EM®SBP – Sub-bottom profiling with EM®304/124

EM®SBP gives you as a user of EM® 304 or EM® 124 multibeam echo sounders the unique opportunity to add sub-bottom data to your survey, without needing to buy or install sub-bottom specific transducers or electronics.

At a user selectable interval, the EM® 304/124 system can be instructed to issue sub-bottom specific signals that converts into parametric low frequency chirp pulses in the water column. The EM® receiver unit picks up the returned echoes from the sub-bottom transmissions and forward these observations to the EM®SBP software for sub-bottom specific processing and imaging.

Multibeam echo sounders supported

  • EM 304 MKI or MK2
  • EM 124


Basic system information

  • Operating system: Windows 10/11, 64-bit
  • Hardware: Hydrographic Work Station (HWS)
    This is an IEC 60945 and E10 maritime-certified computer. We recommend installation in a 19" rack.
  • Software license: Software key that will be provided as agreed.
    License can be time limited or with no time limits.
    License will work with any of the supported multibeam echo sounder systems

Key feature

  • Full sub-bottom functionality with your EM® 304 MKII or EM® 124 hardware
  • Sub-bottom or multibeam pinging at user selectable sequence
  • Simultaneous sub-bottom imaging from primary and parametric signals
  • Performance given by the EM® 304/124 configuration
  • Attitude compensation
  • Automated transmit and receive settings
  • Data storage and export to SEGY
  • Replay


Close-up of sub-bottom imaging by EM SBP. The software offers full resolution zooming, numerous colour schemes and dynamic gain settings of the echogram.

Simultaneous primary and parametric sub-bottom profiling

Depending on sediment types and conditions, water depths and external noise levels, the primary and parametric signals may come out with different properties and advantages. The source level of the high frequency primary signals is significantly higher than that of the generated parametric signals, whereas the low frequency parametric signal is less attenuated in the sediments. Which one gives the best sediment imaging depends on the conditions. EM®SBP gives you the benefit of both signal types, and you can see for yourself which methodology gives the best solution for your specific conditions.


The performance capabilities of a sub-bottom profiler system are primarily determined by its source level, transmit beam width and frequency band. For EM®SBP these parameters are given by the applied EM® multibeam echo sounder system. For a 1 by 1 degree EM® 124 and EM® 304 MKII configurations, the EM®SBP performance is given as follows:

EM 304 MKII (1x1°)2 EM 124 MKII (1x1°)2
Primary frequency range (B) 20-32 kHz 10.5-13.5 kHz
Primary source level [dB re 1 μPa ref 1m]   Up to 237 dB Up to 240 dB
Parametric frequency range 2-12 kHz 1-3 kHz
Parametric source level @4 kHz [dB re 1 μPa ref 1m] 1)   201 dB N/A
Maximum vertical resolution (1/B) 0.10 ms 0.33 ms
Beam width along
Beam width across 6.5°

1) Equivalent source level @4kHz in the far field estimated based on expected parametric signal conversion
2) Several other configurations are available


High-performance state-of-the-art software architecture

The EM®SBP software provides real-time high-resolution display of the echograms and traces. The echograms can be enhanced by your colour preferences, dynamic gain, and envelope display. The software supports full resolution zooming of the echogram. Windows can be torn-off, and you can create as many instances of the echogram as you need. You can tag features of interest, and EM®SBP will store the annotated positions with your description in a separate XML file. A map view is also available which you may find useful for visualizing your survey track. The map is provided by Gebco, and is available for offline use. The map must not be used for navigation.

EM®SBP is by its web-based designed well suited for remote operation, and the user application runs well on other devices, e.g., tablets or mobile telephones.

Simultaneous imaging of parametric and primary sub-bottom signals.

Software features

  • Several simultaneously updated echograms
  • Echogram colour selection
  • Dynamic gain adjustments
  • Logarithmic or linear view
  • Trace view
  • Offline available map view
  • Annotation

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