Navigation/Compass

Question 1

How does a compass work?

Answer 1

A compass works on the principel that the north point always points to magnetic north.

Question 2

Label a compass.

Answer 2

Refer to notes

Question 3

List and define the three norths.

Answer 3

True north - is the position of the Earth’s north pole.
Grid north - is the north point on the topographical maps. It is depicted by parallel lines.
Magnetic north - is the direction a compass need points to when it is suspended freely.

Question 4

What is magnetic variation?

Answer 4

The error in the compass caused by the earths magnitude of field. It is the angular difference between true north and magnetic north.

Question 5

Write a brief on how to take a compass bearing.

Answer 5

1. Face object and place compass in a horizontal position with the ‘direction of travel’ arrow facing the way you wish to go.
2. Hold the compass and turn the housing until the orientating arrow inside is directly beneath the red compass needle.
3. Read the magnetic bearing on the housing where the index line interests. Add/subtract magnetic variation if needed.

Question 6

How to take a grid bearing.

Answer 6

1. Place the ‘direction of travel’ arrow on the map pointing in the way you wish to travel.
2. Place the long end of the compass on the desired route.
3. Rotate the housing so that the orientating lines are parallel with gridlines (north on compass should be north on map).
4. Read grid bearing on housing where index line intersects it.

Question 7

How do you avoid an obstacle?

Answer 7

• detour at 90 degrees until the obstacle is cleared

- ensure you measure the distance

Question 8

What is a GPS?

Answer 8

• Global positioning system

- Fixes its position on the ground by referring satellites which orbit the earth.

Question 9

Is 1:2500 a small or large scale? And what is it equivalant to in meters?

Answer 9

Large scale, 2.5m on ground.

Question 10

What is triangulation?

Answer 10

The process of pin pointing the location of something by taking bearings to it from 3 remote points.q

Question 11

What are the 5 steps used for triangulation?

Answer 11

1. orientate your map so it is facing north.
2. take a bearing of ‘landmark 1’, point the direction of travel arrow towards it and turn housing until red is in the shed.
3. Place compass on the map so that the orientating lines are parallel to the maps north meridian lines.
4. Draw a line along the edge of your compass from the landmark and the bearing you took.
5. Repeat 1-4, 2 more times. Where the lines intersect, you are somewhere in this triangle.

Question 12

What are 5 map types?

Answer 12

• Topographical

Question 13

When going from magnetic to grid bearing with a 5 east variation do we add or subtract?

Answer 13

Add.

Question 14

When going from grid to magnetic bearing with a 5 east variation do we add or subtract?

Answer 14

Subtract.

Question 15

When going from magnetic to grid bearing with a 5 west variation do we add or subtract?

Answer 15

Subtract.

Question 16

When going from grid to magnetic bearing with a 5 west variation do we add or subtract?

Answer 16

Add.