1. Map and Compass Topic 1106
Mr. Christensen

2. 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

3. 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

4. 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:

5. 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

6. 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?

7. Compass Rose
3600

8. 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

9. 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:

10. 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

11. 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

12. 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

13. 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

14. Map Legend Features

15. 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

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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

22. 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

23. 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

24. 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

25. 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