CONVIS and visual prominence

[Christian-Shom]

I have found nothing in the guidance document on how attribute values for S-57 CONVIS will be converted to S-101 attribute visual prominence.
I remember this has been discussed during one S-101PT meeting, but I can't remember which one...
I suggest the following:

• S-57 CONVIS=1 --> S-101 visual prominence=1 (visually conspicuous)
• S-57 CONVIS=2 (not visually conspicuous) --> S-101 visual prominence=3 (prominent)
• S-57 CONVIS=empty value (null) --> S-101 visual prominence=empty (null)
• S-57 CONVIS=Not populated (notNull) --> S-101 visual prominence=2 (not visually conspicuous)

This is based on how Shom has been using value 2 in S-57. Other data producers may have a different rule.