It is not advisable to follow your bearing
by looking at the compass and watching the movement of the needle.
As you walk you will have to move from side to side to avoid
obstacles so this method of following the bearing is discouraged in
favour of line of sight identification method.
However, if you find yourself in heavy fog or at night you will
use the method of looking at the compass to find your way. In fog or
at night you could use members of your party to line up on the
bearing under your direction and you then travel to these members.
This is a more accurate method than looking at the compass.
Back bearing
If you think you have erred from your line of travel you can check
your bearing by using a back bearing. To do this you turn around and
point the compass back to your last location. The white part of the
needle should now point north. If it is slightly out then it is
possible, by walking left or right until the needle lines up, to
correct your line of travel.
Finding your position on a map
To find your position an a map we use a process called resection.
This is preformed by plotting at least two points on the map to
determine your position.
First select a landmark that you can identify on the map and from
the position you are standing.
Point the compass at the landmark and move the housing until the
needle and north - south marking align. Read off the bearing on the
dial. Now subtract 8 degrees from that bearing. (e.g. bearing of 88
degrees less 8 degrees total 80 degrees). You then place the compass
on the map with the edge of the base plate on the symbol for
identifiable feature. Without adjusting the compass move the whole
compass round this point until north - south lines are parallel with
grid lines. If you have a pencil drawn a light line along the side
of the base plate. Your position is somewhere along this line.
You
now select another feature which can be seen and identified from
your position and repeat the process. If possible choose a feature
which is nearly 90 degrees from your position. By doing this your
new line while precisely cross the line drawn from the other
feature. If the two points selected are two close to each other then
the lines will tend to merge and will result in a less accurate
determination of your position. Where the two lines cross in your
position.
Normally, two bearing are all that is required however, if you wish
you can use three to confirm exactly where you stand.
Nasmiths
Rule
Nasmiths rule is a method of determining our speed of travel over
the countryside. It states that we walk at 3 miles per hour and that
we must add on to this calculation half an hour for every 1000 ft
climbed. This calculation can be converted into a metric measurement
thus - we walk at 5 kilometres per hour and allow 30 minutes for
every 300 meters climbed. For the purposes of calculating time travelled
with young people it is better to use a figure of 4 kms per
hour.
These calculations can be simplified
15 mins per 1 km
7.5 mins per half kilometre
or in the height
1 minute for every 10 meters
These simplifications allow us to calculate with ease. Measure the
distance with the rule on your compass 2 centimetres = 1 kilometre =
15 mins travel time. Count the number of contour lines you pass on
your way up each contour line = 10 meters = 1 minute extra to your
travel time. You do not add on time if you are descending a mountain
or high ground. Be careful reading contour lines on the map. You may
have to calculate the height gained in meters or feet depending on
the map used. ( If you are using the discovery series of maps it
will be meters) Your start of position maybe at the 150 meter line
and you may travel through to the 250 meter line you have therefore
climbed 100 meters meaning you have to add on 10 minutes to your
distance travelled time to give you your correct arrival time.
4 kilometres per hour is a suggested average for hiking across
easy ground with a light pack. If you intend to carry heavy packs or
if you are travelling through rough countryside then you will have to
adjust this figure. The chart opposite will give you some guide, 2.5
kms per hour is the suggested figure for planning your route if you
are participating in a Mountain Pursuit Challenge. In determining
the correct speed of your Troop it is a good exercise to measure out
a set distance and time your Troop over this distance walking at an
average pace, with packs, etc.
This simply rule enable us to navigate across rough ground with
precision. We can also use this calculation to plan hikes and
adventures into wild country without leaving our sitting rooms.
Route cards/planners
Route cards are a device we use to plan our adventures across rough
countryside. The route card/planner tells us essential information
about our purposed route, number in the party, etc. The card also
serves as a safety device as we should leave a copy of the route
card with a responsible person who is not taking part in the hike or
trip. If an emergency arises then this person can advise the rescue
services of your route and aid your rescue. In preparing a route
card we break up our journey into convenient sections or 'legs'.
Each leg is then treated separately to calculate distances ,
bearings etc.
 Filling out a route card
Each point of reference on the route card is identified with a grid
reference. So you will be travelling from grid reference to grid
reference rather than from the edge of the forest to the river. Grid
references give us precise position on the map whereas the edge of
the forest is open to interpretation. The direction of travel
between two points is determined by a compass bearing. These bearing
are obtained from your map ( don't forget to add on magnetic
variation) The next steps are to determine what distances you will
travel between points and the height gained and calculate the total
time for each leg of your journey. You will also need to add in such
things as - stopping to admire the scenery, and rest time. A general
rule is to allow 15 mins per hour. This 15 mins maybe spread over a
number of legs. In arriving at your total time you should also add
in time for lunch or meals as required.
You should take note of the actual time that it takes to complete
each section and put this figure down on your card. This information
will be useful if you decide to do the route again at a later stage.
It is also useful in determining your accuracy, which will improve
with practice.
Nature's Compasses
Finding our way using map and compass can be exciting but what if
you had no map or compass and found yourself stranded in open
countryside. Nature navigation relies on your skills of observation,
through it you can find your way to safety.
Nature provides us with a variety of ways of discovering direction,
the sun, the stars, trees and the wind. The simplest and most
obvious way to find North is by the sun. At dawn it rises in the
east, at mid day it is due south and in the evening it sets in the
west.
Finding your way at night
Except for a few nights every month the moon, like the sun, can help
give you direction. Because the moon reflects the suns light, the
moon always points towards the sun, and thus even at night indicates
the direction of the sun. Whether the moon is waxing or waning, an
imaginary line through the horns of a crescent moon will always give
you, approximately, a North South line.
The location of North can also be determined from the stars using
the pole star. The 'Plough' Constellation is visible all year round
as it moves around the pole star. On a clear night the pole star can
be found by plotting a line through the 'pointers' the pole star can
be found.
As with the sun and moon the stars also appear from the East and
sink in the West. So, if a star rises you are facing East, if it
descends you are facing West.
The wind
Almost every area has what is called a prevailing wind - that is a
wind that blows longest and strongest from a particular direction.
Prevailing winds have their impact on trees, among other things
the land. You can very often observe how trees in a given area have
been influenced by a prevailing wind to lean in a particular
direction. By observing the direction in which trees in an area are
leaning, you can tell from which direction the local prevailing wind
blows. If, say, the trees are leaning North - East you will find
that the prevailing winds blows from the South west. There are but a
few exceptions to this general rule - such as with the trees on some
of our coastlines.
Nature also provides other wind - influenced indicators. Spiders,
for example, do not construct their webs against the wind, so
observation of the general direction in which spider webs are laid
can be helpful.
Birds and insects almost always build their nests in positions that
will protect then against the prevailing wind, so keep your eyes
open.
Trees as indicators
We have talked about the prevailing wind effect on trees which
causes them to lean in a particular direction. Further studies of
trees however can reveal many ways in which a tree can indicate
direction.
Concentrate your observations primarily on indigenous trees, because
nature designed trees in different shapes, with the main object of
enabling then to receive as much light as possible. Below we outline
a number of pointers that will be useful. These observations are
only generalisations. Trees are affected by many factors, and you
should not jump to conclusions after studying a single trees only,
but confirm your findings by observing several trees in the same
vicinity.
Most trees tend to develop more foliage on the sunny side.
In many species the branches exposed to the arc of the sun and thus
receiving more sunlight will tend to be branches that are more
developed and that reach out southwards at an angle nearer the
horizontal, while the branches on the Northern side lacking sunlight
will tend to grow at a more acute upwards angle.
The tree trunk itself may lean sunwards, slightly. ( while the
prevailing wind usually cause a tree to lean with the wind, the sun
can also affect its angle)
Though not always, mosses and lichens will tend to grow on the North
side of a tree trunk, rather than on the Southern, sun facing side.
Note however that mosses and lichens are also affected by humidity -
they flourish best where moisture is retained longer. You can also
observe a green strip on the North side of wooden telephone poles
and similar pole.
The bark on the North side will often be darker and more tightly
grained than on the Southern sun facing side.
If the tree has been felled the rings on the stump will be spread
further apart on the southern side.
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