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Instructional Materials ServiceTexas A&M University

- 8987E -

Compass & Pacing

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Compass & Pacing

• Baseplate Compass

• Engineer’s Lensatic Compass

• Pacing

• Compass Use

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Baseplate Compass

There are several grades and types ofcompasses. A good baseplate compass willhave a:

• Rotating, fluid-filled housing• Baseplate • Compass needle• North alignment needle • Direction-of-travel arrow

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Baseplate Compass

Scale

Direction-of-travel arrow

Magnifier

North alignment

Rotating housing

Compass needle

Orientation lines

Compass housing

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Baseplate Compass

Baseplate compassesmay include:

• A scale• A magnifier• Templates• Lanyard (a wrist, or

neck travel cord)

Scale

Direction-of-travel arrow

Magnifier

Slot for lanyard

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Baseplate Compass

• The fluid-filled housing slows the motion of the needle so the operator does not need to hold the compass motionless during use.

Housing

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Baseplate Compass

• The compass housing includes degree marks, 0° to 360°.

• The reading for North is both 0° and 360°.

Housing

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Baseplate Compass

• The red end of the compass needle always points to Magnetic North.

Compassneedle

Northalignment

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Engineer‘s Lensatic Compass

Compass includes:

• A fluid-filled housing • A Magnetic North arrow• Directional marks• A magnifying lens• A line-of-sight

directional viewfinder

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Pacing

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Pacing

Two methods of pacing:

1. Pace equals two steps

2. Pace equals steps traveled in a 100-foot distance

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Method 1:

Pace Equals Two Steps

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Pace Equals Two Steps

Determining an accurate pace:

• Measure a 100-foot distance between two markers, Point A and Point B.

• The area between the markers should be flat and free of obstacles.

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Pace Equals Two Steps

• Travel from Point A to Point B, counting off each step.

• Repeat several times recording step count each time.

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Pace Equals Two Steps

• Divided total number of steps recorded (120) by number of attempts completed (3)(120) steps ÷ (3) attempts = 40 steps

• Average equals (40) steps.

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Pace Equals Two Steps

• Divide (100) distance by (40) step average 100 ÷ 40 = (2.5) step length

• Multiply (2.5) step length by (2). 2.5 x 2 = 5 Pace = 5 feet

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Method 2:

Steps Traveled in 100 Feet

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Steps Traveled in 100 Feet

• Once an average pace is established, it is possible to determine how many steps it will take to travel a given distance.

In this example, 40 steps = 1 pace

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Steps Traveled in 100 Feet

Distance from point A to point B = (160) steps Pace = (40) steps

Divide (160) distance from A to B by (40) steps 160 ÷ 40 = 4 Multiply 4 by (100) distance used to find pace 4 x 100 = 400 Distance to target is 400 feet

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Steps Traveled in 100 FeetCalculate the number steps to travel adistance of 185 feet.

• Divide (185) distance by 100 185 ÷ 100 = 1.85 Remember: 40 steps = 1 pace• Multiply 40 by 1.85 1.85 x 40 = 74

It will take 74 steps to travel 185 feet.

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Pacing (Obstacles)

• It is necessary to determine pace on uneven terrain, through ditches, grasses, trees, brush of various heights, and other obstacles.

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Pacing Beginners should: • Use a measuring tape to accurately measure a

100-foot distance.

• Practice on clean, level ground, using a natural walking gait.

• Maintain a constant, reliable pace, regardless of the obstacles.

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Compass Use

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Compass Use

• The Earth’s North and South poles act like a huge magnet. One pole is positive and one pole is negative.

• Because magnetic and true North are not the same, corrections are made in surveying to compensate for this difference. The difference is referred to as magnetic declination.

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Compass Use• The compass needle,

which floats in the fluid-filled chamber, is magnetized.

• Regardless of the compass position, the red needle is drawn to the Magnetic North Pole.

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Compass Use

• The circular rotating housing enclosing the needle is marked in degrees in increments from 0° to 360°.

• Degrees are also referred to as the azimuth or bearing.

Housing

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Compass Use

• Directional letters N, S, E, and W, are identified on the housing.

NorthSouthEastWest

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Compass Use

Example: To find the direction-of-travel based on a compass reading of 210 feet at 320° from a specific location:

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Reading 210 feet at 320°

• Rotate the housing on the compass until the 320° mark lines up with the direction-of-travel arrow.

320°

Direction-of-travel arrow

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Reading 210 feet at 320°

• Rotate the entire compass until the compass needle lines up in the North alignment position.

Direction-of-travel arrow

Needle in the North Alignment Position

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Reading 210 feet at 320°

• Holding the compass at eye level, use the direction-of-travel arrow to identify a distant landmark.

• Walk in a straight line as indicated by the direction-of-travel arrow for a distance of 210 feet to the recorded location.

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Compass Reading 210 feet at 320°

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Compass Use

• Note: All magnetic objects, such as belts, watches, keys, and other metal objects can interfere with the compass reading.

• Hold compass away form metal objects when taking a reading.

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Compass Use

• Aerial maps are available through the Natural Resource Conservation Service or the Soil and Water Conservation District.

• Maps should be read with a compass on a flat, horizontal surface, away from metal objects.

• Readings may be taken from maps based on specific location and the direction to be traveled.

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Compass Use

• The ability to use a compass effectively is an essential skill for wildlife managers, biologists, and other scientists who work outdoors. It is also a beneficial tool for the outdoor enthusiast.

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Acknowledgements

Dr. Joe Dettling, Associate Professor, Instructional Materials Service, Texas A&M University, researched and developed the information used in this PowerPoint Presentation.

Jerry Dornak, Agricultural Science & Technology Instructor, Goliad High School, Goliad, Texas and Dr. Terry Blankenship, Wildlife Biologist, Welder Wildlife Foundation, Sinton, Texas, reviewed material used this PowerPoint.

Christine Stetter, Artist, Instructional Materials Service, Texas A&M University, developed and illustrated this PowerPoint Presentation.

Vickie Marriott, Office Associate, Instructional Materials Service, Texas A&M University, edited the material in this PowerPoint Presentation.