SONAR

1
SONAR
2
SONAR

• SONAR stands for SOund NAvigation and Ranging.
• It is a device that is used mainly for the
  detection and location of underwater objects by
  reflecting acoustic/sound waves.

3
(No Transcript)
4
(No Transcript)
5
Sidescan SONAR

• It is towed behind a boat, close to the ocean
  floor.
• It is used for mapping the ocean floor, but does
  not give the depth of the water.

6

• There are 2 SONAR units designed to send out fan
  shaped beams on either side of the device to a
  total distance of 200 m.
• They can locate objects as small as 10 cm and
  will give an image of the object.

7

• The sound beams move horizontally, creating
  shadowing, so the image stands out by the shadow
  it casts.
• The stronger the return echo the closer an object
  is, and the darker it appears.

8
Multibeam SONAR

• It is built into the hull of a boat.
• It is similar to sidescan SONAR, but it gives
  depths rather than images.
• It is mainly used to survey the ocean floor.

9

• It measures and records the time for the signal
  to travel from the transmitter to the ocean floor
  and then back.

10

• The coverage area is dependent on the depth of
  the water, but is typically 2-4 times the water
  depth.
• The signal is transmitted in pulses of 64 beams 4
  times per second.

11
A multibeam image of the seabed of Halifax
Harbour between north McNabs Island and Point
Pleasant Park showing the location of two
shipwrecks the Havana and the Gertrude de Costa.
12
Multibeam sonar image looking west from Georgian
Bay at the submerged Niagara escarpment and the
sill between the Huron and Georgian Bay basins
(Parks Canada, Canadian Hydrographic Service and
Tekmap Consulting).
13
Echolocation

• Echolocation is the ability to locate objects
  (food, barriers etc) by projecting sound and
  then listening to the return echo.

14

• From their echolocation they can determine the
  following about an object (such as a fish)
• Size, shape, distance, speed, direction, internal
  structure
• Echolocation enables the dolphin to see in a much
  more complex way than it might seem. Depending on
  the object, sound waves can enter beneath the
  surface therefore giving feedback and information
  of the internal structure of an object.

15

• The dolphin sends out sound waves from its nasal
  cavity, they return along the jaw bone and enter
  the melon from there they are sent to the brain
  for processing.

16
Echolocation Facts

• Dolphins can detect a 2.5 cm object from 72 m
  away.
• Some humans are able to echolocate this usually
  happens in those who are blind.
• Other creatures that echolocate include whales
  and bats.