Is sonar really necessary?

C

Chester

New member
We don't fish, the boat is only used for cruising. We're planning a new nav system and wondering if there are will be any real disadvantages if a depth sounder is used rather than sonar.
Steve
 
Milehog":1kecu30x said:
We don't fish, the boat is only used for cruising. We're planning a new nav system and wondering if there are will be any real disadvantages if a depth sounder is used rather than sonar.
Steve
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I too chose to install only a depth sounder as I do not fish.
 
Depthfinder or fishfinder, either way you are going to need a transducer. And if you have chosen an integrated unit like a Raymarine E-80 to accommodate your radar, chartplotter, etc., you will have a fishfinder-capable display. At that point you can decide whether to actually display the underwater info or only show the number of feet under your hull. But keep in mind that having the fishfinder display is useful for more than just seeing fish -- you can see the bottom sloping up, for example, or you can get an idea if a bottom is hard or soft from the strength of the signal coming back from the transducer.

Warren
 
What's the real question? A depth sounder uses sonar. Fish finders are depth sounders that also use sonar.

For cruising, you need a GOOD depth sounder. When you're fishing you know the depth, you're just looking for very specific returns from the sonar transducer.

We used the heck out of our depth sounder when we we're anchoring at San Miguel Isl yesterday. Mandatory for cruisers (like us.)

Boris
 
We fish a little and I like to see where they are down below, but mainly use the fish-finder (sonar) to know what the bottom consist of, its depth and how its changing for exploring in thin water areas. What worked the best for us was a inexpensive low wattage separate unit.

Jay
 
For thousands of years, knowing the quality and nature of the sea bottom has been critical to navigation. That has not changed. GPS units can go awry, lose a sattelite or two, blocked by storm, trees, etc..

You could have a depth of 35 feet in an area of submerged timber and not know how close to the surface that submerged timber is. Also, sub surface, half floating log jams can be encountered. You may be in a big hurry trying to find a crew member who fell overboard, etc..

To understand the bottom contours with a depth finder only, you'd have to constantly watch the numbers and memorize them and run them over in your mind when having a full function fish finder model will print all that on a screen which you can review in a quick glance.

With the low cost of "fish finders" and the great detail they provide, not to mention that even the most primitive depth finder needs a transducer of similar size to a good, full range sonar, I don't think there is any good reason a prudent skipper would choose to run "blind" to what is under his/her boat.

John
 
drjohn71a":g0m5wuzh said:
For thousands of years, knowing the quality and nature of the sea bottom has been critical to navigation. That has not changed. GPS units can go awry, lose a sattelite or two, blocked by storm, trees, etc..

You could have a depth of 35 feet in an area of submerged timber and not know how close to the surface that submerged timber is. Also, sub surface, half floating log jams can be encountered. You may be in a big hurry trying to find a crew member who fell overboard, etc..

To understand the bottom contours with a depth finder only, you'd have to constantly watch the numbers and memorize them and run them over in your mind when having a full function fish finder model will print all that on a screen which you can review in a quick glance.

With the low cost of "fish finders" and the great detail they provide, not to mention that even the most primitive depth finder needs a transducer of similar size to a good, full range sonar, I don't think there is any good reason a prudent skipper would choose to run "blind" to what is under his/her boat.

John
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Hi John,
I think your points are all valid. I do think there are other reliable sources for this information though. In terms of bottom composition, you can find that in a Coast Pilot book (I'm blanking on the exact name of this book....ahh..brain cramp!) I don't believe one of our standard fish finders is going to reveal a dead-head any more than a depth gauge would. If you lost someone overboard, you will not see them waving to be picked up from beneath your boat on the fish finder (ha ha).

Now "real sonar" is a totally different story, but what we're talking about here is a "good fish finder" of the $800 - $1000 variety of course but nothing that would be used commercially to find shipwrecks or any serious bottom research.

It's not that I don't think there is value to the good fish finders we are talking about, but they are not worth the cost in my opinion. I did not see the value in paying $800 for a fish finder that I personally never use except to read the depth.

I installed a Raytheon ST-40 and an Airmar 600w shoot-thru hull transducer and I could not be happier with it. I have bottom lock through WOT.
 
Well, Matt,

I guess, when you do not know for certain where you are, you can toss a lead line with the hollow tip to penetrate the bottom, read the depth from the line ties and clean out the hollow end to see what type of bottom you are over and keep doing that a few thousand times a minute to match the info an inexpensive depth finder/sonar would give you. An you can troll a knotmeter on a line out of the helm window and keep pulling that up to check speed and, if the sun is shining just right at sunset you can take your position off the horizon I guess.

While the corpses we have recovered have not been "waving" to us as we have helped local authorities, I can't imagine why anyone would try to do that type of work with a digital depth readout when a picture is so readily available. And, recovering a loved one rapidly after an aquatic accident greatlly increases the chance of saving their lives. But you can just turn your readout off if that appeals to you.

No book nor chart knows where you are. It is up to the captain to determine position and local conditions, structures, to validate that position shown on a gps, etc.. And I know for certain that those gps's go down, esp. in big storms. There have been several times when our sole guidance back to saft harbor has been from the sonar readout.

John
 
drjohn71a":2qxrbpoz said:
Well, Matt,

I guess, when you do not know for certain where you are, you can toss a lead line with the hollow tip to penetrate the bottom, read the depth from the line ties and clean out the hollow end to see what type of bottom you are over and keep doing that a few thousand times a minute to match the info an inexpensive depth finder/sonar would give you. An you can troll a knotmeter on a line out of the helm window and keep pulling that up to check speed and, if the sun is shining just right at sunset you can take your position off the horizon I guess.

While the corpses we have recovered have not been "waving" to us as we have helped local authorities, I can't imagine why anyone would try to do that type of work with a digital depth readout when a picture is so readily available. And, recovering a loved one rapidly after an aquatic accident greatlly increases the chance of saving their lives. But you can just turn your readout off if that appeals to you.

No book nor chart knows where you are. It is up to the captain to determine position and local conditions, structures, to validate that position shown on a gps, etc.. And I know for certain that those gps's go down, esp. in big storms. There have been several times when our sole guidance back to saft harbor has been from the sonar readout.

John
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Hi John,
I don't understand why you have appeared to take offense. I'm not disparaging your value of a fish finder, I'm just presenting an alternative view of the usefulness from my perspective and experience.

I find it hard to believe you or other Search and Recovery personnel in your area use a Raytheon fish finder on a C-80 system to find victims. If they do, then I will stand corrected. Of course I'm not suggesting this kind of recovery is done with a digital depth gauge. At least around here they use only divers for that and real side-scan sonar (the $6000 and up variety) for shipwreck research.

Navigating only on your fish finder would be a hell of a trick. I assume you meant you had to navigate with a compass and your fish finder. Were you using the bottom composition for that effort or just the depth? One of my reasons for my particular setup was so that I would have a critical system (depth gauge) NOT part of my chart-plotter/radar system. My depth gauge is on it's own circuit and display. A fish finder is as much at risk to fail as is your GPS or radar or anything else.

Maybe my perspective is a little different because I'm a diver. I know the topography and bottom composition from my own eyes and hands at least in the areas where I will ever anchor on purpose. If I need to throw anchor due to emergency, the bottom composition is not going to change whether or not I release the windlass. It would change my retrieval technique but that again I can figure out as I go. A fish finder is not going to tell you about a submerged dead-head until you're right on top of it (as would my depth gauge) and then it's too late anyway.

It is indeed the Captain's job to know where he is and certainly not from one source. I don't follow what you're trying to say there....

If I had the choice between a fish finder and my depth gauge for the same price, I would have bought the fish finder just to have the extra bells and whistles. My depth gauge system was around $250 and as I recall the fish finder would have been over $800. For my uses, based on my experience, it was not worth it and I don't need it.
 
heres what I think. a chart plotter is only a facsimile of reality, a depth finder/fishfinder is reality. chart plotters are only stored information, a depthfinder/ fish finder are real time information of reality. you can get a chart plotter/fish finder for under $500. The more info you have the better off you are. if I had to choice between the two I would only have a depth finder not a chart plotter. I had only a fish finder for years and it is a world of information to back up what the charts are telling you. chart plotters are not always correct.
 
here one for under $400 ff/gps


I re read the post above and cant figure out why anyone would want a "depthgage" only when fishfinders are so dam cheap? dam cheap fish finder
I mean for $80 you can have a much better fish/depthfinder then my first one at a far lower price then my first one. more info is good info. And how does your depth gage see dead heads or are you saying it does not just as a ff does not? well guess what neither does a gps. those dead heads come and go as they wish. Great thing about a gps is that after you find one, with a near miss most times, you can add it as a way point to you map so you always know where it is.

ok I just re read again. matt you have a better transducer then I have hooked up to my c-80. you talk about the cost but you bought a transducer that is way over kill for your use. you should hook up a ff to that thing its going to waste just giving a number. and by the way you could hook that transducer to almost any ff on the market including my c-80. alot more power then the transom unit I have. Wow, $250 for a transducer to hook it up to only get a depth number :cry
 
Don't ordinarily enter into long discussions with differing viewpoints -- but, simply said, we believe that for modern cruising, regardless of how you determine it, knowing depth is often critical -- as all above have said. In summary:

1. Important for navigating (if chartplotter fails) or to supplement the gps data.

2. Finding uncharted bottom conditions -- we have often observed uncharted rocks that are hazards.

3. Gives an audible (and visual) warning if off-course and approaching shallow water.

4. Aid in anchoring -- must know depth to determine proper length of rode and helpful to know if there are weeds or rocks.
 
The Garmin 4210 chart plotter we are considering has the option of using a 'smart' transducer that will give depth readings without the need of a remote sonar module. For about $300 more the remote box and matching transducer will give a picture of the bottom, though price isn't the only factor driving our decision. We have a small Lowrance chart plotter-sonar and we've only used the sonar's depth function. Maybe I don't know what I'm missing.
 
with the invent of multi function systems the fish finder screen info providing soft ware and processing hard ware has been removed from the screen unit and placed into the "module " unit. That way the manufacturer can keep down the cost of the base unit for those that just want the chart plotter radar unit. I think that if you are dropping 30 to 50k on a boat short cutting your ability to see the whole picture over $200 bucks is kind of cheap. If you want to cut cost then stay away from the multisystem and go to one of the cheaper one that I listed above. Unfortunately there are no cheaper map/radar only systems that do not have a option for a depth finder. In order to get radar you have to have either a multi-function system or a standalone unit. A cheap gps / ff unit and a standalone radar might be a cheaper option.

One other thing, I noticed that there is confusion about a "sounder" and”sonar" just a different word for the same thing. Sonar is sound that is reflected of the bottom. A depth gage is only looking for the biggest strongest signal and reports that to the screen as a depth. A fish finder takes the same signal from the same sending unit and looks at all the information and reports it on a screen as the bottom and fish and bait and weeds. etc... it’s more a function of the software as to what you get to see and how it is presented not a function of the sonar or sounder, they are the same thing.
 
Milehog, as you've read above, knowing your depth whilst cruising is important. And I'm thrilled that you're going to get something that indicates depth.

As to the Garmin chartplotter, I would guess that there is a remote transducer involved in getting the depth. Something has to send the sound signal through the water and measure the arrival time of the echo ( which is what is called sonar.) I don't know to what Garmin is referring, but it just may be included in the price.

I happen to have a depthsounder that looks forward, but that is just to make me happy. The minimum is one that looks down at all times. Fishfinders don't look anyway but down, they just keep and display a record. My advice is to get the cheapest unit with which you feel comfortable.

Boris
 
I am of the school which subscribes to the use of a fish finder (we used relitatively inexpensive units: a $160 Hummingbird in the CD 25) (The Tom Cat has a better Lowrance integrated unit). The $100 units will give you the information which you need, and it is vital--as noted above. We always "troll" over the area where both we are going to drop the anchor and where the boat will swing when on anchor, looking for rocks, logs, cables (all of these will show up with a cheap unit, with the bottom zoom in the display). I prefer the separate units, because I want a full screen chart plotter, as well as full screen of the depth sounder (fishfinder--bottom history) display.

First time you hook onto a cable, hit a rock or have bad holding, because you didn't know about the bottom, the "Fish finder" becomes a cheap investment--plus it is often cheaper than a "digital depth sounder).

Incidently don't forget the tallow for the hollow in the lead line weight!
 
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