K-Index for Compass Swings

The numerical value of the K Index for each 3 hour interval is indicated with each bar graph. Green bars indicate conditions where compass swings could be executed without a risk, whereas red bars indicate conditions where accuracy risks may be encountered if a compass swing is to be done against a non-magnetic reference. The right-most bar graph indicates the preliminary K Index for the new 3-hourly interval, calculated in real time for the past 3 hours at any given time. This bar is the best estimate of the current magnetic conditions and would thus be the indication used by the SAAF to determine whether a compass swing could be executed.

Thus, before a compass swing is executed, the SAAF personnel would check the last (right-most) bar on the K Index. If the bar on the right is green, the compass swing can be executed. If the bar on the right is red the compass swing should be postponed to a magnetically quieter time.