Thread: A Questioning Mind

I agree the near field is not the only problem (because the beam form is going to be in this area of possible surface clutter for a greater distance than a "down pointing" beam form)...

And from the "calculated" beam form depiction (see below)...I can't see where there is any measured "depression angle"...because the sound pulse (in both frequencies)...reaches all the way to the water's surface...albeit at "ever-decreasing pulse strength"...

The echoes are there (if the beam form is there)...the processor (and/or it's associated filters)...decides which of the total echoes are painted into the SI image..



I'm only guessing that there is a specific filter used for omitting "surface clutter" type echoes in the processing of the SI image...(there is no setting for SI surface clutter...but that doesn't mean one doesn't exist...we just don't have access to it)...

Maybe I'm mis-understanding your meaning of "depression angle" (as relating to an SI image)...(or it's delving into an area of sonar technical data I have yet to learn)...

Because in SI sound pulses thru water ...there is no measured angle (that I know of)...from the water's surface to the "edge" of the SI beam...

There is no "edge" in any sound pulse beam form...only the brand's own criteria for how they measure the "ever-decreasing strength" of the sound pulse before it reaches 0db ...or "Absolute Silence"...

And of course there is the measured angle at 0db "Absolute Silence"...but that angle is way out past the "advertised beam angle"...(brands have no need in advertising this 0db angle...so we never see it in advertising)...

Rickie