Ba k a e -A aly e 
12 
Hydrographische Nachrichten 
UNIVI USITÉ 
LAVAL 
UNIVtRSITf 
gjjj LAVAL 
was» 0 km 
10 km 
Fig. 1: Basemap tiles of the 
Canadian Arctic Archipelago 
from data collected In 0 4 
with the bathymetrlc surface 
(a left) and the rst order 
angular compensated BS 
mosaic (b, right) 
in the echo sounder’s runtime parameters Rg. 
illustrates the correlation between changes in the 
BS and changes to the Depth Mode parameter. 
The Depth Mode, Swath Type and Rjlse Type are 
three parameters that collectively determine the 
Transmission Mode of the echo sounder. Wiile not 
depicted in the Rg, changes in Swath Type and 
Rjlse Type are also likely to induce changesto the 
BS level of survey lines During normal operation, 
the EM will automatically nd the most appro 
priate combination of Depth Mode, Swath Type 
and Rjlse Type (i.e. Transmission Mode) to t the 
current range to the bottom and along track data 
density. Each Transmission Mode uses a number 
of transmission sectors with each sector’s pattern 
possessing auniquesignature.EM echo sound 
ersactuallydo compensate in real time forthe sec 
tor patterns However, they utilise default models 
which do not necessarily re ect the real patterns 
Any discrepancy between the models and real 
ity will lead to residual overprinting visible on the 
backscatter level of individual survey lines, a situa 
tion clearly visible in Rg. b. Luckily, the sector pat 
tern modelscan be adapted by appropriately mod 
ifying a con guration le known as the bs . x 
le. Wth an appropriately con guredbs .x le, 
no further modulation of the sector patterns will 
be visible in the real time collected data. 
IFREMERbackscalter calibration 
procedure 
Attemptsto calibrate echo sounder beam patterns 
are not new. Rjote et al. ( ) and more recently 
Lanzoni and \Afeber ( ) ha/e detailed procedures 
to achieve such results under controlled settings 
However, these procedures are limited to relatively 
compact and high frequency echo sounders Rjr 
medium to deep depth echo sounders, thistype of 
Rg. 2: Angular compensated 
BSimagesin ping vs beam 
geometry (direction of travel 
left to right) and parameter 
values of the Transmission 
Modes used i n two su rvey I i nes 
(Depth Mode: = Shallow; 
3= Medium;4= Deep. 
Rjlse Type: 0 = ON; = FM. 
Swath Type: = Sngle; = Dual) 
KM Seabed Image 
nui lu ifnri n 1 ni alili 1 niAMir muh h 111 it 1 «imi.u i n irlif i 
V. ..JA... 14 « ■ 4-J 
100 300 300 400 900 G00 TOD 600 
Depth Mode 
! I ~\ = f == \ 
100 2ÛO 300 400 SOD 600 ?CQ SOD 
Pulse Type 
■0 
too a» 300 «O soo oh to ra 
Swath Type