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# Map and Compass Topic 1106 Mr. Christensen.

## Presentation on theme: "Map and Compass Topic 1106 Mr. Christensen."— Presentation transcript:

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 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

Advanced Compass Features
Circular rotating housing for the needle marked with 360 degree 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 Before proceeding to the next slide ask the question is magnetic north true north?

Compass Rose 3600

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

Azimuth—A horizontal angle measured clockwise from a north base line.
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 Adirondacks in New York 15 degrees West declination Mt Rainier (WA) 19 degrees East declination From: Michigan Forests Forever Teachers Guide

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 Distribute Government Peak map sheets

Map Legend Features

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 Black-man-made features (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

Finding Your Location Using Triangulation
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 Distribute copied map sheet portions

plot from hill 456 you a re somewhere along that line
2110 Radio Tower azimuth from your location is 310 the back azimuth is = 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 = 1820 Your azimuth to Government Peak is , the back azimuth will be – 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 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

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