mWL hHWLT hHWMT lLWMT lLWLT lNT
A list of the tidal surfaces presently used in Canadian waters is given below (Canadian Tidal Manual, 1983). Designations for U.S. and British Admiralty charts are not directly comparable.
mWL: (Mean Water Level) The average of all hourly water levels over the available period of record.
hHWLT: (Higher High Water, Large Tide) The average of the highest high waters, one from each of the 19 years of prediction.
hHWMT: (Higher High Water, Mean Tide) The average of all the higher high waters from 19 years of predictions.
lLWMT: (Lower Low Water, Mean Tide) The average of all the lowest low waters from all the 19 years of prediction.
lLWLT: (Lowest Low Water, Large Tide) The average of the lowest low waters, one from each of the 19 years of prediction.
lNT: (Lowest Normal Tide) In present usage it this is synonymous with the lLWLT, but on older charts may refer to a variety of low water chart datums.