# Warning about cruising the ICW



## ebs001 (May 8, 2006)

The magenta line on charts not the authority for navigation. Yesterday a boat was hard aground when the captain chose to follow the magenta line rather than honour the markers. 

Always honour the markers and buoys.

A prudent navigator should peruse the intended track to determine if there are any problem areas beforehand as there are some glaring errors in the indicated route. For example ICW marker 58A and buoy 60 in St. Augustine the magenta line takes you over a shoal.


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## xort (Aug 4, 2006)

Lots of places like that on the icw. Today we went on the "wrong" side of a green can as charted. In the real world outside of our chartplotter we passed well to the correct side of that can.


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## PCP (Dec 1, 2004)

It is like that not only on the ICW but everywhere, not only because buoys and channels are actualized more frequently but because not always the chart coincides with the GPS. GPS is very accurate, maps, that many times are yet based on old charts are not always correct regarding GPS position.

Those that have already navigated with their boats over land (at least on the plotter chart) will understand perfectly what I am talking about


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## T34C (Sep 14, 2006)

So you are saying a prudent navigator should actually use the aids to navigation and not rely on a graphic animation to choose their course!?


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## boatpoker (Jul 21, 2008)

So everyone agrees the magenta line should not be trusted. Let me suggest that the marks are not infallible either. If we had rounded the marks in the following photos as we should have .........

Sorry guys , had several photos to illustrate the folly of blindly following marks but get a message saying "Internal Aerver Errpr" that won't let me upload.


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## svHyLyte (Nov 13, 2008)

More information on this subject is available at: http://www.sailnet.com/forums/gener...a-magenta-line-icw-cruisers-may-interest.html


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## Minnewaska (Feb 21, 2010)

Clearly, visual reckoning and charts are mandatory.

That said, with all the cruisers that transit the ICW every year, one would think there would be a way to chart it properly. Google has a pic of everyone's house for goodness sake. Put one of those things on top of the next clorox bottle to run the thing.


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## boatpoker (Jul 21, 2008)

Minnewaska said:


> Clearly, visual reckoning and charts are mandatory.
> 
> That said, with all the cruisers that transit the ICW every year, one would think there would be a way to chart it properly. Google has a pic of everyone's house for goodness sake. Put one of those things on top of the next clorox bottle to run the thing.


the problem is that the whole thing is sand and it moves, sometimes dramatically within a few days. On our 2005 trip we had 2002 charts that were useless between Atlantic City and Manesquan but our 1971 charts were bang on.


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## PBzeer (Nov 11, 2002)

First of all, there is a great source of info at Salty Southeast Cruisers. Second, your eyes and your depth sounder are your friends.


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## JimMcGee (Jun 23, 2005)

boatpoker said:


> the problem is that the whole thing is sand and it moves, sometimes dramatically within a few days. On our 2005 trip we had 2002 charts that were useless between Atlantic City and Manesquan but our 1971 charts were bang on.


These are my home waters and the channels and shoals tend to migrate. I never assume the charts are correct and I don't assume I can follow a previous route that I call up from the plotters memory unless it's very recent. These are shallow waters so I always have one eye on my depth. Probably a good strategy wherever you sail.


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## vega1860 (Dec 18, 2006)

T34C said:


> So you are saying a prudent navigator should actually use the aids to navigation and not rely on a graphic animation to choose their course!?


As my flight instructor used to say "Get your head out of the cockpit"


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## svmeanderer (Sep 21, 2013)

PBzeer said:


> First of all, there is a great source of info at Salty Southeast Cruisers.


Who can possibly find what's important on that mess of a website? I search in SC and then have to wade through a bunch of individual postings to hopefully find something that matters to me. I've given up.

And what happens when you're in the Chesapeake Bay?


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## kellymj (Jun 18, 2008)

We just finished most of the ICW, from Norfolk to Stuart, FL. I would strongly agree that you cannot rely on the magenta line!

We relied heavily on Active Captain and found it extremely helpful through areas of low water and confusing markers. We had it running on an iPad with Garmin Bluechart mobile app at the helm along with chart plotter, charts and cruising guides. 

Waiting for a deeper draft vessel to lead the way also works wonders.

Marty


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## boatpoker (Jul 21, 2008)

I once followed a 65 footer in my 37' trawler which drew 4'
big mistake .... he drew 3' !

Gotta love cheap TowboatUS


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## Argyle38 (Oct 28, 2010)

I've done the ICW a few times on deliveries. I've never even assumed that the magenta line was ever even close to authoritative. I'm actually surprised that it was ever a NOAA feature. 

The only thing I've ever used it for was at the entrance of a large bay, when you are using a chart book, the magenta line would indicate the course to the next creek or canal on the other side of the bay. Otherwise we always just ignored it.


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## ebs001 (May 8, 2006)

There are other areas in addition to large harbours where the magenta line is very handy to have such as the section from Fernandina, Fl south for about 20 miles. In these sections there are numerous off shoots and creeks as the channel meanders through the marsh lands. 

If the magenta line didn't exist a prudent captain would make his own.

Most people do not subscribe to Notice to Mariners and update their charts accordingly. As a result buoys are changed and don't always agree with the chart either. The markers and buoys are the ultimate authority.


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## piclarke (Nov 19, 2001)

PCP said:


> It is like that not only on the ICW but everywhere, not only because buoys and channels are actualized more frequently but because not always the chart coincides with the GPS. GPS is very accurate, maps, that many times are yet based on old charts are not always correct regarding GPS position.
> 
> Those that have already navigated with their boats over land (at least on the plotter chart) will understand perfectly what I am talking about


Please 
What does ICW stand for.

C Maps if not pirated are very accurate so stating every where is inaccurate and if not updated in non coastal areas by C maps then you don't know how to realine using the top leading markers in harbours when you line them with your electronic charts / chart plotters. Also C maps when they licence their maps / to the competion they don't licence their full chart infomation. You will always find C maps have more information than the oppositions electronic licenced charts.

If you are using a main harbour chart or navigating a commercial shipping lane and your charts have you sailing on land then you are using a pirated version in most cases based on the free russian c map series in all probability or a copy has been given to you from a mate.

Or You have discontinued updating them probably for costs reasons if they are legit.


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## boatpoker (Jul 21, 2008)

ICW stands for Intracoastal Waterway

as for the rest of your post. I disagree.


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## xort (Aug 4, 2006)

What?


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## bjung (Apr 8, 2009)

As for the ICW magenta line, there are many cases where following the line will take you on the wrong side of a buoy, with the chart being correct, but the line obviously drawn wrong.



PCP said:


> It is like that not only on the ICW but everywhere, not only because buoys and channels are actualized more frequently but because not always the chart coincides with the GPS. GPS is very accurate, maps, that many times are yet based on old charts are not always correct regarding GPS position.
> 
> Those that have already navigated with their boats over land (at least on the plotter chart) will understand perfectly what I am talking about


I will agree partly with the above. However there are instances where I am not sure about GPS accuracy.
Example: I currently keep my boat at a friends dock, accessed through a 40 ft wide channel. For easy nighttime entrance I dropped waypoints along the way. They are all on land, and over 50 ft from the channel. No problem, right, I assume the chart is simply wrong and just follow waypoints. Well, depending on the day, my waypoints are sometimes spot on, and sometimes they are up to 50 ft off from where I should be!
So, what is really wrong in this case: GPS? Obviously, the WPTs did not move, but does the chart overlay differ from time to time?


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## piclarke (Nov 19, 2001)

bjung said:


> As for the ICW magenta line, there are many cases where following the line will take you on the wrong side of a buoy, with the chart being correct, but the line obviously drawn wrong.
> 
> I will agree partly with the above. However there are instances where I am not sure about GPS accuracy.
> Example: I currently keep my boat at a friends dock, accessed through a 40 ft wide channel. For easy nighttime entrance I dropped waypoints along the way. They are all on land, and over 50 ft from the channel. No problem, right, I assume the chart is simply wrong and just follow waypoints. Well, depending on the day, my waypoints are sometimes spot on, and sometimes they are up to 50 ft off from where I should be!
> So, what is really wrong in this case: GPS? Obviously, the WPTs did not move, but does the chart overlay differ from time to time?


Ponder this.

The Globale Positioning System is a American military system.
They can alter the accuracy when ever they like and it has been known during war ,attack activities they switch the civillian sytem to read in accuate co ordinances so the oppostion can not get accurate fixes on the US, NATO allies targets. On precise secret missions it is completly turn off.

It happened to us some years ago. No gps readings for 20 minutes only to read in the news off an american attack at approx the same time the gps went on blink.

Think about if the enemy had a gps infiltrated a stronghold sent the co ordinates to their attack command. BANG.

Why do you think the Russians have or are in the process of launching their own GPS systems via their own Satellites and like wise the French.

Soon there will be 3 gps systems in operation, whether they will be made available to civillian uses is any bodies guess.

It does not pay to get caught with a handheld gps in a third world country in turmoil or in the process off a government overthrow as one news reporter found to his dismay in an african territory supposedly to to get a exclusive story either on a drug cartel or a rebel leader. Cant remember if he was rescued,- released or shot. Approx 6 years ago. If you do you will have to have a bloody good story.


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## piclarke (Nov 19, 2001)

ebs001 said:


> There are other areas in addition to large harbours where the magenta line is very handy to have such as the section from Fernandina, Fl south for about 20 miles. In these sections there are numerous off shoots and creeks as the channel meanders through the marsh lands.
> 
> If the magenta line didn't exist a prudent captain would make his own.
> 
> Most people do not subscribe to Notice to Mariners and update their charts accordingly. As a result buoys are changed and don't always agree with the chart either. The markers and buoys are the ultimate authority.


Not always.

Markers and buoys including lights have been known to drift, move or completely disappear.

C maps alter their charts inaccordance with notices to mariners or marine authorities. However I do not know to time lag period before they get around to providing a update off the chart. Chart information is provided within the c maps format giving no off paper char tdate ect. c- maps chart it pays to update if you have a legit copy as often as possible.

Then you have to add or subtract the corrections in accordance with the fine print at the bottom of the chart if you are transferring from gps to paper chart when plotting on the paper chart.

The paper chart is supposidely the most accurate if it is the latest chart and update as you state correctly inaccordance with notices to mariners.


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## boatpoker (Jul 21, 2008)

On the way to Dry Tortugas from Toronto in 2002 we passed through Norfolk about 4 weeks after 911. Our radar, depth sounder and GPS blanked out all the way through Hampton Roads. I'm quite sure the military were jamming everything in the harbour. Same thing happened around Kingsbridge sub pens in Georgia a week or so later.


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