Image on the Screen- Where is it under the Boat?

[slaters#1]

I have my transducer mounted on my trolling motor in the front of the boat. Let's say I am moving along at 1 to 2 mph, and an object appears on the screen (perhaps a stump). OR I see some fish suspended at 6'.

How do I know where that stump is on the bottom? Can I assume that once I see it on the screen the stump is immediately in front (say 5-10 feet) of the boat, thus I should stop to fish?

Can someone explain how they actually locate a point on the bottom?

I usually fish oxbow lakes and farm reservoirs, rarely over 15 feet deep.

Thanks for any advice

[CrappieLab]

It depends on what kind of transducer you are using but at shallow depths the image is going to be pretty close to right under the boat. At shallow depths you are not going to get as wide a sonar cone causing the image to be closer before it appears.

[CatFan]

Once you see enough to tell what it is, it's behind the transducer. You can't really be sure whether it's off to one side or the other though. All you can really say for sure is that the peak of the arch occured when the transducer was closest to the object.

You can stop and change directions and locate the object that way.

[slaters#1]

thanks men. there is a wealth of knowledge on this board.

[rnvinc]

One trick I've used in the past with regular 2d sonar on the TM is to tilt the back of the xducer down about 5 degrees...

This will sort of "aim" the downward looking sonar cone to point in front of the xducer somewhat which will show the brush before it is actually directly under the xducer....

Because my long pole baits are hanging straight down under the rod tips and 10-12 ft in front of the xducer ....the baits can get hung up in the brush before I even see the brush on the DF....

So, in effect, by tilting the xducer to read a little forward instead of straight down ...the brush will show on the DF about the same time that the baits reach the brush...

Rickie

[mduncan62]

Tilting the transducer will change your depth reading, making it inaccurate, to some degree.

[derick37335]

put some heavy sinkers on and hang them down by the transducer to see if it is pointing where you need it to be.(in com water)And if your running at that speed keep a marker bouy close at hand when it looks like it maybe something come up pitch it back a foot or two and come back with rod in hand bottom bounce with the heavy sinkers to see what it is.Big rocks and stumps look a like but a good size brush will have lines all over the screen. hope this help

[Ranger R61]

My unit (HB 788ci) has dual frequencies at 200kHz it has a cone width of 1/3 of the depth. In water 12 ft deep the cone width is 4 ft. It also has a frequency of 83kHz. Using that frequency the cone width is the same as the water depth. In 12 ft of water the cone width is 12 ft.

Hope this helps.

[slaters#1]

thanks again. gonna try to match what i feel with a sinker at the end of a line compared to what i see on the screen.