Peter you requested this I think.

[IMG]http://i1084.photobucket.com/albums/j404/moveon100/BlindSpotsonDepthFinders.jpg[/IMG]

[IMG]http://i1084.photobucket.com/albums/j404/moveon100/scan0001-1.jpg[/IMG]

Here is the image or picture that you asked about some time ago. It's taken from a Fishing Facts Magazine Article on depth sounders.

This picture shows you why fish arches don't always show up as a arch. Same principle applies to schools of bait fish etc.

The fish had to pass though the axis of the sonar theoretical cone in order to get a good arch on the screen or graph.

This Fishing Facts Article is old March 1976 but the principles of sonar have been around since WWII.

Hey thanks alot! I've been looking for something like that for awhile now. The one in my Eagle manual doesn't explain as clearly as this one does, and doesn't mention schools of bait at all.
Cheers!