acoustic signal may be attenuated by overlying
sediment.
. Bottom clutter — This phenomena results in
non-mine targets being detected by a minehunting sonar
system. This makes it difficult for the operator to
identify targets from the ambient noise.
. Sediment resistivity — This is the ability of
sediment to conduct electrical current.
Resistivity
depends upon salinity, electrical conductivity of the
sediment, and the thickness of the sediment.
MAGNETIC ENVIRONMENT
The factors that affect the sensitivity of magnetic
sweep equipment are as follows:
l The effectiveness of magnetic sweep equipment
is influenced by the water depth and the conductivity of
the water (salinity and temperature).
. Magnetic storms cause momentary fluctuations
in the earth’s magnetic field. These storms sometimes
closely resemble the magnetic signature of a ship and
may result in magnetic influences firing mines
prematurely.
ACOUSTIC ENVIRONMENT
Ambient noise can create problems for mines and
MCMs in shallow water.
. High ambient noise levels present a problem for
the performance of acoustic influence mines, since the
target must be discriminated from ambient noise over
relatively long ranges.
. High-frequency components of ambient noise
tend to have little effect on minehunting operations
because of the high receiver directivity characteristics
of minehunting sonar systems.
PRESSURE ENVIRONMENT
Water pressure can play a significant role in MIW
operations.
l The effective pressure change caused by wave
heights at the surface diminishes with increasing depth.
l Generally, pressure mines require other
influences, such as acoustic or magnetic influences to
be present simultaneously in order for the mine to
explode.
BIOLOGICAL ENVIRONMENT
Biologics may influence sonar detection, the
neutralization of mines by EOD divers, and the
performance of acoustic influence mines.
l Marine biofouling — Both plant and animal
forms constitute major fouling agents in shallow waters,
animal forms being dominant in deeper waters.
. Marine life — Divers can be exposed to
dangerous marine life in open waters.
. Bioluminescence — Bioluminescent displays
may reveal minedrops or outline moored mines and
cables.
l Biological ambient noise — Minehunting sonars
and most acoustic mines are not seriously affected by
this type of ambient noise.
PHYSICAL CHARACTERISTICS
Water temperature, and temperature profile versus
depth can play a significant role in MIW operations.
Temperature
Strong negative temperature gradients found in
shallow water will result in strong bottom reverberation.
Detection ranges may be sharply reduced.
Variable Depth Sonar (VDS) Transducers
Depth and tilt angles can be adjusted to be optimally
tuned to existing environmental conditions.
Diving Operations
Diver performance is affected by water temperature
as well as water clarity.
. In cold water, a diver’s ability to concentrate and
work efficiently will be greatly reduced.
. The possibility of exhaustion exists when diving
operations are conducted in the vicinity of industrial
outflow due to higher temperature waste water.
Salinity
There are salinity considerations that must be
addressed in the planning and conducting of MIW
operations.
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