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Old 09-05-2019, 07:51   #1
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Best Depthfinder for Bottom Composition

I'm looking for a depthfinder that will provide information on what the substrate consists of for anchoring. Specifically, one that will let me know it I am dropping in rocks or weed. Currently I am getting depth information from an Airmar DS200 transponder using a Simrad NSS7 MFD. I would like to stick with Navico for compatability and am looking at either Structure scan from Simrad or Forward scan from B and G. Either way it looks like I will need a new MFD to support either of these. I should mention that fish finding capabilities an not important to me as I don't fish. Mainly I'm just looking for better information on where I am dropping my hook. Also, the Airmar transducer has a nasty habit of jumping from 100m to 2m, especially when I am in poorly charted areas. This renders the depth alarm pretty useless.

Structure scan looks like it gives a very nice picture of what is on the bottom, whereas Forward scan lets you know what is coming up, but only provides a 2D picture of bottom contours. If I have to spring for a new MFD, I am leaning towards B and G as the sailing functions appear better.

Anybody using either of these? Any other options I have not considered?
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Old 09-05-2019, 09:15   #2
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Re: Best Depthfinder for Bottom Composition

Forward looking sonar is going to have limited depths and will be looking forward, not down. That would be more appropriately used to detect things in or below the water while underway.

Sonar to deduce bottom Type (e.g. grass, rock, coral, etc) You'll see depth and contour, and maybe be able to glean a little, but I don't know if you're going to achieve your proposed goals.
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Old 09-05-2019, 09:20   #3
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Re: Best Depthfinder for Bottom Composition

Lead line w/hollow to insert tallow. This will tell you the bottom type and depth.



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Old 09-05-2019, 09:25   #4
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Re: Best Depthfinder for Bottom Composition

Your best bet is to look at the chart! If the spot is where you want to be throw out anchor and see if it sets.
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Old 09-05-2019, 10:01   #5
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Re: Best Depthfinder for Bottom Composition

I used an older Garmin black and white trace that gave me a better idea of bottom hardness than the new breed. My surveying days using a Raytheon survey fathometer gave me a second trace at double the depth over rock and a softer trace at depth over weed with a harder trace of the bottom just under that. Sometimes an even harder trace under the bottom profile indicated rock under sediment.
The new breed seem to constantly change the ping intensity to give a more consistant bottom trace with auto modes. I am still learning to interpret a new Lowrance Carbon unit with too many colour options, bells and whistles.
Whatever you choose you will have to learn to interpret by experimentation. I wouldn't worry too much about brand names and I certainly wouldn't bother with forward looking sonar, it will only tell you if you are about to unavoidably run into something.
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Old 09-05-2019, 10:12   #6
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Re: Best Depthfinder for Bottom Composition

"Any other options I have not considered?"


It's pretty hard to beat the Garmin (or any other brand) fishfinder. They are cheap (under USD100) and give you a pretty good indication of bottom type. A plus is the transducer can be mounted inside the hull (no hole in the hull) and they provide other data such as battery voltage, water temperature and even show the fish under your hull. I have 2 on my boat and they're terrific.
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Old 09-05-2019, 11:08   #7
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Re: Best Depthfinder for Bottom Composition

Isnít there a Simrad depth module you install?
My small Zeus has a depth finder built in,and while itís not structure scan which I believe requires chirp, itís excellent for determining bottom type.
I canít understand why the small, less expensive plotters have great built in depth finders, but the larger more expensive ones donít.
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Old 09-05-2019, 23:31   #8
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Best Depthfinder for Bottom Composition

Donít laugh but we use a fish finder in the tropics and love it. It shows the bottom make up and where the bommies are located. Sometimes in the atolls the water is not that clear. For example where are are anchored in the Tuamotus itís coral bommies all around us. By using the fish finder we were able to pick a sandy location to drop the hook. But we had to float the chain to keep it off the bommies.

We use a Garmin fish finder with the transducer mounted on the inside of the hull
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Old 10-05-2019, 13:13   #9
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Re: Best Depthfinder for Bottom Composition

Quote:
Originally Posted by mikereed100 View Post
I'm looking for a depthfinder that will provide information on what the substrate consists of for anchoring. Specifically, one that will let me know it I am dropping in rocks or weed. Currently I am getting depth information from an Airmar DS200 transponder using a Simrad NSS7 MFD. I would like to stick with Navico for compatability and am looking at either Structure scan from Simrad or Forward scan from B and G. Either way it looks like I will need a new MFD to support either of these. I should mention that fish finding capabilities an not important to me as I don't fish. Mainly I'm just looking for better information on where I am dropping my hook. Also, the Airmar transducer has a nasty habit of jumping from 100m to 2m, especially when I am in poorly charted areas. This renders the depth alarm pretty useless.

Structure scan looks like it gives a very nice picture of what is on the bottom, whereas Forward scan lets you know what is coming up, but only provides a 2D picture of bottom contours. If I have to spring for a new MFD, I am leaning towards B and G as the sailing functions appear better.

Anybody using either of these? Any other options I have not considered?

These old posts may help. / Len
Fishfinder For Anchoring



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Old 10-05-2019, 13:50   #10
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Re: Best Depthfinder for Bottom Composition

I also like the fishfinder with transducer mounted forward on inside of hull. Garmin is good. Perhaps check out color screens for best UW details.
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Old 11-05-2019, 03:55   #11
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Re: Best Depthfinder for Bottom Composition

Quote:
Originally Posted by mikereed100 View Post
I'm looking for a depthfinder that will provide information on what the substrate consists of for anchoring. Specifically, one that will let me know it I am dropping in rocks or weed.
...
I should mention that fish finding capabilities an not important to me as I don't fish. Mainly I'm just looking for better information on where I am dropping my hook. Also, the Airmar transducer has a nasty habit of jumping from 100m to 2m, especially when I am in poorly charted areas. This renders the depth alarm pretty useless.

Use a fishfinder and ignore the fish.

Weeds will be hard, no matter what.

We had an eventual problem with an earlier DST100, NMEA2000 version... lost depth, erratic readings, etc. Easy replacement with a new DST800. No other bottom info from these, though, only basic DST.

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Old 11-05-2019, 20:38   #12
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Re: Best Depthfinder for Bottom Composition

Quote:
Originally Posted by Copacabana View Post
"Any other options I have not considered?"


It's pretty hard to beat the Garmin (or any other brand) fishfinder. They are cheap (under USD100) and give you a pretty good indication of bottom type. A plus is the transducer can be mounted inside the hull (no hole in the hull) and they provide other data such as battery voltage, water temperature and even show the fish under your hull. I have 2 on my boat and they're terrific.
Agree with this. We have pre-chirp humminbird fishfinder/plotter & have no trouble seeing bottom type. Ladyfriends chirp Lowrance even better. Helps if you are a diver & can look for yourself to interpret signals but chirp types you don't even need to do that.
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Old 12-05-2019, 00:14   #13
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Re: Best Depthfinder for Bottom Composition

Fishfinder is the way to go. You can get a colour Hummingbird for less than the cost of the transducers that go with the MFDs.

One of the advantages with the fishfinder is that you can instantly see the depth trend when entering shallow waters. Slowly shoaling waters are more likely to be sand or mud.

With a bit of practice you can also get a good idea of bottom conditions. If it's flat and featureless you are more than likely going to get a good hold and the more character the bottom has less likely.
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