This document discusses techniques for deep sea underwater surveying. It describes digital sonar, side-scan sonar, sub-bottom profiling systems, differential GPS, electronic tide gauges, and digital CCTV cameras that are used to determine the seafloor conditions, depth, sub-bottom profile, and locate hazards and resources underwater. Data from these techniques provides accurate location information and mapping of submerged areas and hazards in low visibility waters. Underwater surveying allows for identifying specific resources and hazards at low cost and in an environmentally friendly way.

1. DEEP SEA UNDERWATER
SURVEYING
B.BINITHA
M.TECH ENV ENGG
14220002
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2. INTRODUCTION
Underwater survey is the technique used for
conducting impact analysis and shoreline
inventory of submerged aquatic resources.
It is used to determine the depth, sea floor
conditions , sub bottom profile, tracking ,
positioning etc in the marine water.
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3. It provides location data of previously
unobtainable accurately for specific sample
sites, hazards, and marine resources.
Identifying, mapping and recording the exact
locations of submerged aquatic resources and
unwanted hazards in low visibility waters.
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4. METHODS
• Digital sonar
• Scanning or side-scan sonar
• Sub-bottom profile system
• Differential global positioning system (DGPS)
• Electronic tide guide
• Digital CCTV
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5. Digital sonar
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6. • A narrow-beam sonar head generates a
sound pulse from the sonar.
• The sound frequency and pulse can be
modified to suit conditions.
• When the sound pulse hits a target, it
bounces back and the echo appears as a
data point. 6

7. • Data points are calculated using the angle of
the sonar head, the speed of sound in water
and the travel time.
• Using sonar, data can be gathered from a
vertical dam face, across the bottom, under
overhangs or other vertical structures, or
inside pipes and sewers.
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8. Scanning or side-scan sonar
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9. • Side-scan sonar is used to investigate
seafloor conditions such as scour patterns,
obstructions, the type and size of debris, and
the condition of pipelines and cables.
• Side-scan sonar is also used for dredging
operations and environmental studies.
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10. • It uses a sonar device that emits fan-shaped
pulses toward the seafloor across a wide
angle perpendicular to the path of the sensor
through the water.
• Side-scan data are frequently acquired along
with sub-bottom profiler data.
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11. Sub-bottom profile system
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12. • Especially useful in surveys of river
crossings.
• Sub-bottom profiling systems measures
the positions of objects that exist below
the bottom.
• A sound source emits a signal
downwards into the water and a receiver
records the reflected return. 12

13. • The system uses this reflected energy to
provide information on features beneath the
bottom.
• Sub-bottom profiling systems can be useful
for calculating pipe cover or exposure, or
areas of concern.
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14. Differential global positioning
system (DGPS)
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15. • DGPS uses a network of fixed, ground-based
reference stations to broadcast the difference
between the positions indicated by the
satellite systems and the known fixed
positions.
• Depending on the accuracy required, it uses a
Trimble Pro XRS (sub metre) or RTK GPS
(centimetre) receiver. 15

16. • The Pro XRS offers GPS, WAAS(Wide Area
Augmentation System) , EGNOS(European Geostationary Navigation
Overlay Service),satellite differential, and beacon
capabilities.
• It also uses patented multipath rejection
technology to remove multipath signals in
reflective environments.
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17. Electronic tide guide
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18. • To track water elevation a submersible
pressure transmitter is used.
• The tide gauge stores pressure, temperature
and time data, and the data is also monitored in
real time via a radio link.
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19. Digital CCTV
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20. • Digital CCTV cameras provide high resolution
images that do not suffer degradation in
transmission or when copied.
• The images can be digitally enhanced for
greater clarity, and can be easily catalogued
and reviewed.
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21. • Images acquired in this way can also be
displayed in combination with sonar
information.
• The images are recorded in digital format to
DVD’s.
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22. Conclusion
Underwater surveying can be used for
locating specific hazards and marine
resources with previously unobtainable
accuracy at a low cost.
And it could be helpful for determining various
underwater parameters in an environmental
friendly way.
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23. Reference
• http://www.aquacoustic.com/technology.p
hp
• aaus-underwater-survey-technique-08
• http://link.springer.com/chapter/10.1007%2F97
• Wikipedia
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24. THANK YOU
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