Indeed some de-cluttering sometimes may be necessary, but plain filtering out Class B seems unfair ... Maybe just enhance the display/warning/alarm system instead?
Much more often than Class B one encounters problems with dense Class A traffic ... When entering a busy harbour shorthanded, fiddling with many filter/alarm settings, etc. is quite distracting.
So, just filtering out Class B will help only in very few cases. Also, quite large vessels carry Class B transponders - I do not want 300 tons filtered out with all the small boats. On the other hand, more and more yachts around 20m LOA
carry Class A.
Some interim measures could be taken to show a lighter icon for these presumably smaller vessels ( some time ago I experimented with a smaller size ). Many nav programs show Class B as tiny circle, but I never got used to that, since it just does not _look_ like a ship. However, the main thinking should be about coping with AIS congestion in general, not just Class B.
What one might do (just thinking aloud)?
- limit the range of displayed targets (already available in the target list, but not on the chart)
- limit the warnings/alarms per CPA/TCPA (already available, but perhaps specify limits per vessel size <24m | >24m, or at least per-Class, not one-limit-for-all)
- reduce the work needed to handle the alarms ( 1. allow manual acknowledge by any keypress, without delicate mouse pointing; 2. optionally set automatic acknowledgement after 1-2-3... alarm
rings, so no need to go below to handle the keyboard )
- make the icons reflect actual size of the vessel (already available? but maybe progressively drop the smaller ones from display as one zooms out, stepping through COLREGS ranges 7m-12m, 24m, 50m, 100+m, or select minimum size to show in the Target List dialog).
- show very condensed Dangerous Target list only, sorted by CPA/TCPA, with ability to display on chart just selected/dangerous targets (probably this is most important, and this is what big ships have).
By example, Furuno
ECDIS allows quite flexible filtering/alarm strategies (attached), but next to it sits an MKD device, where no filtering is allowed at all, just switching between All/DangerousOnly target lists. OCPN operators usually have no MKD nearby...
It also might be, that in extreme cases AIS needs a separate screen, and a separate person to handle it ...