Specify hydrographic survey equipment from the deliverable backward: required coverage and feature detection, depth and uncertainty requirements, water conditions, positioning, vessel integration and field quality checks.
Single-beam or multibeam: choose the coverage you need
| Decision | Single-beam echo sounder | Multibeam echo sounder |
|---|---|---|
| Measurement pattern | Depth observations along survey lines | Multiple soundings across a swath |
| Typical planning fit | Cross-sections and line-based work where the specification permits sampled coverage | Area mapping or feature investigation requiring a defined coverage pattern |
| Integration | Position, draft, time alignment, sound speed and the applicable water-level or height reduction | Those components plus suitable attitude/heading integration, alignment calibration and sound-speed profile control |
| Planning limitation | Unsurveyed gaps between lines must not be represented as verified full-bottom coverage | Usable swath changes with depth, bottom slope, environment and quality criteria |
| Budget comparison | Consider line density, repeat work and the deliverable—not the sensor price alone | Include integration, calibration, processing, storage and trained operators |
Dual-frequency single-beam is not multibeam: two acoustic frequencies do not create a multibeam swath. Neither instrument label alone proves compliance with a survey order. Continue to the river echo-sounder selection guide for the sensor decision.
Shallow-water surveys: separate draft from usable depth
A vessel’s draft is its immersion below the water surface. It is not the echo sounder’s minimum reliable depth and does not include every payload’s lowest point. Establish the operating envelope using loaded draft, transducer immersion, sensor minimum range, bottom clearance, debris, current and water-level variation.
- Inspect the launch and recovery route and define shallow exclusions before the mission.
- Measure the loaded configuration and confirm transducer mounting and immersion.
- Run a representative test line; inspect bottom tracking, bubbles, vegetation returns and GNSS quality.
- Choose speed and line spacing from the actual sensor performance and deliverable requirements.
- Mark inaccessible margins and coverage gaps explicitly; use a separately validated complementary method where the scope requires it.
The shallow-water planning and field checklist provides the detailed workflow.
Configure the unmanned survey boat as a complete system
A USV carries the survey equipment; it does not automatically provide a complete, calibrated survey package. Match the payload, positioning and processing chain to the project. Start with what a USV is and how it works if the platform is new to your team.
- Platform: water conditions, loaded stability, payload mass and mounting, transport and recovery arrangements.
- Depth sensor: selected sonar, minimum range, required coverage, power and data interfaces.
- Position and motion: GNSS correction route, heading and attitude requirements, measured sensor offsets and common timing.
- Mission control: route planning, communications coverage, operator intervention and documented lost-link behavior.
- Data: compatible acquisition software, raw logs, time tags, coordinate references and processing outputs.
- Power: propulsion and payload load, realistic endurance under current and a recovery reserve.
Use the TBoat10 versus TBoat20 configuration comparison to shortlist a platform, then verify the exact sensor package. Browse the TOKNAV USV range and hydrographic survey applications.
Hydrographic data quality: checks before, during and after survey
Set acceptance criteria before mobilization. Where a contract cites IHO S-44, identify the required order and applicable edition alongside any local or client requirements. The IHO standards register lists S-44 Edition 6.2.0 (October 2024). The order concerns survey results and uncertainty, not a product certification implied by buying a sonar.
| Stage | Check and record | Hold or rework trigger |
|---|---|---|
| Before acquisition | Reference systems, sensor offsets, draft, timing, positioning checks and sensor-specific calibration | Unverified geometry, reference or calibration |
| Water column and level | Sound-speed observations appropriate to the system and water conditions; water-level or GNSS height-reduction method | Unexplained changes or missing records affecting depth reduction |
| During acquisition | Bottom tracking, solution state, corrections, attitude, line adherence, speed and raw-data recording | Dropouts, bubbles, invalid positioning or other periods outside the agreed limits |
| Independent checks | Check-line differences, repeated features or approved reference checks; conditions and times | Differences outside the project criteria requiring diagnosis and possible reacquisition |
| Office acceptance | Coverage gaps, uncertainty assessment, edits, rejected observations and reproducible processing settings | Unsupported interpolation, unexplained bias or missing source data |
Cross-line agreement is useful evidence but cannot by itself reveal every common systematic error. Assess the full positioning, motion, sound-speed, geometry and reference chain. Keep rejected data and processing decisions traceable rather than smoothing away a discrepancy.
What should the final data package contain?
Agree formats in advance. A practical handover includes raw observations, navigation and quality logs, calibration and offset records, sound-speed and water-level inputs where used, processing settings, accepted outputs, a coverage plot and a list of exclusions or unresolved limitations. Maintain a clear distinction between measured depth and interpolated surfaces.
Build a hydrographic survey configuration
Send the survey area, minimum and maximum depth, water conditions, launch access, required coverage and output, selected sonar if known and the acceptance specification.