2
4. Sight a bearing
1. Keep both eyes open and look through optics towards
target object. An optical illusion makes the object and
sighting line appear to overlap, allowing an accurate
reading.
2. Read value from sighting line.
The main scale is the bearing from you to the object. The
secondary scale is the reverse bearing from the object to you.
NOTE: IF YOUR EYES ARE NOT PARALLEL, AS IN THE CASE OF
HETEROPHORIA, YOU MAY NEED TO SIGHT WITH ONE EYE.
CHECK BY FIRST TAKING A READING WITH BOTH EYES OPEN.
THEN CLOSE THE EYE LOOKING AT THE OBJECT. IF YOUR
READING CHANGES SIGNIFICANTLY, USE JUST ONE EYE TO
SIGHT OBJECT AND TAKE READING.
5. Triangulation
You can sight two or more bearings and use triangulation to
accurately determine where you are.
1. Take reverse bearing of at least two objects visible from
your viewpoint and indicated on your map.
2. Using a protractor and straight line tool, draw lines on map
from position of objects according to measured bearings.
3. Estimate your current position based on where the lines
intersect.
A
10
0
350
190
180
170
N
S
E
W
B
2
1
1
2
90
90
180
0
180
0
