Tidal Heights Table

Tidal Heights Table

Towards the bottom of RYA Training Chart 3 there is a table (Fig 2.37) that gives us some basic information about tidal heights in the area covered by the charts.

Screen Shot 2016-01-03 at 17.06.04There is a list of place names in the first column, with Victoria at the top, then a list of position coordinates pinpointing the exact location where the tidal height data was gathered. We are then given five columns of data corresponding to abbreviations of specific tidal levels. We can see from the column headings that this data is referred to Metres above Chart Datum (CD).

Screen Shot 2016-01-03 at 17.06.15We have already mentioned Chart Datum (CD) and encountered Highest Astronomical Tide (HAT) and Mean High-water Springs (MHWS) which are the levels where we take height measurements from. On this table other tidal levels are mentioned. Mean High Water Neaps (MHWN), the average hight of the highwater Neap tides. Mean Low Water Neaps, the average height of the low water Neap tides and MLWS which is the the average height of the low water Spring tides. All these discreet tidal levels are measured from Chart Datum (CD) which is down near LAT, the Lowest Astronomical Tide. Fig 2.38 illustrates these levels graphically. The locations listed on the table have the specific latitude and longitude positions and tell us how much water we have above chart datum at the specific heights of tide mentioned in the table, HAT, MHWS, MHWN, MLWN, MLWS.