Vertical Scale:	-4.00 to +6.00 ODN (Ordnance Datum Newlyn). Note that ODN level figures are usually much lower than CD Chart Datum level figures. Chart Datum 0.00 will be close to LAT
Horizontal Scale:	Is in TIDEMINUTES (like LIGHTYEARS only a little shorter!) The places are shown at distances proportional to the time High Water takes to travel between them. Tides here all travel North to South (Right to left). From Wick to Sheerness takes the tide about 13.5 hours. There is a tidal wave approaching at 38 miles per hour!
Cues:	HAT Highest Astronomical Tide; LAT Lowest Astronomical Tide; SPRINGS (MHWS)Mean High Water Springs; NEAPS (MHWN)Mean High Water Neaps; PRE PREdicted level without surge.
Updating?	The graphs from which the figures come are renewed only every 30 minutes or so. But they contain the Predicted levels for the rest of the day to a resolution of about 5 minutes. The levels shown are on the basis of the Predicted level now plus the surge at the original time.