I am getting about a 3' - 4' difference in depth reading between my structure scan (down imaging) and sonar? Any ideas as to what the problem is. The structure scan is reading correctly and matching my HDS 10 at the console.
Make sure you do not have the depth adjusted in the settings. Other than that. The only think I can think of is your bow unit is in shallower water(transducer on trolling motor) versus the transducer at the stern.