HOW TO USE A MAP AND COMPASS

First, you need to determine your bearing (the direction you need to travel). Use the following procedure to obtain an exact travel direction towards your desired destination. The procedure will work if the magnetic North-South lines are drawn on the map.

Sample map used at the O Challenge at Bastrop State Park: MAP

1 a) Place the compass on the map so that the long edge connects the starting point with the desired destination.
b) Make sure that the direction arrows are pointing from the starting point to the place of destination (and not the opposite way).
c) At this point, you may want to use the scales on your compass (if available) to determine the distance you need to travel.

 
2 a) Hold the compass firm on the map in order to keep the base plate steady.
b)Turn the rotating capsule until the North-South lines on the bottom of the capsule are parallel with the North-South lines on the map.
c) Be sure that the North-South arrow on the bottom of the capsule points to the same direction as North on the map. It is here you will make adjustments for declination SEE BELOW, if necessary.

 
3 a) Hold the compass in your hand in front of you.  Make sure that the base plate is in horizontal position, and that the direction arrows are pointing straight ahead.
b) Rotate your body until the North-South arrow on the bottom of the capsule lines up with the magnetic needle, and the red end of the needle points in the same direction as the arrow.
c) The directional arrows on the base plate now show your desired travel direction.

 

Now that you have determined your necessary bearing, you need to make sure you maintain an accurate bearing. First, you should find a suitable target in the terrain (e.g., a tree, boulder or a bush) towards which the direction arrows point. Walk towards the chosen object without looking at your compass. When you reach your target, find a new object that is aligned with your bearing, and repeat the process.

 

Tip 2: Sometimes the compass capsule may get turned accidentally while you are walking. Remember to check from time to time that the capsule has not deviated from the direction that had been set on the compass.

Tip 3: Remember the difference between the magnetic needle that always points to the magnetic North Pole and the direction arrows that show the travel direction.

WHAT IS DECLINATION

NOTE: For the Orienteering Challenge in Bastrop, the maps are oriented to magnetic north, so no math is required.

To understand declination you must first realize that there are two North Poles.  There is a True Geographic North Pole at the top of the world, and a Magnetic North Pole which is over 1,250 miles from the True North Pole.  A magnetic compass always points toward the Magnetic North Pole.  Maps are oriented to the True North Pole.  The angular difference between True North Pole and Magnetic North is called declination.  Declination varies from 0 to 30 degrees in most populated regions of the world.  These declination values usually change slightly over time, as the earths plates shift.  The actual value of declination and its annual rate of change for your area will usually be shown on your map.  This will be expressed as either a Easterly or Westerly declination, depending on your location.

Round Rock's declination is 5 degrees 30 minutes EAST!

EXAMPLE

If you have declination value of +6 (this is the same as 6 degrees Easterly), then when your compass indicates you are bearing a 90 degree course, you are actually bearing at 96 degrees. If you really do want to head with a bearing of 90 degrees, you will have to set your compass to a bearing of 84 degrees, to compensate for your local error.