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 allowed to move freely, points in the direction of Magnetic North.

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

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

Compass Directions North Northeast East Southeast South Southwest West Northwest

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

How does a Compass work? A compass works with the earth’s magnetic field to find ‘North.’

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).

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

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.

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. 

What is Magnetic North? The ends or poles of the magnet do not match the Earth’s 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.

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.

Does a compass work if you are standing at the North Pole?

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

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

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.

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

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°

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

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

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.

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

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.

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.

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

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

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.

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

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.