Brunton ECLIPSE 8099 Manual De Instrucciones página 9

9. Keeping the clear base stationary on the map,
rotate azimuth ring until blue orienting circle
points in a northerly direction, and the
on graduated circle are aligned with the drawn
true north-south lines (figure 21).
10. Read bearing from the green scale in magnified
index lens (figure 21).
If using a map other than a USGS or BLM map,
check that the map's margin is aligned to true
north. If not aligned, it is necessary to draw true
north-south lines from the true north indicator
(indicated by an arrow with an "N" or a star).
Then, find map bearing.
8 -- Triangulation
In this section, you will determine field bearings to
three visible landmarks and plot them as map bearings.
The intersection of the bearing lines indicate your approximate position. A landmark can be a
mountain peak, a cliff, or any visible object displayed on your map. The following example uses a
USGS topo-map, and forward mirror sighting for bearing determination.
1. Adjust for magnetic declination.
2. Find three prominent landmarks in the field.
3. Orient the map to true north.
· See Section 7.1, Map Alignment, for help.
4. Find all three landmarks on the map, place an 'X' at the positions and label them '1', '2' & '3'
(figure 22).
1
red lines
Figure 21
2
Figure 22
3
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5. Sight a field bearing to
landmark '1' – 320° (green
scale), this example.
· See Section 4.1, Forward
Mirror Sighting, for help.
6. With both covers open to
180°, place clear base of
compass next to landmark
'1', on the map.
7. With green scale set to
320°, pivot compass around
landmark '1' until blue
orienting circle outlines red
circled "N" (figure 23).
8. Draw the 320° map bearing
line using the side of the
base, passing through
landmark '1'.
· Your position is some
where along this line
(figure 23).
9. Repeat process for
landmarks '2' (50°) and
'3' (90°).
Either a point or a small
triangle will form at the
intersection of the three
lines. Your position is at
the point, or within the
small triangle (figure 24).
Figure 24
Figure 23
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