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Old 09-07-2012, 20:07   #1
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GPS and tide tables

A funny thing happened on the way to the Forum today or better, make that on my way to Vineyard Haven. My trusty old Garmin GPS chart plotter no longer gives tide information. Does this mean that there is something wrong with Old Garmin or are tide tables no longer available on GPSs? I needed this important information to learn the time of currents in the sound via charts.

It is a no brainer that companies that publish/sell books each year with tidal information must be feeling pain when free access is given to those who own a now common GPS instrument.

Foggy
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Old 09-07-2012, 23:13   #2
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Re: GPS and tide tables

My android phone continues to give not only tide info but current info for my GPS location. Believe it or not, at the mouth of the Columbia those are two different values. My Simrad chartplotter also gives the lastest tide info.
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Old 10-07-2012, 06:11   #3
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Re: GPS and tide tables

Newt--

Thanks for replying! Must be something wrong with my GPS, time for a code update or a replacement!

Foggy
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Old 10-07-2012, 06:19   #4
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Re: GPS and tide tables

Well I haven't checked it this morning, but my Raymarine gave tidal information yesterday. As of right now, 2:14 p.m. in Copenhagen, my iPhone is giving me current tide data for Copenhagen
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Old 10-07-2012, 07:41   #5
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Re: GPS and tide tables

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Originally Posted by s/v Beth View Post
Believe it or not, at the mouth of the Columbia those are two different values.
This is almost always the case. Current change usually lags the tide change by quite a bit. How much depends somewhat on the size of the inlet and the volume of the inland body of water. The high and low tides measure at or outside of a particular inlet only tell you the water level at that station. Because the inlet is restrictive the water level inside cannot rise or fall as fast as that on the outside. Current is driven by the difference in water levels. On an incoming tide (current not level) the water level on the outside of the inlet is higher than on the inside. The outside water level reaches it's peak and though it starts back down on the outside it is still higher on the inside for some time, thus the current keeps coming in the inlet until the level on the outside gets down to the level on the inside. The same is true for the outgoing current. That is the water level on the outside reaches it's lowest level and starts back up before the water on the inside of the inlet can all drain out. Of course if you measure the tide levels inside the inlet you'll note that the range inside is much lower than the range outside.

River mouths complicate the problem even more because the amount of water flowing down the river also affects the current. A river in flood may not change to an incoming current because the water inside the river is higher than the level of high tide on the outside of the inlet. In rivers with large volumes and swift currents it's even possible that one gets an outgoing tidal current that lasts much longer than the incoming current.

All of this is pretty much unique to each inlet and local knowledge is your best indicator. In the absence of local knowledge I usually figure on the current change happening 1.5 to 2 hours after the tidal change, at least in areas not fed by large rivers.
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Old 10-07-2012, 08:03   #6
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Re: GPS and tide tables

i love my paper charts. garmin only tells a part of the story.......
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Old 10-07-2012, 08:59   #7
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Re: GPS and tide tables

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Originally Posted by foggysail View Post
A funny thing happened on the way to the Forum today or better, make that on my way to Vineyard Haven. My trusty old Garmin GPS chart plotter no longer gives tide information. Does this mean that there is something wrong with Old Garmin or are tide tables no longer available on GPSs? I needed this important information to learn the time of currents in the sound via charts.

It is a no brainer that companies that publish/sell books each year with tidal information must be feeling pain when free access is given to those who own a now common GPS instrument.

Foggy
It seems that you may be suffering from a misconception in how your plotter works. If I understand what you said correctly you think that the tide information is somehow supplied via the GPS system. It is not. It is actually stored as part of your chart data in the memory of the chartplotter. I note that you refer to your system as "old". It's quite likely that the table in your unit had tide data only up to a certain date. After that your out of luck. Depending on your unit and what kind of charts it uses you may be able to get new tide tables simply by updating your chart data, but that somewhat depends on the model. I would check on the Garmin site and see if you can update your tide tables.
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Old 10-07-2012, 09:08   #8
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Download the garmin update software, plug In your gps, update the firmware and viola functional tide tables. I did this with our garmin 176 and the tide tables reappeared.
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Old 10-07-2012, 09:20   #9
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Re: GPS and tide tables

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Originally Posted by Captain Bill View Post
It seems that you may be suffering from a misconception in how your plotter works. If I understand what you said correctly you think that the tide information is somehow supplied via the GPS system. It is not. It is actually stored as part of your chart data in the memory of the chartplotter. I note that you refer to your system as "old". It's quite likely that the table in your unit had tide data only up to a certain date. After that your out of luck. Depending on your unit and what kind of charts it uses you may be able to get new tide tables simply by updating your chart data, but that somewhat depends on the model. I would check on the Garmin site and see if you can update your tide tables.


Weeeell, Capt Bill, you're RIGHT!!! It just never occurred to me that the tide info was stored in rom/ram whichever the case is. And further, there is another tip, the map chip is dated April 02 which would almost makes one assume the tide data is limited to 10 years.

Old... almost reminds me of me except my GPS is in better shape to get rejuvenated. And like many things old, self included, value remains. For example, check out Ebay! These 10 year old machines now are being bid between $255-305! Garmin should be proud for designing a quality product. Ebay also offers a USB cable to upgrade the software for $15 or so with free shipping.

EVEN BETTER!!!!!!!!! GARMIN WILL SHIP AN UPGRADE CHIP TO THOSE WHO HAVE MY PROBLEM FOR $50!!!!! This gets even better! After you upgrade your software via removing the map chip and installing the software upgrade chip, upgrading your software, YOU CAN RETURN THE CHIP BACK TO THEM AND THEY WILL CREDIT YOUR $50 BACK!!!

I learned all this this morning doing searches along with calling Garmin. To help minimize searching for others, Garmin's phone number is 800.800.1020!

HEY!!! WHAT A GREAT FORUM HERE AT CRUISERS!!!!

Foggy
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Old 30-07-2013, 07:52   #10
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Re: GPS and tide tables

I know this is an old thread, but.... My Garmin 152 ( I know it's old, but I like it ) is saying innacurate result when viewing tide info. I called Garmin and they basically said tough "you know what" Buy a new one. Planned obsolescence imho. Why can't tidal data be updated in memory. The tekkie said the memory coudn't be expanded. What has expanded got anything to do with it. Overlay with new. TECH SUPPORT IS NOT TECH SUPPORT. I love Garmin don't gt me wrong. And I will probably buy another. I like the tidal data function helps with planning and I've used it when on approach. Very useful.
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Old 30-07-2013, 16:23   #11
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Re: GPS and tide tables

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Originally Posted by gpshephe View Post
I know this is an old thread, but.... My Garmin 152 ( I know it's old, but I like it ) is saying innacurate result when viewing tide info. I called Garmin and they basically said tough "you know what" Buy a new one. Planned obsolescence imho. Why can't tidal data be updated in memory. The tekkie said the memory coudn't be expanded. What has expanded got anything to do with it. Overlay with new. TECH SUPPORT IS NOT TECH SUPPORT. I love Garmin don't gt me wrong. And I will probably buy another. I like the tidal data function helps with planning and I've used it when on approach. Very useful.
If you've never done this

Garmin | WebUpdater

you'll probably have a lot of updates waiting.......may even fix the tides data.
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Old 05-08-2013, 15:44   #12
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Re: GPS and tide tables

Another piece of data that can expire in older GPSs is the magnetic variation model, usually good for 5 years. The GPS computes bearings using True direction. If you choose to display bearings in magnetic, it's a good idea to check and see if the imbedded model is up-to-date.
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