
Appendix A. CSAT3B Orientation
A-2
Declination angles are always subtracted from the compass reading to find
True North. A declination angle East of True North is reported as positive a
value and is subtracted from 360 (0) degrees to find True North as shown
. A declination angle West of True North is reported as a negative
value and is also subtracted from 0 (360) degrees to find True North as shown
. Note that when a negative number is subtracted from a
positive number, the resulting arithmetic operation is addition.
For example, the declination for Longmont, CO (10 June 2006) is 9.67 degrees
(the angle is East of True North, so it is reported as positive), thus True North
is 360 degrees
˗
9.67 degrees, or 350.33 degrees as read on a compass.
Likewise, the declination for Mc Henry, IL (10 June 2006) is
˗
2.68 degrees,
and True North is 0 degrees
˗
(
˗
2.68 degrees), or 2.68 degrees as read on a
compass.
FIGURE A-2. A declination angle east of true north (positive) is
subtracted from 360 (0) degrees to find true north
FIGURE A-3. A declination angle west of true north (negative) is
subtracted from 0 (360) degrees to find true north