Unit 2.b. Phases of a Hydrographic Survey Captain M K Barritt RN

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Unit 2.b. Phases of a Hydrographic
SurveyCaptain M K Barritt RN
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Phases of a Hydrographic Survey

• Preliminary Liaison
• Establishment of control and calibration of
  equipment
• Area search
• Investigations
• Ancillary observations

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Preliminary Liaison

• Before a survey commences, liaison with other
  authorities is essential.
• Fishery Liaison Officers for de-confliction.
• Port Control Offices.
• Coast Guard for Navigational Warnings.

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Preliminary Liaison

• Before a survey commences, liaison with other
  authorities is essential.
• Fishery Liaison Officers for de-confliction.
• Port Control Offices.
• Coast Guard for Navigational Warnings.

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Establishment of control

• Horizontal How will I fix my position, and
  preferably with more precision than the
  subsequent chart user?
• Vertical How can I make allowance for change of
  tidal height?

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Calibration of equipment

• Performance of equipment must be validated before
  and during survey
• Static and dynamic validation of navigational
  aids used for position-fixing.
• Target or patch tests of sonar devices.
• Constant monitoring of sound velocity.
• Sampling of seabed.

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Error Budget - Example
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Tidal Reduction
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Comparison with previous work

• What did previous surveyors find, and have we
  relocated or disproved their findings?

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Area Search

• What tool is best MBES /- DCSS, SBES /- DCSS?
• What sort of traffic will navigate in this area?
  Who are the customers?
• What are the general depths?
• What sort of topography is expected?
• Are many wrecks and obstructions expected?

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Sidescan Sonar
c.15 m
Up to 1,200 metres
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SONAR COVERAGE
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SEABED DEPRESSIONS ELEVATIONS
Seabed depression identified by shadow preceding
hard return
Seabed elevation identified by shadow following
hard return
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HAND-COMPILED SEABED TEXTURE TRACING
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MULTI-BEAM ECHO SOUNDERS
Beam angle
Depth
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Investigations
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Ancillary Observations