Garmin GPSMAP 178C Sounder Manual de usuario descargar pdf (Pagina 124)

114

Appendix G

Understanding the Graph

Whiteline

The GPSMAP 178/178C can help you to determine if the bottom is hard or soft. When the sonar

soundwaves are reﬂected back by the bottom, a hard bottom returns a stronger signal than a soft bottom.

A thin whiteline indicates a softer bottom while a thick whiteline indicates a harder bottom. Normally,

a red/dark line is used to show the point where water meets the bottom. This line follows the bottom

contour, along with any signiﬁcant objects lying on the bottom. The unit uses the whiteline function to

make this bottom layer information easier to distinguish.

With the GPSMAP 178/178C, active whiteline helps accentuate where strong signals are located,

which make bottom type determination easier. The example to the right shows the bottom return with

and without the whiteline activated.

Whiteline can also help you to determine the type of bottom

structure that is displayed on the chart. By determining the

hardness of the structure, you can make a better informed

decision on the type of structure.

Structure is hard—

probably a rock or stump

Structure is soft—

probably a mud pile

Example 4.

Whiteline Turned OffHard Bottom

Whiteline

Soft Bottom

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Garmin GPSMAP 178C Sounder Manual de usuario Pagina 124