Wednesday, 14 May 2025

MULTIBEAM AND SHIPWRECKS.

 





GROK


Autonomous and ship-deployed multibeam echosounders (MBES) are critical tools for detecting shipwrecks in shallow waters (under 100 meters deep), offering high-resolution seafloor mapping and precise identification of underwater objects. These systems are widely used in maritime archaeology, navigation safety, and environmental monitoring due to their ability to produce detailed bathymetric maps and backscatter data. Below is a detailed review of autonomous and ship-deployed MBES for shipwreck detection in shallow waters, including technology, applications, advantages, limitations, and costing.
Overview of Multibeam Echosounders for Shipwreck Detection
Multibeam echosounders are active sonar systems that emit fan-shaped acoustic waves to map the seafloor and detect objects like shipwrecks. Unlike single-beam echosounders, MBES use multiple simultaneous beams to cover a wide swath, providing comprehensive bathymetric and backscatter data. They can be deployed on crewed vessels (ship-mounted) or autonomous platforms like Autonomous Underwater Vehicles (AUVs) and Uncrewed Surface Vessels (USVs).
Key Components
  1. Transducer Array:
    • Consists of multiple acoustic transducers that emit and receive sound pulses in a fan-shaped pattern (e.g., 100–512 beams).
    • Common systems: Norbit Winghead i77h, Teledyne RESON SeaBat T50, Kongsberg EM 2040.
    • Shallow-water MBES operate at high frequencies (200–700 kHz) for better resolution (e.g., 5–10 cm at 50m depth).
  2. Auxiliary Sensors:
    • Inertial Navigation System (INS): Measures pitch, roll, heave, and yaw (e.g., iXblue Phins Subsea).
    • GNSS/RTK: Provides centimeter-level positioning (e.g., Trimble RTK GPS).
    • Sound Velocity Profiler (SVP): Measures water column sound speed for accurate depth calculations.
    • USBL (Ultra-Short Baseline): Tracks AUV position underwater (e.g., Kongsberg HiPAP 501).
  3. Platforms:
    • Ship-Mounted: Hull-mounted or pole-mounted on survey vessels (e.g., NOAA’s Okeanos Explorer).
    • AUVs: Compact, autonomous vehicles like Advanced Navigation’s Hydrus or HUGIN 3000, ideal for near-seafloor surveys.
    • USVs: Saildrone Voyager or Surveyor-class vehicles, solar/wind-powered for extended missions.
  4. Data Processing:
    • Software like CARIS HIPS/SIPS, QPS Qimera, or Hypack processes raw data into 2D/3D bathymetric maps and backscatter mosaics.
    • Machine learning (e.g., YOLOv5, U-Net) enhances automated shipwreck detection from sonar imagery.
Applications in Shipwreck Detection
  1. Maritime Archaeology:
    • Mapping historical shipwrecks, such as the 4th-century B.C. Chios wreck, with 5 cm resolution using AUV-mounted MBES.
    • Example: The 2022 Thunder Bay expedition used an IVER-3 AUV to survey 8.04 km², identifying shipwrecks with side-scan and MBES data.
  2. Navigation Safety:
    • Locating uncharted wrecks to update nautical charts, as demonstrated by Saildrone’s 2019 Gulf of Mexico mission, which discovered an uncharted shipwreck at ~20m depth.
  3. Environmental Monitoring:
    • Assessing wrecks for leakage (e.g., MV Schiedyk, leaking diesel at 106–122m depth, mapped with Norbit Winghead i77h).
  4. Cultural Heritage:
    • Documenting wrecks for public archives, such as the 100-year-old coal hulk mapped by Hydrus off Rottnest, Australia.
Advantages of Autonomous and Ship-Deployed MBES
  1. High-Resolution Mapping:
    • Shallow-water MBES achieve resolutions of 5–25 cm, ideal for identifying shipwreck features like hulls, masts, or debris fields.
    • Example: The Chios wreck survey gridded data at 5 cm resolution, revealing individual amphoras.
  2. Wide Swath Coverage:
    • Covers 100% of the seafloor in a single pass, with swath widths 3–4 times the water depth (e.g., 60–80m swath at 20m depth).
  3. Autonomous Efficiency:
    • AUVs and USVs operate without human intervention, reducing crew costs and risks. Hydrus completed a 64m shipwreck survey in <5 hours, cutting costs by 75% compared to ROVs.
    • USVs like Saildrone Voyager map up to 300m depth with minimal emissions, ideal for remote areas.
  4. Backscatter Data:
    • Provides seafloor hardness information, distinguishing hard wrecks from soft sediments.
  5. Versatility:
    • Ship-mounted systems are robust for large-scale surveys, while AUVs/USVs excel in shallow, near-shore areas with complex navigation.
Limitations
  1. Resolution vs. Depth:
    • Resolution decreases with depth due to beam spreading. At 100m, resolution may drop to 50–100 cm, limiting detection of small artifacts.
    • Near-seafloor AUVs outperform ship-mounted systems in shallow waters for high-resolution needs.
  2. Environmental Challenges:
    • Turbidity, thermoclines, or gas bubbles (e.g., from leaking wrecks) can degrade data quality.
    • Shallow waters with currents or vegetation complicate AUV/USV navigation.
  3. Cost and Complexity:
    • MBES systems are expensive ($50,000–$500,000), with high-end models requiring skilled operators.
    • Data processing is time-intensive, often requiring expert hydrographers or AI tools.
  4. Platform Limitations:
    • Ship-mounted MBES are less effective in very shallow waters (<10m) due to draft constraints.
    • AUVs/USVs have limited battery life (e.g., Saildrone’s 10-day MBES limit) and payload capacity.
  5. Regulatory Constraints:
    • Operations in protected marine areas or near cultural heritage sites require permits, as per the UNESCO 2002 Convention.
Performance in Shipwreck Detection (Under 100m)
  • Detection Capability:
    • MBES detect wrecks as bathymetric anomalies (e.g., raised features) or high-backscatter targets against soft sediments.
    • Example: Saildrone SD 1024 mapped a shipwreck at 20m depth with 25 cm resolution, identifying its outline and debris.
    • AUVs like Hydrus achieve 4K geo-referenced imagery, enabling 3D digital twins of wrecks.
  • Survey Efficiency:
    • Ship-mounted MBES cover large areas (e.g., 10 km²/day), suitable for initial surveys.
    • AUVs/USVs are slower (1–2 km²/hour) but provide higher resolution for targeted wreck sites.
  • Case Study:
    • The 2015 West India survey used an AUV-mounted EM 3002 MBES at 30–105m depth, mapping a wreck with sub-meter accuracy, supplemented by side-scan sonar for verification.
Costing Analysis
Costs vary based on platform, equipment, and project scope. Below is a detailed breakdown:
1. Equipment Costs
  • Multibeam Echosounders:
    • Norbit Winghead i77h: $50,000–$100,000. Compact, 400 kHz, ideal for AUVs/USVs.
    • Teledyne RESON SeaBat T50: $100,000–$200,000. High-resolution, 200–400 kHz, for ships or AUVs.
    • Kongsberg EM 2040: $200,000–$500,000. Premium, 200–700 kHz, for large vessels.
  • Platforms:
    • AUVs: Advanced Navigation Hydrus ($50,000–$100,000); HUGIN 3000 ($500,000–$1M).
    • USVs: Saildrone Voyager ($200,000–$500,000); custom USVs ($100,000–$300,000).
    • Survey Vessels: Hull-mounted systems require vessels costing $1,000–$10,000/day to lease.
  • Auxiliary Sensors:
    • INS (e.g., iXblue Phins): $20,000–$50,000.
    • RTK-GNSS: $5,000–$15,000.
    • USBL (e.g., Kongsberg HiPAP): $50,000–$100,000.
    • SVP: $5,000–$10,000.
  • Software:
    • CARIS HIPS/SIPS, QPS Qimera: $5,000–$20,000 (one-time or subscription).
    Total Equipment Cost: $100,000–$1.5M (AUV/USV setups); $300,000–$2M (ship-mounted).
2. Operational Costs
  • Personnel:
    • Hydrographer: $100–$250/hour.
    • AUV/USV operator: $50–$150/hour.
    • Ship crew (3–5 people): $1,000–$5,000/day.
    • Typical team: $1,000–$3,000/day.
  • Survey Duration:
    • AUV/USV: 1–2 km²/hour, ~2–5 days for 20 km².
    • Ship: 5–10 km²/day, ~1–2 days for 20 km².
    • Data processing: 1–3 days ($500–$2,000).
  • Logistics:
    • Vessel fuel, transport, permits: $2,000–$10,000.
    • AUV/USV recovery: $500–$2,000.
  • Maintenance:
    • Annual MBES/AUV maintenance: $5,000–$20,000.
    Total Operational Cost: $5,000–$20,000 (AUV/USV, 20 km²); $10,000–$50,000 (ship, 20 km²).
3. Comparison with Alternatives
  • Side-Scan Sonar:
    • Equipment: $20,000–$100,000.
    • Operational: $5,000–$15,000/day (towed or AUV-mounted).
    • Lower resolution (0.25–0.5m) but effective for large-area searches.
  • ROV Surveys:
    • Equipment: $100,000–$500,000.
    • Operational: $20,000–$100,000/day (divers or ROVs at >50m).
  • MBES Advantage: Higher resolution and bathymetric data, but more expensive than side-scan for initial surveys.
4. Example Project Cost
For a 20 km² shipwreck survey at 50m depth:
  • AUV Setup: Hydrus ($100,000) + Norbit Winghead i77h ($75,000) + sensors/software ($50,000) = $225,000 (one-time). Operational: 5 days @ $2,000/day + $5,000 logistics = $15,000. Total: $240,000 (first project); ~$15,000 subsequent.
  • Ship Setup: Kongsberg EM 2040 ($400,000) + vessel lease ($5,000/day) + sensors/software ($100,000) = $500,000 (one-time). Operational: 2 days @ $5,000/day + $10,000 logistics = $20,000. Total: $520,000 (first project); ~$20,000 subsequent.
  • USV Setup: Saildrone Voyager ($300,000) + MBES ($100,000) + sensors ($50,000) = $450,000 (one-time). Operational: 4 days @ $1,500/day + $5,000 logistics = $11,000. Total: $461,000 (first project); ~$11,000 subsequent.
Recommendations for Shipwreck Surveys
  1. Platform Selection:
    • Use AUVs (e.g., Hydrus) for high-resolution surveys in shallow, complex areas (<50m).
    • Use USVs (e.g., Saildrone Voyager) for cost-effective, large-area surveys with moderate resolution.
    • Use ship-mounted MBES for rapid, broad-scale surveys or when AUV/USV access is limited.
  2. MBES Choice:
    • Norbit Winghead i77h for AUV/USV due to compact size and affordability.
    • Kongsberg EM 2040 for ship-mounted systems requiring deepwater capability (up to 300m).
  3. Data Integration:
    • Combine MBES with side-scan sonar for initial large-area searches, as MBES provides depth and backscatter, while side-scan offers higher-resolution imagery.
    • Use AI (e.g., YOLOv5 for object detection) to automate wreck identification.
  4. Optimize Operations:
    • Conduct surveys with sufficient overlap (20–30%) to ensure data quality.
    • Use USBL and INS for precise AUV positioning in shallow waters.
  5. Regulatory Compliance:
    • Obtain permits for surveys near cultural heritage sites, adhering to UNESCO guidelines.
Conclusion
Autonomous and ship-deployed multibeam echosounders are powerful tools for shipwreck detection in waters under 100m, offering high-resolution bathymetric and backscatter data. AUVs and USVs provide cost-effective, high-resolution options for targeted surveys, while ship-mounted systems excel in large-scale mapping. Equipment costs range from $100,000–$1.5M (AUV/USV) to $300,000–$2M (ship), with operational costs of $5,000–$50,000 per project. By combining MBES with side-scan sonar and AI, surveyors can maximize efficiency and accuracy. For pricing details on related services (e.g., SuperGrok), visit https://x.ai/grok.[](https://www.oceansciencetechnology.com/news/3d-shipwreck-model-built-from-auv-imagery/)[](https://ihr.iho.int/articles/usability-of-multibeam-echosounder-for-wreck-investigations-using-backscatter-and-water-column-data-in-shallow-waters/)[](https://www.saildrone.com/solutions/ocean-survey)






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