Forward Scanning Sonar

[Kashmir cat]

It's been a while since I have used the Interphase Probe (2002), but I think Interphase mentions this shallow depth limitation in their Probe manual and it was certainly true in usage. Maybe the new Probe is different and works better in shallow water, I don't know. But realistically, I think it is physically impossible for the Probe to forward scan in shallow water to any degree because of the wide scanner beam width. I think it would work well if you are in say 100+ feet of water and a submerged container is floating just below the surface, or the superstructure of a sunken wreck is sticking up from the bottom, or a unchartered seamount, or the tip of an giant iceberg, or the tail of the Lochness monster. Of coiurse you would have to be cruising slow enough with your eyes glued to the scanner screen to see any of these hazards in time. I'm not sure if the alarms work that well because all sorts of things are picked up (like schools of fish) in normal usage and they would drive you crazy with false alarms. Anyway you get my drift. It is ironic that the very depths that you would use the sonar the most are the depths that it doesn't work that well.
Now to be fair I have not used the twin phase unit in which you can switch the scanning beam from up/down (Probe) to side to side. Maybe the side to side scanner works in shallower water, but I would doubt that it would work in REAL shallow water (less than 10 feet) because of the same beam width limitation. I think the side to side mode would probably be the most useful in determining if there is a navigable passage in a reef in front of you when the water is murky. Thats all I know. Erik

[Dockhead]

I inherited an Echopilot Gold FLS installed by the PO on our new boat. I can't tell yet whether it is really useful or not. I am still trying to learn to interpret it. So far I am only able to discern the vaguest trends in the bottom. But I do like having a second depth sounder close to hand, at the very least.

It works flawlessly, with no interference with the regular Raymarine sounder.

[Jim Cate]

Originally Posted by Kashmir cat

I cruised with an interphase probe for years. When the water was 20 feet or less, the unit was unable to forward scan and became a really expensive depth sounder (but it looked cool!).

G'Day again, Jack

The above does NOT reflect our experience. The Probe, as it says in their manual, will look forward a distance that is a function of the depth. Depending on turbidity and the nature of the bottom surface, the distance ranges from around 3 times the depth to as much as 7 times the depth... but the latter is rare. So, in 20 feet of water, it will give a picture showing the bottom somewhere between 60 and 140 feet ahead of you. For us, this is useful. Further, if there is an obstruction sticking up, say a reef, it will appear out near the longer end of those ranges.
In really shallow water -- less than 10 feet, say -- the ability is reduced. We find that in such depths we tend to be going pretty slowly, and it will give some warning of diminishing depth... certainly more warning than a regualr sounder can give, which is none!

A typical use for us would be in seeking an adequate place to anchor under conditions where the visibility into the water is reduced due to muddyness or darkness. Creeping in at idle speed into say 25-30 feet depths we can see far enough ahead to avoid banks or rocks. Once in our preferreed depth, we will do a slow turn, checking for obstructions within our swinging circle. Being able to see things 150 feet or so away makes this easier! If all is clear, down goes the hook.

As I said before, the Probe is not a panacea, but is another tool that helps us stay off the putty in conditions where the Mk One eyeball is handicapped. Others may not think this warrants the high price -- we do!

Cheers

Jim and Ann s/v Insatiable II Lying Lake Macquarie NSW Oz

[44'cruisingcat]

Originally Posted by cat man do

Really?
That's when I want it to work

I'm not really that concerned about hitting anything if the depth is 20ft or more as I'll only draw 3ft anyway

Has anyone else had these or heard of these issues?

As has been said, forward scanning range is a function of depth. The Echopilot "sees" forward around 4 or more times the depth. Mine has kept working to depths of half a metre, although the forward scanning isn't particularly useful then.

Something I really like about the Echopilot, (apart from it's price) is that the transducer is much smaller than the interphase one. The Echopilot one fits a roughly 1' skin fitting, and can be withdrawn through it.

The Intrephase transducer is sort of like a plastic icecream container, but triangular, and probably more than a litre in volume.

[Stevens 47]

The Intrephase transducer is sort of like a plastic icecream container, but triangular, and probably more than a litre in volume.

Yes it is like a fist. If I had a performance hull I would think twice about installing it. There is nothing performance like about the keel on my boat...massive.

Jim thanks for the feedback.

Jack

[Randyonr3]

I agree with what Jim is saying , And I'm not saying all of the adjustments are the same on all the units but in shallow water, we adjust the beam to forward scan and forget about depth under us.. we have a raymarine depthsounder for that..
Being in 15 to 20 feet of water and being able to look out in front of us 100 to 150 feet is a plus..
Ours has saved our Butt more than once..
Once, while comming into "Moss Landing" in Montery Bay, On the California Coast, we were well withing the chanel markers and the wife looked over at the "Probe" and said we were about to hit the rocks about 80 feet forward.. My reply was "cant be as we're inside the markers", she said "I dont care what the markers are doing, you're going to hit the friggin rocks"..
A quick look at the scanner and a hard pull to port and we missed the rocks..
Later that afternoon, while talking to some locals at the yacht club, we were informed that durring a really low tide, the channel markers drift to the south over the rocks and to stay on the north side of the channel..
And thats just once over the years that the unit has saved my tail..

[Stevens 47]

Once, while comming into "Moss Landing" in Montery Bay, On the California Coast, we were well withing the chanel markers and the wife looked over at the "Probe" and said we were about to hit the rocks about 80 feet forward.. My reply was "cant be as we're inside the markers", she said "I dont care what the markers are doing, you're going to hit the friggin rocks"..
A quick look at the scanner and a hard pull to port and we missed the rocks..

The unit paid for itself many times over by the sounds it...thanks for the info.

[EchoPilot]

Hello,
If you are running any form of sonar you only should use one system at a time. All modern systems will have built in autogain to some degree. As soon as there is another sonar running then this gain will be turned down in an attempt to reject the signals from the other sonar as it will be seen as noise, this has the effect of considerably reducing the performance of your sonar.
with two systems running on the same frequency you can even get into a situation where the foreign signals can e received as real leading to inaccurate depth readings.
Even if you are running in different frequencies you will get harmonics that will interfere, particularly if the two frequencies are multiples of each other.

The main advantage of the echopilot system over the competitors is the shallow water performance. The echopilot will work down to under a meter. As with all forward sonars the forward range is dependant on the depth.
The best forward range to depth ratio achieved by any of our competitor is eight times the depth ahead.
The bottom of the range echopilot bronze can achieve 10 times the depth ahead, and the echopilot platinum and echopilot 3d can achieve up to 20 times the depth ahead. For more detailed information check out the echopilot website.