map reading section 3 - b continuation of compass section
TRANSCRIPT
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