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Find Your Way Back
Copyright
Stay Alive: Navigate Your Way Back
Learn the basics of reading a map and compass.
By John D. McCann
© 1998 Tim Bottomley
Navigation skills are essential for survival and you should be well versed in
using both a map and compass. Either one will assist you in the ability to
navigate, but together they are a team that can’t be beat. This chapter provides
the basics of how to select the proper equipment, and what a map and compass
can do for you. Although the basics of use are provided, I highly suggest that
you take a good course where you can get hands-on instruction. The use of a
map and compass takes practice, and there are no shortcuts.
Maps and their use
A map is nothing more than a pictorial representation of the surface of the
earth, drawn to scale and reproduced in two dimensions. If you are a driver, you
know there are all kinds of maps, such as road maps, etc. Although these maps
can get you from one place to another using the highway system, when you go
into the wilderness, they are of little use. What you need is a topographical map.
Although there are many makers of topographical maps, we will limit our
discussion to USGS maps with a scale of 1:24,000. The smaller the number to
the right of the “1” in the scale of a map, the more detail you will find. Although
larger scale maps show a larger area, for the purpose of navigation, I suggest a
map with a 1:24,000 scale which provides enough detail to be usable.
A topographical map provides a three-dimensional representation, viewed
from overhead. It portrays terrain and landforms in a measurable form using
contour lines. However, before we get in to the specifics of contours, a
discussion of the information provided on a maps borders, and colors used to
identify specific features, is important.
Symbols and colors
The symbols give a quick visual description of things that appear on a map.
An example is a small black square with a cross on top, which denotes a church.
Some maps provide some of the symbols in a legend at the right bottom of the
map. USGS maps use so many symbols that they provide a separate sheet called
Topographical Map Symbols. If you don’t want to carry this sheet with you,
become familiar with the major symbols used so you can identify them on your
map.
USGS maps are printed in seven colors. Color is used to more easily identify
specific information or features. The following describes each color and what it
represents:
White: An area of none or little vegetation, cleared land, desert, rocky areas.
Green: An area of substantial vegetation, forest, brush, orchards, etc.
Blue: Water such as ponds, lakes, rivers, canals. Note: A green area with
small blue tufts of grass indicates a marsh or swamp.
Brown: Contour lines showing elevation.
Black: Manmade objects such as buildings, railroads, water towers, roads, and
all names.
Red: Prominent roads and survey lines.
Purple: Revisions and updates added from aerial photographs (not field
checked).
A mountain is built by adding one contour line section at a time. The result is an actual view of the
mountain the contour lines represent.
Contour lines
Topographical maps have a bunch of little brown squiggly lines which are
called contour lines. They represent the elevation above sea level for all land
features. The difference in elevation between each contour line remains the same
on a specific map. This allows you to view the topography in three dimensions,
but you have to understand how to read them.
Certain rules pertain to all contour lines. If we understand the rules, then we
better understand what contour lines show us.
The height, or vertical distance, between each contour line, known as the
contour interval, is indicated at the bottom center of a map, below the scale. If it
has a contour interval of 20 feet, then the vertical distance between each line
has a contour interval of 20 feet, then the vertical distance between each line
either increases or decreases by 20 feet. Each fifth line will be thicker and will
notate the actual elevation for that line.
If you continue to cross contour lines that increase in number, then you are
going uphill. If the numbers decrease, then you are going downhill.
Contour lines have no beginning or end. No matter how irregularly shaped
they are, they are all a closed loop. The entire line is at the exact same height and
you could follow it around until you came back to where you started and never
go up or down in elevation.
The closer the space between contour lines, the steeper the slope. A gentle
slope is represented by the contour lines being spaced farther apart from one
another. However, if the lines are spaced very close together, it indicates a very
steep topography, such as a cliff.
V-shaped lines that face uphill, increased elevation, indicate a valley, ravine,
etc., and always point upstream. V or U shaped lines that point downhill indicate
a ridge or spur.
An hourglass shape with increasing numbered contour lines on each side
indicates a saddle or pass.
The peak of a hill or mountain is normally marked with an X or the actual
elevation.
Remember that not all topography is shown on a map. If the contour interval
is 20 feet and there is a decrease in height, but is less than 20 feet, then it will not
appear on the map. I warn of this so you do not come to an 18-foot cliff and,
because it does not appear on the map, start questioning where you are. Being
the cliff is less than 20 feet (or whatever the contour interval is for that map) it
won’t appear on the map.
Students find contour lines difficult to comprehend at first. I often thought that
if I could only take a section of a map and build a mountain depicting the various
heights the contour lines represented, a student would better comprehend
contour lines, as they could see a three dimensional representation of the lines.
So finally, my wife and I spent a weekend, first hand drawing a section of a map
So finally, my wife and I spent a weekend, first hand drawing a section of a map
with contour lines, and then building a mountain that could be assembled one
contour line at a time. After cutting, carving and installing wooden pegs to hold
it together in the proper position, we had what we needed for our students. A
little paint and when our students see the mountain built, one contour line at a
time, they always exclaim, “Now I get it!”
To measure distance of a curvy trail, bend a piece of wire to follow the trail, then straighten it and measure
using the scale at the bottom center of the map.
As we learned above, the scale at the center bottom of the map provides a
means to measure distance on a map. Unfortunately, you may not always want to
measure with a straight line; you may want to measure the distance of a road or
trail. My dad taught me to use a string, which could be wound around a trail,
then straighten it out and measure it on the scale at the bottom of the map.
However, always looking for a better way, I started using a piece of bendable
wire, usually red in color. This way I can bend it around the trail, or whatever,
and it stays in the shape until I need to straighten it for measuring.
The C-Thru Compass Protractor and the Land Measure Compass with Arm help you plot compass headings
and courses on a map.
Map tools and aids
Map tools and aids can help you determine bearings and navigate with a map,
as well as provide a means to determine where you are located on a map using
UTM (Universal Transverse Mercator) coordinates. These are handy devices and
can be carried with your maps in a survival kit.
Two real handy devices are made by the C-Thru Ruler Company. They
manufacture the compass protractor which allows you to easily plot your
compass headings on a map. It can also be used to determine if the degree angle
on the declination diagram of a map is accurate. The protractor is a transparent
circle that measures 3.5 inches in diameter, which measures in degrees (360). It
can be conveniently carried in a kit, shirt pocket, with your map, in your pack or
with your notebook.
The next item they make is the Land Measure Compass with Arm. This is a
great land navigation tool when plotting courses on a map. The meridian lines
can be lined up with those on your map, and the moveable arm swung to
determine your heading in degrees. It measures five inches in diameter with a
three-inch arm. Larger than the compass protractor, it can be stored in larger kits
or map cases.
Many maps today are marked with UTM grid coordinates. Unlike the latitude
and longitude system where you deal with minutes and seconds, the UTM
system is decimal based, dealing with ones, tens, hundreds, and so on. All
coordinates are measured in metric distance units of meters or kilometers. Each
map using UTM can be divided into one kilometer grid squares and you read the
grid values from left to right and bottom to top. To divide these one kilometer
grids into smaller units, which is handy when trying to determine your specific
location in a grid, a grid protractor comes in real handy.
A company that makes some of the best UTM protractors out there is
MapTools. They make some full size protractors that meet the military GTA 5-
MapTools. They make some full size protractors that meet the military GTA 5-
2-12 requirement, as well as some small protractors that can fit in the palm of
your hand. These smaller items are really great for smaller survival kits.
The first tool is equivalent to the Graphic Training Aid 5-2-12 Coordinate and
Protractor used by the United States and NATO military forces around the
world. However, this tool offers significant benefits over the standard issue GTA
5-2-12. It is printed on 30 mil plastic stock with a protective coating. This makes
it about the thickness and stiffness of a credit card. It’s 33% thicker than the
standard military issue version, so it’s less likely to be bent or broken when you
need to use it. It also has rounded corners to keep it from wearing holes in your
pockets. It offers Scales: 1:25,000 × 1km/1:250,000 × 10km, 1:50,000 ×
1km/1:500,000 × 10km, 1:10,000 × 100m/1:100,000 × 1km and measures 5×5
inches.
The next tool is an improved version of the Graphic Training Aid 5-2-12
Coordinate Scale and Protractor, discussed above. By using a slot on one side of
the tool for access to the map, the tool can be more compact than the traditional
GTA tool. The tool features several additional map scales, including 1:24,000,
which is the most common topographical map scale found within the United
States, including the 7.5 minute USGS maps. The 1:100,000 scale spans 5km
grid lines, making it much more usable. The overall dimensions have been
reduced so that it is the size of a music CD, easily fitting into a pocket or any
slot where you could store a CD. This tool is also printed on 30 mil plastic with a
protective coating. It has rounded corners which keep it from wearing holes in
your pockets. Scales: 1:24,000 × 1km, 1:25,000 × 1km/1:250,000 × 10km,
1:50,000 × 2 km/1:500,000 × 20km, 1:10,000 × 500m/1:100,000 × 5km.
Compass Rose in both Degrees and Mils. Measures 4.5×4.5 inches.
Clockwise: the Military Style MGRS/UTM Grid Reader and Protractor, both the New Style and the GTA 5-
2-12; the MapTools UTM Book, and the Pocket sized UTM Corner Ruler and Grid Plotter.
MapTools also manufactures two really small, hand held UTM corner ruler
and grid plotters. They are real handy little items and fit most anywhere. They
have also published a small booklet called “UTM” which is a great starting point
for beginning GPS users and folks that want to learn about UTM, MGRS, and
USNG coordinates. With lots of illustrations and step by step instructions, it
provides readers with the ability to convert between map locations and UTM
coordinates quickly. The booklet includes a 1:24,000 scale “Pocket Sized Grid
Plotter” (see above) for use with 7.5 minute USGS topographical maps. This
may be a small booklet (50 pages) but provides a wealth of information and
great graphics!
Compasses
An item that should be in every survival kit, no matter how small, is a
compass. A compass is the basic tool of navigation. They come in all shapes and
sizes. Choose a liquid filled compass (this slows the swinging of the needle,
called damping, and makes the needle stop faster).
