Great idea.
What is the time interval represented by your kymograph?
From the time interval one can jnfer the period of the oscillation w/ assumption about hull length.
If you had to guess, do you think your kymograph is measuring pitch, roll, or yaw?
[POTUS] quarters facing direction of travel or perpendicular to it?
Data on average pitch, roll, and yaw periodicity for warships?
Have you used a higher resolution (less than one sec intervals) and if so does the kymograph show high-frequency oscillations?
There are three special axes in any ship, called longitudinal, transverse and vertical axes. The movements around them are known as roll, pitch, and yaw respectively.
Pitch
The up/down rotation of a vessel about its transverse/Y (side-to-side or port-starboard) axis. An offset or deviation from normal on this axis is referred to as trim or out of trim.
Roll
The tilting rotation of a vessel about its longitudinal/X (front-back or bow-stern) axis. An offset or deviation from normal on this axis is referred to as list or heel. Heel refers to an offset that is intentional or expected, as caused by wind pressure on sails, turning, or other crew actions. The rolling motion towards a steady state (or list) angle due to the ship's own weight distribution is referred in marine engineering as heel. List normally refers to an unintentional or unexpected offset, as caused by flooding, battle damage, shifting cargo, etc.
Yaw
The turning rotation of a vessel about its vertical/Z axis. An offset or deviation from normal on this axis is referred to as deviation or set. This is referred to as the heading of the boat relative to a magnetic compass (or true heading if referenced to the true north pole); it also affects the bearing.
May be some roll in the timeseries too.
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0206476