The Compass
Some History• As far back as 2500 BCE the Chinese knew  that a loadstone on a piece of floating wood,  would always point ...
The Modern Compass• Modern compasses typically have a  magnetic needle or capsule that floats freely  on a central pivot, ...
Angular Measurement• A compass will have a angular measurement ring to  observe the angle between the compass needle and t...
Sighting Mechanism• Many compasses include some mechanism  for sighting to a distant point to measure the  angle of the li...
Other Features Abound•   Distance Scales•   Magnifying Lens•   Slope Measurement•   etc…
Compass Uses• In wilderness navigation a compass is used  to do the following.  –   General orientation to the 4 cardinal ...
A Look at Some Common    Compass Types
Zipper Pull Compass• Good for general  direction
Lensatic• 5° markings• So-so for sighting• Useless for plotting
Baseplate• 2° markings• Good for map plotting• Hard to sight on  a distant object
Mirrored•   2° markings•   Good for sighting•   Good for plotting•   May have    adjustable declination
Sighting Baseplate•   1° markings•   Best for sighting•   Good for plotting•   No declination    adjustment• My personal f...
Parts of a compass
Taking a bearing to an object• Sight to the object with the compass.• Turn the ring to align the orienting arrow  with the...
Needle ParallaxView from Above   View from Behind
Parallax Side View
Needle Parallax      Good                         BadKeep the needle parallel to the meridian lines.
Taking a back bearing• A back bearing is taken looking back to  where you took the original bearing.• A back bearing is 18...
Classroom compass exercise•   Pair up with another student•   Take a bearing and a back bearing on each other.•   Bearings...
Compass
Upcoming SlideShare
Loading in …5
×

Compass

779 views
684 views

Published on

Published in: Technology, Business
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total views
779
On SlideShare
0
From Embeds
0
Number of Embeds
1
Actions
Shares
0
Downloads
0
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

Compass

  1. 1. The Compass
  2. 2. Some History• As far back as 2500 BCE the Chinese knew that a loadstone on a piece of floating wood, would always point itself in the same direction.• Later with the move from bone to iron needles, it was noticed that an iron needle placed near a loadstone would also take on these directional properties.
  3. 3. The Modern Compass• Modern compasses typically have a magnetic needle or capsule that floats freely on a central pivot, so that it can align itself with the earth’s magnetic field.• Electronic compasses, with no moving parts, are made by measuring small currents in coils of wire, induced by the earth’s magnetic field.
  4. 4. Angular Measurement• A compass will have a angular measurement ring to observe the angle between the compass needle and the compass body.• The most common angular measurement system is a 360° circle.• Other systems include – Four 90° quadrants – Mills, a system that divides a circle into 6400 parts – Avoid these for wilderness navigation purposes
  5. 5. Sighting Mechanism• Many compasses include some mechanism for sighting to a distant point to measure the angle of the line to that object relative to the compass needle.
  6. 6. Other Features Abound• Distance Scales• Magnifying Lens• Slope Measurement• etc…
  7. 7. Compass Uses• In wilderness navigation a compass is used to do the following. – General orientation to the 4 cardinal directions – Taking a bearing to a distant object – Traveling along a heading – Plotting or measuring a bearing on a map • This is using the compass as an expensive protractor, and does not use it’s magnetic direction capabilities.
  8. 8. A Look at Some Common Compass Types
  9. 9. Zipper Pull Compass• Good for general direction
  10. 10. Lensatic• 5° markings• So-so for sighting• Useless for plotting
  11. 11. Baseplate• 2° markings• Good for map plotting• Hard to sight on a distant object
  12. 12. Mirrored• 2° markings• Good for sighting• Good for plotting• May have adjustable declination
  13. 13. Sighting Baseplate• 1° markings• Best for sighting• Good for plotting• No declination adjustment• My personal favorite!
  14. 14. Parts of a compass
  15. 15. Taking a bearing to an object• Sight to the object with the compass.• Turn the ring to align the orienting arrow with the red end of the magnetic needle.• Read the bearing from the ring at the index line.
  16. 16. Needle ParallaxView from Above View from Behind
  17. 17. Parallax Side View
  18. 18. Needle Parallax Good BadKeep the needle parallel to the meridian lines.
  19. 19. Taking a back bearing• A back bearing is taken looking back to where you took the original bearing.• A back bearing is 180° different from a forward bearing.• An easy technique is to align the south end of the needle rather than the north end.
  20. 20. Classroom compass exercise• Pair up with another student• Take a bearing and a back bearing on each other.• Bearings should agree within +/- 2°• Try other positions in the classroom• Try using other types of compasses

×