Tides and Currents


Notes

  • Tide and Current predictions are not available for all areas.
  • As with all predictions, the displayed values are calculated using mathematical models and actual tides and currents will vary

Enable Tides and Currents Display

  • Click the toolbar button  to see tide stations.
  • Select  to see current stations.
  • Important: tide and currents will not be displayed unless these toolbar buttons are selected.

 

Displaying Tides

  • Available tide stations will show on the chart as green graphs with a "T" logo:
  • The "T" becomes a yellow and blue vertical bar when the scale is greater than 1:500.000



  • The vertical bar contains a lot of information at a glance.
  • The tidal rise is 2.5m above the chart datum. The blue part is "water". The  "V" inside he bar indicates that the tide is decreasing towards Low Water.
     
  • Here, the tide is rising towards High Water.
  • Low Water looks like this.
  • High Water Looks  like this.
  • Right click the middle of either icon to see the tidal graph:

 

  • The Yellow box, with the tidal rise and time, follows the cursor when hovering over the dialog. The time axis at the bottom displays the time, in this case he timezone is "Z +01:00", which is the same as one hour ahead (east) of UTC, that used to be called GMT.
  • In North America it is common to use a three or four letter acronym for timezones.

 

CODE
UNITED STATES TIME ZONE CODES
UTC OFFSET
AST
ATLANTIC STANDARD TIME
UTC - 4
EST
EASTERN STANDARD TIME
UTC - 5
EDT
EASTERN DAYLIGHT TIME
UTC - 4
CST
CENTRAL STANDARD TIME
UTC - 6
CDT
CENTRAL DAYLIGHT TIME
UTC - 5
MST
MOUNTAIN STANDARD TIME
UTC - 7
MDT
MOUNTAIN DAYLIGHT TIME
UTC - 6
PST
PACIFIC STANDARD TIME
UTC - 8
PDT
PACIFIC DAYLIGHT TIME
UTC - 7
AKST
ALASKA TIME
UTC - 9
AKDT
ALASKA DAYLIGHT TIME
UTC - 8
HAST
HAWAII-ALEUTIAN STANDARD TIME
UTC - 10
HADT
HAWAII-ALEUTIAN DAYLIGHT TIME
UTC - 9
SST
SAMOA STANDARD TIME
UTC - 11
SDT
SAMOA DAYLIGHT TIME
UTC - 10
CHST
CHAMORRO STANDARD TIME
UTC +10
 


 

Displaying Currents

  • Available current stations will show on the chart as orange diamonds, when zooming in arrows will appear pointing in the direction of the set. Note that "current" here is the same as the UK term "tidal stream".
  • Master current stations are shown like this in all scales. No direction is associated with these stations but they can be queried, trough a right click, for the magnitude of the current.

 

  • Arrow indicates current direction and strength - the bigger the arrow, the more current.
  • The size of the arrows can be customized by users in the opencpn.ini (opencpn.conf) file.
    In the [Settings/Others] section you can set the option CurrentArrowScale to a positive number representing a percentage scaling factor of the current arrows. The values bellow 100 mean the arrows will be smaller than now, the values above 100 will cause them to be bigger.
  • Right click the orange box  to see current graph:

  • The Yelow box, with time,speed and direction, follows the cursor when hovering over the dialog.

 Using an alternative data set

  • The default dataset for tides and currents is limited, mainly for copyright reasons.
  • A number of different datasets are available on the Internet, with vastly greater coverage. Some of this data is getting aged, and they also contains glitches and errors, many of which has been corrected in the default dataset.
  • In many areas there are no free alternatives, and OpenCPN makes it possible to quickly switch between data sets.
  • Create a folder UserTCData in your user data folder. Under this subfolder you can then create any number of subfolders, each containing the HARMONIC/HARMONIC.IDX file pair with different data. It will look something like this
  • Go to Toolbox->Settings->Tides & Currents. The button to the right will now look like this:
  • To use a different dataset than the default, simply click it.