Ba k a e -A aly e 
HN104 — 06/2016 
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calibrated setup is not posable in a laboratory en 
vironment due to the aze of the instruments and 
acoustic range requirements Deviations from the 
laboratory measurementsare also likely to occurfol 
lowing the nal installation con guration on board 
a ship and due to normal wear and tear of elec 
tronic and acoustic components For these reasons 
it is imperative that a eld calibration procedure be 
performed to account for the sector patternsof me 
dium and deep seamultibeam echo sounders 
Thecalibration proceduredeveloped bylFFEMER 
aims at more accurately modelling the sector pat 
terns of multi sector, multi swath multibeams by 
direct analysis on real time collected backscatter 
images To be successfully completed, the proce 
dure requiresacalibration survey to be performed 
and subsequent analysisof the backscatter images 
using the IFPEMERsoftware SbnarStope. The cali 
bration survey areas must be chosen carefully in 
order to optimise the quality of the analysis Rat, 
suitably deep and geologically uniform seabed 
areas must be pre selected for the calibration sur 
vey. A series of opposite running survey lines are 
then run for each Transmission Mode. 
SLich a calibration survey and subsequent 
backscatter data analysis was performed for the 
EM of OOGS>Amundsen«. The guresdemon 
stratethee ectivenessof the procedure. The Shal 
low, Dual, CWTransmission Mode isused asacase 
example. 
Rg. a shows the angular compensated ESim 
age in ping vs beam geometry resulting from the 
fongsberg real time data reduction process for 
the Shallow, Dual, CWTransmission Mode. Rg. b 
shows the mean ESangular curve obtained from 
the EBimage by averaging the ESvaluesin ° bins 
and colour coding curve segments by unique 
transmission sector. 
9ep of the calibration procedure consists in 
removing the ESangular response model used in 
Rg. 3: Angular compensated 
ESimage In ping vsbeam 
geometry (a, left) and 
corresponding angular 
response (b, right) for the 
Shallow Dual CWTransmission 
Mode 
Rg. 4: Transmission sector 
patterns Image In ping vs 
beam geometry (a, left) 
and corresponding angular 
response (points) and models 
01 nes) (b, right) for the Shallow 
Dual CWTransmission Mode 
Rg. 5: Calibrated and angular 
compensated BSImage In 
ping vsbeam geometry 
(a left) and corresponding 
angular response (b, right) 
forthe Shallow Dual ON 
Transmission Mode