Topic: Depth Offset

[bobn]

When useing the depth offset  the digital depth readout is changed  to reflect the offset.  But will the NMEA  DPT  output sentence reflect the offset  and  if recording a .SON  file will the  200 khz  B001.SON reflect the offset?   

[RGecy]

Very good question.  I have never tested this.  The depth used to not be recorded in the son files and was only calcualted on playback.  An educated guess, the raw data does not reflect the depth offset when its recorded.  It records the actual depth.  The depth offset is a "post processing" feature.

I will verify this for you.  Excellent question!

Robert 

[Humminbird_Greg]

I’ll agree with Robert that someone will have to verify this (I do not have a way to do so) but I thought that the Depth Offset menu setting did affect the NMEA DPT sentence data.  Not sure about the recorded data but would agree with Robert that the depth is recalculated when it is played back.

[bobn]

I  took the boat out to try and answer my question ,  didn't get the result I expected.  What I found is the NMEA  output depth is the actual water depth and the 997 depth offset  had no effect , but it does change the unit digital depth readout.  Surprisingly  the depth offset  appears to effect the 200 khz beam  recording , the depth is the offset depth.   I find that hard to believe.  Unfortunately , I needed to winterize and putup the boat for the season.  Hopefully  someone  down south can take a test .   

[bobn]

The DPT NMEA sentence includes transducer depth along with the offset from the transducer to the surface.  So its up to the receiving program or device to utilize the offset.