Thread: Difference between depth and range?

Sonar measures 2 things....

* "Time of the sound pulse ("ping")....thru the water and back"...and
* "Strength of individual echoes in the return" ...

"Time of the sound pulse thru the water and back" ...is what the processor uses to determine distance (range) to the object....

The "Strength of individual echoes" ...is what the processor uses to determine what the processor "thinks" that echo is bouncing off of...

Even the digital depth number is a mere "Range" calculation of the "Strongest reoccuring echo return" (in the beam shape)...to get back to the xducer...

The processor "interprets" this strong reoccuring echo return as [i]"Hey that echo must be the bottom because that echo return is very strong and it's occurring in every ping"...

The "Range Lines" at the bottom of the SI image are just that..."range" (distance)....to a point away from the xducer...

If we tie a 10ft rope to a ball and attach one end of the rope to the xducer....and then we swing the ball in an "arc" (within the confines of the SI beam shape)... this "arc-ed" path that the ball traveled would be the "10ft Range" from the xducer....

So any "echo target" that falls into this "arc-ed" path of the ball ...should show in the SI image directly on the displayed 10ft "Range Line"...

So...in a nutshell...

"Range" is a mathematical derivative of the "time" it took for the sound pulse to travel thru the water, bounce off something, and return to the xducer....

"Depth" (the digital depth number)... is a processed derivative of the "strongest reoccurring echo return" in the emitted sound pulses ("pings")...

Rickie