In my opinion the value of 2D/DI split screen views on SI and DI units is in availability to see fish on both views simultaneously, and compare theirs arcs and dots for more efficient fish definition. I do not know any advantage of what horizontal splitting provides for seeing structure or fish:
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ImageShack.usthe structure can be much better seen on full DI view that is available, and the fish can be much better seen and compared on vertical splitting:
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ImageShack.usHumminbird provides this view at bigger screens, but it does not make big difference in the views on large screens. It is critical for smaller screens, and all sonar companies realized this, but the originator did not.