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I'm sure this has been answered before, but I will ask again. My 2d sonar ducer is mounted on the transom. When I pick up say a brush pile on the screen, where about is it under my boat? Is the ducer directly over it, or closer to the front of the boat?
That will depend a lot on depth of water because the cone gets larger the deeper the water ...
And it also will depend on beam frequency used ... the 200kHz cone is generally 20° ... the 83kHz cone is generally 60° ...
The cone in Fishton's video below is a general understanding for a Sonar cone about 60° ...
https://www.youtube.com/watch?v=R4T0...ature=youtu.be
Rickie
Before I started using GPS on sonar. I would pass over Brush,habitat,structure,etc. and as soon as I seen it I would throw out a buoy and then turn around and go right back by that buoy over whatever,etc. and as soon as I seen it on my sonar I would throw out another buoy then I would know that what I seen was in between the two buoys A lot of the time I would have a distance of about 20' between the two buoys. Has a lot to do with depth and speed but almost always when you see something on your sonar you have done passed over it. I love the new sonars with GPS just freeze the sonar picture curser over to whatever and mark a waypoint hit go too and go right to it.
If your unit has both DI and 2D, you can use them in a split screen. As you approach the brush pile (best to come in from down wind), the leading edge of the 2D beam will pick up the brush pile first. As you continue to move slowly forward, the DI will pick up the brush pile.....when that happens, the transducer is directly over the brush pile. If you continue to move forward and throw a marker buoy when the brush pile drops off the 2D....it will be placed just upwind of the brush pile.
If you pick up the brush pile on DI, but not on 2D, you are off to one side of the brush pile.