Tides at a glance

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Frequently asked questions

What do the blue, green, and yellow markers on the map mean?

Markers signify areas or places of interest. Which markers are shown depends on how far the map is zoomed in; as you zoom in, more blue tide markers will appear. Markers show current tides so you can see the tides in your area at a glance.

Each green marker represents a country. Click the marker once to zoom in so that the country fills the window.

Each yellow marker represents a state, for those countries that have them. Similarly, you can click a yellow marker once to zoom in so that the state fills the window.

The blue markers mark a place where tide data is available. The closer in you zoom the map, the more markers are shown. Each blue marker has an arrow showing which way the tide is currently moving - in or out. The dark blue approximates the level of the water at the current time. These markers will continue to update while the page is displayed.

Hover your mouse over the blue marker to see details of the place, the current time there, and when the next high or low tide will occur. Click the marker for a tide table, a graph, and possibly a photo of the place.

When a blue marker is clicked, the place is added to the top of the most recently used place list, under Places in the drop-down panel area on the left. A maximum of 15 places are kept in the list.

Right-click a place marker for a choice of ways to display tides and other information for the place. Also, in the Tides panel to the left of the map, you can customize what a left-click on a marker does - it contains the same options as the right-click menu.

For what time zones are the times shown, and can I change the display format?

Tide times are always given in Local Time for the place whose tides you are viewing and are corrected for daylight saving wherever possible. The header section of a blue marker's information window will show the time zone name (PST, PDT, etc) as well as the time offset that has been applied from UTC.

Places for which we have no time zone information will be shown as UTC, which is essentially the same as GMT.

You can display times in 12 hour (eg 11:53pm) or 24 hour (eg 2353) format by checking or unchecking the box in the Time panel to the left, or you can click the "12" or "24" on a blue marker's information window.

Where can I find more information about tide levels and datums?

All our published tide heights and the heights shown in the tables and the graph are relative to the zero height used in official marine charts. This zero height is known as the datum. Standard ports and tide stations have a physical marker that can be used to relate the datum to the height of a real world place.

For Continental USA, the Carribean, and many Pacific Islands, NOAA has full information on datums and benchmarks here.

For New Zealand, datum information can be found here.

Do you have Moon and Sun rise and set information?

Yes, after clicking on a blue place marker you'll see a "Moon Sun etc" tab in the balloon that is displayed.

All times shown are local times with daylight saving adjustments already applied. The times and moon phase diagrams pertain to the day that is currently chosen - to change days click the required day along the bottom of the balloon.

Under the sun picture you'll see the rise and set times for the sun.

There are two moons shown. The moon thumbnail in the middle shows the phase of the moon as it is on the day, and underneath we show the percentage of the disk that is illuminated, whether it is waxing (bright area growing) or waning (bright area shrinking), and also the moon's rise and set times for the day.

The moon on the right shows the next phase (New moon, First quarter, Full moon, or Last quarter) and approximately when it will occur.

The moon thumbnails are taken from actual moon photographs with a little touching-up to make them work on the page. You can visit the web site of John French where the striking originals can be seen.

Where can I find tide graphs for other parts of the world?

If it's not on our map, then we can't supply the information. We are in the process of obtaining data for some other countries.

What causes tides to occur?

Tides are caused by the gravitational attraction of the moon upon the earth's oceans and to a lesser degree, the Sun. These attractions, combined with the daily rotation of the earth, produce the periodic motion of the tides. The positions of the sun, moon, and earth are entirely predictable, and so we can predict tides well into the future.

Unfortunately, a large number of factors make the prediction process quite complex. As we demand more and more accuracy in the times and heights our predictions, so the process becomes more complex.

For any given place, factors that affect tide heights and times include the location of the place on the globe, the depth of the sea, the shape of the coastline, the presence of rivers, bays and inlets, and other nearby land masses. Tides are also affected by non-predictable factors such as wind and the barometric pressure.

Further information may be found at these sites:

How should I interpret the graph?

The graph shows the tide height for all times over a 24-hour period. The height is relative to Chart Datum which is the zero depth for marine charts. The slope of the curve implies the strength of tidal flows; a steep slope means stronger currents, a flat slope (tops of peaks and bottoms of troughs) means slack water. High tide occurs at the top of a peak on the graph, and low tide occurs in the centre of a valley.

Note: The vertical scale is calculated on-the-fly and it may change as you look at different places or dates, thus a tide curve that "looks big" may in fact be considerably smaller in reality than another that appears smaller, and vice-versa. Always refer to the height scale at the left if your interest is in the actual height.

Can I find out the exact height for a given time?

Click a place and the Tabular tab for a list of times and heights. You can also find the time and height of a high or low tide by hovering the mouse pointer above a peak or valley on the Graph tab; the next high or low tide will be shown. For the height at a particular time you must estimate it from the height curve.

My computer won't remember the last places I visited, and it loses other settings.

The Tide Graph puts a "cookie" on your computer which contains the names of the last places you selected, plus other settings. If you have disabled cookies in your browser or you have cleared the cookie files from your computer, then nothing will be remembered from your previous visit. This is the reason cookies were invented, and disabling them has its disadvantages.

The cookie will remain on your computer for 100 days. If you don't visit the graph within that time, then your last places and settings will not be remembered.

We will use your cookies for no other purpose than to improve your experience on this site.

Explain the Best Fishing Times on the Sun-Moon tab.

The best fishing times are computed from the position and phase of the moon and the sun.

Solunar theory tells us that the best times for fishing and hunting is close to when the moon is directly overhead or directly underfoot. The Best fishing times on the Sun-Moon tab shows these times for the selected day.

Best fishing occurs for half to one hour either side of the tabulated time.

The tabulated times are similar to the solunar major periods. To see the Solunar major and minor times for the day, right-click the blue marker and choose one of the Full page options (not available with Internet Explorer version 6.0 and earlier).

Can I make a bookmark for a particular place?

There are two ways to do this; you can bookmark a map position, or a blue marker.

To bookmark a map position, locate the map at the place and zoom level that suits you. On the left, open the Position panel and click the "Bookmark this position" link. Depending on your browser, you will get some kind of dialog containing a bookmark. You can Ok the bookmark to save it, or copy the link and paste it elsewhere.

To bookmark a place (blue marker), right-click the marker and choose the Bookmark item. Follow the instructions on whatever kind of dialog you get. Using this bookmark will position the map and display the tides for the chosen place.

To obtain a link for your website, click a blue marker and choose the Tabular tab. This tab has a "link this page" on it. Clicking the link opens a popup window - copy the html to put a link on your own web page. Using this link will show the map and open an information balloon for the place as though the blue place marker had been clicked.

You can also embed an interactive tide graph on your site with a little work. Please see our Tidespy Tools For Webmasters for details about how you can do this.

How can I find out tides for a place that is not on the map?

If the area of interest has no markers, then we have no data and TideSpy can not help you.

If there are blue markers nearby, then you can estimate the tide by finding a place either side of your desired place and split the difference in tide times and heights. Most places will have a marker somewhere nearby where the tides are only a few minutes different. Take care: places within estuaries, inlets and rivers will be affected by the flow of water from the inlet or river and may not be so easily calculated this way.

Can I use your graph on my website?

We are open to a variety of ways to do this. The easiest is for you to add a link to TideSpy, and you are welcome to do this. Use the bookmark feature (see above) to make a link so that your visitors will see the map already positioned and zoomed to a place relevant to your website.

If you want the map or graph directly on your own web site then an arrangement is possible, and it is possible to configure the tide graph for almost any coastal region on the planet, if data is available.

You can also embed an interactive tide graph on your site with a little work. Please see our Tidespy Tools For Webmasters for details about how you can do this.

The graph is empty or says "Tide data not available". What's wrong?

Ensure that your Internet connection is still up and running, and that you are not using an Ad blocker. If you get this message repeatedly then the data you are requesting may not be available on our website. Let us know with an Email - and please remember to tell us which month and place you are having problems with, or we can't really help.

Are the tide graphs accurate?

We use the best tide data available. For many places (Pacific Islands, USA, and Carribean), the tide data comes directly from the Government agencies and may therefore be relied upon to be computed from the most recent constituents. Some other websites use data of questionable accuracy and do not get updated in a timely manner.

Tide heights and times can be affected by several factors, the two most common being the air pressure (low air pressure means higher tides) and by winds (a strong onshore wind will increase the height and bring the time forward, and an offshore wind will do the opposite). After considering these factors, if you feel our data is consistently wrong then please contact us. We put a lot of effort into getting the data correct, but inevitably the occasional error does slip through (and they not all of our own doing, I might add).

The quality of information varies between places. For some places we have no height information, so we draw the graph using the heights for the nearest standard port. The times for high and low tides will generally be quite accurate but the true heights of the tides may vary from those shown on the graph. Heights that are shown in this way will be preceded by a tilde character (eg ~ 1.3 ft or ~ 0.7 m).

How can I print the TideGraph?

This is not presently provided. On a computer running Windows you can press Alt+PrintScrn, paste the resulting image into a paint or photo editing program, clip off what you don't want, and print the result.

We have other better ways of obtaining printed tide graphs, soon to be announced.

What's the story with Daylight Saving time and Time Zones?

Tide times and graphs are normally corrected for daylight saving, so you should not need to do this manually. We assume a Standard Time Zone and Daylight Saving regime for each place, and all times are corrected for the places whose tides you are viewing.

When local time changes to and from daylight saving time there will be a jump in the tide height, and since there is no correct way to show this on the graph (between 2am and 3am) you will have to use your head and figure out the correct height yourself.

Please note: While we strive to present correct time zones and Daylight saving information for all places, there may be occasional errors. Please check the time zone displayed with the tide times, and also that the correct time is shown. Factors beyond our control may produce incorrect times on rare occasions.

I only see a broken image icon, or a blank space, in my browser. What could be wrong?