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I haven't ran aground in 27 years, the last time I did I had a depth sounder. Since then I have been using a lead line although I really don't use it that often. Sure there are forward facing sonars but I doubt many of us have those. So with all the excellent charts and charting devices we have these days is there really any reason to cut another hole in your hull? It seems like a depth sounder is really only good for telling you what you just hit but my guess is by that point you don't need an electrical device to inform you that you are hard aground or sinking.
 

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When you are using a chart plotter/GPS instrument, you likely need not to refer to depth all that much. I do still use the depth meter to double check depth that is supposed to be under the keel - since (rarely) there can be a GPS error, or (more likely) a chart error (where I sail some charts have not been updated since first plotted in the late 1800s...). When the GPS/chartplotter relies on an incorrect chart, it is prudent to have something else to help you out.

I do rely on the depth meter when anchoring to determine required scope as well as to assist in ensuring that I have sufficient swing room.

Of course you can do all this with a lead line, but I doubt that is very practical when you are about to set anchor - that little gadget does the job just fine.

Now, all of this is true so long as you have electricity to power your electronics, and electronics that work... but that is another chapter in the Book of Purists.
 

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Why do people still use depth sounders? = to ease the surprise of running aground!
 

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I just delivered my boat (~5'1" draft) down a part of the ICW from Savannah to the Thunderbolt boatyard and part of the channel that meanders through the two rivers narrowed down to maybe 50 yards, and I have zero local knowledge of that area. I was going solely on my plotter telling me where it thought I was and avoiding the shallows by keeping an eye on depth. In that area, to me, knowing depth trends was pretty valuable.
 

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Charts, plotters can be accurate and useful, Until a major hurricane, or storm comes through and changes everything. Since Sandy, my depth sounder has probably been the most useful instrument on the boat.
 

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Congratulations on not running aground in all those years. You must know your local waters well.

I rarely day sail with GPS or chartplotter on. I, too, know my local waters fairly well. In most cases I stay away from thin water. However, there are times when I am cutting some of those corners on a tack and I like to know if I am flirting too much with the bottom. The depth sounder tells me that, and usually in those cases a lead line would do me no good. I find it a great tool when making sure I find the deepest part of a strange channel as well.
 

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Obviously asked by someone who doesn't sail in the Chesapeake Bay! We sail where we sometimes have less than a foot under the keel. Depth sounder is less expensive than using the keel as a feeler :)

And as others stated, no reason to put a hole in your hull--a shoot thru transducer works for most boats.
 

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Onboard True Blue we not only have a depth sounder but we have another one for backup. Most important gauge on the boat for both safety and peace of mind.
 

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I can think of 3 general reasons with my limited experience:

1. GPS errors/problems, which are rare but do happen. Software/hardware/comms issues occur, and likely right at the wrong time;
2. Depth trends can be another source of confirmation of your preplanned route, and/or of any pending issues if you happened to deviate; and
3. Chartplotters/GPS are only as good as the data that is entered in them, and in some locations the data is not good at all.

Context is everything though. Where you tend to sail, none of this may really matter.
 

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I haven't ran aground in 27 years, the last time I did I had a depth sounder. Since then I have been using a lead line although I really don't use it that often. Sure there are forward facing sonars but I doubt many of us have those. So with all the excellent charts and charting devices we have these days is there really any reason to cut another hole in your hull?
The underwater topography changes faster than the charts are updated. For example I keep my boat at Shilshole Marina (I think you used to sail near here) and the sand bar off of Meadow Point is considerably different this year than last year -- you need to stay much farther off of Golden Gardens to avoid grounding than you used to. I've been on and have watched multiple race boats touch bottom here because people are used to the old configuration.

A depth sounder gives you warning of this, charts would not.

No electronics are necessary, most people have sailed without them.
 

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the depth sounder(either manual or electronic) is the single most important thing on a boat for me, after that its a trusty and reliable compass.

with those 2 you can navigate safely provided all else fails, some binoculars and youre golden.

of course if you live in waters you know perfectly and have been doing so for many years then yes of course you dont "need" a depthsounder

however that knowledge has to be daily knowledge, as you never know if a boat just sunk during the middle of the night, or a huge storm surge created a new sand bar where there wasnt one before(very common down here) or a submarine or whale decided to surface under you, or some mermaids are caressing your hull and you need to go check it out

all of which a depthsounder warns you about! jajaja

even lake sailing a depthsounder is helpful although not really needed, once again depends on the user.

btw you can put me in the fisfinder as depthsounder happy camp crowd...just installed on my boat no thruhull and reading real well

and falls in the $500 a month crowd category jajja
 
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Wow... Really? I love my depth sounder and value it far more than any gps-dependent plotter. A sounder (or lead line ... same thing) is giving real data about your actual situation. Your chartplotter is an approximation of where you are. This approximation can be very accurate, or it can be significantly off depending on the quality of the baseline chart, and also the current gps error factor. There's many a time when I've been 1/4 mile on shore according to the plotter when gunkholing.

When water gets thin I relay on eyes and direct observations first, followed by use of a good chart and my sounder. Chartplotter info is great, but I use it very much as a secondary source. If the plotter and my sounder differ I always believe my sounder.

Shoot-thru-the-hull transducers work great in solid boats. No need for more holes.


Why go fast, when you can go slow
 

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...So with all the excellent charts and charting devices we have these days is there really any reason to cut another hole in your hull? It seems like a depth sounder is really only good for telling you what you just hit...
First of all...as Joe said you don't need a hole in the hull to install a good depth sensor head. They will shoot a signal through a FRP hull (don't know about wood or steel...coupling with the water column might be more problematic).

Second...because unlike the plotter position you suggest most rely on...a depth system is nearer to real time output and more likely to warn you of impending doom.

Third...only the highly trafficked world traveled by first world nations have excellent charts. Many soundings are a century or two old...and the soundings may be quite accurate but charted positions were very inaccurate until the satellite navigation age. So your position on the physical world may be accurate but the chart may not reflect that physical world but be offset by several miles. There are several stories of such occurrences with both good and bad endings in the coral shoals of the South Pacific.

Fourth...as pointed out charts in plotters and on paper are aged data...not real time and likely to be in error due to intervening storms or just simply because it's impossible to keep all chart info near real time.

Fifth...a good sounding in the absence of other navigation info can sometimes give you a pretty good fix on your position depending on bottom slope and contour.

Sixth...it's one of the lowest cost systems you can get to assist in puttering about in the water...less than a hundred bucks for a reliable no frills system...

...so why wouldn't you have one since they provide such important navigation info?
 

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Most important, simplest and most reliable electronic instrument on a boat. Anyone who has done any mileage in unfamiliar waters would know that.

1. The normal shallow water pilotage as stated previously.

2. It gives you a line of position (i.e. the contour line) which when added to a bearing of a know object on shore gives you a reasonable manual fix (after your chartplotter has crapped out).

3. It alerts you when you are approaching shore after an offshore passage. (set the alarm at 200ft or whatever you choose)

4. It allows you to run soundings, e.g. when heading South, at night, on the Florida coastline to stay out of the Gulf stream use the 200 ft contour to keep you off the shore.

They almost never break and if it is inoperative on a boat that I'm moving, I'm not very happy. I will go as far as installing a cheap one by gluing it on the inside of a solid fiberglass hull.

Just my 2cents

Gerry
 

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following contour lines is an art...only acheivable with a depthsounder...its a great way to navigate "known" and unknown waters

the offshore alarm is also a great plus especially singlehanding...

like everyone says its the single most important navigation aid we can use....
 

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a. Sometimes charts say "buoys not charted: see note XX," since the sands move. Yes, you could use a lead line or a stick for that matter, but a sounder is faster and thus safer. Old school guys can and do run aground.

b. Charting errors. In remote areas charts are often a joke book.

Yes, for years I poked around using the senses and charts, and never got stuck that I couldn't get off. When the bottom is mud, you either "feel" it once is a while or never go anywhere interesting. If my sounder broke I certainly wouldn't run home. But it's useful.

I'm guessing the OP comes from an area where rocks abound. Still, I use my eyes and don't trust charts completely. What are the odds that everything beneath the surface has been found?
 

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We used a lead line for poking into shallows while cruising from 1972 to the eary 1990's and now, for the last 20+ years, we've had a depthsounder. During our time without the depthsounder, we did not have a GPS as they did not exist for most of that time and we judged out depth by knowing our position from DR navigation and parallax views of on shore marks or navigation aids. Of course, the electronic depth sounder can provide hundreds of data points in the time it takes to get one lead line reading. In this respect they are the same except for the speed of gaining information at any depth.

So, for me, the original "Why use a depth sounder?" question is all about speedy information.
 

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One more thing came to mind while reading this thread. A good sonar plot (usually called a "Fish Finder" instead of a "Depth Finder") also provides useful information about the bottom composition. It is easy to see the difference between a rocky bottom, grassy bottom, or sandy/muddy bottom by looking at the bottom plot. A chart or leadline doesn't provide the same information.

I used this last weekend when anchoring off of Hat Island to find out where the eel grass stopped and the clean bottom started. I also used the depth finder plus two waypoints on the GPS to figure out the closest point that I could anchor to shore with my intended scope without having any chance of touching the bottom. This was helpful when anchoring on a large shallow beach like the one on the SW corner of Hat Island. I could have done it without electronics, they just made it easier.
 
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