Humminbird 987C SI COMBO SONAR User Manual


 
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WhiteLine® highlights the strongest sonar returns in white, resulting in a distinctive
outline. This has the benefit of clearly defining the bottom on the display.
UNDERSTANDING SIDE IMAGING
It is important to understand how Side Imaging technology produces the display
available on the 900 Series™. The images you see on the display are produced using
sonar technology. The special transducer produces three distinct beams – one beam
facing down and two beams pointing out to the side. These “side beams” are aimed at
right angles to the path of the boat and, unlike the “down beam” which provide conical
coverage, the side beams provide coverage which is very thin front to back, yet very
wide top to bottom.
The narrow aspect (front to back) of the beam illuminates a small strip of the bottom
perpendicular to the direction of the boat. Each time the unit “pings”, a strip of data
representing all the echoes received by the transducer, are put together on the display
to form the image that you see. The rows closest to the boat icon at the top of the
display are the most recent sonar data. The information is scrolled down the screen as
new data, drawn at the top of the screen, becomes available.
The side beams can be operated at one of two frequencies: 262 kHz or 455 kHz.
Selecting 455 kHz produces the sharpest image while selecting 262 kHz provides greater
bottom coverage area. It is important to understand that when the boat turns, the strips
to one side will begin to overlap and the strips on the other side will fan out, providing
some distortion to the image. Side beams look out 240 feet, with a depth limitation of
100 to 150 feet, depending on the contour of the bottom. Please see the Side Imaging
Sonar Tutorial at www.humminbird.com for a more detailed explanation.
Your Side Imaging transducer also provides traditional sonar imaging at 50/200 kHz.
Total coverage under the boat is 180°.
Side Imaging
160º Total Coverage
40
o
455 kHz
40
o
455 kHz
50 kHz
74
o
200 kHz
20
o
455 kHz provides highest resolution with 160° total beam width
Side Imaging
262 kHz - Maximum Coverage
180º Total Coverage
84
o
262 kHz
84
o
262 kHz
50 kHz
74
o
200 kHz
20
o
262 kHz provides maximum coverage with 180° total beam width
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