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IOGP-649: Seawater Pressure to Depth Conversions


This Report was written by the Pressure to Depth Conversion Expert Group, part of IOGP’s Geomatics Committee, with contributions from the Surveying and Positioning Subcommittee, Geodesy Subcommittee, and the Metocean Committee.


Vertical positioning has emerged as a topic of growing interest in the oil and gas community, but there remains no common industry standard of practice for the conversion of depth measurement from seawater pressure measurements. Accurate and repeatable depth measurements are critical for the successful installation of wells and other subsea infrastructure within their vertical design tolerances, and most high accuracy depth surveys are conducted using pressure sensors.

The lack of industry standardisation on this subject raises the risk of incompatible depth surveys, installation mishaps, or costly design rework.

The purpose of this guidance note is to explain the fundamental processes of pressure to depth measurement conversions and provide a list of known conversion methods currently used in the industry, with recommendations on their implementation, intended use, relative merits, and comparative accuracies.

The aim is not to provide any guidance on topics of tidal adjustments, vertical survey reference systems, or acoustic depth measurement systems, or to set out or enforce any mandatory technical specifications or requirements and the guidance is provided for information purposes only.

See link below to the IOGP Website:

Seawater pressure to depth conversions | IOGP Publications library

For more information, please contact [email protected] or [email protected]

Related Guidance

  • American Meteorological Society. Glossary of Meteorology. Boston, Massachusetts. (
  • Fofonoff N, and Millard Jr, R. Algorithms for the computation of fundamental properties of seawater. (Unesco technical papers in marine science; 44. UNESCO. Paris. 1983)
  • Hofmann-Wellenhof B, and Moritz H. Physical Geodesy, 2nd ed. New York: SpringerWienNewYork, 2006.
  • IOC, SCOR, and IAPSO. The international thermodynamic equation of seawater – 2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission: Manuals and Guides 56. 2010.
  • Knauss J, and Garfield N. Introduction to Physical Oceanography, 3rd ed. Long Grove, IL, USA: Waveland Press. 2017.
  • Leroy C and Parthiot F. “Depth-pressure relationships in the oceans and seas.” Journal of the Acoustical Society of America 103(3).1997.
  • McDougall T and Barker P. Getting started with TEOS-10 and the Gibbs Seawater (GSW) Oceanographic Toolbox. SCOR/IAPSO WG127. 2011.
  • Moran M. et al. Fundamentals of Engineering Thermodynamics. 8th ed. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2014.
  • Moritz, H. “Geodetic Reference System 1980.” Journal of Geodesy. 2000. p. 128–133.
  • NIST. “The International System of Units (SI).” NIST Special Publication 330: 2019 edition (Newell and Tiesinga, Eds.). Gaithersburg, MD, USA: U.S. Department of Commerce, 2019.
  • NOAA. Tools & Software: DYNAMIC_HT. 2022.
  • (Accessed 26 August 2022).
  • Paroscientific, Inc. DigiquartzR Pressure Instrumentation. Standard Products Installation Guide,
  • Document G8203 Rev D. Redmond, WA, USA, 2000.
  • Paroscientific, Inc. DigiquartzR Pressure Instrumentation. User Manual For Intelligent RS-232 Only Instruments, Document No. 8107-001 Revision AD. Redmond, WA, USA, 2008.
  • Perry K. ATMOS 5000 Lecture 2: Hydrostatic Equation derivation. 2015. YouTube. Saunders PM. “Practical Conversion of Pressure to Depth.” Journal of Physical Oceanography 11. 1981. p. 573–574.90 Seawater pressure to depth conversions
  • Sea-Bird Electronics, Inc. Conversion of Pressure to Depth. Application Note No. 69. Bellevue, WA, USA. 2002.
  • Tritech International Limited. TIL-Endg-Spec-017 (Issue 7). SeaKing SONV3 Bathy System Operator Manual.
  • Tipler P and Mosca G. Physics for Scientists and Engineers. New York: W.H. Freeman and Company. 2004.
  • Torge W. Geodesy. 2nd ed. New York: Walter de Gruyter & Co. 1991.
  • UNESCO et al. Background papers and supporting data on the International Equation of State of Seawater 1980. Unesco technical papers in marine science; 38. UNESCO. Paris. 1981.
IMCA Contact

Roger Moore
Technical Adviser – Remote Systems and ROV, Offshore Survey

Information Note Details

Published date: 19 July 2023
Information note ID: 1642


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