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Frequently asked questions
Typical tidal clock
Tide clocks
Most tide clocks work by using a 12 hour 25 minute cycle. Generally in the UK and Ireland they would vary in accuracy between plus or minus 30 minutes over a 30 day period. Therefore it is necessary to reset them using local tide tables every month or so.
Tidal/tide watches
Typical tidal watch
Some watches with a moon/tide mode require lunitidal intervals for predicting high and low waters.
High water lunitidal intervalThe high water lunitidal interval (or high water interval) is the time interval between the moon's transit and the next high water. The interval may be taken from the local time of moon's transit to the local time of high water, or it may be taken from the Greenwich time of the moon's transit to the standard time of high water.
Mean high water interval
The mean high water interval is the mean value of all the high water intervals throughout at least a lunation of 29 days.
Use the table below to set the moon/tide mode of your watch
Mean lunitidal intervals (mean high water intervals) have been calculated using
Interval (hrs) = M2 phase (degrees) x M2 period (hrs) / 360 (degrees)
These values should be sufficient information for watches that use the lunitidal interval to indicate high and low waters. (List below ordered by latitude.)
Please note:
If your UK location is not mentioned try using the nearest one or average between the two nearest ports on either side.
This is not guaranteed to work. Check your watch against local tide tables to confirm your setting.
| Port/Location | Latitude | Longtiude | Interval (hrs : mins) |
| ST. HELIER | 49° 11'N | 2° 7'W | 6:18 |
| ST. MARY'S | 49° 55'N | 6° 19'W | 4:31 |
| NEWLYN | 50° 6'N | 5° 33'W | 4:36 |
| FALMOUTH | 50° 9'N | 5° 3'W | 5:02 |
| PLYMOUTH (DEVONPORT) | 50° 22'N | 4° 11'W | 5:18 |
| NEWQUAY | 50° 25'N | 5° 5'W | 4:53 |
| TORQUAY | 50° 28'N | 3° 31'W | 5:51 |
| PORTLAND | 50° 34'N | 2° 26'W | 6:40 |
| WEYMOUTH | 50° 36'N | 2° 27'W | 6:36 |
| BOURNEMOUTH | 50° 43'N | 1° 52'W | 9:24 |
| CHRISTCHURCH (QUAY) | 50° 44'N | 1° 46'W | 10:37 |
| LYMINGTON ENTRANCE | 50° 44'N | 1° 30'W | 11:02 |
| ISLE OF WIGHT - COWES | 50° 46'N | 1° 18'W | 11:21 |
| NEWHAVEN | 50° 47'N | 0° 3'E | 11:05 |
| PORTSMOUTH | 50° 48'N | 1° 7'W | 11:16 |
| LITTLEHAMPTON | 50° 48'N | 0° 32'W | 11:08 |
| SHOREHAM | 50° 50'N | 0° 15'W | 11:06 |
| DUNGENESS | 50° 54'N | 0° 58'E | 11:14 |
| SOUTHAMPTON | 50° 54'N | 1° 24'W | 11:19 |
| DOVER | 51° 7'N | 1° 19'E | 11:27 |
| ILFRACOMBE | 51° 13'N | 4° 7'W | 5:36 |
| HINKLEY POINT | 51° 13'N | 3° 8'W | 6:19 |
| MINEHEAD | 51° 13'N | 3° 28'W | 6:11 |
| MARGATE | 51° 24'N | 1° 23'E | 11:47 |
| SHEERNESS | 51° 27'N | 0° 45'E | 12:12 |
| TILBURY | 51° 27'N | 0° 22'E | 0:18 |
| NORTH WOOLWICH | 51° 30'N | 0° 5'E | 0:44 |
| SHIVERING SANDS | 51° 30'N | 1° 5'E | 11:59 |
| LONDON BRIDGE | 51° 30'N | 0° 5'W | 1:10 |
| AVONMOUTH | 51° 31'N | 2° 43'W | 6:57 |
| SOUTHEND | 51° 31'N | 0° 43'E | 12:11 |
| CORYTON | 51° 32'N | 0° 31'E | 12:24 |
| NEWPORT | 51° 33'N | 2° 59'W | 6:44 |
| MUMBLES | 51° 34'N | 3° 59'W | 5:57 |
| SWANSEA | 51° 37'N | 3° 55'W | 5:57 |
| MILFORD HAVEN | 51° 42'N | 5° 3'W | 5:58 |
| RINGASKIDDY | 51° 50'N | 8° 19'W | 5:15 |
| COBH | 51° 50'N | 8° 18'W | 5:09 |
| WALTON-ON-THE-NAZE | 51° 51'N | 1° 16'E | 11:25 |
| CORK CITY | 51° 54'N | 8° 27'W | 4:15 |
| HARWICH | 51° 57'N | 1° 17'E | 11:18 |
| MISTLEY QUAY | 51° 57'N | 1° 5'E | 11:30 |
| FELIXSTOWE | 51° 57'N | 1° 21'E | 11:05 |
| FISHGUARD | 52° 1'N | 4° 59'W | 7:09 |
| ROSSLARE HARBOUR | 52° 15'N | 6° 21'W | 5:25 |
| BARROW BRIDGE | 52° 16'N | 7° 0'W | 5:25 |
| ABERYSTWYTH | 52° 25'N | 4° 6'W | 7:55 |
| LOWESTOFT | 52° 28'N | 1° 45'E | 8:57 |
| GORLESTON | 52° 34'N | 1° 44'E | 8:17 |
| RIVER SHANNON TARBERT ISLAND | 52° 35'N | 9° 22'W | 5:17 |
| BARMOUTH | 52° 43'N | 4° 3'W | 8:14 |
| KING'S LYNN | 52° 45'N | 0° 24'E | 6:34 |
| WEST LIGHTHOUSE | 52° 49'N | 0° 13'E | 6:17 |
| WEST STONES | 52° 49'N | 0° 21'E | 6:19 |
| ROARING MIDDLE (WASH) | 52° 55'N | 0° 18'E | 6:04 |
| TABS HEAD | 52° 56'N | 0° 5'E | 6:13 |
| HUNSTANTON | 52° 56'N | 0° 29'E | 6:11 |
| CROMER | 52° 56'N | 1° 18'E | 6:29 |
| GIBRALTAR POINT | 53° 5'N | 0° 20'E | 5:54 |
| SKEGNESS | 53° 9'N | 0° 21'E | 5:47 |
| GALWAY | 53° 16'N | 9° 3'W | 4:50 |
| BOYGRIFT | 53° 18'N | 0° 18'E | 5:38 |
| EASTHAM | 53° 19'N | 2° 57'W | 11:22 |
| HOLYHEAD | 53° 19'N | 4° 37'W | 10:04 |
| INNER DOWSING (WASH) | 53° 19'N | 0° 35'E | 5:35 |
| LLANDUDNO | 53° 20'N | 3° 49'W | 10:41 |
| DUBLIN (NORTH WALL) | 53° 21'N | 6° 13'W | 11:16 |
| HILBRE ISLAND | 53° 23'N | 3° 13'W | 10:57 |
| BIRKENHEAD (ALFRED LOCK) | 53° 24'N | 3° 1'W | 11:09 |
| LIVERPOOL (PRINCES PIER) | 53° 25'N | 3° 0'W | 11:09 |
| LIVERPOOL (GLADSTONE LOCK) | 53° 27'N | 3° 1'W | 11:04 |
| BULL SAND FORT | 53° 33'N | 0° 4'E | 5:16 |
| SPURN POINT | 53° 35'N | 0° 7'E | 5:12 |
| IMMINGHAM | 53° 38'N | 0° 11'W | 5:35 |
| BLACKTOFT | 53° 41'N | 0° 42'W | 6:58 |
| HULL | 53° 44'N | 0° 21'W | 5:59 |
| WITHERNSEA | 53° 44'N | 0° 2'E | 4:37 |
| FLEETWOOD | 53° 55'N | 3° 0'W | 11:15 |
| HEYSHAM | 54° 2'N | 2° 55'W | 11:14 |
| HALFWAY SHOALS | 54° 2'N | 3° 12'W | 11:11 |
| ROA ISLAND | 54° 4'N | 3° 10'W | 11:20 |
| PORT ERIN | 54° 5'N | 4° 46'W | 11:05 |
| BARROW (RAMSDEN DOCK) | 54° 6'N | 3° 13'W | 11:24 |
| DOUGLAS | 54° 9'N | 4° 28'W | 11:16 |
| SCARBOROUGH | 54° 17'N | 0° 23'W | 3:49 |
| WHITBY | 54° 29'N | 0° 37'W | 3:35 |
| BELFAST | 54° 36'N | 5° 55'W | 10:54 |
| RIVER TEES ENTRANCE | 54° 38'N | 1° 9'W | 3:18 |
| WORKINGTON | 54° 39'N | 3° 34'W | 11:27 |
| BANGOR (N.IRELAND) | 54° 40'N | 5° 40'W | 10:57 |
| PORTPATRICK | 54° 51'N | 5° 7'W | 11:27 |
| LARNE | 54° 51'N | 5° 47'W | 10:55 |
| RIVER TYNE (NORTH SHIELDS) | 55° 0'N | 1° 26'W | 3:04 |
| LONDONDERRY | 55° 0'N | 7° 19'W | 8:10 |
| COLERAINE | 55° 10'N | 6° 46'W | 6:50 |
| PORTRUSH | 55° 12'N | 6° 40'W | 6:47 |
| MALIN HEAD | 55° 18'N | 7° 15'W | 6:07 |
| ISLAY (PORT ELLEN) | 55° 38'N | 6° 11'W | 3:07 |
| MILLPORT | 55° 45'N | 4° 54'W | 11:49 |
| GREENOCK | 55° 58'N | 4° 49'W | 11:55 |
| LEITH | 55° 59'N | 3° 11'W | 1:54 |
| ROSYTH | 56° 1'N | 3° 27'W | 1:53 |
| OBAN | 56° 25'N | 5° 29'W | 5:38 |
| TOBERMORY | 56° 37'N | 6° 4'W | 5:49 |
| ABERDEEN | 57° 9'N | 2° 4'W | 0:50 |
| MORAY FIRTH | 57° 36'N | 4° 0'W | 11:37 |
| CROMARTY FIRTH | 57° 41'N | 4° 1'W | 11:33 |
| ULLAPOOL | 57° 54'N | 5° 9'W | 6:55 |
| STORNOWAY | 58° 12'N | 6° 23'W | 6:49 |
| WICK | 58° 26'N | 3° 5'W | 11:07 |
| KINLOCHBERVIE | 58° 27'N | 5° 3'W | 7:10 |
| LERWICK | 60° 9'N | 1° 8'W | 10:45 |
| SULLOM VOE | 60° 27'N | 1° 18'W | 9:13 |
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