Humminbird 343c Operation Manual page 63

Fish Arch: A Fish Arch is the apparent "arch" that appears on the display when any
object moves through the sonar cone. The arch results from a gradual decrease in
distance to an object as it moves into the sonar cone. The distance to an object
changes due to the conical shape of the sonar beam, which causes the distance to
be greater at the edges of the beam than at the center of the beam. When this
distance change is graphed on the display, an arch appears.
Fish ID+™: Fish ID+™ is a Humminbird® feature that uses advanced sonar processing
algorithms to determine if a detected object is likely to be a fish. When the sonar
signal from an object meets strict parameters, the unit draws a Fish Symbol (or
icon) and the digital depth of the target. On DualBeam and DualBeam PLUS™ units,
fish detected in the narrow center beam are shown as shaded symbols, and fish
detected in the wider beam are shown as hollow symbols.
Fish Symbol: A Fish Symbol is the graphic that is displayed on the screen when Fish
ID+ determines that a sonar return is likely to be a fish. See Fish ID+.
Freeze Frame: Freeze Frame is a Humminbird® feature that pauses the sonar
scrolling so that the image on screen can be studied with greater detail. See Instant
Image Update.
Frequency: Frequency is a measure of the number of sound wave cycles per second
of a sound impulse transmitted underwater. A typical frequency for fishfinders is
200 kHz, which offers a good balance of performance under many conditions.
Lower frequencies, such as 50 kHz, are capable of penetrating to greater depths, but
with less resolution. Higher frequencies, such as 455 kHz, offer greater resolution,
but are limited in depth performance. Humminbird® uses a variety of frequencies
that are optimized for specific applications.
Grayscale: Grayscale is the use of varying shades of gray to represent the strength
of the sonar signal on the display, and is a very intuitive method of presenting
information. Traditionally, the strongest sonar signals are represented in black, and
progressively weaker signals are represented in progressively lighter shades of gray.
Grayscale, Inverse: Inverse Grayscale is a Humminbird® feature that reverses the
correlation of sonar signal strength and the shade of gray typically used to
represent it. The strongest sonar signals are represented by "white", and
progressively weaker signals are represented in progressively darker shades of gray.
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