Transcript Plotting a bearing on your map

Plotting a bearing on your map
Castle Rock
Quad
• You have just located the first point in an
orienteering course. The clue indicates that
the next location is 1.2km away on a
bearing of 286° True. Your GPS indicates
that you are currently at 586362m E
4113408m N.
• Use the Castle Rock Quad and follow along
as we locate our next course point.
You can use your compass
as a protractor
Plotting a bearing on your map
• You have just located the second point in an
orienteering course. The clue indicates that
the next location is 1.9km away on a
bearing of 138° True. Your GPS indicates
that you are currently at 585220m E
4113710m N.
• Use the Castle Rock Quad and follow along
as we locate our next course point.
Plotting a Magnetic Bearing
• Standing at a known road junction, we sight
a bearing to a nearby mountain top. We get
234° Magnetic as our bearing.
• The local declination is 15°E
so we add 15° to 234° to get 249° True.
Plotting a Magnetic Bearing
• We set our compass to 249°
• We line the north-south parallel lines in the
bezel up with a north-south line on the map.
• We move the compass until the edge is on
the road junction.
• We draw the bearing line onto the map.
Plotting a Magnetic Bearing
Getting a Bearing from the Map
• Place the edge of the compass along the
desired line of travel.
• Rotate the bezel until it is lined up with true
north.
• Read the true bearing
• Convert to magnetic by subtracting the 15°
declination.
Compass Plotting Exercise
• Castle Rock USGS Quadrangle
• What is the true bearing from White Rock
to the small pond just west of Zayante
Road?
• What is the magnetic bearing?
• What water feature might you be looking at
from White Rock at a bearing of 208° M?
Orienting your map
using your compass
• Adjust the compass to look like the
declination diagram.
• Set the compass down on the map with its
edge parallel to a true north line.
• Rotate the map and compass until the
magnetic needle is boxed.
• Don’t do this on a metal surface.