Error budget analysis for hydrographic survey systems; implemented on a pipeline inspection campaign by an AUV

12 January 2017

Geraud Naankeu Wati wrote the paper ‘Error budget analysis for hydrographic survey systems; implementation on an inspection campaign of pipelines by an AUV’ in 2016. This earned him a Student Award 2016 from IFHS (International Federation of Hydrographic Societies) for the best final year project in hydrography.

We agree that the paper indeed is worth a read if you are interested in error budget estimation. The paper even shows a missing link in the calculation of the transformation matrix between the INS/IMU frame and the local navigation frame. In general, the standard method did not take into account misalignment angles. Nor was the contribution of the latency taken into account perfectly.

You can find the paper on page 21 in this edition of International Hydrographic Review published on iho.int.

Paper summary

Expression of the sounding process in the Terrestrial frame

Expression of the sounding process in the Terrestrial frame

For the installation of subsea infrastructures (pipelines, subsea wells, etc.) required for the extraction, storage and supply of hydrocarbon resources, the oil and gas company TOTAL regularly contracts hydrographic survey companies to provide positioning and hydrographic survey services. These companies mainly use two types of systems for these operations: surface and underwater survey systems.

In preparing for these operations, the contractor needs to estimate the error budget – also called the “error budget or Total Propagated Uncertainty (TPU)” - for the hydrographic survey systems to be used. The error budget estimation of an hydrographic system is an important part of an hydrographic survey which enables to identify and determine the contribution of all various sources of uncertainty which affect the acquired data quality and to check if the measurement uncertainty of the sounding position meets the minimum survey specifications described by International Hydrographic Organization (IHO) as adopted by TOTAL. The error budget is obtained by combining all the sources of uncertainty contributing to the measurement uncertainty of the sounding position using a statistic method called the “law of propagation of uncertainty” and in common parlance the "root-sum-of-squares".

This paper gives an in-depth analysis on the error budget estimation of surface and underwater survey systems; describes briefly these state-of-the-art systems and proposes an estimation method of error budget of these systems. This work also contributes to improve bathymetric sounding position equations

Measurement of uncertainty of sounding position

Measurement of uncertainty of sounding position

Author biography

Geraud NAANKEU WATI received his Master I in Mechanical and numerical simulation from the University of Maine, Le Mans, France, in 2013 and his Master’s degree in engineering in Hydrography and Oceanography from the ENSTA Bretagne, Brest, France, 2015. In 2015 and 2016, he completed his internships at TOTAL E&P, focused on the error budget analysis for hydrographic survey systems and the calculation of AUV’s trajectory for hydrographic campaigns. Since September 2016, he has been working at SUB-C-MARINE as specialist in positioning and geomatics.

Geraud NAANKEU WATI
Specialist in Geomatics and Positioning at SUB-C-MARINE
Trainee at TOTAL/ENSTA Bretagne
+ 33 (0) 6 60 12 82 33
wgeraud@yahoo.fr /  geraud.naankeu@ensta-bretagne.org

You can find the paper on page 21 in this International Hydrographic Review edition published on iho.int.

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