What is the difference between SBES and MBES?

SBES (Single Beam Echo Sounder) measures depth only directly beneath the transducer, making it suitable for simple profiles and dredging monitoring. MBES (Multibeam Echo Sounder) maps a wide swath of the seafloor in a single pass, essential for 3D bathymetric surface modeling and high-resolution mapping.

What is the Time of Flight formula in hydrography?

The Time of Flight formula is d = (v × t) / 2, where d is depth, v is the speed of sound in water (~1500 m/s), and t is the time taken for the sound pulse to travel to the seabed and back.

What is Side Scan Sonar (SSS) used for?

Side Scan Sonar (SSS) provides photo-like imagery of the seafloor, used to identify shipwrecks, pipelines, cables, debris, and seabed features. It is essential for hazard detection, archaeological surveys, and sediment classification.

Modern Hydrographic Equipment (SBES, MBES & SSS)

Modern Hydrographic Equipment – SBES, MBES & Side Scan Sonar Complete Guide

ACOUSTIC SENSORS

Modern Hydrographic Equipment – SBES, MBES & SSS

A complete, standalone guide to the core tools of a hydrographer — Single Beam, Multibeam & Side Scan Sonar.

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📡 Modern Tools: SBES, MBES & Side Scan Sonar

Engineer Rokib Hossain | Hydrographic Expert

In this comprehensive guide, we transition from theory to technology. Modern hydrography relies on sophisticated acoustic sensors and satellite positioning to map the underwater world with surgical precision. Whether you are a field surveyor, a marine engineer, or a student, understanding these core tools is essential for accurate seafloor mapping.

📡 SBES

Single Beam Echo Sounder: Measures depth directly beneath the transducer. Best for simple profiles, dredging monitoring, and shallow water surveys.

🛰️ MBES

Multibeam Echo Sounder: Maps a wide "swath" of the seafloor in a single pass. Essential for 3D bathymetric surface modeling, high-resolution mapping, and offshore construction surveys.

📸 SSS

Side Scan Sonar: Provides photo-like imagery of the seafloor. Used to identify shipwrecks, pipelines, cables, debris, and seabed sediment features.

📐 The Core Logic: Time of Flight

All acoustic sensors work on a simple mathematical principle. The sensor transmits a sound pulse and measures the time it takes to return from the seabed.

d = (v × t) / 2 d = Depth (m) · v = Speed of Sound (~1500 m/s in seawater) · t = Time of Flight (seconds)

Pro Tip: Accurate positioning using GNSS (GPS/RTK) is mandatory to tag these depths to a specific X, Y coordinate. Without precise positioning, even the best acoustic data is useless.

🌊 Why This Matters for Your Surveys

Choosing the right sensor depends on your survey objective:

Use SBES for simple cross-sections, dredge progress monitoring, and shallow water channels.
Use MBES for full seafloor coverage, 3D modelling, hazard detection, and engineering-grade surveys (IHO S-44 Special Order).
Use SSS to locate objects, map seabed texture, and conduct archaeological or pipeline route surveys.

In many modern surveys, MBES and SSS are used simultaneously to collect both bathymetry (depth) and imagery (backscatter) data in a single run.

Engr. Md. Rokib Hossain | Hydrographic & Marine Engineering Specialist