Humminbird 408120-1 GPS Receiver User Manual


 
5
How Sonar Works
Down Imaging™ Sonar
(Down Imaging™ models only
[587ci HD DI, 597ci HD DI])
Your 587ci HD DI/597ci HD DI Fishfinder
uses Down Imaging™ technology. The Down
Imaging™ transducer scans the water with
razor-thin, high-definition beams. The beams
are wide (side to side) but very thin front to
back.
The Down Imaging™ beams can be operated
at two frequencies: 455 kHz (75°) or 800 kHz
(45°). Select 455 kHz for the best overall
image quality and depth. Select 800 kHz for
the sharpest image. See Sonar Menu Tab:
Imaging Frequency for more information.
The transducer also uses conical beams to
provide data in traditional 2D format (see
What’s on the Sonar Display). Select 455 kHz
for a narrowly focused 16° center beam, or
select 200 kHzfora wider 25° beam (seeSonar
Menu Tab: Beam Select).
Depth capability is affected by such factors
as boat speed, wave action, bottom hardness,
water conditions, and transducer installation.
75 Degree Total Coverage
16°
75°
25°
455kHz
200kHz
455kHz
45°
800kHz