How to Navigate with a Map and Compass

Step 3 Taking a Bearing on a Map

This step is pretty simple. When doing any map work, be sure you ignore your compass needle and declination arrow. Those guys are only helpful when you're using the compass in relation to the world around you. For now, consider it more of a protractor.

This is the simplest of the exercises. Imagine your on a mountain lookout. You see another mountain, what heading is it?
1. Open the Compass, and lay it flat on the map.
2. Move the compass so that the base is along point A (where you are), and the mirror is along point B (the other mountain).
3. Rotate the bezel until North matches the maps north, and the meridian lines line up with a north south line (lat/ long lines, UTM grids*).
4. Read the bearing at the top of the compass.**

*The edge of the map is the ideal line. Any lines that parallel it will work too.
**On the bottom of the compass, 180degrees around, is the bearing from Point B to Point A.

Comments

[bellrom]

Thanks for the instruction. I have a question, however: since I've already adjusted my Silva Ranger Compass for magnetic declination in my area, when I place the compass on my map to sketch a bearing I have taken in the field, I am lining up the orienting lines in my compass housing with the UTM grid lines on the map. These orienting lines in my housing are no longer parallel with the black north arrow outline on my baseplate ... since the north arrow outline reflects the adjustment I made for declination. Does this make a difference when plotting a bearing on the map? That is, do I continue to line the orienting lines in my housing with the grid lines on the map, or do I try to line the grid lines on the map so they are parallel with the black north arrow outline in my housing? ... hope this makes sense!

[GrapeApe226]

If you've noticed, some of the grid lines move a tad. nothing on the map seems to be static except the edges. Those are true North. This is because they warp the terrain just a tad so the map lays flat. Look at a master map and you will see all the little section maps are pointing to the top of the planet, slightly smaller at the top of each section; and slightly larger at the bottom. Put that map flat and it has to fit in a square. They stretch the top of the terrain out to fill that void so every square inch of your map is square with the paper.

Put your compass bezel on the declination setting that is printed on the map. Then put the straight ruler edge of your compass base on the edge of the map along the black line against the white boarder, NOT a grid line on the map face. Turn your map until your compass red/white arrow lines up with the north in the bezel window and your map will be "orientated" to true north. The red tip and the white painted arrow in the bottom of the bezel will be magnetic north and the edge of the compass along with your entire map will be dead on true north.

After you orient the map, any reading you take on the compass will give you the correct magnetic reading. When you see a peak at 43 degrees on the paper, you can look up and it will be exactly 43 degrees from where you are sitting.

I recomend ya'll get down to the Boy Scout Office in your area and buy the "Orienteering" Merit Badge Book! It's the best, easiest to read, common language book ever writen on map and compass, not to mention one hell of a great sport. Find a local Orienteering club in your area. Warning: it's an adictive sport lol!!