Depth Sounder Calibration Poll.

[Lodesman]

Originally Posted by aqfishing

Ok, but your point is?

The point is the transducer is not at the waterline generally, so transducer depth is not the same as waterline depth.

Since most depthsounders have the function to add or subtract an offset amount, you can either: (a) add the depth of the transducer to give the depth of the water you are in; this makes it slightly easier to compare actual depth to charted depth; or
(b) subtract the vertical distance between where the transducer is mounted to the lowest hanging part of your boat (keel, rudder, prop, other); this gives you the actual amount of water that separates your tender bits from the sea bottom.

[Training Wheels]

So much for a poll and only a poll! [emoji23]

[StuM]

Originally Posted by aqfishing

Is to the transducer and the waterline not the same thing.

No, the transducer is usually somewhere on the bottom of the hull, which could easily be a meter or so below your waterline and a meter or more above the bottom of your keel.

If you set the depth of your transducer on your sounder you are the measuring actual depth, i.e. to your waterline.

Agreed, but that is not calibrating to the transducer, setting it's depth below the waterline is calibrating to the waterline.


If you set the depth of your transducer on your sounder to a negative value equal to the distance from your transducer to the bottom of the keel, you are calibrating to your keel.


If you don't set the depth of your transducer on your sounder (leave it at zero), you are calibrating to your transducer.

[aqfishing]

Sorry Guys, I must apologise. I did not explain myself properly in my first post. This happens when you are on typing on a phone and lazy to do so properly and in a rush.

I was actually referring to the poll questions not the physical placement of the transducer. I guess I was trying to say everything is calibrated from the transducer at the end of the day, so I felt that the poll "to the transducer" was the same question. However in hind sight I now realise that "to the transducer" would simply mean you have not calibrated it all, i.e. the offset is set to 0.

[Mr B]

Transom Transducer is at the water line,
Hull transducer is usually at the bottom of the hulls,

My transducer is under my hull, So When I run out of depth. My transducer is sitting on the bottom, Grounded, So is my boat, Its a Cat,
There is nothing under my transducer,
Its the bottom of my boat, Hull,

The offset of my transducer to my hull, is about 1/4 of an inch,
Thats why I leave a foot extra under my hull, To give me that bit of play because the bottom is not flat and level,

I can have a foot of depth under me, But the bow may be aground, 15 feet forward,

It all depends on where your Transducer is located in your boat,