Simrad PI GEOMETRY User manual

Simrad PI Geometry
Sensor system for trawl and danish seine
(CD012221-002)
TECHNOLOGY FOR SUSTAINABLE FISHERIES
www.simrad.com
Simrad’s latest sensor system measures the geometry
of you gear. If your trawl or danish seine is skewed and
misadjusted, you will know right away!

From the main Geometry sensor mounted on the middle of either the headrope or
the footrope, you measure the distance to the two “Mini-R” responders mounted on
each door or wing ends. These measurements will immediately tell you if the trawl
(or danish seine) is skewed due to water current or incorrect warp lengths. You will
thus easily detect large or small changes in the trawl geometry, and can rapidly take
corrective actions to maintain maximum catch efficiency.

A
A
B
B
C
C
(CD012221-008)
In order to maximize the performance
and the catch efficiency, the trawl and the
warps must be adjusted properly. This
is essential to ensure a square trawl and
minimum skew. This is also important
for danish seines, as the ropes must have
identical length.
Any disturbance to the trawl movements
may have a negative effect on the catch.
This is particularly important on a bottom
trawl. Askewed bottom trawl will result
in unstable bottom contact, and create
escape routes for fish below the gear
and through the side panels. On pelagic
trawls and danish seines a skewed net
will make the gear unstable, and the catch
be reduced. Optimal trawl geometry is
therefore vital for maintaining the catch
efficiency.
A trawl or danish seine may be skewed
for several reasons. Some of these reasons
are:
• Incorrectriggingoftrawl,sweep
lines or trawl doors
• Misadjustedwarplengths
• Sidecurrent
• Towinginsteeporslopededges
If the rigging of the trawl is correct,
you can easily compensate for skew by
adjusting either port or starboard wire
length.
The PI Geometry sensor system is based
on the fact that a correct rigged trawl and
danish seine has exactly the same distance
measured from the centre of the headrope
or footrope to either door or trawl
wing. These distances must be identical
independent of weather conditions, sea
state or water currents.
Advantages
Bottom and pelagic trawls:
• Measuresifthetrawlisskewed.
• Allowsyoutocorrectthetrawl
geometry by adjusting the warp
lengths.
Danish seines:
• Detectsvariationsinthedistance
from the centre of the headrope (or
footrope) to either wing of the seine.
• Detectsdifferencesintherope
lengths when the seine is closed
(distances between the wings should
then be close to zero).
Why use the PI Geometry sensor system?
On the left trawl,
distance “A” on the
port side is longer
than distance “B”
on the starboard
side. The trawl is
unbalanced. On
the right trawl,
the distances are
identical. Measuring
the door spread
(“C”) will not detect
a distorted trawl
geometry.

326136 / Rev.A / September 2008
Kongsberg Maritime AS
Strandpromenaden 50
P. O.Box111
N-3191 Horten,Norway
Simrad
Telephone: [phone]
Telefax: [phone]
[e-mail]
www.simrad.com
1
X1 [m]
143.5

1
X2 [m]
143.5

(CD012221-007)
ABC
I
E
D
F
H
G
1
1
Clear and precise
numerical information
The numerical presentation of the PI
Geometry data is automatically shown
in the relevant display modes. Since this
is a “dual” sensor two yellow rectangles
are used to indicate which two numerical
displays that provide information from the
same sensor.
ASensor identification
BUnit of measurement
CDistance
DDistance changes per minute
EArrows pointing “out” means that the
distance is increasing, arrows pointing
“in” means that distance is decreasing
FVisual alarm
GSensor transmission indicator
HInterference warning
IDual sensor identification
Graphic presentation
This example shows a graphic display
with PI Spread and PI Geometry sensors
connected. The top line shows the
distance between the trawl doors. It is
currently 69,5 meters, and the distance
is increasing with 2 meters per minute.
The PI Geometry sensor detects that the
distances between the centre of the trawl
opening and the two trawl doors are
currently identical and 147,0 meters. The
distances are changing with 0,5 meter per
minute. The graphical presentation further
presents the historic values from within
the past 17,5 minutes.
17.5 12.5 10 7.5 52.5
15 min
38kHz 1000W MEDIUM T 22.5 C
oS 7.2kn DK 1050 m
(CD012106-001)
S1[m] X2[m]
69.5147.0
0.5
2
X3[m] 147.0
0
50
100
150
200
250
0.5
In this example the two responders are positioned with identical distances to the PI
geometry sensor. The gear is in balance, and no adjustments are required.