6-6
6.2 Bottom tracking layer
6.2.1 Bottom Lock (BTM)
・Function・ Absolute Current of Sea Bottom: The measurement depth of layer changes
automatically according to ups and downs in bottom of the sea if the measurement depth of
E layer is set to BTM (bottom lock). (*1)
This is convenient for the measurement of the bottom of the sea layer.
Relative Current based on the bottom of the sea layer: When the standard layer of
drum is set to E layer when a relative current is measured, and the measurement depth of
layer is set to BTM (bottom lock), a relative current (AE-DE layer) based on the bottom of
the sea layer (E layer) can be measured by the bottom of the sea tracking.
Operation Standard Menu: [DEPTH] key/”Current Depth setting” menu/E Layer: 150/Bottom Lock
(End: [DEPTH] key)
Selection Frame Menu: [□] key/ Enclose “Current direction/Current speed” with the frame
/[MENU] key/”Current speed and direction/relative current layer” menu/ E Layer: 150/
Bottom Lock
Fig. 6.2.1 Bottom Lock
Note: Because the device cannot recognize ridge when the 4-beam of the transducer
steps over ridge in sea bottom, it measures as a measurement layer. In this case,
the current measurement layer of the lower layer including the bottom lock layer
might become a mis-display.
Fig. 6.2.2 Mis-display by ridge
*1 The maximum measurement depth of the current is about 200m. The maximum measurement depth of layer is different
depending on the oceanographic condition.
The bottom of the sea depth value is a mean value of the measured four beams. It might be different from the depth value of the
right under.
*2 In case of the shallow sea bottom or the slant sea bottom, %-value decreases.
The depth of about 80% of
bottom of the sea depth is
The measurement depth
changes automatically
according to ups and
downs in bottom of the
sea if the measurement
depth of E layer is set to
Bottom Lock.
Present tracking depth is displayed,
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