Map & Compass

I.	Map To Field (Ground)

A.	True Bearing (True North) To Magnetic Bearing

1.	Declination E (DE)—Subtract

2.	Declination W (DW)—Add

II.	Ground (Field) To Map

A.	Magnetic Bearing To True Bearing (True North)

1.	Declination E (DE)—Add

2.	Declination W (DW)—Subtract

Adjusting The Compass To True North: Why Magnetic Declination adjustment?

Because all USGS Topo (see page 61; Map & Compass; Geary's book) maps are set to true North because the location of the North Pole remains constant–it does not change, and when you add or subtract magnetic declination the magnetic needle will point to true North and not to magnetic North (see II); or, to magnetic North and not to true North (see I).

The compass and true North on the map are now one for 'I', and in 'II,' the compass and magnetic North on the map are one.

III.	Map is Not Used:

A.	Do Nothing With I- & II-A!

Using The Orienteering Compass

I.	Orient The Map.

A.	Place the map in a North-South position. Then take a one-dimensional landmark or baseline on the topo map and find it in the three-dimensional world that your map is representing. Adjust (orient) the map to a position that illustrates this. If it is to the right and up, slide the map to correspond to that position in the real world. Having done so, you have now placed yourself on the map.

B.	Set to compass to Magnetic North; then, place compass on topo map on the North-South Lines or left/right straight-edge of the map, and turn the map until the magnetic needle is "boxed" (in "dog house," or in orienting arrow) and the orienting lines of the compass capsule are parallel to the North-South Lines. Map is now oriented to Magnetic North.

1.	The Reasons For This :

a.	When a bearing is shot and magnetic declination is accounted for, placing the compass on the map at a landmark and sliding it around, one may not properly get the orienting lines of the capsule parallel to the North-South Lines of the topo map without being off.

b.	When you draw the line from the landmark to your position, you may be off a number of degrees or more which translates to distance on the ground. This can be proven from a known landmark to a known position.

C.	Remove Compass from Map

II.	Point Direction of Travel Arrow at Landmark

III.	Turn Dial Until Orienting Arrow and "N" Letter On Dial is Aligned With Red Magnetic North Arrow (Needle in "Doghouse").

IV.	Read bearing at Index Line.

A.	Then add or subtract magnetic declination while holding compass.

B.	Do this by rotating compass dial such that the bearing of the landmark is corrected to the magnetic declination by aligning the bearing index line with the correct magnetic bearing.

V.	Keep the new setting, as you now place the compass on the map.

VI.	Rotate the whole compass, not the compass housing (rotate base plate) until the orienting arrow points N on the map. (That's why we orient the map — see No. I).

VII.	While keeping the orienting arrow pointing N that includes the magnetic declination adjustment setting, slide compass around the map until the long edge of the baseplate goes through the landmark and the (1) orienting arrow boxes the magnetic North needle and (2) the orienting lines—both (1) & (2)—are parallel with the North-South Lines of the Topo Map or edge of the map if North-South Lines are not evident or quickly ascertained. When that is aligned, then...

VIII.	Draw the line.

Three Basic Operations of The Compass

(See Map & Compass–Don Geary)

I.	Navigating With Compass Only–page 33.

A.	Shoot a compass bearing to a known landmark; using sighting and compass bearing, go to the landmark. Then, calculate the back bearing (back sighting) or turn directly around and point the compass directly back to the point of origin. If not capable of doing this, simply move your body such that the magnetic needle aligns in the orienting arrow. However, the magnetic red portion will not be in the magnetic north boxing portion of the orienting arrow. The white part of the magnetic needle will be there. Now, just turn the capsule (aka as rose, azimuth ring, bezel, and housing) to place the red into its proper portion of the orienting arrow. Now read bearing at Index Line.

B.	This is the bearing you follow back from a relative straight trip to a baseline and then back again. Say you want to hike to a mountain and then back, but have to traverse a forest on the way there, the back bearing will help you get back safely.

II.	Adjusting The Compass Reading To True North—page 65.

A.	See above if using a map: Map to Ground (I) and Ground to Map (II)

III.	Adjusting The Map To Magnetic North–page 69 (We don't do this procedure, as I & II are sufficient).