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Pressure Inverted Echo Sounder

Engineered for: Seabed

Pressure Inverted Echo Sounder (PIES) is a long-life sensor logging node that accurately measures the average sound velocity through a column of water from the seabed to the sea surface.

At a glance

Use it to measure average sound speed in the water column

Developed for marine seismic and ocean science applications

Harvest data using ROV, AUV, USV or surface vessel

Integrated acoustic release for easy recovery at conclusion of survey

Depth ratings to 6,000 m

Choice of form factor to suit your concept of operations

Delivering insight for your surveillance surveys

Want to know more?

PIES is built on our 6G instrument platform with a global track record of reliability

A telemetry link allows recorded data to be transmitted to surface at data rates ranging from 100 to 9,000 bits per second

Average water column velocity is calculated directly from the depth and travel time data, noting that speed = distance / time

Both versions of PIES feature an integrated acoustic release for simple recovery

Benefit of PIES for your applications

Long endurance

Monitor for months or years - PIES is engineered for sustained observation campaigns and can be deployed for up to five years.


PIES helps oceanographers and geophysicists to better understand the physical processes that occur in the deep ocean, guiding policy and operational decisions.

Data on demand

Harvest your data when you want, how you want using an uncrewed surface vessel to lower your costs and reduce emissions.


PIES is a long endurance oceanographic instrument for precisely measuring average sound speed in the water column.

The instrument has been developed for marine seismic and ocean science applications to gather valuable physical oceanography data. PIES can be configured for autonomous monitoring over periods of several months or years. One key operational advantage for users is that minimal conductivity and temperature profiling is needed over the seismic survey period.

PIES uses an up chirp to accurately measure two-way travel time through the water column. It simultaneously measures pressure at the seabed. Pressure measurements are converted to depth to find the acoustic distance travelled from the seabed to the surface and back again. By combining the depth and travel time, the average sound speed in the water column can be calculated.

An embedded acoustic modem allows you to retrieve via USV or crewed vessel. Alternatively, the PIES unit can be retrieved to the surface. The SD card extractor software gives you access to the raw data gathered by the instrument. Accurate conversion from pressure to depth can be achieved by allowing you to include local barometric pressure, seawater density and gravity with the PIES data.

A PIES unit is user-configurable to capture at a programmable ping rate ranging from one minute to many minutes or even hours. The choice of ping rate enables you to balance the conflicting demands of battery life with the need to average out effects from the instantaneous sea state at the time of acoustic measurement.

Although data can be harvested at any time without recovering the instrument – using a vessel-of-opportunity or uncrewed surface vessel equipped with a Sonardyne modem-enabled instrument – logged data is typically retrieved once the survey is completed and the PIES unit is recovered on the surface.

PIES data is retrieved using the SD Card Extractor software and the raw measurements are post-processed with geophysical data. The set-up for the SD Card Extractor is partially automatic and can detect the current baud rate, minimising the time spent completing the extraction process.

Why invest


  • Integrated modem with data rates ranging from 100 to 9000 bps

  • LMF (14–19 kHz) operating frequency

  • 190–202 dB (4 Levels) Transmit source level

  • 80–120 dB (7 levels) Receive sensitivity


  • Easy to set up with configuration and sampling period programmable via telemetry link

  • Glass sphere or hard anodised aluminium housing options

  • Customisable sensor payload options


  • 3,000 or 6,000 m depth rated

  • Up to five year deployment life

  • Vessel, USV or AUV data harvesting options

  • Anti-trawl fame option available


  • Warranty: 1-year return to Sonardyne service centre

  • ITAR Controlled: No

  • UK Export License: Not required


Feature Type 8302-3116 Type 8306-3816
Depth Rating 3,000 or 6,000 m 3,000 or 6,000 m
Operating Frequency LMF (14–20 kHz) LMF (14–20 kHz)
Transmit Source Level (dB re 1 µPa @ 1 m) 190–202 dB (4 levels) 190–202 dB (4 levels)
Receive Sensitivity (dB re 1 µPa) 80–120 dB (7 levels) 80–120 dB (7 levels)
Battery Life (Capacity) Multi-years life, dependent on sensors and sampling interval (100 Ahr) 5 years life (dependent on sensors and sampling interval (180 Ah)
Mechanical Construction Hard anodised aluminium housing, duplex stainless steel guards Glass sphere, galvanised stand, duplex stainless steel guards and connectors
Weight in Air/Water Fetch 30.6/16.1 kg 43/-10 kg (upthrust buoyancy)
Stand n/a 60/52 kg
Sensor Options
Temperature (±0.1°C) Standard Optional
Tilt Switch (±30–45°) Standard Standard
High Precision Strain Gauge (±0.01%) Keller or Presens Optional Optional
Paroscientific DigiQuartz Pressure Sensor (±0.01%) 1,350 m, 2,000 m, 4,130 m, 6,800 m Standard Standard
High Accuracy Inclinometer Range: ±90° Accuracy: ±0.05° over 0–±15°; ±0.2° over 0–±45° Optional Optional
Sound Velocity Sensor ±0.02 m/s Accuracy Under Calibration Conditions Optional Optional
External Sensor Options Turbidity, Conductivity, ADCP n/a Optional
Release Mechanism (Screw-off) Standard Standard
Connector Type Subconn MCIL8M Impulse MCIL-8-MP
(See Compatt 6 and AMT datasheets for more information)

Manuals and quick start guides

Software and firmware

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Delivering insight for your surveillance surveys