IMSARU
IMSARUIMSARU NavigationIMSARU
IMSARU website home Check out Mission reports in our Newsletter Some of our favorite links Stay on top of activities - our Calendar How did it all begin? Here is the History of IMSARU Our SAR Dogs are the best Safety Education is where its at IMSARU needs a few good people, Join today Member information, contacts, training photos Without our Sponsors we would not be here

Navigation
Basic Compass Techniques
compass parts

Dead reckoning, bearing straight, finding your way in a whiteout. Whatever you call it, learning to find your way from a known position using direction and distance traveled is the best option for getting safely back to where you started.

The steps to accomplish this task are easier to learn than it may sound. Let's start with the basic components of a good orienteering compass. The compass should be attached to a clear rectangular base plate which can be rotated (the compass housing should rotate on the base plate).

step 2

Step 1 Use the edge of the compass baseplate and a pencil to connect where you are on the map to where you want to go (A to B on the photo). Measure that distance against the scale printed at the bottom of the map.

Step 2 With the compass baseplate aligned to the line you just drew, twist the compass housing until the orienting arrow aligns with map north. Ignore the needle. Where the direction-of-travel line intersects the rotating dial is the map heading - the direction you want to travel.

Step 3 Find the declination diagram in the bottom left margin of your USGS topo map. It looks like a little V (see photo below). It shows the difference in degrees between map north and magnetic north for that particular map. If magnetic north (MN) is left of map north, add the degrees of the declination to your map heading. If MN is right of map north, subtract the degrees of the declination from your map heading. HINT: remember "LARS" for "left add, right subtract".

step 3

Step 4 Twist the housing so it reflects the declination. You have your bearing, but don't trust it to memory. Write down the distance and magnetic heading for each leg.

Step 5 Follow the magnetic bering by holding the compass in front of you and rotating your body until the red compass needle sits within the orienting arrow. Pick out a small landmark ahead of you on the line of travel. Walk to that tree, bush, rock or whatever and maintain your pace count. Repeat the process until you've paced off the full distance.

These compass techniques were taken from BACKPACKER magazine April 1999 issue.

----- Back to top

Using the Sun and Shadows

    Shadow-tip method.
  1. Find a straight stick about 3 feet (1 meter) long and a fairly level, brush free spot (so that the stick will cast a definite shadow.
  2. Push the stick in the ground so it stands upright. It doesn't need to be perfectly vertical to the ground.
  3. Mark the tip of the shadow cast by the stick.
  4. Wait until the shadow moves 1.5 to 2 inches (approximately 10-15 minutes).
  5. Mark the tip of the second shadow.
  6. Draw a line from the first mark through and about a foot beyond the second mark.
  7. Stand with your left foot on the first mark and your right foot on the end of the line you drew.
If you are in the northern temperate zone, you will be facing in a northerly direction and you will know the other directions by recalling their relation to north.
If you are in the southern temperate zone, you will be facing in a southerly direction.

Watch method. You can also determine the direction using a watch. The steps you take will depend on whether you are in the northern temperate zone or in the southern temperate zone (and whether you have a conventional or digital watch). The northern temperate zone is located between 23.4o north and 66.6o north. The southern temperate zone is located between 23.4o south and 66.6o south.

    Northern Temperate Zone (conventional watch)
  1. Place a small stick in the ground so that it casts a definite shadow.
  2. Place your watch on the ground sot that the hour hand points toward and along the shadow of the stick.
  3. Find the point on the watch midway between the hour hand and 12 o'clock and draw an imaginary line from that point through and beyond the center of the watch. This imaginary line is a north-south line.
NOTE: If your watch is set on daylight savings time, then use the midway point between the hour hand and 1 o'clock to draw your imaginary line.
    Southern Temperate Zone (conventional watch)
  1. Place a small stick in the ground so that it casts a definite shadow.
  2. Place your watch on the ground sot that 12 o'clock points toward and along the shadow of the stick.
  3. Find the point on the watch midway between the hour hand and 12 o'clock and draw an imaginary line from that point through and beyond the center of the watch. This imaginary line is a north-south line.
If you carry a digital watch, simply draw a conventional watch face on the ground with the hands indicating the proper time (as shown on your digital watch) - following the same steps as listed above.

The Sun and Shadow techniques were taken from the US Army Survival Manual FM21-76 (Dorset Press, 1992).
----- Back to top