Friday 20 July 2018

Tide & Current Infomation

Websites we use for tide information:

Tides and currents:
Web sites we find very helpful.
Tide forecast, a world wide tide forecasting site. We have found them to be fairly accurate in Asia.

Department of Survey and Mapping Malaysia, reports the major Malaysian ports tide times and heights. This link takes you to the main page. Scroll to the bottom of the page where you will find the Tide Forecast Table. Just select the closest port to your location. 

Tidetech is a very informative web site detailing ocean and tidal currents world wide. If you have ever tried to get your head around the currents in the Singapore and Malacca Strait this will shed light on this and many more, this did have a great free trial that has since been removed which was great for those one off's when you transit Singapore Strait or the Malacca Strait. However if you have the money they do have subscriptions and at the time of writing this it was 9 euro you get an month of information. For 9 euro you could almost save that in one transit and still arrive quicker.   

Tide Programs for your PC when off line:

OpenCPN: We use the tide and current information in OpenCPN now that we have worked out how to get it working. If you run OpenCPN and find its not working where your sailing you could try and change the tcdata file used to predict the tides.  There is how we did it on our PC and Raspberry Pi running OpenPlotter here and here is a setup guide for OpenCPN down load the latest  PDF or DOCX file open it and scroll down looking for   "Terry's tips rev ?" and there is also a guide to get the tide function working in other places in the world besides the US and Australia.  

For worldwide there is also a free download shareware from the UK Hydrographic Office, TotalTide software gives users access to detailed tidal information for over 7,000 ports and 500 tidal streams worldwide. We have used it and found it to work well. 

WXTide32 we use this and while its not always exact, however it is in the ball park as far as time and heights are concerned.

XTide was designed for Unix and X11, not Microsoft Windows, so if your savy with Unix, here is the original version.

For Australia, PNG, Solomons, Timor there is a free download from the Australian Hydrographic Office for a install program for the coming years tides. 

Tide Predictions for Australia, South Pacific and Antarctica: Online
Tide Predictions for Australia, South Pacific and Antarctica < internet required
Willy Weather can drill down tide time for different locations in the same bay (e.g Peel Island in Moreton Bay)< internet required
Tide tables for Australia and a tide prediction program < Stand alone once installed

Forecast and past tidal currents for the Au east coast 
DownLoad the KML file for Google Earth overlay tidal currents for the Au coast 

Tidal Stream – Computation of rate

Range of tide for day
_________________         x Spring tide rate of tidal stream
Spring tide range

Why do we need to know this? It’s for working out tidal drift.  If the chart has a tidal arrow its value should have been referenced to the spring tide rate. So if you are there in a neap tide and require the tidal rate this is the formula to use for the job.

Or the easy way, if you have integrated instruments connected to the chart plotter, in most cases the drift/tidal rate can be displayed, the chart plotter uses data from several inputs to calculate tidal drift when on passage.  However this doesn’t work when passage planning. If the chart has tidal diamonds then you will have a good source of rate and direction. Not all charts have these tidal diamonds but have tidal arrows so if you can remember the formula for the computation of tidal rate it may help get you out of a slow trip. 

Assuming that the tide in your area has a normal semi-diurnal cycle, The rules of 12ths can be used to provide a quick estimate of the height and flow of the tide for times in between high and low water.

For the first hour of tide one 12th of the tide will move
For the second hour of tide two 12th of the tide will move
For the third hour of tide three 12th of the tide will move
For the forth hour of tide three 12th of the tide will move
For the fifth hour of tide two 12th of the tide will move
For the sixth hour of tide one 12th of the tide will move


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