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Do as follows if there is a boundary on the map that you
wish to walk out in the terrain (Fig. 2)
Preparations prior to fi eldwork
1. Place the course protractor on the map with the cross over
the starting point of the boundary.
NOTE: The lower tip of the course protractor must point
down (south) on the map.
2. Keep the cross on the starting point and turn the course
protractor until the line on the protractor follows the
direction of the boundary on the map. Fig. 3
NOTE: The lower tip of the course protractor will no longer
point down (south). Make sure, however, that it does NOT
point up (north) on the map. It should point in a direction
on the map that is no more than due east or west.
3. Move the course protractor on the map along the boundary
until the cross, which was previously over the starting point
of the boundary, reaches a meridian. NOTE: Be careful not
to confuse meridians with coordinate system lines, such as
“Rikets nät” (Swedish grid), on the map. Fig. 4
4. Read off the boundary bearings from the scales found on
the lower edge of the graduated disc. The correct bearings
are where the meridian passes the scales. Fig. 5
NOTE: Select a scale based on in which direction the
boundary extends. If it goes in a southeast direction, use
the scale marked SO. If it goes in a northeast direction, use
the scale marked NO, etc.
5. Note the desired boundary bearing.
6. Magnetic declination which is normally specifi ed on the
map, must be taken into consideration to ensure bearings
are accurately obtained (If no declination is specifi ed, this
can be obtained from the local land survey authority or the
like).
The calculation can also be done on the Internet:
http://www.ngdc.noaa.gov/cgi-bin/seg/gmag/fl dsnth1.pl
NOTE: You must enter your approximate position in
latitude/longitude on this website to obtain the local
magnetic declination.
7. If declination is east (positive), the value should be
subtracted from the boundary bearing obtained with the
course protractor. If the declination is west (negative), the
value should be added to the boundary bearing obtained
with the protractor.
Example: Boundary bearing 147
°
with 3
°
east (positive)
declination gives an actual magnetic compass bearing of
144°.
8. Correct all compass bearings the same way and note them
so that they can be used in the fi eld when marking the
boundary in the terrain.
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Meridian
Read boundary bearing
Meridian
