© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon Assessing target detection capability using single and dual swath sonars with high definition beam forming John E. Hughes Clarke (1) David Fabre (1), Rebecca Martinolich (1) and Melvin Broadus (2) Peter Milner and Ernest Sargent (3) (1) Ocean Mapping Group, University of New Brunswick (2) US Naval Oceanographic Office, MS, USA (3) Canadian Hydrographic Service – Pacific, Sidney, BC

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon USNS Bowditch and Sumner EM °x1.0° - dual swath - 37m depth 0.5, 1.0 and 2.0m cubes EM °x1.0° - dual swath m 40m high, 300wide knolls CCGS Vector EM °x1.0° - dual swath- 40m depth 1 and 2m boulders. 40m 60° Most demanding interpretation of IHO target detection: Special and 1 2.5% and 5% Cube equivalents across +/-60+° sector at survey speed 8-10 knots The requirement: 2.5%Z cube equivalents

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon Principal Controls on Topographic Resolution: 1 - Sampling Density 2 – Bottom Detection Method

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon Comparison of sounding density as a function of angular sector 12 knots, 20m of water, 1° beam spacing +/-45° sector +/-60° sector +/-75° sector

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon 100 knots (for clarity) 1 Transmit sector 3 Transmit sectors 8 Transmit sectors How to Implement Dual Swath

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon (+/-70°) at 10 knots dual swathe at 5 Hz (10Hz effective) 1 Transmit sector 3 Transmit sectors 8 Transmit sectors

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon EM °x1.0° dual swath Water Column Imaging USNS Bowditch target detection trials 2.0m,1.0 m and 0.5m Steel mesh cubes 32-37m of water

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon 2m cube 1m cube 0.5m cube EM °x1.0° dual swath Water Column Imaging USNS Bowditch, June Target detection trials Released with the permission of U.S. Naval Oceanographic Office

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon T01T T02T02 3 T03T03 4 T04T04 5 T05T05 6 T06T06 “Duel” Swath – 6 Ping Cycle 81kHz 97kHz89kHz 73kHz 81kHz EM710 Very Shallow Mode 0.3ms pulse (~3.3kHz bandwidth) 0° +30° +60° -30° -60°

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon 2.0m cube EM °tx x 1.0°rc Dual-swath +/-60° - 6 knots 7m 30m USNS Bowditch – July Saipan trials Released with the permission of NavOceano SUN ILLUMINATED DTM (0.25m resolution 25m x25m view) BACKSCATTER MOSAIC (-10 to -35 dB) ALONG TRACKACROSS TRACK WATERCOLUMN ANIMATION (10m x 10m view) 50° 30° 0°

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon 1.0m cube EM °tx x 1.0°rc Dual-swath +/-60° - 6 knots 7m 30m USNS Bowditch – July Saipan trials Released with the permission of NavOceano SUN ILLUMINATED DTM (0.25m resolution 25m x25m view) BACKSCATTER MOSAIC (-10 to -35 dB) ALONG TRACKACROSS TRACK WATERCOLUMN ANIMATION (10m x 10m view) 50° 30° 0°

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon Savary Island – Glacial Erratic Boulder Fields Intertidal to at least 90m. Using Naturally- Occuring Boulders as Test Targets 60m 50m

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon Naturally-occurring boulders rarely have an aspect ratio approaching 1 to 1

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon 1m boulder – 40m – 10 knots EM °x1.0° - dual swath CCGS VECTOR April °0°40°45° 60° WATERCOLUMN ANIMATION (10m x 10m view) SUN ILLUM. DTM (0.25m res. 25m x25m view) ACROSS TRACK vert. lines = 1m horiz.bar = 1m ALONG TRACK vert. lines = 1m horiz.bar = 1m

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon 20°35°45°50° 60° 2m boulder – 40m – 10 knots EM °x1.0° - dual swath CCGS VECTOR April 2009 WATERCOLUMN ANIMATION (10m x 10m view) SUN ILLUM. DTM (0.25m res. 25m x25m view) ACROSS TRACK vert. lines = 1m horiz.bar = 1m ALONG TRACK vert. lines = 1m horiz.bar = 1m

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon The “footprint” depends on beam width and depth ACROSS ALONG Does HDBF have any real benefit? EQUI-ANGULAR Independent Beam Footprints EQUI-DISTANT Just picking beam centre Partially Independent Beam Footprints + High Definition Beam Forming Non Independent Beam Footprints tmtm tntn Across track resolution Based on time-sampling

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon ? Centre ? Amplitude Detection: A: Peak based on running average B: Centre of Mass based on window about A Estimated Noise Level A B Phase Detection: C: intersection based on linear or quadratic regression through window from B D: IF low residual for C, reduce window by 10% and repeat E: IF low residual for D …. F: If low residual for E. …. …until < 5 samples or high residual F ED   C ? Centre ? B2B2 A2A2

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon   What is “High Definition Beamforming” ? If the S/N is sufficient to use a small subset of the phase slope, can choose multiple points on the curve (0, -  /4,  /4,  /2, 3  /4 etc..) ONLY possible if no layover within beam footprint

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon Comparing Field Trial Results With a Numerical Model Specify targets to resolve amplitude wavelength backscatter angular response of region of target 1 - Field Trials: Solutions + Water Column 2 - Modelling: Know sonar configuration: Beam widths/spacing Source Level w,r,t. Noise Pulse Length Pulse Repetition rate Bottom Detection Methodology

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon 10 knots - 40m +/-65° Shot cycle – 5Hz 1m per cycle (10 Hz – dual swath 0.5 m per cycle) 5 shots RESON °tx. – 0.5°Rc. single swath EM °tx. – 1.0 Rc. dual swath EM °tx. – 1.0 Rc. dual swath EM °tx. – 2.0 Rc. dual swath EM °tx. – 2.0 Rc. single swath 1.0m fore-aft 2.8m across track ~1.0° spacing 1.0m fore-aft 1.4m across track ~0.5° spacing 2.0m fore-aft 2.8m across track ~1.0° spacing 0.5m fore-aft 1.4m across track ~0.5° spacing 1.0m fore-aft 0.7m across track ~0.5° spacing SONAR MODEL GEOMETRIES

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon Propagating AnnulusTime Slices Tx. Rc. Product + seabed BS AR Differential Phase Zero Phase Phase Wrap

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon TARGET GEOMETRY 1m and 2m Pseudo-Boulders at 40m depth 5 swaths 50cm spacing along track 0.5° beam spacing 2m radius 1m height 1m radius 1m height 2m wavelength 0.4m amplitude 10° 45° 60°

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon Peak DetectionWMT Detection Full Beam Phase Detection Within Beam Phase Sweep 1x1x1 m “boulder” 40m – 10° incidence 0.5°x1.0° - dual swath +/-65° - 10 knots.

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon Peak DetectionWMT Detection Full Beam Phase Detection Within Beam Phase Sweep 1x1x1 m “boulder” 40m – 45° incidence 0.5°x1.0° - dual swath +/-65° - 10 knots.

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon Peak DetectionWMT Detection Full Beam Phase Detection Within Beam Phase Sweep 1x1x1 m “boulder” 40m – 60° incidence 0.5°x1.0° - dual swath +/-65° - 10 knots.

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon Peak DetectionWMT Detection Full Beam Phase Detection Within Beam Phase Sweep 2x2x1 m “boulder” 40m – 10° incidence 0.5°x1.0° - dual swath +/-65° - 10 knots.

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon Peak DetectionWMT Detection Full Beam Phase Detection Within Beam Phase Sweep 2x2x2 m “boulder” 40m – 45° incidence 0.5°x1.0° - dual swath +/-65° - 10 knots.

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon Peak DetectionWMT Detection Full Beam Phase Detection Within Beam Phase Sweep 2x2x2 m “boulder” 40m – 60° incidence 0.5°x1.0° - dual swath +/-65° - 10 knots.

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon The equivalent of a 1m cube at 40m (2.5% of depth) at 5000m is a 125m "cubic" object. In ~4870m of water lie two knolls: knoll A - "gaussian" shape, ~ 400m wide at base - ~50m high knoll B - "gaussian" shape, ~300m wide at base - ~35m high Deep Water (~5000m) Target Detection EM122 1° x1° 8km 6km 4km 2km 125m 5m contours

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon 0000m 0° 2000m 22° 4000m 39° 6000m 50° 8000m 58° EM m – 8 knots.

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon 0000m 0° 2000m 22° 4000m 39° 0000m 0° EM m – 8 knots. +/- 45°+/- 25°

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon Summary A 2.5% cubes are achievable – BUT requires: A - High and Even Sounding Density: at 10 knots, requires – dual-swath No point in dual swath if no multiple sectors. No point if not multi-sector pitch and yaw stabilized. Barely 3 strikes on a 1m 3

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon Summary B B - Bottom Detection: As across-track dimension larger than required resolution, rely heavily on HDBF. – only useful at lower grazing angles (no layover) Where target aspect ratio is too high, will track common slant range (peak or WMT detect) over sector significantly wider than physical beam width. - O.5° Rc (7125 – superior). Within Beam Phase Sweep Peak Detection

© J.E. Hughes Clarke, OMG/UNB Swath Sonar Training 2008Swath Sonar Training 2009 FEMME Lisbon Now that we actually “detect” 2.5% cubes... The next challenge is to resolve their shape Q’s ?