Map and Compass Topic 1106

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# Map and Compass Topic 1106 - PowerPoint PPT Presentation

Map and Compass Topic 1106. Mr. Christensen. Today’s Objectives. Learn the basic features of a compass Learn how to use a compass to plot a azimuth (direction of travel) Learn the basic features of a map Utilize a map and compass to find a location from known points

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### Map and CompassTopic 1106

Mr. Christensen

Today’s Objectives
• Learn the basic features of a compass
• Learn how to use a compass to plot a azimuth (direction of travel)
• Learn the basic features of a map
• Utilize a map and compass to find a location from known points
• Learn to pace, and using a compass define a given area
The Compass
• A magnetized needle that responds to the earth’s magnetic field
• A freely rotating magnetic needle-one end is usually a different color (red) from the other so you know which end is pointing north

From: Michigan Forests Forever Teachers Guide

http://www.dsisd.k12.mi.us/mff/TreeBasics/mapcompass.htm

• Circular rotating housing for the needle marked with 360degree markings
• Index line to read/set bearings/azimuths
• Sighting mechanism
• Straight edge

From:http://www.georgia-outfitters.com/_lensatic/instructions.htm

When Using a Compass
• Insure the compass is level and the needle is allowed to swing freely
• Large metal objects (18 yards*), magnets and power lines (55 yards*) affect accuracy
• Local magnetic anomalies (iron ore deposits)

* Distances to be maintained for accurate compass readings

Uses of the Compass
• Determine magnetic north
• Orient a map
• Determine azimuths (go from point A to B)
• Describe the area of a feature in the landscape—traverse
• Find your location on a map from known points

A azimuth (horizontal angle measured clockwise from a north

base line) of 900 has been established and is being followed

Magnetic North

Direction of

Travel

Rotate the compass until the desired azimuth falls under the fixed black index line

Turn the bezel ring until the luminous line is aligned with the north-seeking arrow

Turn your body until the north seeking arrow is aligned with the luminous line

Sight on a distant fixed object and use that

direction of travel

Plotting a Azimuth

From:http://www.georgia-outfitters.com/_lensatic/instructions.htm

Magnetic North Versus True North Versus Grid North

Most places true north does not equal magnetic north

• True north = magnetic north = agonic line
• Earth’s magnetic field is not static declination lines change
Magnetic Declination
• Ironwood or Benton harbor magnetic declination is 0 degrees
• Detroit or Sault Saint Marie = 6 degrees west

New York 15 degrees

West declination

Mt Rainier (WA)

19 degrees East

declination

From: Michigan Forests Forever Teachers Guide

http://www.dsisd.k12.mi.us/mff/TreeBasics/mapcompass.htm

Declination
• West declination—from compass to the map--direction of travel minus declination equals map course
• From map to field--map course plus declination equals direction of travel
Topographical Maps
• Simulate 3-D land formation
• Based on lines of latitude and longitude
• Legend: tells you when the map was made, location, adjacent land, magnetic declination, map scale
Brown Contour Lines
• Represent equal points of height above sea level (five foot intervals are marked)
• Steep slopes lines are very close together
• Valley contours form a V, point up the hill to indicate drainage
• Summits forms circles
• Depressions: from circles with lines radiating into center
TOPO Map Colors

(buildings)

• Blue-water
• Brown-contour lines
• Green-vegetation

(forests, orchards)

• White-light vegetation
• Red- major highways

From the U.S. Geological Survey 1:24,000 East Lansing Michigan map sheet

• Situation you are lost but you can determine azimuths to Government Peak, the Radio tower on Hill 456 and Cuyahoga Peak, three locations you can find and identify on the map
• Calculate the back azimuths from the known locations and plot on the map
• Where the map plots cross is my location

2110

the back azimuth is

310 + 1800 = 2110

plot from hill 456 you a re somewhere along that line

310

U.S. Geological Survey 1:24,000 map of Government Point, Michigan

Government Peak azimuth 2600 the back azimuth is

2600 – 1800 = 800 plot from Government Peak where

the lines intersect is your location

2600

800

U.S. Geological Survey 1:24,000 map of Government Point, Michigan

To verify your location use TRIANGULATION

Cuyahoga Peak azimuth is 3240

Back Azimuth from Cuyahoga is 3240 – 1800 = 1440

plot from Cuyahoga you are located in the triangle

1440

3240

U.S. Geological Survey 1:24,000 map of Government Point, Michigan

You Are Lost Again

Your azimuth to Cuyahoga Peak is 20 the back azimuth will be 20+ 1800 = 1820

Your azimuth to Government Peak is 225.50, the back azimuth will be 225.50 – 1800 = 45.50

Plot the back azimuths to determine your location

What We Did Today

• Function and use of the compass
• Finding a location using Triangulation
• Used a topographical map and looked at map versus land features
• NOW LETS LOOK AT PACING
Pacing
• A pace is two steps, begin on the left foot and count is made each time the right foot strikes (normal strides)
• Pace a 100 foot course three times take the average
Calculating the length of your pace

First trial 20 paces

Second trial 22 paces

Third trial 21.5

Total 63.5 paces

Total paces/3 = 21.2 paces = average # of paces for 100 feet

Average length of pace:

100 feet/Average # of paces for 100 feet = Average number of feet per pace

100 feet/21.2 = 4.7 feet per pace

Compass and Pace Course
• Set azimuths to follow
• Determine # of paces on that azimuth

I

30 feet at 900

S

Start

50 feet at 1500

30 feet at 1200

II

III

50 feet at 1920

IV