Last week I saw a discussion initiated by Daniyar at Schlumberger asking what LTL means. I have not encountered this terminology before, either in offshore operations or as a part-time yachtsman.
Nevertheless, I would bring to your attention an alternative datum, Lowest Astronomical Tide (LAT). It is defined as 'the lowest level to which the tide is ever predicted to fall, without allowing for possible meteorological effects.'
The Chart Datum (CD) for navigational charts for UK and other waters in North West Europe corresponds to LAT.
I attach a cartoon from UKHO Chart 5011 Ed 2 1998 which depicts CD, LAT and other tidal levels in everyday global use for marine operations. Trust this helps.
________Note from moderator:
Thanks, Tim. I had actually deleted the original post, and. few others, because it felt like some of the authors are using SPREAD instead of Google and/or turning to it before making any effort themselves to find the answer. Over the years that is the feedback we have had from some of our respected members.
Whilst we appreciate that at this time of COVID-19, it may not so easy to turn to a colleague or walk down the corridor to ask a more learned person, we do ask the members to respect that this forum is designed to test out ideas and seek alternative opinions rather than as a source of (very basic) knowledge.