1. BSIP: Backscatter Software Intercomparison Project
Preliminary Evaluation of Multibeam Backscatter Processing Consistency
(A project of Geohab Backscatter Working Group)
Project Facilitators:
Mashkoor Malik, NOAA, USA
Giuseppe Masetti, UNH CCOM/JHC, USA
Alexandre Schimel, NIWA, New Zealand
Marc Roche, ECONOMIE, Belgium
Margaret Dolan, NGU, Norway
Julian Le Deunf, SHOM, France
Project Collaborators:
SonarScope, IFREMER
FMGT, QPS
HIPS & SIPS, Teledyne CARIS
MB Process, Curtin University, CMST
US Hydro Conference March 2019
Biloxi, MS, USA

2. BSIP → Rationale Significant differences in backscatter products
generated by different software
using the same dataset
Major limitation for:
Quantitative analysis
Combining multiple sources
Time-monitoring of seafloor changes
Data quality validation
Although backscatter mosaics of the seafloor are now routinely produced from multibeam sonar data, significant differences have been observed in the products generated by different software when processing the same dataset.
This represents a major limitation to a number of possible uses of backscatter mosaics, including quantitative analysis, monitoring seafloor change over time, and combining results from multiple data sources.
BSIP: Backscatter Software Intercomparison Project

3. Example of end user frustration (mosaics comparison)
Coarse
Fine
End result of backscatter mosaic offers little insight as to
what went wrong and where?
Lurton and Lamarche (2015); Lucieer et al. (2018); Roche et al. (2018)

4. BSIP → Processing Steps
Currently produced
results
BL0
Level “as read from datagram”
BL3
Level after all corrections applied before mosaicking
BSIP requested intermediate levels
(provided by software developers)
Radiometric corrections:
-Gains applied in reception
-Propagation through the water-column
-Interaction with the seafloor
-Mechanical properties of the transducer
Schimel et al. (2018)

5. Carré Renard reference area
BSIP dataset
Kongsberg EM302
Johnston Atoll area
NOAA - USA
Teledyne 7125
Wembury Bay UK
Shallow survey 2015
Kongsberg EM710 and EM3002
Carré Renard reference area
SHOM - FRANCE
Kongsberg EM2040
Kwinte reference area
FPS Economy - BELGIUM
BSIP: Backscatter Software Intercomparison Project

6. EM 2040 Bathymetry Software results match !!
Sonar
Scope
CARIS
QPS
Kwinte reference gravel and sandy gravel area
RV Simon Stevin EM2040 single Rx L0005_ _ all (300 kHz, 216µs)
Depth (m)

7. EM 2040 Backscatter CARIS BL3 -11.5 dB CARIS BL0 FMGT BL3 FMGT BL0
SonarScope BL3
SonarScope BL0
-17 dB dB

8. EM 2040 Backscatter

9. Large differences not an isolated case !!
EM 302
RESON 7125
EM 710
Johnston Atoll area
EM302 L0213_ _112534_EX1706.all (main frequency = 27.75kHz, pl = 40ms)

10. Intermediate processing stages enable further insights
BL3 - BL0
(CARIS BL3 - CARIS BL0) - (FMGT BL3 - FMGT BL0)
(CARIS BL0 - FMGT BL0)
CARIS / Sonar Scope
FMGT/ Sonar Scope
Sonar Scope
CARIS / FMGT
CARIS
FMGT
Processing of BL3 from BL0 is different for each software
Difference in processing relative to starting value

11. Summary
Intermediate processing stages provides insights into differences between software outputs
A variety of processing approaches available
A possible method without compromising proprieatary information
Round 2 processing in progress
Software developers requested to provide outputs from other intermediate stages
We need your help !!
Users: To demand that results processed by different software should agree with each other
Software developers: To work together to implement best practices for backscatter processing
Backscatter Working Group: To continue to provide a platform to facilitate these discussions

12. Thanks to software developers
Questions ?
Mashkoor Malik
Giuseppe Masetti
Alexandre C. G. Schimel
Marc Roche
Margaret Dolan
Julian Le Deunf
Thanks to software developers

13. References
Lucieer V, Roche M, Degrendele K, Malik M, Dolan M, Lamarche G User expectations for multibeam echo sounders backscatter strength data-looking back into the future. Mar. Geophys. Res. 39:23-40.
Roche M, Degrendele K, Vrignaud C, Loyer S, Le Bas T, Augustin J-M, Lurton X Control of the repeatability of high frequency multibeam echosounder backscatter by using natural reference areas. Mar. Geophys. Res. 39:
Schimel ACG, Beaudoin J, Parnum IM, Le Bas T, Schmidt V, Gordon K, Ierodiaconou D Multibeam sonar backscatter data processing. Mar. Geophys. Res. 39:
Lamarche G, Lurton X Recommendations for improved and coherent acquisition and processing of backscatter data from seafloor-mapping sonars. Mar. Geophys. Res. 39:5-22.
Lurton X, Lamarche G Backscatter measurements by seafloor-mapping sonars. Guidelines and recommendations. Retrieved 27th April 2018 from
Malik, M.; Lurton, X.; Mayer, L A framework to quantify uncertainties of seafloor backscatter from swath mapping echosounders. Mar. Geophys. Res. 39, 151–168.