Simrad AP28 Operator's Manual page 33

Depth Contour Tracking, DCT
With input from an echo sounder, the autopilot can be set
to steer the boat to a set depth. This is very useful if you
want to follow a depth contour. Make sure you have
depth reading available in the system.
Smooth seabed
Slope
Do not use this feature unless the seabed is
suitable. Do not use it in rocky waters where the
depth is varying significantly over a small area.
TURN
TM
Rocky waters
Narrow channel Ridge
Operation | 33