map reading section 3 - b continuation of compass section

Map Reading Section 3 - BMap Reading Section 3 - B

Continuation of Compass section

Finding your locationSuppose you are lost and know that you are located someplace on this map

You can see two mountains that show up on your map

If you had the skill to measure the two lines as shown, you could find your location by the intersection of the two lines

Let’s do it

Measure a Bearing Line up your compass with the red MN needle pointing towards the North sign on the compass

Point the compass towards the top of the mountain

Read the baring to the top of the mountain

Do this for both mountains

You now have two bearings but

You could be anyplace on the map

You know Round Mt is 180o bearing from your location

But, you don’t know your location

You do know the location of Round Mt

You are going to have to measure from Round Mt

Drawn a 138o line from the top of Round Mt

This line is going in the wrong direction

You calculated the bearing from you to Round Mt, not the other way around

138 + 180 =318You are off by 180 so do the math

0 360

180

90270

45

135225

315

Place a protractor on Round

Mt and mark 318

138 + 180 =318

0 360180

90

270

Draw a 318o line from R.M.

I you don’t have a

protractor when in the

field, you can make one.

Trace a water bottle or a

compass onto a piece of paper

0 360

180

Draw the lines

0 360

180

90270

0 360

180

90270

45

135225

315

0 360

180

90270

45

135225

315

138 + 180 =318

You have a magnetic bearing, but to draw on a map you have to convert

138 + 180 =318

TB = MB + D

MB = TB - D

318 + 10 =328

0 360180

90

270You now can draw

your line

138 + 180 =318 TB = MB + D

MB = TB - D318 + 10 =328196 + 180 =376376 –360 = 1616 + 10 = 26

Now do the other mountain

Additional Pointers

Some compass's have a built in declination adjustment.

You set the 10o and the compass converts declination

for you.

Don’t forget to adjust this if you are not in CB.

If using old maps, update the declination by using key words “magnetic declination “ on the internet.

You must orient your map.

TN

Orient the MapOnce in the field you must orient the map.

Place your compass on the map near the declination marking

TNMN

Turn the map till the red line on your

compass lines up with the grid on your map

TNMN

The map is oriented with TN but if you don’t have declination built into your

compass, you must turn the map more to line up with MN

TNMN

Your map is now oriented

You are ready to navigate

Traveling with a compass1. Determine the bearing you

will travel.

2. Select a landmark in the distance that lines up with the bearing. This can be a mountain, or in the dark it could be a partner with a light.

3. Travel towards the distant landmark … this prevents you from always looking at the compass.

4. Occasionally check the compass and select a new target when necessary.

4. When going around an obstacle (such as a pond or a hill) select a landmark on the other side.

5. Travel to the landmark and when you arrive select a new landmark as your target.

6. You can use time to measure the distance traveled … you can travel about 1 to 2 miles per hour on a trail but less than this if you are bushwhacking.

End of Compass SectionEnd of Compass Section

Next section

G. P. S.

Global Positioning System