Hi Rudy: I have not seen the term of air clearance on the charts. The appropriate term Vertical clearance is still used.  Here in Canada the charts refer to vertical clearance from higher high water .Regards Leonard Stern, INDIFFERENCE

It seems to be a rather accepted term: https://en.wikipedia.org/wiki/Air_draft https://www.dco.uscg.mil/Portals/9/TVNCOE/Documents/SafetyAlerts/AirDraft.pdf?ver=2017-08-11-142836-740

I think vertical clearance is more used for fixed objects. It relates to tidal activity, chart datum, how much extra is left beyond the exact amout when you're talking catenary of 10,000v cable, etc. Air draft is the movable vessel and doesn't concern tides, charts and such like. Match the two = happy camper. Mismatch = sadness... On Mon, 23 Sep. 2019, 12:36 pm Al Thomason via Trawlers-and-Trawlering, < trawlers@lists.trawlering.com> wrote: > It seems to be a rather accepted term: > > https://en.wikipedia.org/wiki/Air_draft > > > > https://www.dco.uscg.mil/Portals/9/TVNCOE/Documents/SafetyAlerts/AirDraft.pdf?ver=2017-08-11-142836-740 > > > > > > > > _______________________________________________ > http://lists.trawlering.com/mailman/listinfo/trawlers_lists.trawlering.com > > To unsubscribe or modify your subscription options (get password, change > email address, etc) go to: > http://lists.trawlering.com/mailman/listinfo/trawlers_lists.trawlering.com > Trawlers & Trawlering and T&T are trademarks of Water World > Productions. Unauthorized use is prohibited. >

What he said! Rich Gano Frolic (2005 Mainship 30 Pilot II) Panama City area Subject: Re: T&T: Terminology Questions I think vertical clearance is more used for fixed objects. It relates to tidal activity, chart datum, how much extra is left beyond the exact amout when you're talking catenary of 10,000v cable, etc. Air draft is the movable vessel and doesn't concern tides, charts and such like. Match the two = happy camper. Mismatch = sadness...