
7 – Operating Procedure
DPN 402197 © TSS (International) Ltd Page 25 of 30
Figure 7–4: Sloping target
In Figure 7–4 the coil array G measures the shortest distance to the target I.
Similarly, the measurements of ALT will be the shortest distance between the altime-
ter and the seabed within the beamwidth of the altimeter H.
The depth of cover COV = VRT – ALT. However, because the seabed is sloping, the
measurements of VRT and ALT are valid for different locations on the seabed.
Because of this, errors will appear in the depth-of-cover measurements. Errors of this
type will be larger if the altimeter and the coil array are at opposite ends of the ROV.
Since the slope of the seabed will vary unpredictably, there might be some random
elements of error in all these measurements.
Summary:
Be aware of the potential measurement errors that might appear when operating over
a sloping target.
Make certain there is a negligible fore-aft offset distance between the coil array and
the transducer face of the altimeter. Angles of slope less than half the beamwidth of
the altimeter will not affect the measurements in this way.
Reduce the potential errors caused by a sloping seabed by operating the ROV as
close as possible to the seabed.
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