Underwater Search Techniques and Methods

Posted on Dec 4, 2024 in Geology

Underwater Search Techniques

Factors influencing the choice of search techniques include depth, visibility, object size, search area dimensions, terrain clearance, equipment and personnel requirements, and currents.

Underwater searches can be categorized into visual, touch, coupling, and electronic methods.

Circular Search Patterns

· Circular Search

Factors:
– Depth: Up to 30 m
– Visibility: From 0.5 m to infinity
– Object Size: Small to Medium
– Area Size and Shape: Circular, 60 m diameter
– Terrain: Flat or slightly hilly
– Divers: 2-6
– Currents: Low (max 0.5 Kn)

· Filigree Search

Factors:
– Depth: Up to 30 m
– Visibility: From 0.5 m to infinity
– Object Size: Small to Medium
– Area Size and Shape: Lane, 500 m by 60 m
– Terrain: Flat or slightly hilly
– Divers: 2-6
– Currents: Low (max 0.5 Kn)

· Coupling Circular Search

Factors:
– Depth: Up to 30 m
– Visibility: Not applicable
– Object Size: Large (1 m or more above background)
– Area Size and Shape: Circular, 60 m diameter
– Terrain: Flat, object height greater than terrain variations
– Divers: 2
– Currents: Low (max 0.75 Kn)

· Towed Rake Circular Search

Factors:
– Depth: 30 m to 50 m
– Visibility: Not applicable
– Object Size: Large (1 m or more above background)
– Area Size and Shape: Circular, 100 m diameter
– Terrain: Completely flat
– Divers: 2
– Currents: Low (max 0.75 Kn)

· Fan Search

Factors:
– Depth: Up to 30 m
– Visibility: Minimum 0.1 m
– Object Size: Small
– Area Size and Shape: Sector, 30 m radius
– Terrain: Flat or small slopes
– Divers: 2-4
– Currents: Low (max 0.75 Kn)

Rectangular Search Patterns

· Filigree Rectangular Search

Factors:
– Depth: Up to 30 m
– Visibility: 0.1 m or less
– Object Size: Small to Medium
– Area Size and Shape: Lane, 2-20 m wide (depending on visibility and object size) by 500 m long
– Terrain: Smooth to medium slopes
– Divers: 2-4
– Currents: Medium (max 1 Kn)

· Double Filigree Rectangular Search

Factors:
– Depth: Up to 30 m
– Visibility: 2 m or more
– Object Size: Small to Medium
– Area Size and Shape: Lane, 6-40 m wide (depending on visibility and number of divers) by 500 m long
– Terrain: Smooth to medium slopes

· Enhanced Search Between Two Rectangular Filigree Lanes

Factors:
– Depth: Up to 30 m
– Visibility: Not applicable
– Object Size: Large (minimum 1 m)
– Area Size and Shape: Lane, 30 m wide by 500 m long
– Terrain: Flat
– Divers: 2
– Currents: Low (max 0.75 Kn)

· Rectangular Search with Current

Factors:
– Depth: Up to 30 m
– Visibility: By touch
– Object Size: Medium to Large
– Area Size and Shape: Channels, 50 m wide and 200 m long (often shorter)
– Terrain: As plain as possible
– Divers: 2
– Currents: 1 to 4 Kn

· Progressive Grid Search

Factors:
– Depth: Up to 30 m
– Visibility: By touch or poor visibility
– Object Size: Very small
– Area Size and Shape: Grid, 30 x 100 m
– Terrain: Flat or inclined
– Divers: 2
– Currents: None

Special Search Techniques

· Linear Towed Rake Search

Factors:
– Depth: 30 to 50 m
– Visibility: Not applicable
– Object Size: Large (1 m or more)
– Area Size and Shape: Rectangle, 100 m wide
– Terrain: Completely flat
– Divers: 2
– Currents: Little

· Glider Search

Factors:
– Depth: Up to 30 m
– Visibility: Minimum 6 m
– Object Size: Medium to Large
– Area Size and Shape: Lanes, 12 m wide and several km long
– Terrain: Variable depth
– Divers: 1 or 2
– Currents: Little

· Spiral Search

Factors:
– Depth: Up to 30 m
– Visibility: Minimum 3 m
– Object Size: Medium
– Area Size and Shape: Grid, 30 x 30 m
– Terrain: Can be abrupt
– Divers: 2
– Currents: Absent