🆕Tidal Boundary Continuous High Description Value

This page details upcoming data that will be provided for the new Tidal Boundary Continuous High Description Value Code List in the OS NGD from the end of September 2025 to give you early insight. This code list is currently not available through the live access services. The information on this page is as accurate as possible, but is subject to change before launch.

This code list is used in association with the Description attribute which is present within the Tidal Boundary Continuous High Feature Type. The code list describes the state of the tide that the feature represents (for example, Mean High Water or Normal Tidal Limit).

Label	Definition
Mean High Water	The average alignment of the high tide line that occurs halfway between spring and neap tides. Represented in England and Wales only.
Mean High Water Springs	The average alignment of the high tide line that occurs when the effects of the sun and moon are in alignment, resulting in a larger than normal tidal range. Represented in Scotland only.
Normal Tidal Limit	The highest point in tidal rivers to which mean tides (in Scotland, mean spring tides) flow at high water where there is no other feature present.