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Forest Ecology Contest
Map and Compass Section
Intermediate Level
People who
enjoy the forests should know how to use maps to navigate in unfamiliar territory.
In fact, youngsters may enjoy their experience
in a forest more if they are confident in their ability to read a map. Maps
can convey information about what to expect, what you might see and how to
prepare for a hike. Maps can help you identify
where you are and the easiest route to travel to arrive at your destination.
Different
types of maps convey different information. A road map shows highways, towns,
and interesting features to visit by car. A
sanitation map shows the location of the storm and wastewater sewers. A boating
map shows water depth and underwater features like sandbars, sunken ships,
and reefs. A topographic map shows landscape features such as
mountains, flat lands, water ways, major forms of vegetation,
roads and different types of structures. For this contest, youth should know
how to read a topographic map. Specifically, they should be able to:
- Interpret features of a topographic map
- Identify 30 different symbols on a USGS
topographic map (indicated in italics)
- Calculate distance from a topographic
map
Interpreting Topographic Features
The surface of the earth is not flat, but a two-dimensional map is. The strategy
for converting the planet's hills and valleys to a flat piece of paper
involves all the little brown contour lines on
a topographic map. They indicate topography – the shape of the land. A contour
line joins all the places of equal elevation. The value of a contour interval
depends on the map. Every 5th line
is usually an index contour line; it is heavier and has an elevation reading
along it. By subtracting two elevations and dividing by the number of intermediate
contour lines between them, you can determine
the vertical distance between two adjacent lines. In flat landscapes that
may be 10 feet. In mountainous areas it may be 100 feet.
The way the lines are drawn indicate the shape
of the land. Ridges and valleys, peaks and flat land,
saddles (the low part between two hills) and depressions
(noted by hatch marks inside a contour line)
can be interpreted from the lines on a map.
Identifying Symbols
The symbols on a topographic map are used consistently to identify key,
relatively stable features of the landscape. The
most widely used symbols are for ecosytems. Green shading indicates wooded
areas; open grass and farmlands are white. Sand
dunes and coastal dunes are tan with speckles. Lakes and
oceans are colored blue and perennial streams and rivers are
blue lines. An intermittent stream
is a broken blue line of dots and dashes; a spring is a circle
with a squiggle. Marshes have short blue horizontal lines. A town
or city is shaded in gray or red, and new information
added by aerial photograph to the map is shown in purple.
There are symbols for land uses that are common across this country. Gravel
pits, quarries, and mine tunnels
have symbols, as well as powerlines, railroads (single
and double track), campgrounds, primary roads, unimproved roads,
bridges, and trails . Common features
of towns have special symbols: church, school, cemetery, inhabited building,
uninhabited building, and tank. These symbols are illustrated
on the National Forestry Invitational Website:
http://www.aces.edu/N4HFI/
Calculating Distance
Each topographic map has a legend at
the bottom that indicates the correlation between inches on the map
and inches in the real world. A 7.5 minute map (indicating the
latitudinal distance covered in one map) usually has a scale of
1:24,000, or 1 inch on the map equals 24,000 inches on the ground
(24,000 inches equals 2,000 feet). The legend also provides a scale
(which resembles a ruler) that shows miles, feet, kilometers, and
meters. You can use this scale as you would a ruler to determine the
straight line distance between points on a map.
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Forest Ecology Contest
Map and Compass Section
Senior Level
A compass
can tell you the direction you are traveling. Combined with knowing your
pace, you can measure distance, communicate
a location with others, return to the same spot again, and find your way
home. In conjunction with a good map, you can comfortably move across a landscape
you have never seen before.
Seniors competing in the Forest Ecology Contest are
expected to be able to:
- Determine a distance by using their own pre-established pace
- Determine the bearing (compass reading)
of a given destination
- Travel to a destination by following
a compass direction and pacing
Determining Distance
Each person
has their own comfortable way of walking. When you aren't thinking about
how you are walking or trying to hurry, you are probably using your normal
pace. A pace is the distance from the heel of
one foot to the heel of the same foot the next time it hits the ground. To
establish your natural pace, mark out a distance of 100 feet on flat land
and walk along that line, counting each time
one foot (the one you didn't start on) hits the ground. Do it several times
and average the result. If it takes Chris an average of 21 paces to cover
100 feet, Chris's pace is about 4 feet 9 inches (4.76 feet).
Start
>>>
>>>
>>>
Finish
|----one pace---|
|
xx
xx
xx
xx
xx
|xx = 5 paces
xx
xx
xx
xx
xx |
To determine
an unknown distance, merely count the paces Chris walks from start to finish,
and multiply by 4.76. It helps if the unknown distance is on flat, cleared
land.
Questions:
- When pacing out of a dry sinkhole, would you be likely to underestimate
or overestimate the distance? Why?
- When pacing through thick palmetto,
would you be likely to underestimate or overestimate the distance?
Why?
- Sam is 6 feet tall and wears a size
15 shoe. Juanita is 4 feet tall and wears a size 6 shoe. Is Sam likely to
count more or fewer paces than Juanita when they pace out 100 feet?
Determine
a Bearing
A compass has
the following components:
- A magnetic compass
needle with one end painted red; it always points to the Earth’s North
pole
- A movable housing
with marks that indicate 360 degrees
- An orienting arrow
that is painted on the bottom of the housing that always points to the
N marked on the housing
-
A direction of travel arrow on the base plate of the compass
The red and black arrow is called the
compass needle. On some compasses it might be red and white, but the
point is, the red part of it is always pointing towards the earth's
magnetic north pole.
To determine a bearing, or compass reading, face the direction you wish to
travel. Hold the compass level on your open palm, at waist height or higher.
The direction of
travel arrow should point to your fingertips and the destination.
There is a turnable circle on your compass called the
compass housing. On the edge of the compass housing,
you will probably have a scale from 0 to 360. Those are the degrees, also
known as the bearing or the azimuth
. You should also have the letters
N, S, W and E for North, South, West and East.
Twist the compass housing without moving the base plate so the magnetic needle
lies over the north arrow and points to the letter N on the housing. Read
the compass bearing off the housing at the direction of travel arrow.
You are facing that bearing.
Follow a
Compass Direction
What if you want to go in a particular direction?
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Let's use 300 degrees as an example: What you do, is find
out where on the compass housing 300 degrees is. Then you turn the compass
housing so that 300 degrees on the housing comes exactly there where the
large direction of travel-arrow meets the housing. |
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Hold the compass in your hand. And you'll have to hold it quite flat, so that
the compass needle can turn. Then turn yourself, your hand, the entire compass,
just make sure the compass housing doesn't turn, and turn it until the compass
needle is aligned with the N inside the lines of the compass housing. You
are facing 300 degrees. Sight across the direction of travel arrow and pick
out an object that is exactly in line with the direction of travel arrow.
Start walking toward that object. |
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Now, time to be careful!
It is important that the red, north part of the
compass
needle points at north in the compass housing. If you forget and line up
the other end of the needle, you will be going in the exact opposite direction
of what you want! Always take a second look to make sure you did it
right!
When you are sure you've got it right, walk off in the direction
the direction of travel-arrow is pointing. To avoid getting off the course,
make sure to look at the compass quite frequently, say every fifty feet.
However, you shouldn't stare down on the compass. Once you
have the direction, aim on some point in the distance, and go there.
Reference:
http://www.learn-orienteering.org/old/lesson1.html
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