Wreck & Risk Detection with Side-Scan Sonar: An 8-Step Playbook
A practical 8-step playbook for detecting wrecks, debris, and cable/pipe risks using side-scan sonar in ports and coastal projects. Planning, acquisition, QA/QC, and deliverables.
Wreck & Risk Detection with Side-Scan Sonar: An 8-Step Playbook
Underwater “seeing” often means listening well. Side-Scan Sonar (SSS) delivers fast, detailed, and cost-effective coverage for ports, berths, cable/pipe corridors, and hazard-prone zones. Here’s CAC Mühendislik’s field-tested playbook to turn raw echoes into confident decisions.
1) Define the Target First
Wrecks, snagging ropes, timber, armour stones, shifted rubble, sand waves over a route—each target class demands a specific range, scale, and contrast setup. Write the brief → pick sensor settings → design the line plan.
2) Line Planning & Overlap
Run parallel lines with 20–30% overlap to minimise gaps. Use high frequencies (600–900 kHz) in shallow/medium depths for detail; go mid-band (300–600 kHz) for wider swaths. Goal: coverage and clarity.
3) Speed & Altitude Discipline
Quality hinges on stable tow-fish altitude (or pole-mount depth) and steady SOG (typically 3–5 kn). If towed, compute layback; for pole-mounted SSS, dampen vessel motion. Shadow length should be readable and repeatable.
4) Clean the Acoustics
Exclude tight turns near line ends, avoid bubble curtains, keep prop regime steady. Small habits, big improvements. Aim to reduce stitch artefacts in your final mosaic.
5) Calibrate & Reference
Refresh SVP/SSP (sound-speed profile). Secure navigation with GNSS/DGNSS/RTK; add USBL when high-accuracy tow-fish positioning is critical. Tune range/contrast/gain with a pilot line before production.
6) Mosaic & Classify
Merge strips into a geo-referenced mosaic. Classify targets (A/B/C) by size, shadow, and risk. Store thumbnails, dimensions/angles, and approximate volumes into GIS layers for rapid review.
7) QA/QC That Proves Reliability
Overlap report (coverage percentage, stitch seams)
Positional consistency across lines
Second-pass checks over suspicious backscatter
Metadata hygiene (sensor, firmware/software, filters, timestamps)
8) Deliverables That Drive Decisions
Decision-makers want clarity: Where is it, what is it, what’s next?
Ship a bundle with GeoTIFF mosaic, vector target list (SHP/GPKG), a concise PDF summary, a red-amber-green risk map, and—if required—an ROV verification plan. Ideal before maintenance or dredging.
