Basic Navigation Leading Cadet Training The Compass and

Basic Navigation Leading Cadet Training The Compass and Bearings Lecture 2

Points of the Compass NW N NNW NNE WNW ENE W ? E ESE WSW SW NE ? SSW S SSE SE

Points of the Compass 0º & 360º NNW NNE 45º North East North West : NW 315º NE N WNW ENE 270º W 90º E W ESE WSW South West : SW 225º SSW SSE 180º S 135º SE South East

The Silva Compass The main compass we use for navigating when walking is the SILVA COMPASS Consisting of A Base Plate displaying a variety of information e. g. scale, rulers etc. The Compass Housing giving the points of the compass on a rotating bezel.

The Silva Compass The Magnetic Needle coloured and white, points to the Magnetic North Pole, and is suspended in liquid help it and settle down quickly. It is important to hold a compass horizontally when taking a reading to ensure the needle floats freely. The Orienting, or Meridian Lines are displayed within the housing and are designed to be aligned parallel with the Eastings on a map.

The Silva Compass The Direction of Travel Arrow indicates the direction along which you wish to travel or take a bearing. The Index Line is a fixed mark in line with the direction of travel arrow. It marks the bearing you set by rotating the bezel. The Scale Indicators on the sides of the base plate are used with the scale at the bottom of the map to calculate distance on the ground.

The Compass Points 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 Bearings Setting a Map with a Compass You can orientate yourself, and the map to 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 Bearings When 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 Magnetic and Magnetic 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

Compass Bearings Map to Ground Bearings You are at Point A and need to walk to Point B but you can’t see Point B Place the Compass on the Map with the direction of travel arrow pointing in the direction you wish to go. B A Keep 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 Map to Ground Bearings Read the Compass Bearing shown on the housing from the Index Line If the grid magnetic angle is 6 degrees west, add this to your bearing. (From Grid to Mag = Add) and you have the magnetic bearing of your course as 316 degrees. The next step is to orientate yourself. B x For example 310 degrees. A

Compass Bearings Map to Ground Bearings Hold 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. B A

Compass Bearings Map to Ground Back Bearings Place the Compass on the Map with the direction of travel arrow B pointing at the feature, to take a normal bearing. Keep the Base Plate static turn the Compass Housing until the Orienting Lines are REVERSE PARALLEL with the Eastings A

Compass Bearings Map to Ground Back Bearings Read the bearing If the grid magnetic angle is 6 degrees west, subtract this from your bearing. Remember – Mag to Grid = Get Rid This is the back bearing of your feature. B x For example 130 degrees. A

Check of Understanding What is the purpose of liquid in the capsule of a compass? Allows the needle to be seen more clearly Increases the needles sensitivity Slows the swing of the needle Allows the needle to settle quickly

Check of Understanding What is the compass we use for navigating when walking? Standard RAF compass Primatic compass Silva compass Orienting compass

Check of Understanding On a Silva walking compass what colour is the magnetic needle: Red and White Blue and White Red and Black Blue and Black

Check of Understanding When changing magnetic bearing to grid bearings Which of the following is correct? Mag to grid - Multiply Mag to grid - Add Mag to grid – Get Rid Always an addition

Check of Understanding When using a compass to take a bearing on a distant object, you would first? Turn the compass housing so that the orienting arrow points at the object Point the direction of travel arrow at the object Turn the compass housing to subtract the GMA Align the red compass needle to point at the object

Check of Understanding The direction of a line drawn between two places on a map in measured against the grid lines and found to be 110 degrees (Grid). If magnetic north is 6 degrees west of grid north what is the magnetic bearing of the line? 98 degrees M 104 degrees M 116 degrees M 122 degrees M

Check of Understanding To take a bearing on a map you would place the compass on the map so its longest edge runs through both features and its direction of travel arrow points in your intended direction of travel. You would then? Turn the compass housing so the orienting lines are parallel to the north-south grid lines Turn the compass housing until the needle falls into the orienting arrow Turn the compass housing to deduct the grid magnetic angle Turn the map and compass together until the needle falls into the orienteering arrow

Check of Understanding You are at a point where variation is 1 degree W, and Grid Magnetic Angle is 6 degrees W. If the magnetic bearing of a trig point is 150 degrees what is its Grid bearing? 143 degrees 144 degrees 156 degrees 157 degrees

Check of Understanding The direction of a track drawn between two places on a map is measured against the grid-lines and found to be 102 degrees (Grid). If magnetic north is 5 degrees west of grid north, what is the magnetic bearing of the track? 95 degrees M 97 degrees M 102 degrees M 107 degrees M

Check of Understanding A grid bearing from a M 726 series OS map on which the magnetic variation is westerly, can be converted to a magnetic bearing by: Adding the angular difference between magnetic north and grid north Adding the angular difference between grid north and true north Subtracting the angular difference between magnetic north and grid north Subtracting the angular difference between grid north and true north

Basic Navigation Leading Cadet Training End of Presentation