| ta || Approximate mean sea-level
|-
| tb = || Local
| tc = || Local LWM
| td = || Local MSL
| te = || Mean sea-level
| tf = || None
| tg = || Arbitrary
| th = || Mean low water
| ti = || Mean low water Springs
|| tj = Mean lower low water
| tk = || Mean lower low water Springs
| tl = || Lowest normal low water
| tm = || Lowest low water
| tn = || Indian Spring low water
| to = || at or near the level of lowest astronomical tide
| uu = || unknown vertical datum
| zz = || other known vertical datum
|}