Installation
ing. Allow sufficient bend radius for the cable (see paragraph 2.4.5.2) and ensure
that there is no strain at the connector when the structure is in either the stowed
or operating position. If cable clamps are used, protect the cable jacket from
sharp edges on the clamps. Position the head so that the projector and hydro-
phone have an unobstructed line of sight to forward and a minimum of 75 de-
grees to either side (105 degrees for a 210 degree head).
The location of the head should be chosen to be as far away from other sources
of acoustical energy and mechanical hull-borne noise as possible. High ambient
noise will degrade 8101 system performance. In addition, the location should al-
low relatively easy access to the head for preventative maintenance and inspec-
tion. In the case of an ROV installation, place the head in a location to ensure
that it does not "see" any part of the ROV structure. A typical location is slightly
forward and above the bottom plane of the ROV.
2.4.2
Installing the Sonar Head
The sonar head may be permanently mounted, as part of the vessel's structure
or mounted on a temporary structure such as a pivoting or retractable pole. The
head requires accurate placement and precise alignment in azimuth and eleva-
tion. In addition, the head must be securely mounted to ensure that both location
and alignment cannot shift during a survey. Careful consideration must be given
to the routing of the sonar head to sonar processor cable to avoid cutting or
abrading the outer waterproof jacket. If the installation is part of an ROV/UUV,
locate the sonar head as far from hydraulic pumps or other rotating machinery as
is possible in the confined space of the vehicle. In addition, place the head as far
forward as possible and at least a meter above the bottom plane of the vehicle.
2.4.3
Orientation of the Sonar Head
The sonar head should be mounted with the array center scribe mark oriented
straight down with the projector pointing aft (see Chapter 9, Drawing 10723).
Care should be taken to ensure that the head is parallel, as closely as possible,
to the horizontal plane of the vessel or ROV. Small errors in mounting can be
compensated for by post-processing data acquisition software.
2.4.4
Sonar Head Acoustic Center
Figure 8 provides the acoustic center location (the intersection of lines Y-Z and
X-Z) required for Vessel Reference Point (VRP) measurement. This is the point
to which the offset measurements (in relation to the VRP) are made for the multi-
beam system. Figure 8 illustrates a sonar head with a stick projector installed.
For sonar heads equipped with an Extended Range (ER) projector, the acoustic
center will be the same as shown in Figure 8 (the slight offset is compensated for
in the system’s software). See also paragraph 3.10.5.
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SeaBat 8101 Operator's Manual
2-4
Version 3.02
