NorthStar Navigation Echo Sounder NorthStar 491 - Manual (Page 25)

491 Echo Sounder Operations Manual Page 21
Using bottom lock/
center zoom
When you select bottom lock/center zoom, the sea bottom is
flattened out and displayed in the center of the screen. You
can see any fish near the bottom, as with the bottom lock
zoom, and also examine the seabed’s composition.
Using marker zoom When you select marker zoom, you can choose the part of the
water column to magnify. The top edge of the magnified area
is determined by the location of the depth marker. To move