Humminbird 987C SI COMBO User Manual

When Fish ID+™ is turned off, the 900 Series™ shows only the raw sonar returns on the
display. These returns will often result in "arches" forming on the display, indicating
potential targets. Due to the transducer beam angle, the distance to a fish decreases
as the fish moves into the beam, and then increases as it moves out again, creating a
Fish Arch when this distance change is shown on the display. Boat speed, chart speed,
and the position of the fish within the sonar beam greatly affect the shape of the arch. 

1.  Highlight Fish ID+ on the Sonar main menu.

2.  Use the LEFT or RIGHT 4-WAY Cursor Control keys to turn the Fish ID+™ setting

On or Off. (Off, On, Default = Off) 

Fish ID Sensitivity adjusts the threshold of

the Fish ID+™ detection algorithms. Selecting a higher setting allows weaker returns
to be displayed as fish. This is useful for identifying smaller fish species or baitfish.
Selecting a lower setting displays fewer fish from weak sonar returns. This is helpful
when seeking larger species of fish. Fish Sensitivity is used in conjunction with Fish
ID+™. Fish ID+™ must be On for Fish Sensitivity to affect the ability of the 900 Series™
to identify sonar returns as fish.

1.  Highlight Fish ID Sensitivity on the Sonar main menu.

2. Use the LEFT or RIGHT 4-WAY Cursor Control keys to change the Fish Sensitivity

setting. (Low = 1, High = 10, Default = 5)

RTS® Window sets the RTS® Window to either Wide or Narrow, or turns it off in the
Sonar View. The RTS® Window always updates at the fastest rate possible and only
displays returns that are within the transducer beam. (See Getting Started - Using Your
900 Series™: Real Time Sonar [RTS®] Window for more information.)

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