High-resolution bathymetric mapping with the new
broad-bandwidth, split- beam, scientific, multibeam sonar installed
on the new NOAA FSVs G. R. Cutter Jr. 1 D. A. Demer 1 L. Berger 2 1
NOAA NMFS Southwest Fisheries Science Center, La Jolla, CA 2
IFREMER, Dpartement NSE, Plouzan, France. [email protected]
[email protected] [email protected] Slide 2 NOAA ME70s
NOAA FSVs Mount: ME70 transducer in centerboard Nav/Pos: POS/MV
NOTE: SWFSC methods & IFREMER methods differ slightly but
result in statistically the same FM bathymetry. Therefore, we
present SWFSC results. Description and demonstration of seafloor
characterization results available from ME70 (following methods
developed for EK60) New NOAA Fisheries Survey Vessels (FSVs) Oscar
Dyson, Bigelow, Pisces, Shimada, FSV5, FSV6 Equipped with the
Simrad ME70 Quiet vessels (ICES spec.) Slide 3 ME70 Scientific
multibeam echosounder Developed by Simrad and Ifremer Principally
designed for fisheries research Two operational modes: Fisheries
Mode (FM) and Bathymetric Mode (BM) Either Mode 800 element array
Split-aperture processing for all beams Motion-compensated to 10
roll, 5 pitch, and heave Calibration (by standard sphere) NOAA FSVs
Mount: ME70 transducer in centerboard Nav/Pos: POS/MV NOTE: SWFSC
methods & IFREMER methods differ slightly but result in
statistically the same FM bathymetry. Therefore, we present SWFSC
results. Description and demonstration of seafloor characterization
results available from ME70 (following methods developed for EK60)
ship ps -3030 0 Slide 4 The configuration used for the calibration
and SAT is: SAT Config 2. This config forms 17 beams in the fan,
and 2 reference beams. The frequency of the beams in the fan range
from 70 to 120 kHz. ME70 Operational Modes Fisheries mode FM
Records from entire water-column USER-CONTROLLED CONFIGURATION:
Number of beams (3 to 45) Beam directions, swath span and overlap
Beam opening angles (min. 2) Beam frequencies WIDE-BAND (70-120
kHz) frequency transmission Two-way sidelobe suppression Adjustable
sidelobe levels (to -70 dB) Calibrated S v, TS, and single target
detections over entire water column Depth estimation, by built-in
amplitude bottom detection (with backstep) Control and interface:
ME70.exe software (We implement bottom-detection for FM data using
amplitude and phase) Slide 5 The configuration used for the
calibration and SAT is: SAT Config 2. This config forms 17 beams in
the fan, and 2 reference beams. The frequency of the beams in the
fan range from 70 to 120 kHz. ME70 Operational Modes Bathymetric
mode BM Requires additional processor machines (bathymetric module)
FIXED CONFIGURATION Equidistant or equiangle beams, *2 possible
pulse options. 80 narrow beams (up to 200 soundings per swath)
Beams formed during reception One-way sidelobe suppression (-35 dB)
SINGLE FREQUENCY transmission Bottom-detection using amplitude near
normal-incidence and phase for more oblique angles Control and
interface: Standard Simrad EM processor station and SIS software
(as for EM series multibeams) BM is like a typical seafloor-mapping
multibeam Integrates ancillary data, and produces.ALL format files.
Slide 6 NOAA FSVs ME70s with Fisheries Mode only Q1 - In addition
to water-column fisheries survey data, can the ME70 FM provide
bathymetric data for hydrographic or habitat studies? For this, we
need FM mode to deliver: High-resolution bathymetry, comparable to
BM & standard MBES Backscatter data for seafloor
characterization Q2 - Do we really need the BM? This study: derives
and compares bathymetry collected with and without the bathymetric
processor unit (BM & FM) NOAA ME70s NOAA FSVs Mount: ME70
transducer in centerboard Nav/Pos: POS/MV NOTE: SWFSC methods &
IFREMER methods differ slightly but result in statistically the
same FM bathymetry. Therefore, we present SWFSC results.
Description and demonstration of seafloor characterization results
available from ME70 (following methods developed for EK60) Quiet
vessels (ICES spec.) Slide 7 ME70 Flowchart.ALL Files Bathymetric
Mode (fixed configuration) SIS work station Hydrographic-data
processing software (e.g. Caris HIPS, Hypack) IMUGPSCT Seabed
bathymetry and classifications.RAW Files ME70 workstation Simrad
ME70 Custom software Fishery Mode (custom configuration)
Fishery-data processing software (e.g. Movies 3D, Echoview) Animal
classifications, abundances, distributions, and 3D images Slide 8
France + Survey Area * Survey Thalassa See Ifremer articles for
vessel and equipment details, Or get from L. Berger. Particularly,
Nav/Pos ME70_Ifremer_UTM_OverviewMap.png ME70 on blister on hull
Pic in Berger paper Date: 19 March 2008 Vessel: R/V Thalassa Survey
speed: ~10 knots (BM) Conducted by Ifremer Bay of Biscay, west of
France R/V Thalassa Currently, the only vessel with ME70 with FM
& BM Slide 9 >250 m >240 m >230 m Common coverage betw
BM and FM Study Range setting for FM used during survey of data4:
232 m Comparisons using ME70 data collected in bathymetric and
fisheries mode from overlapping coverage Range setting for FM: 232
m Show swath with depth > range Common coverage from BM and FM
Drop these? Slide 10 Bathymetry from Bathymetric Mode Processing of
Simrad ME70 Bathymetry Mode data using CARIS HIPS Import.ALL Remove
outliers (editor or filter) Examine motion data Apply tide Merge
Create surface Export Notice the few bad detections from sidelobes,
Auto-removed by filter. BM Bathymetry Standard hydrographic data
processing methods and software: CARIS HIPS Only gross outliers
were removed Other options: Ifremer software, Hermes, Movies3D, and
perhaps Hypack, or Triton Slide 11 Bathymetry from Fishery Mode
SWFSC Estimation of Depth from ME70 FM.RAW files z corr (t) = z u
(t) + z tdcr + heave(t) z tide (t) Trigonometric solutions for
local x,y and then conversion to global coordinates E, N E, N, z
Tdcr zz r z rr Heave from the IMU and Tdcr depth are recorded in
the raw file. Theta(a) is recorded in the raw file (beam direction,
compensated for motion). Range r(a) is estimated from a
bottom-detection method using amplitude or phase; converted to
uncorrected depth (z_u); then corrected for transducer depth,
heave, and tide, giving corrected depth (z_corr); and its
associated local horizontal coordinate values (x,y) are converted
to global values (E, N; UTM Zone 30 north). Tdcr aa seafloor r( a )
zuzu Tdcr depth heave z tide Revise fig w/ swath where sf is not so
flat, And aligning the ray with an actual beam Post-proc tools for
ME70 FM data are lacking, so we have to implement ourselves. This
bucket is your ship. The orange Tdcr is the sonar transducer....
The tdcr transmits a pulse of sound. It travels through the water
and reflects or scatters off organisms, density interfaces, and the
seafloor, and some of it travels back to the receiver, We use the
time of travel to estimate the range to the targets (in this case
the sf); that is r(theta_a) where theta_a is the angle of arrival.
We know the angle of arrival for each formed beam, and use that to
estimate the depth relative to the tdcr (giving z_uncorrected) If
we know tdcr depth, heave (we do), and estimate water elevation due
to tide (we did), then we can compensate for those, resulting in an
estimate of corrected depth, by beam direction and time,
z_corrected(t,beamdir). FM Bathymetry Custom Matlab code Other
options: Myriax Echoview, Ifremer software Depth estimation: Not
compensated for refraction Slide 12 Center of mass of e or S v
Differs from peak if noisy Bottom detection Amplitude e or S v
Differential phase Alternatives CUBE (Calder et al.) Bayesian model
including amplitude and phase information from several beams and
transmissions (Bourguignon et al., 2009) More robust
phase-differencing (Demer et al. 2009) Clarify What BM uses, What
Ifremer uses, What SWF uses * S v (dB) Thr Range (m) Show waves
arriving at 2 tdcrs That allow phase diff meas Slide 13 Seafloor
grid models (5 by 5 m grid cell size) from FM Zpzc and BM ZBM
plotted using identical colormaps. Soundings Sounding locations
resulting from ME70 BM & FM Mean depth in this subregion: 220 m
FM: 21 beams, each ~ 3 BM: 80 beams Up to 200 soundings per ping
(~150 soundings per ping with valid bottom detections for this
dataset) Number of soundings per 10 by 10 m grid cell, for a) BM,
and b) FM. # per 10-m cell 100 m Slide 14 Note In BM, the ME70
swath spans 120 In FM, the user specifies the swath span for the
ME70 or wider For this study, the ME70 swath span in FM was chosen
to be 60. Slide 15 FM ampl FM ampl&phase BMFM Bathymetry
Results Slide 16 BM FM 205 240 Depth (m) Comparison Perspective
view from NW Interpolated surfaces FM (ampl. detect only) Explain
the two datasets, the viewpoint, The colorscale and interval, the
similarity, and differences, Replace FM results from
phase-detection only With FM results from combined ampl/phase
detec. If outer beam artifacts apparent, show a swath where depth
> range. Maybe, enhance boundaries in 3d ? Diffs for normal inc
beams and where bottom exceeded range (outer beams in deep water)
Explain the two datasets, the viewpoint, The colorscale and
interval, the similarity, and differences, Replace FM results from
phase- detection only With FM results from combined ampl/phase
detec. If outer beam artifacts apparent, show a swath where depth
> range. Differences are practically zero Slide 17 205 240 Depth
(m) Comparison Perspective view from NW Interpolated surfaces FM
(ampl. & phase detect) Explain the two datasets, the viewpoint,
The colorscale and interval, the similarity, and differences,
Replace FM results from phase-detection only With FM results from
combined ampl/phase detec. If outer beam artifacts apparent, show a
swath where depth > range. Maybe, enhance boundaries in 3d.
Diffs for normal inc beams and where bottom exceeded range (outer
beams in deep water) BM FM Differences are practically zero Slide
18 % Difference Difference BM FMpzc_with_outliers % difference in
depth between BM and FM grids ME70_comparisons_BMtc-FMpzctc.png
Path: C:\Cutter\ME70\Collaboration\IFREMER\GIS\map_images Measured
diffs Betw BM, FM grids -0.5 to +1 m Difference BM FM pSv
Comparison Slide 19 Difference BM FMpzc_with_outliers Comparison
Difference in depth between BM and FM grids Green: -0.5 < dz
< 0.5 m Mean difference: -0.5 to +1.5 m for a depth range from
200 to 230 m Overall mean difference (SD): 0.58 (0.40) m
Differences may be due to refraction or tide
ME70_comparisons_BMtc-FMpzctc.png Path:
C:\Cutter\ME70\Collaboration\IFREMER\GIS\map_images Measured diffs
Betw BM, FM grids Calc proportion of diffs. Maybe Combine with
previous slide -0.5 to +1 m dz (m), BM-FM Difference BM FM pSv but
not stationary Slide 20 Seafloor slope BM FM Slide 21 Seafloor
roughness BMFM Slide 22 205 240 Depth (m) Seafloor backscatter FM
Calibrated Seafloor BS (from FM) Sv Ss Normalized for slope Map of
FM BS. Plot of BS vs Slope BM DN Note outline of FM on BM Ss (dB)
Slide 23 Seafloor classification Roughness & hardness index
from backscatter and seafloor slope See: Demer et al. 2009. ICES J.
Mar. Sci, 66. SSID Demer et al. (2009) Relies on incidence angle of
each beam Slide 24 Conclusions Accurate and precise bathymetry can
be obtained from ME70 operating in FM and BM BM FM: dz 95% of the
common coverage area Differences were < 0.25% for more than 40%
of the common coverage area By accounting for refraction, using
alternative bottom detection methods, for FM solutions differences
could be reduced Possible limitations of FM Reduced ping rate
Reduced number of beams Some new methods have promise to overcome
these limitations Lack of post-processing software Advantages of FM
Two-way beamforming and lower sidelobe levels Water-column data
Multiple-frequencies Do we need the Bathymetric Mode? Consider the
quality of FM bathymetry Resources for FM data processing could be
a better investment Accurate and precise bathymetry can be obtained
from ME70 operating in FM and BM Differences between bathymetry
surfaces from BM and FM* were 90% of the common coverage area
Differences were < 0.25% for more than 40% of the common
coverage area By accounting for refraction for FM solutions
differences could be reduced Possible limitations of FM Reduced
ping rate Reduced angular span of the swath Reduced number of beams
Some new methods have promise to overcome these limitations Lack of
post-processing software Advantages of FM Two-way beamforming and
lower sidelobe levels Water-column data Multiple-frequencies Do we
need the Bathymetric Mode?
