A Rolling period diagram is -

1. Way to find at any given time, the GM of the ship
2. Used by the ship up to 70 meters in length
3. The formula used for calculation is GM = (fB/T)^2; where
f= factor for the rolling period or rolling period coefficient
B=Breadth of the ship
T= time taken by the ship to complete one full roll

4. The roll is started by swinging a weight of centre line or men running on the deck in unison
5. Once the rolling is induced, time is noted down for the 5 or more continuous rolls using a stopwatch
6. The average value of T is found
7. GM is then calculated