lecture leading cadet training basic navigation 2 the compass and bearings
Post on 24-Dec-2015
238 Views
Preview:
TRANSCRIPT
Lecture
Leading Cadet Training
Basic Navigation
2The Compassand Bearings
The Compass
LanyardBase Plate
Non-slip Feet x3
Imperial Ruler(inches)
Metric Ruler(cms)
Magnifying Glass
Check Point Marker
Direction of TravelArrow
Rommers1:250001:500001:63360
Compass Housing
Index
Meridian Lines x 4Orienting Lines
Outer Circle = milsInner Circle =
degrees
Illuminating MarkUnder index.
Aside north arrowOn mag needle
North ArrowOrienting arrow
Magnetic Needle
Parts of a Compass
The Compass
Base Plate
Compass Housing
The Base Plate is the mountingfor the housing and displays a variety of information e.g. Scale ruler.
The Compass Housing containsa magnetic bar, called the Needleand defines the points of the compass on a rotating bezel.
Magnetic Needle
The Magnetic Needle is suspendedin liquid, enabling it to move freely, and settle quickly when pointing North.
The Compass
The Index Line is a fixed line within the Compass Housing and is in linewith the direction of travel arrow.
The Index Line marks the bearingyou set by rotating the bezel.
The Direction of Travel Arrow indicates the direction along which you wish to travel or take a bearing.
It is fixed in the base plate and thesides of the base plate runparallel to the arrow.
Index Line
Direction of Travel Arrow
The Compass
The Orienting, or Meridian Lines are displayed within the rotating Compass Housing and are designedto be aligned parallel with the Eastings on a map.
The lines on some compass models are show as one half in red to depict north.
Meridian Lines x 4Orienting Lines
The Compass
Nearly all compasses have a scale along the edge of the base plate to enable you to measure distances.
Used in conjunction with the scale at the bottom of the map, the compass scale enables you to calculate the distance on the ground.
Imperial Ruler(inches)
Metric Ruler(cms)
The CompassPoints of a Compass
N
S
EW
?NE
SW
NW
SE
?ESE
?
WNW
SSESSW
WSW
NNW NNE
ENE
The Compass
ESE
NEN
S
EW
SW
NW
SE
WNW
SSESSW
WSW
NNW NNE
ENE
0º & 360º
270º
180º
90º
Points of a Compass
45º North East
South West : 225º 135º South East
North West : 315º
The CompassSetting a Map with a Compass
You can orientate yourself, and the mapto the ground by using this system:
Lay the compass on the map.
Line up the edge of the compass and the compass orienting lines with the Eastings.
Turn your body until the red end of the needle is in line with the ‘N’ on the Housing.
You and your map are now facing North.
Compass BearingsPoints to Note
Stand clear of metal objects, they cause the needle to deviate and create inaccurate bearings.
Hold the compass as flat as possible to allow the needle to move freely.
Look after your compass – try to avoid dropping or knocking it.
Store away from other compasses and electrical equipment.
Your compass may need replacing if an air bubble forms in the Compass Housing.
Compass BearingsWhen working from a map we deal with Grid Bearings.
When following a compass on the ground we work with Magnetic Bearings.
There is a simple system which enables us to convert Grid to Mag and Mag to Grid,
The system refers to whether we add or subtract the magnetic variation to convert the bearing.
Mag to Grid…………..GET RID
Grid to Mag……………….ADD
You are at Point A and need to walk to Point B
Unfortunately, you can’t see Point B
Place the Compass on the Map like so:
The direction of travel arrow should point in the direction you wish to go.
Compass Bearings
BB
AA
Take a Bearing
Map to Ground
Keeping the Base Plate static –
Turn the Compass Housing
until the Orienting Lines
are parallel with
the Eastings
And the ‘N’ is pointing to North on your map.
Compass Bearings
BB
AA
Take a Bearing
Map to Ground
Read the Compass Bearing shown on the housingfrom the Index Line
Don’t forget the difference between Grid North and Magnetic North.
Add this to your bearing.(From Grid to Mag = Add)
and you have the magnetic bearing of your course.
The next step is to orientate yourself
Compass Bearings
BB
AA
Take a Bearing
Map to Ground
x
Compass Bearings Take a Bearing
Map to GroundHold your Compass level and steady.
Turn until the red end of the Needle is in line with the ‘N’ on the Housing
The Direction of Travel Arrow is now pointing along the route you plotted on the map, and you are ready to travel.
Point the Direction of Travel arrow at the feature, and take a normal bearing.
Turn the Compass Housing until the Orienting Lines are REVERSE parallel with the Eastings
Read the bearing and subtract the GMA.Remember – Mag to Grid = Get Rid
This is the back bearing of your feature.
Compass Bearings
BB
AA
Back Bearings
Map to Ground
x
Check of UnderstandingWhat is the purpose of liquid in the capsule of a compass?
Allows the needle to settle quickly
Allows the needle to be seen more clearly
Slows the swing of the needle
Increases the needles sensitivity
Check of UnderstandingWhen changing magnetic bearing to grid bearings
Which of the following is correct?
Always an addition
Mag to grid - Multiply
Mag to grid – Get Rid
Mag to grid - Add
Check of UnderstandingWhich of the following would be more likely to cause
magnetic deviation if close to a compass?
A river
A cattle grid
Aluminium tent poles
A large tree
Check of UnderstandingHow can a grid bearing from a map
on which the magnetic variation is westerly be converted to a magnetic bearing?
Subtract the angular difference between grid north and true north
Add the angular difference between magnetic north and grid north
Subtract the angular difference between magnetic north and grid north
Add the angular difference between grid north and true north
Check of UnderstandingTo take a bearing on a map,
having set the compass so that the Direction of Travel Arrow points at the feature,
what do you do next?
Turn the capsule until the needle falls into the orienting arrow
Turn the capsule to deductthe grid magnetic angle
Turn the map and compass until the needle falls into the orienting arrow
Turn the capsule so the orienting lines are parallel to the north-south grid lines
Check of UnderstandingA line on a map is found to be 110 degrees grid.If magnetic north is 6 degrees west of grid north,
what is the magnetic bearing of the line?
122 degrees M
98 degrees M
116 degrees M
104 degrees M
Leading Cadet Training
Basic Navigation
End of Presentation
top related