Is sonar really necessary?

Chester · Posted: Mon Jul 14, 2008 4:04 pm Post subject: Is sonar really necessary?

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

matt_unique · Posted: Mon Jul 14, 2008 4:17 pm Post subject: Re: Is sonar really necessary?

Doryman · Posted: Mon Jul 14, 2008 4:39 pm Post subject:

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

cemiii · Posted: Mon Jul 14, 2008 5:12 pm Post subject:

and you will eventually probably dramatically widen your resale market.

Chris

dotnmarty · Posted: Mon Jul 14, 2008 9:51 pm Post subject:

Warren and Chris-both points are very good!

journey on · Posted: Mon Jul 14, 2008 11:00 pm Post subject:

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

Hunkydory · Posted: Mon Jul 14, 2008 11:07 pm Post subject:

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

drjohn71a · Posted: Tue Jul 15, 2008 10:20 am Post subject:

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

matt_unique · Posted: Tue Jul 15, 2008 11:37 am Post subject: Sonar

drjohn71a · Posted: Tue Jul 15, 2008 12:31 pm Post subject:

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

matt_unique · Posted: Tue Jul 15, 2008 1:26 pm Post subject: Sonar

starcrafttom · Posted: Tue Jul 15, 2008 4:38 pm Post subject:

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.

starcrafttom · Posted: Tue Jul 15, 2008 9:29 pm Post subject:

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

El and Bill · Posted: Wed Jul 16, 2008 10:52 am Post subject:

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.

Chester · Posted: Wed Jul 16, 2008 1:53 pm Post subject:

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.