Teledyne 440, System Manual, Page: 31 / 256

2 – System Overview
DPN 402196 Issue 4.1 © Teledyne TSS 2- 7
2.3.3 Search-coils
Teledyne TSS supplies three search-coils as part of a standard package. A drawing showing
dimensions is available in
Chapter 10 "System Drawings" and details of specification can be found in
Chapter 8 "System Specifications" .
See section 3.1.3 "Coil Array" on page 3-5 for full instructions to assemble the coils and mount them
onto an ROV.
2.3.4 Altimeter
The main function of the 440 System is to locate and survey a target lying on or buried beneath the
seabed.
If the 440 System measures the altitude of its coil array above the seabed, then it can also deliver a
good estimation of the depth of target cover. A sub-sea altimeter can supply such altitude
measurements to the 440 System.
The standard 440 System includes a sub-sea altimeter. You will need to install this on the ROV frame
close to the centre of the coil array. See
section 3.1.4 "Altimeter" on page 3-13 for instructions to install
the altimeter on the ROV, and section 4.1.6 "Sub-sea Altimeter" on page 4-6 for instructions to connect
it directly to the SEP.
NOTE
You should remember that an altimeter measures to a point on the seabed directly
beneath its transducer face. This single-point measurement may not be the same
as the local mean seabed level.
This means that an uneven seabed topography might degrade the quality and
accuracy of depth of cover measurements derived using a single altimeter.
For surveys where you must measure an accurate and certifiable target burial
depth, you should use an independent seabed profiling system. Log the measure-
ments from such a system separately and then use the post-processing operation
to merge them with data acquired by the 440 System.
On some types of tracked ROV, you may arrange to keep the coil array of the 440 System at a fixed
height above the seabed. In these circumstances you could avoid the need for an altimeter by
configuring DeepView for Windows to use a fixed coil height.
See Chapter 5 "System Configuration" for instructions to configure the altimeter after installation.