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Using a Compass

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Using a Compass What is a compass? How does a compass work? What are the parts of a compass? Using a compass. What is a compass? A compass is a magnetized needle When ... – PowerPoint PPT presentation

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Title: Using a Compass


1
Using a Compass
  • What is a compass?
  • How does a compass work?
  • What are the parts of a compass?
  • Using a compass.

2
What is a compass?
  • A compass is a magnetized needle
  • When allowed to move freely, points in the
    direction of Magnetic North.

3
Compass Directions
  • This needle gives you a reference point for
    measuring all other directions.
  • North top of needle
  • South bottom of the needle
  • East right of the needle
  • West left of the needle

4
Compass Directions
  • Half the distance between North and East is
    Northeast.
  • Half the distance between South and West is
    Southwest.

5
Compass Directions
  1. North
  2. Northeast
  3. East
  4. Southeast
  5. South
  6. Southwest
  7. West
  8. Northwest

6
Compass Directions
  • Splitting the directions again gives the compass
    user sixteen distinct directions.

7
How does a Compass work?
  • A compass works with the earths magnetic field
    to find North.

8
How does a Compass work?
  • Every magnet has at least one north pole and one
    south pole. 
  • Unlike poles attract (Top).
  • Like poles repel (Bottom).

9
How does a Compass work?
  • In magnets, opposite poles attract each other.

10
How does a Compass work?
  • Think of the Earth as having a gigantic bar
    (actually molten core) magnet buried inside.
  • In order for the north end of the compass to
    point toward the North Pole, you have to assume
    that the buried bar magnet has its south end at
    the North Pole.

11
How does a Compass work?
  • The "opposites attract" rule of magnets would
    cause the north end of the compass needle to
    point toward the south end of the buried bar
    magnet.
  • The magnetic field created by the molten core of
    the earth attracts the "N" end of our bar magnet
    and compass needles. 

12
What is Magnetic North?
  • The ends or poles of the magnet do not match the
    Earths geographic poles.
  • The bar magnet does not run exactly along the
    Earth's rotational axis.
  • It is skewed slightly off center.
  • This skew is called declination.

13
What is Magnetic North?
  • A compass points to magnetic north known as the
    Magnetic North Pole.
  • The magnetic pole tends to drift, so its location
    can change over time.
  • The drift is minor.

14
Does a compass work if you are standing at the
North Pole?
15
Can you use a compass near the North Pole?
  • A compass becomes erratic as you approach the
    Magnetic North Pole and the true North Pole and
    becomes unusable.
  • Yellow zone compass erratic
  • Red Zone compass unusable

16
Types of Compasses
  • Compasses are marked in several very different
    ways
  • The Quadrant Compass
  • The Military Compass
  • The Azimuth Compass

17
Types of Compasses
  • The Quadrant Compass
  • Have a scale divided into four segments of 90
    each
  • Used primarily by surveyors for establishing base
    lines and datum lines.

18
Types of Compasses
  • Military Compass
  • Is read in mils.
  • Marked from 0 to 6400

19
Types of Compasses
  • Azimuth Compass
  • The dial on an azimuth compass is marked in
    degrees proceeding clockwise from the north.
  • North is 0 or 360
  • East is 90
  • South is 180
  • West is 270

20
Types of Compasses
  • Azimuth Compass
  • The azimuth compass is best suited for outdoor
    activities.
  • Marked from 0 to 360

21
Parts of a Compass
  • A compass has three main parts.
  • Base (base plate)
  • Housing
  • Lid (cover)

22
Parts of a Compass
  • Base
  • On most compasses this is a rectangle made of
    plastic.
  • It will have scales on both sides.
  • The scales will have inches on one side and
    centimeters on the other. These are used with a
    map scale to determine the distance between two
    points.

23
Parts of a Compass
  • Housing contains
  • The needle (usually in a liquid filled container)
  • The dial (azimuth dial) that can be turned to set
    or determine directions and is marked from 0 to
    360 degrees

24
Parts of a Compass
  • The Cover or Lid
  • Mirror on the inside with a direction of travel
    line down the middle.
  • A sight to aim the compass is located on top of
    the lid.

25
Parts of a Compass The Housing
  • Housing - This is the dial that can be turned to
    determine and set bearings or directions.
  • Bearing/Sighting Line - Like the sights on a gun,
    this line is used to point the compass directly
    at a target.
  • Needle - The needle is a thin strip of magnetic
    iron on a frictionless pivot. The red tip will
    always point toward the magnetic north pole in
    the northern hemisphere.
  • Orienting Needle - The orienting needle is an
    arrow outline painted below the needle. It is
    part of the housing, and rotates with the
    housing. The top or front of the orienting needle
    is aligned with the north end of the needle when
    navigating.
  • Grid Lines - Grid lines are used to align north
    on a map.

26
Parts of a Compass
  • 1. Sight
  • 2. Direction of Travel Line
  • 3. Needle
  • 4. Orienting needle
  • 5. Housing (dial)
  • 6. Grid Lines
  • 7. Sight
  • 8. Scales

27
Using a Compass
  • A compass needle is sensitive to metal and
    magnets and can be affected by
  • Metal belt buckles, rings, and watches
  • Metal fences
  • Metal buildings
  • Automobiles
  • Gun barrel
  • Electronic accessories
  • Be aware of similar objects to eliminate false
    readings

28
Using a Compass
  • To use the compass , you need to
  • Hold it steady and keep it away from metal.
  • Place the compass in the palm of one hand and
    place that hand in the palm of your other hand.
  • Pull your elbows firmly into your side.
  • Hold the compass steady and level, this allows
    the needle to move freely.

29
Using a Compass
  • While holding the compass level, point the
    direction-of-travel arrow (or sight) in the
    direction you want to travel.

30
Using a Compass
  • Then turn the compass housing until the compass
    needle aligns with the arrow marks drawn on the
    bottom of the compass. Remember, the colored end
    of the compass needle points north.
  • Now move so that you are looking straight ahead
    in the direction in which you want to travel. Be
    sure that the magnetic needle still points north.
  • To keep from straying too far to the left or
    right of direction-of-travel, pick an object as
    far away as possible to align yourself.
  • Stop occasionally to make sure you are headed in
    the correct direction. Keep repeating this
    process to stay on course.
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