Mastering the Seafloor: Your Comprehensive MBES & Side Scan Sonar Operations Manual
Unlock high-quality hydrographic data with this step-by-step guide covering everything from pre-launch checks to advanced data processing.
Highlights
- Systematic Workflow: Follow detailed procedures for pre-launch preparation, mission planning, navigation, data acquisition, and post-mission tasks to ensure consistent and reliable survey results.
- Integrated Technology Guidance: Understand the specific operational nuances and processing requirements for both Multibeam Echo Sounders (MBES) for bathymetry and Side Scan Sonars (SSS) for high-resolution seabed imagery.
- Quality Assurance Focus: Implement rigorous checklists, calibration routines, real-time monitoring, and post-processing quality control steps to maximize data accuracy and minimize errors.
1. Pre-Launch Preparation: Setting the Stage for Success
Thorough preparation is paramount for safe operations and high-quality data acquisition.
Before deploying any Multibeam Echo Sounder (MBES) or Side Scan Sonar (SSS) equipment, meticulous preparation is essential. This phase minimizes potential issues during the survey and ensures the collected data meets project specifications. Allow ample time (ideally 24-48 hours) before deployment for these crucial steps.
Equipment Inspection and Setup
A physical check of all hardware components is the first step. Inspect the MBES and SSS transducers, sonar heads/arrays, control units, cables, and connectors for any signs of damage, corrosion, wear, or fouling. Ensure secure mounting, whether hull-mounted, pole-mounted, or towed. Verify power supplies and interfaces are functional. Critically, confirm installation offsets (the physical distances between the sonar heads, positioning sensors like GPS, and the vessel's reference point or Calibration Reference Point - CRP) are accurately measured and defined within the operating software, as incorrect offsets introduce significant position errors.
MBES and associated survey equipment prepared for deployment.
System Calibration and Testing
Perform necessary calibrations according to manufacturer specifications. This includes:
- Sound Velocity Profile (SVP): Measure the speed of sound through the water column. An accurate SVP is critical for both MBES bathymetry and SSS slant range correction.
- MBES Calibration (Patch Test): Determine residual biases in sensor offsets (pitch, roll, yaw, latency) by running specific survey lines over a distinct seafloor feature.
- System Function Tests: Power on all systems (sonars, computers, navigation equipment). Run diagnostics and self-tests. Perform a shallow water test ping to confirm operational readiness. Verify communication between all components. Ensure software and firmware are up-to-date.
- Frequency Checks: Confirm the correct operating frequencies are set for both MBES (e.g., 100 kHz, 250 kHz, 500 kHz) and SSS (e.g., dual frequencies like 230/550 kHz or 540/850 kHz).
Environmental and Safety Assessment
Assess the survey environment and safety aspects:
- Review weather forecasts, tidal predictions, and water current information for the survey period.
- Identify potential hazards within the survey area (e.g., shallow waters, obstructions, vessel traffic).
- Ensure all necessary permits are obtained.
- Verify all safety equipment (PFDs, first aid kit, fire extinguishers, communication devices) is present, functional, and compliant with regulations.
- Brief the crew on safety protocols and emergency procedures.
Vessel Readiness
Inspect the survey vessel, checking fuel levels, engine operation, steering, and navigation lights. Ensure the vessel is suitable for the planned operations, including potential towing of SSS equipment. Verify secure mounting points for all survey gear.
2. Pre-Survey Checklist: Ensuring Nothing is Missed
A systematic check guarantees readiness before leaving the dock.
This checklist provides a final verification step before commencing the survey. Mark each item as completed.
| Category | Task | Status |
|---|---|---|
| Safety Equipment | Inspect PFDs, fire extinguishers, first-aid kit, flares | [ ] Done |
| Safety Equipment | Test emergency communication devices (VHF radio) | [ ] Done |
| Safety Equipment | Confirm compliance with local maritime regulations | [ ] Done |
| Sonar Systems | Inspect transducers and cables for damage/fouling | [ ] Done |
| Sonar Systems | Verify power sources (batteries, generators) | [ ] Done |
| Sonar Systems | Confirm sonar system settings (frequency, pulse length, range) | [ ] Done |
| Sonar Systems | Verify synchronization of MBES & SSS (if applicable) | [ ] Done |
| Sonar Systems | Test data logging configuration and storage capacity | [ ] Done |
| Navigation & Positioning | Verify GPS/GNSS status and correction source (DGPS/RTK) | [ ] Done |
| Navigation & Positioning | Check Motion Reference Unit (MRU) and Gyrocompass function | [ ] Done |
| Navigation & Positioning | Confirm Sound Velocity Sensor (SVP) calibration/readiness | [ ] Done |
| Navigation & Positioning | Verify system offsets entered correctly in software | [ ] Done |
| Mission Plan | Load mission plan (survey area, tracklines) into navigation software | [ ] Done |
| Mission Plan | Review planned survey lines and coverage overlap | [ ] Done |
| Vessel | Check fuel, oil, and bilge systems | [ ] Done |
| Vessel | Inspect hull, propulsion, and steering | [ ] Done |
| Documentation | Confirm permits, logs, and manuals are onboard | [ ] Done |
| Documentation | Backup survey software configurations | [ ] Done |
| Environment | Review final weather and tidal conditions | [ ] Done |
Note: Do not proceed with the launch if any critical item on this checklist fails. Address the issue first.
3. Mission Planning: Designing the Survey Strategy
Define objectives and plan survey lines for optimal coverage and efficiency.
Effective mission planning translates project goals into an actionable survey strategy. This involves defining the scope, required data types, spatial coverage, and operational parameters.
Define Survey Objectives
Clearly state the purpose of the survey. Is it primarily for:
- Bathymetry Mapping: Obtaining accurate depth measurements (MBES is primary).
- Seafloor Imagery: Generating high-resolution images of the seabed texture and features (SSS is primary, MBES backscatter secondary).
- Feature Detection: Locating specific objects like wrecks, pipelines, or hazards (SSS often preferred for resolution, MBES for precise positioning).
- Habitat Mapping: Classifying seafloor types based on acoustic properties (often uses combined MBES bathymetry/backscatter and SSS imagery).
The objectives dictate the choice of sonar systems, operational settings, and required data density.
Determine Survey Area and Parameters
- Define Boundaries: Accurately delineate the survey area using coordinates, often within GIS or survey planning software (e.g., QGroundControl, HYPACK). Include buffer zones and identify any exclusion zones or known hazards.
- Select Sonar Configuration: Choose MBES, SSS, or both based on objectives. Consider desired resolution, water depth, and accuracy requirements.
- Establish Operating Parameters:
- Line Spacing: Calculate based on the effective swath width of the sonar(s) at the expected water depth, ensuring sufficient overlap (e.g., 20-50% for MBES, 50-100% for SSS depending on goals) for complete coverage and data quality control.
- Survey Speed: Select an appropriate speed (typically 4-8 knots) that balances efficiency with data quality. Higher speeds can degrade SSS imagery and may affect MBES data density.
- Frequency Selection: Choose optimal frequencies based on depth, resolution needs, and potential interference. Higher frequencies offer better resolution but less range.
4. Waypoint and Survey Area Setup: Translating Plan to Action
Configure navigation software with precise boundaries and tracklines.
This step involves loading the planned survey geometry into the vessel's navigation and data acquisition software.
Survey Area Definition
Input the defined survey area boundaries (polygons) into the navigation system. Ensure the correct coordinate system and datum are used (e.g., WGS84).
Trackline Planning and Configuration
Design the survey tracklines based on the calculated line spacing and overlap. Parallel lines are most common for systematic coverage. Consider:
- Orientation: Align lines generally parallel to depth contours where practical to maintain consistent swath width, but perpendicular lines may be needed for cross-checking.
- Run-ins and Run-outs: Extend lines beyond the survey area boundaries to ensure stable data acquisition at the edges.
- Cross-Lines: Plan perpendicular cross-lines (typically 5-10% of total line kilometers) for quality control, especially for MBES bathymetry.
Configure these tracklines within the navigation software, often by defining start/end waypoints or generating an automated grid pattern over the defined polygon.
Example of planned survey tracklines in navigation software.
System Offset Application
Double-check that the accurately measured installation offsets (X, Y, Z distances from the vessel reference point to the GPS antenna, motion sensor, and sonar transducer(s)) are correctly entered and applied within the navigation and acquisition software. Errors here directly impact the final georeferencing accuracy.
Survey Workflow Overview
Visualizing the MBES/SSS Survey Process
The following diagram provides a high-level overview of the key stages involved in conducting an MBES and SSS survey, from initial planning through to final data products.
(Lines, Overlap)"] id1e["Logistics & Safety"] id2["2. Pre-Launch"] id2a["Equipment Inspection"] id2b["System Calibration
(SVP, Patch Test)"] id2c["Offset Measurement"] id2d["Software Setup"] id2e["Checklist Completion"] id3["3. Data Acquisition"] id3a["Vessel Mobilization"] id3b["Waypoint & Area Setup"] id3c["Navigation Control
(Manual/Autonomous)"] id3d["Real-time Monitoring"] id3e["Data Logging"] id3f["SVP Casts"] id4["4. Post-Mission"] id4a["Equipment Demobilization"] id4b["Cleaning & Maintenance"] id4c["Data Backup"] id4d["Initial QC"] id4e["Debrief"] id5["5. Data Processing"] id5a["Import Raw Data"] id5b["Apply Corrections
(Motion, SVP, Tide)"] id5c["Data Cleaning/Filtering"] id5d["MBES Bathymetry Processing
(Gridding, DTM)"] id5e["SSS Imagery Processing
(Slant Range, Mosaicking)"] id5f["Integration & Analysis"] id6["6. Deliverables"] id6a["Bathymetric Charts"] id6b["Seafloor Mosaics"] id6c["Feature Reports"] id6d["3D Models"] id6e["Metadata & Survey Report"]
5. Navigation Control: Steering the Survey
Precise navigation ensures accurate data positioning.
Accurate positioning and consistent line-keeping are critical. Both manual and autonomous methods rely heavily on precise positioning systems (e.g., GNSS with RTK corrections) and motion sensors (MRU/INS).
Positioning Systems Considerations
- MBES: Generally relies on high-accuracy integrated GNSS/INS for positioning.
- SSS (Towed): Inherently has lower positional accuracy as its position is relative to the tow vessel. For higher accuracy, acoustic positioning systems like Ultra Short Base Line (USBL) or Short Base Line (SBL) tracking the towfish position are crucial. Layback calculations (estimating the towfish position based on cable out and vessel position) are less accurate.
Deployment of a Side Scan Sonar towfish requires careful handling and positioning considerations.
Manual Navigation
A skilled operator steers the vessel along the planned tracklines displayed in the navigation software. This requires:
- Constant monitoring of the vessel's position relative to the planned line.
- Maintaining a consistent survey speed.
- Making smooth course corrections to minimize vessel motion artifacts, which can degrade SSS imagery quality.
- Monitoring real-time sonar data displays for coverage and potential issues.
Autonomous Navigation
Utilizes autopilots or autonomous surface vehicles (ASVs) programmed to follow the predefined mission plan (waypoints and tracklines).
- The mission plan is uploaded to the autonomous control system (e.g., ArduPilot integrated with mission planning software).
- The system automatically steers the vessel along the lines.
- Requires careful setup of control parameters and safety features (e.g., obstacle avoidance).
- Continuous remote monitoring is necessary, with the ability for manual override in case of system malfunction or unexpected situations.
- Can improve line-keeping consistency and efficiency, especially for long surveys or complex patterns.
Autonomous systems require careful setup and monitoring during survey operations.
Factors Influencing Survey Success
A Comparative Look at Key Elements
The overall quality and success of an MBES/SSS survey depend on various factors. This chart provides a relative comparison of the perceived importance of key elements. A higher score indicates greater influence on achieving high-quality, reliable results. Note that all factors are important, but their relative impact can vary based on project specifics.
For example, while environmental conditions have a significant impact, they are largely uncontrollable during the survey, whereas factors like calibration accuracy and processing rigor are highly controllable and crucial for final data quality.
6. Data Acquisition: Capturing the Seafloor Secrets
Monitor systems and log data carefully during survey operations.
During the survey execution phase, continuous monitoring and careful logging are essential.
- Real-time Monitoring: Watch the data acquisition displays for sonar coverage, data quality indicators, and system status. Look for gaps in coverage, high noise levels, or equipment warnings.
- Parameter Adjustments: If necessary, adjust sonar parameters (e.g., gain, range, pulse length) to optimize data quality based on changing conditions (depth, seabed type). Avoid excessive changes that complicate processing.
- Sound Velocity Profiles: Collect SVP casts at regular intervals (time or location based) or whenever significant changes in water mass are suspected. This is critical for accurate MBES depths and SSS geometry.
- Log Keeping: Maintain a detailed survey log. Record start/end times of lines, SVP cast details, parameter changes, environmental observations (weather, sea state), and any unusual events or anomalies encountered.
- Data Logging: Ensure all required data streams (sonar, position, motion, time, SVP) are being logged correctly by the acquisition software with accurate timestamps.
7. Post-Mission Care: Protecting Your Investment
Proper shutdown, cleaning, and data backup preserve equipment and results.
Once data acquisition is complete, careful post-mission procedures are necessary.
Equipment Shutdown and Maintenance
- Follow proper shutdown procedures for all sonar systems, computers, and navigation equipment.
- Carefully retrieve towed sonar bodies (like SSS towfish).
- Disconnect cables and protect connectors.
- Thoroughly rinse all equipment exposed to saltwater with fresh water, paying special attention to transducers and connectors, to prevent corrosion and salt buildup.
- Inspect all equipment for any damage or wear sustained during the survey. Note any issues for repair.
- Store equipment securely in protective cases in a dry, climate-controlled environment.
- Recharge batteries as needed.
Careful retrieval and post-mission cleaning are vital for sonar equipment longevity.
Data Backup and Verification
- Immediately back up all raw survey data from the acquisition system hard drives to at least two separate, secure storage locations (e.g., external hard drives, network storage).
- Verify the integrity and completeness of the data transfer. Check file sizes and perform spot checks on data files.
- Organize data logically, using clear file naming conventions and folder structures that include project name, date, and data type.
- Securely transfer data to the processing workstation if it's different from the acquisition system.
Team Debrief
Conduct a post-mission debrief with the survey team to discuss operational aspects, challenges encountered, data quality observations, and any lessons learned to improve future surveys.
8. Post-Data Processing: Transforming Raw Data into Insights
Apply corrections, clean data, and generate final products using specialized software.
Post-processing transforms raw sonar measurements into accurate, interpretable products like bathymetric maps and seafloor imagery mosaics. This often involves specialized hydrographic software (e.g., CARIS HIPS/SIPS, QPS Qimera/Fledermaus, Hypack, SonarWiz, MB-System, ReefMaster).
Initial Data QC and Preparation
- Import Data: Load raw sonar files (MBES and SSS), navigation data, motion data, and SVP data into the processing software.
- Apply Corrections:
- Navigation & Motion: Apply precise post-processed navigation (if available) and correct for vessel motion (heave, pitch, roll, yaw) to accurately georeference each sounding/pixel.
- Sound Velocity: Apply the measured SVP data to correct for sound ray bending.
- Tide/Water Level: Apply tidal corrections or water level adjustments to reduce soundings to a common vertical datum (e.g., Mean Lower Low Water).
- Review Data: Perform an initial review of the data for obvious issues like noise, dropouts, or systematic errors.
MBES Bathymetry Processing
- Filtering/Cleaning: Apply automated filters and perform manual editing ("cleaning") to remove erroneous soundings (outliers, noise spikes) while preserving valid seafloor data. This is a critical and often time-consuming step.
- Surface Generation: Create a bathymetric surface (e.g., a grid or TIN) from the cleaned soundings. Select appropriate gridding algorithms and resolutions based on data density and project requirements.
- Quality Control: Analyze the resulting surface for consistency, check overlaps between lines, compare against cross-lines, and evaluate against survey specifications (e.g., IHO standards).
- Product Generation: Create derived products like contour maps, 3D visualizations, and digital terrain models (DTMs).
Processing software displays multibeam bathymetry data for cleaning and analysis.
SSS Imagery Processing
- Geometric Corrections: Apply slant range correction (converting travel time to horizontal distance across track) and correct for vessel navigation to accurately position the imagery pixels.
- Radiometric Corrections: Apply corrections for signal spreading, attenuation, and potentially beam pattern effects to normalize backscatter intensity across the swath and between lines (radiometric balancing or leveling).
- Mosaicking: Stitch together the corrected imagery strips from adjacent survey lines to create a seamless seafloor mosaic. Address seamline matching and blending.
- Interpretation: Analyze the mosaic to identify seafloor features, textures, and classify substrate types based on backscatter intensity and patterns. Ground-truthing (e.g., video or samples) often aids interpretation.
Data Integration and Reporting
- Combine MBES bathymetry and SSS imagery (e.g., draping the SSS mosaic over the MBES DTM) for a comprehensive understanding of the seafloor morphology and character. Ensure datasets are accurately co-registered.
- Perform final quality assurance checks on all processed data and products.
- Generate final deliverables as per project requirements (maps, reports, digital data files).
- Compile comprehensive metadata and a detailed survey report documenting the entire process from planning to processing, including equipment used, calibrations, corrections applied, and achieved data quality.
- Archive all raw and processed data, along with project documentation, securely.
Video Insights: Data Processing Techniques
Visualizing Advanced Sonar Data Handling
Post-processing is a critical phase where raw sonar data is refined into meaningful products. Software like CARIS HIPS and SIPS offers powerful tools for handling complex datasets, including water column data which can reveal features not directly on the seafloor. The video below provides a glimpse into water column imaging capabilities within such software, illustrating how additional information can be extracted from sonar returns beyond just the primary seafloor detection.
Understanding the tools available for visualizing and processing not just the seafloor bathymetry (MBES) or imagery (SSS), but also the data within the water column itself, enhances the ability to perform thorough quality control and potentially detect mid-water targets or understand acoustic scattering phenomena.
Frequently Asked Questions (FAQ)
References
- NOAA Field Procedures Manual (2020) - NOAA
- Seafloor mapping field manual for multibeam sonar - ResearchGate
- Processing Multibeam Imagery in SonarWiz - Chesapeake Technology
- Survey (Plan Pattern) | QGC Guide - QGroundControl
- EdgeTech 6205s Bathymetry & Side Scan Sonar User Manual - EdgeTech
- USACE Hydrographic Surveying Manual - US Army Corps of Engineers
- IHO Manual on Hydrography Publication C-13 Chapter 4 - IHO
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Last updated April 24, 2025