Transducer Measurements; Transducer Heading; Transducer Roll And Pitch; Transducer Position - Kongsberg EM 122 Installation Manual

EM 122

Transducer Measurements

It may be most practical to perform these measurements on the transducer mounting
frames before installation of the transducer modules. A final verification after module
installation is then required. Note that it also necessary to ensure that the final transducer
array face is flat with a maximum deviation from flatness of 5 mm peak to peak
including any rotation.

Transducer heading

The heading of the transducers is measured as the average heading of the two fore-and-aft
oriented sides of each transducer arrays. Thus, the heading of the transmit transducer is
the heading of the long sides, while the heading of the receiver array is the heading of the
short sides. For the receive transducer it may be better to measure the heading of the
long sides, and then subtract 90º to achieve the correct value. The measurement accuracy
is required to be within one fifth of the beamwidth of the transmit transducer. Note
however that the measurement accuracy of the relative heading between the transmit and
receive transducers must be better than 0.1º.

Transducer roll and pitch

Roll and pitch measurements are made according to standard conventions with positive
pitch angle if the transmitter array's forward end is above the aft end (tilts up), and
positive roll if the starboard side of the receiver array is lower than the port side.
Note that the roll and pitch angles to be measured are relative to the horizontal plane as
defined by the vessel's coordinate system. i.e. for roll the angle that the transducer's
y-axis have with respect to the horizontal and for pitch the angle that the transducers
x-axis have with respect to the horizontal plane. The multibeam echo sounder converts
the measured angles as entered into the installation menu to rotation angles before use
i.e. do not do such a conversion before entering them into the system.
The measurement accuracy is given in the table
Table 5 Transducer roll and pitch
Transmit transducer
Roll
0.2º
Pitch
0.05º

Transducer position

The location of the centre of each transducer array face must be measured in the vessel
coordinate system. This centre must be measured relative to the system reference point.
Measurements must be done in the X, Y and Z directions on both transducers.
100
Receive transducer
0.02º
0.2º
317669/B