Paul BrownTides – Chartwork 2 nd Class Chartwork 2 nd Class Tides (Adapted from RYA Shorebased slides)

Paul BrownTides – Chartwork 2 nd Class What Causes Tides? Gravitational effects of the moon (and sun) which exert a pull on the water on the Earth's surface. What terms have you heard relating to tides? High Slack Ebb Flood Neap Range Stand Low Spring

Paul BrownTides – Chartwork 2 nd Class TIDES Sun Earth Moon

Paul BrownTides – Chartwork 2 nd Class TIDES - SPRINGS Earth New Moon Sun

Paul BrownTides – Chartwork 2 nd Class TIDES - SPRINGS Earth Full Moon Sun

Paul BrownTides – Chartwork 2 nd Class TIDES - NEAPS Earth First Quarter Neaps Sun

Paul BrownTides – Chartwork 2 nd Class TIDES - NEAPS Sun Earth Last Quarter Neaps

Paul BrownTides – Chartwork 2 nd Class TIDE TABLE 18 TH m m m HW LW Range 4.1 metres GMT

Paul BrownTides – Chartwork 2 nd Class TIDE TABLE 18 TH m m m Add an hour for British Summer Time

Paul BrownTides – Chartwork 2 nd Class TIDAL HEIGHTS - DEFINITIONS Chart Datum Charted depth (sounding) MHWS MLWS MLWN MHWN Depth of water Charted height Drying height

Paul BrownTides – Chartwork 2 nd Class TIDAL DIAMONDS & DATUMS Tidal streams referred to HW at PLYMOUTH

Paul BrownTides – Chartwork 2 nd Class TIDAL DIAMONDS & DATUMS 3 hours before HW Stream setting towards 318(T) Springs 2.9 kn Neaps 1.5 kn

Paul BrownTides – Chartwork 2 nd Class TIDAL CURVE

Paul BrownTides – Chartwork 2 nd Class TIDAL CURVE Look up time and height of HW Dartmouth and height of LW HW Dartmouth 1815 BST 4.8m LW 0.7m Is it Neaps or Springs? Close to Springs Use curve to find: Height of tide at Dartmouth at 1415

Paul BrownTides – Chartwork 2 nd Class TIDAL CURVE LW height 0.7m entered here HW height 4.8m entered here HW Dartmouth 1815 BST 4.8m LW 0.7m

Paul BrownTides – Chartwork 2 nd Class TIDAL CURVE HW Dartmouth 1815 BST 4.8m LW 0.7m Draw a line joining the points

Paul BrownTides – Chartwork 2 nd Class TIDAL CURVE HW Dartmouth 1815 BST 4.8m LW 0.7m Write time of HW in box below 1815

Paul BrownTides – Chartwork 2 nd Class TIDAL CURVE HW Dartmouth 1815 BST 4.8m LW 0.7m Write subsequent hours in boxes

Paul BrownTides – Chartwork 2 nd Class TIDAL CURVE Draw vertical line from 1415 to spring curve HW Dartmouth 1815 BST 4.8m LW 0.7m

Paul BrownTides – Chartwork 2 nd Class TIDAL CURVE Draw horizontal line from curve to diagonal line HW Dartmouth 1815 BST 4.8m LW 0.7m

Paul BrownTides – Chartwork 2 nd Class TIDAL CURVE Draw perpendicular to HW line Height of tide at 1415 = 2.9m

Paul BrownTides – Chartwork 2 nd Class RULE OF TWELFTHS 1st hour 1/12 2nd hour 2/12 3rd hour 3/12 4th hour 3/12 5th hour 2/12 6th hour 1/12 HW +1h +2h +3h +4h +5h LW

Paul BrownTides – Chartwork 2 nd Class TIDAL STREAM ATLAS Atlas gives Direction & Rate of tidal stream for each hour 4 hours after HW PORTSMOUTH

Paul BrownTides – Chartwork 2 nd Class TIDAL STREAM ATLAS Thick and long arrows show strong stream Short and thin arrows show weak stream 4 hours after HW PORTSMOUTH

Paul BrownTides – Chartwork 2 nd Class TIDAL STREAM ATLAS 03,05 Rate of stream 0.3 kn at Neaps 0.5 kn at Springs 12,23 Rate of stream 1.2 kn at Neaps 2.3 kn at Springs Stream Slack