Garmin GPSMAP 238 Sounder User Manual download pdf (Page 123)

113

Appendix I

Understanding the Chart

Understanding the Graph

It is important to understand that the unit does not display a 3-D representation of the underwater

environment. The unit can display multiple things at the same time, but cannot determine where the

return originated – only when it was received.

Examples 1 and 2 provide a look at the underwater world from a top view, and illustrate how these

views would be displayed on the graph. On both graphs it appears the ﬁ sh and tree are side by side

as shown in Example 1. However, when we look at Example 2, we see that the ﬁ sh can be several feet

from the tree. It is important to remember that the sonar cannot determine where in the coverage area

the tree or ﬁ sh are, only that the returns were received at the indicated depths in the same time frame.

Remember that the sonar displays a 2-D picture of the

underwater environment. The ﬁ sh and tree could be

located anywhere in the coverage area at that time.

Example 2.Example 1.

Branches

Fish

Enlarged

Transducer

View

Branches

Fish

Enlarged

Transducer

View

)

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Garmin GPSMAP 238 Sounder User Manual Page 123