Chapter: 2. Operation
Principal Functions
Bottom detection
GDS101 employ a bottom detection algorithm that will try to extract the bottom signal from all kinds of
noise and secondary echoes. When GDS101 is tracking the bottom normally, a thick black line is shown, and
below that, a ribbon with a hatched pattern. This pattern has two levels of hatching. The darkest represent
strong and unambiguous bottom echoes. The lighter hatching represents weaker signals possibly occasional
detection misses. If the software can detect no bottom for several pings, the hatched ribbon disappears.
During normal bottom tracking, a digital value is shown by the bottom contour at the right side of the
screen. If the software algorithm looses track of the bottom altogether, a warning beep is heard and the black
line and hatching band disappears. A warning message: “Lost bottom” is shown in the screen’s lower right
corner.
Ping to Ping ltering
Part of the bottom detection algorithm is the ping to ping ltering. The next bottom is searched for in a
time and strength window based on the strength and timing of the previous bottom echoes. This procedure
reduces the probability of tracking schools of sh or secondary echoes as bottom. If no bottom is detected in
the calculated window, the window is gradually increased in size until the full time and strength window is
used.
Bottom Search Range
The FIX RANGE function in screen 9 is used to control the search range for the bottom detection algorithm.
See “Fig. 2.10. Screen 9, System status screen.” on page 21. When this function is on, bottom is only searched
for within the selected display range. When the function is off, bottom is searched for within the entire
functional range of the echo sounder.
System (Power) On/Off
During normal daily operation, the system may be switched off from screen 2. See “Fig. 2.3. Screen 2, 2nd
Operation screen.” on page 14. This operation does not disconnect the system from the power supply, but
all power consuming components are switched off. The system may be switched on again by pressing any
button.
Note: Do not run the sounder for a long time with the transducer in air. The transducer
may be damaged.
Remaining disk size diagnostics
The remaining size of the external Compact Flash is indicated at screen 9 (status),” Disk avail”. The
indication is in percent to the total size. If the external Compact Flash is not installed, the remaining size of
the internal Compact Flash is indicated. See “Fig. 2.10. Screen 9, System status screen.” on page 21.
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