This document is an introduction to how to handle swell in the EIVA offline SW suite.
Swell on bathy generated from surface waves on ROV working in shallow water cannot be smoother away from bathy directly, as this would also smooth the ROV movements in bathy.
If a Doppler is present, Kalman3D filter will use Doppler data in filtering the bathy (and the position) this way removing swell from bathy.
If no Doppler is present Kalman 3D will not filter bathy correct, but just smooth it.
Instead the swell effect on a pipe or flat seabed can be smoothed, and the difference from before smoothing can be added to the bathy, this way swell is reduced in bathy by means of the expected local straightness of a pipe or the short term seabed flatness.