HYSWEEP Overview Sunken DC 3 Fish Habitat SV

® HYSWEEP Overview Sunken DC 3 = Fish Habitat S/V Bufe – USACE Sault Ste. Marie Area Office 10/29/2020 HYPACK® 2006 1

Boats, Mounts and Transducers The Diamond Reef (GLD&D) has a Bow Mounted Fansweep 20. 10/29/2020 HYPACK® 2006 2

Boats, Mounts and Transducers S/V Moritz (USACE NY Dist. ) has Hull Mounted Seabat 8101 and Ross Multiple Transducer. 10/29/2020 HYPACK® 2006 3

Pole Mounts Over the Side (University of East Carolina) Through the Hull (Port of Long Beach) 10/29/2020 HYPACK® 2006 4

Survey Coverage Multibeam The swath coverage varies by depth and by sonar type. Typical sonars produce 3 – 7 times water depth, and full bottom insonification. In 20 meters of water, a swath of 140 meters can be obtained. Single beam bottom coverage limited to a single footprint. Typical beam angle is 3 to 8 degrees. 10/29/2020 HYPACK® 2006 5

Multibeam Systems Increasing coverage with water depth. – Depth Range increases as a function of frequency. – Lower frequency will give the deepest depth. Typical operating depths: – – – 455 k. Hz – 120 meters 200 k. Hz - 300 meters 12 k. Hz – 12000 meters Mounting options: – vertical – rotated 10/29/2020 HYPACK® 2006 6

Multiple Transducer Systems No change in coverage with water depth. Vertical sounding beams. Simple in theory and operation. Works best for shallow water surveying. 10/29/2020 HYPACK® 2006 7

Acoustics - Simple Vertical Beam – SINGLE BEAM and MULTIPLE TRANSDUCER systems – – – No change in direction at velocity change. Average sound velocity is sufficient. SV cast frequency: once daily is adequate. 10/29/2020 HYPACK® 2006 8

Acoustics – Not so simple Slanted beam – MULTIBEAM sonars – Refraction (ray bending) at velocity change. – Processing requires sound velocity profile – SV cast frequency: Every 4 hours or less, depending upon survey requirements 10/29/2020 HYPACK® 2006 9

Acoustics for multibeam systems In this example, the SV changes from 1445 to 1450. If we ignore the SV cast, and used a constant 1500 m/s the position and depth will be wrong. DEPTH At 60 degrees from nadir At nadir SV range 1445 – 1450 m/s 10/29/2020 HYPACK® 2006 Correct SV Constant (SV Corr. File) 1500 m/s 27. 8 m 29. 5 m 25. 8 m 26. 5 m 10

Beam Geometry Roll Pitch Multibeam data collection requires additional measurements: Heave, Pitch, Roll and Heading. Without them, the horizontal and vertical errors will be present, and grow as the swath becomes larger. For example: A 1 degree roll error in 20 meters of water will produce a horizontal error of 5 meters in the outer swath. 10/29/2020 HYPACK® 2006 11

Beam Geometry (cont. ) Vessel heading is required! Unlike Single beam systems, accurate heading is needed to minimize positional errors. For example: A 2 degree error in heading in 20 meters of water will produce a positional error of 2. 6 meters in the outer swath. 10/29/2020 HYPACK® 2006 12