|
|
| |
| If you do not know where you are. Or if you are in open featureless
country, you will have to orientate the map by compass. The best way is
to work out the magnetic variation (MV) from grid north; then lay the compass
so that its north-south axis lies along any north-south grid line and turn
the map until the north point on the compass points north and slightly east
or west of the lubber line by the amount of the variation. If however you
use a SILVA compass, the MV can he set on the compass. The map will then
he accurately orientated. |
| |
|
| In order to find out the MV from grid north, refer
to the top centre of the map to work out the current variation. On MS 99
it can he seen that the MV in June 1999 is 89mils west of grid north, with
an annual change of about 2 mils east. The current MV, in 2001 is 85 mils
west. |
| |
|
| The drawings below show the method of orientating a map using
a SILVA compass and a prismatic compass with a milled vane. In both cases
the MV of 85 mils west is used. |
| |
|
 |
|
