📋 DAY 10: SURVEY PLANNING & EXECUTION

From Project Brief to Final Line – A Complete Field Workflow
Instructor: Engr. Rokib Hossain | River Engineering Solutions
🏠 Course Homepage

📖 Today's Outline

🎯 The Survey Planning Mindset

Hydrographic surveying is 80% planning, 20% execution. A well‑planned survey reduces rework, saves vessel time, and delivers IHO‑compliant data. The planning phase includes:

  • Understanding client objectives and required standards (e.g., IHO S‑44 Order 1a).
  • Selecting the right equipment (MBES vs SBES, GNSS, IMU).
  • Designing line plans to achieve full bottom coverage.
  • Logistics: vessel, fuel, crew, tides, weather windows.
  • Risk assessment and contingency plans.
📌 Key concept: A survey that is poorly planned will always produce questionable data, no matter how expensive the equipment.

📄 Pre‑Planning & Project Brief

Before mobilisation, obtain or create a Survey Specification Document that includes:

  • Area boundaries (shapefile or coordinates).
  • Required horizontal and vertical datums.
  • IHO order or specific accuracy requirements (e.g., 0.25 m depth error).
  • Expected water depth range and seabed type.
  • Existing charts, previous survey data, and known hazards.
  • Permits and environmental restrictions.

From this, you define survey parameters: MBES swath width (typically 3‑5× depth), line spacing (80% of swath to ensure 20% overlap), and line direction (preferably along depth contours or parallel to the area's long axis).

🗺️ [Example: Survey area shapefile with planned line pattern]
(Replace with your own image)

🗺️ Line Planning – Spacing, Direction, Coverage

For MBES: Calculate line spacing = 0.8 × (swath width). Swath width ≈ 2 × depth × tan(swath angle/2). Example: depth 20 m, swath angle 120° → swath width ≈ 69 m → line spacing ≈ 55 m. Always add extra lines at the edges for full coverage.

For SBES: Line spacing depends on feature detection. For IHO Order 1a, maximum line spacing is 3.5 × beam footprint. In practice, use dense spacing (10‑20 m) in shallow water or for wreck searches.

Cross‑lines: Plan cross‑lines (perpendicular to main lines) at 5‑10% of the total line length. They are essential for estimating TPU (Total Propagated Uncertainty) and detecting systematic errors.

📐 Pro tip: Use acquisition software (Hypack, QINSy) to automatically generate line plans and export them to the vessel's navigation screen. Always include a margin around the area (50‑100 m) to account for vessel turning.

🚤 Logistics & Risk Assessment

Field logistics can make or break a survey. Key considerations:

  • Vessel: suitable size, fuel capacity, draft, and mounting points for sensors.
  • Crew: experienced skipper, hydrographer, and assistant.
  • Tides & currents: plan survey during optimal tidal windows (e.g., slack tide for shallow areas).
  • Weather: check wind, wave height, and visibility forecasts. Set thresholds: e.g., abort if wave height > 0.5 m for MBES.
  • Permits: ensure all permissions (environmental, port authority) are in place.
  • Contingencies: backup equipment, spare cables, alternative power sources, and communication.

Conduct a formal risk assessment (RA) before mobilisation. Common risks: equipment damage, GNSS outages, collision with other vessels, personal injury.

⚙️ Field Execution – Daily Workflow

A typical survey day follows this sequence:

  1. Start‑of‑day checks: power up all systems, verify GNSS fix (RTK or PPK logging), check IMU alignment, record sound velocity profile (SVP) cast.
  2. Line start: motor to the first line's start point, allow vessel to stabilise, begin logging.
  3. During survey: maintain constant speed, monitor depths, keep vessel within planned line (use navigation screen), watch for real‑time QC indicators (coverage, heave, roll).
  4. End of line: stop logging, turn safely, verify that no data gaps exist.
  5. Cross‑lines: run a few cross‑lines at regular intervals (e.g., every 10 main lines).
  6. End‑of‑day checks: download data, backup to external drive, fill in logbook, clean equipment.
⏱️ Efficiency tip: Use a pre‑survey "run‑in" line to stabilise speed and heading before starting data recording. This avoids acceleration‑induced heave errors.

✅ Real‑time QA/QC in the Field

While surveying, keep an eye on these QC parameters:

  • GNSS: RTK fix status (FIX, not float), PDOP < 2.5, number of satellites > 12.
  • Motion sensor: heave should be less than 10% of depth; roll and pitch within expected wave conditions.
  • MBES coverage: no gaps between lines; outer beams not excessively noisy.
  • SVP age: If last cast was >4 hours ago, consider a new cast.
  • Water column: check for bubbles, fish, or thermocline artefacts.

Most acquisition software displays a real‑time coverage map and a "depth vs ping" monitor. Pause and re‑run any line that shows poor data.

📊 [Screenshot of real‑time QC panel – coverage, heave, and SVP]
(Replace with your own image)

🔗 External Resources & Templates

Use these resources for survey planning templates and guidelines:

ResourceDescriptionLink
IHO C‑13 (Standards for Hydrographic Surveys)Official IHO survey planning and execution guidelinesiho.int
NOAA Field Procedures ManualDetailed planning and execution chapters (Appendix B)NOAA PDF
Survey Line Planning Calculator (MBES)Online tool to compute line spacing based on depth and swath angleHydro International
Risk Assessment Template (free)Editable risk assessment form for hydrographic projectsHSE UK
🔗 Authority linking: IHO, NOAA, and HSE are trusted sources.

📋 Homework & Fieldwork Checklists

📘 Day 10 – Homework Checklist

  • ✅ Read the entire Day 10 post.
  • ✅ Choose a local harbour or river section and create a mock survey plan: define area, select equipment, line spacing, and number of lines.
  • ✅ Download the NOAA Field Procedures Manual and read the chapter on line planning.
  • ✅ Write a one‑page risk assessment for a small boat survey in a tidal estuary.
  • ✅ Share this post with #Hydrography #SurveyPlanning.

🛠️ Fieldwork Readiness Checklist – Survey Planning & Execution

  • ✅ Before leaving office: generate line plan, obtain permits, check weather windows, prepare backup equipment.
  • ✅ Day before survey: test all sensors, charge batteries, load line plan into acquisition software, verify NTRIP/radio link.
  • ✅ On survey day: start‑of‑day QC, cast SVP, run a short test line to verify offsets and latencies.
  • ✅ During survey: maintain speed, monitor coverage, log all events (tide changes, vessel traffic, equipment reboots).
  • ✅ End of day: backup data twice, fill logbook, clean transducers, secure equipment.
  • ✅ Weekly: reprocess a small subset to check data quality early.
🖨️ Pro tip: Use the Print / Download PDF button to keep these checklists in your field binder.

❓ Frequently Asked Questions

🔹 How much overlap do I need between MBES swaths? ▼
IHO recommends at least 20% overlap between adjacent swaths. Use line spacing = 0.8 × swath width to achieve this. In practice, some organisations use 30‑50% overlap for high‑reliability projects.
🔹 Can I plan lines using Google Earth? ▼
Yes, for preliminary planning you can draw lines in Google Earth and export as KML, then import into acquisition software. However, final line spacing must be calculated based on depth and swath angle.
🔹 How many cross‑lines do I need? ▼
A common rule is 5‑10% of the total main line length, distributed evenly throughout the survey area. Cross‑lines should be run in a perpendicular direction to the main lines.
🔹 What should I do if I encounter unexpected shallow water? ▼
Immediately stop survey, verify chart depths, and if safe, plan a dedicated shallow‑water line set with reduced speed and narrower swath. Adjust line spacing accordingly.
🔹 How do I handle vessel traffic during the survey? ▼
Always prioritise safety. Pause logging, move aside for passing vessels, then resume. Record the interruption in your log. Avoid surveying in narrow channels during peak traffic hours.

✅ Action Items & Internal Linking

🎯 Your Tasks for Today

  • 📌 Step 1: Bookmark the Course Homepage and the IHO C‑13 standards page.
  • 📌 Step 2: Download the checklist PDF using the button at the top.
  • 📌 Step 3: Create a mock line plan for an area you know (e.g., a local lake) using a line spacing calculator.
  • 📌 Step 4: Leave a comment on this post: "The biggest challenge I foresee in survey planning is ____."
  • 📌 Step 5: Proceed to Day 11: MBES Hardware & Setup using the link below.
◀ Day 9: Offsets & IMU Day 11: MBES Hardware & Setup ▶
🔗 Internal linking note: Day 9 and Day 11 are correctly linked. This builds a strong internal network for SEO.

👨‍🔧 Engr. Rokib Hossain | River Engineering Solutions

LinkedIn | Portfolio