Experiences with Hydrographic Data Budgets Using a Low-logistics AUV Platform. Thomas Hiller Teledyne Marine Systems

Transcription

1 Experiences with Hydrographic Data Budgets Using a Low-logistics AUV Platform Thomas Hiller Teledyne Marine Systems 1

2 Teledyne Marine Systems Strategic Business Units 2

3 What is the Gavia? The Gavia is a low-logistics, fully modular AUV. It has fieldchangeable modules that can be replaced in minutes, allowing rapid sensor reconfiguration and battery replacement. Capable of operations in depths up to 1000m. 3

4 Gavia AUV Base System 20cm hull diameter & neutral buoyancy ballasting roughly π kilos per 10cm length. Typical module lengths are between 20cm and 60cm. 4

5 Modularity The Gavia is made up of several individual cylindrical modules forming a single hull All Gavia vehicles start with the 4 basic modules (Nose, Battery, Control, and Propulsion Modules) From this base configuration additional sensor modules can be added All modules are field swappable Ethernet comms and 1PPS line for timing 5

6 Gavia AUV: Modular, Adaptable, Configurable Base AUV Survey Hydrographic Geophysical 6

7 The Gavia Offshore Surveyor: The Gavia Offshore Surveyor: Low Logistics : typically around 75 Kg and 3m in length (depending on configuration) 1000m depth rating Integrated high accuracy INS/DVL Optional LBL / USBL aiding Obstacle avoidance sonar Fully Modular Array of sensors Typical Offshore Surveyor configuration High-precision DVL aided Inertial Navigation System Swath Bathymetry Module Sub Bottom Profiler Module Side Scan Sonar, Camera Sound Velocity Meter, Obstacle Avoidance Sonar, USBL (Teledyne Benthos DAT) DGPS Single, dual or triple swappable batteries 7

8 Gavia Survey Suite Side scan: Marine Sonic dual frequency 900 / 1800 khz Edgetech 2205: 600 / 1600 khz Klein 3500: 450 / 900 khz Swath Bathymetry: 500kHz GeoSwath Plus interferometric sonar Other options coming soon Sub-bottom profiler: Teledyne Benthos CHIRP-III Technology Camera: High-performance low-light variable frame rate digital camera: various resolutions. Color or monochrome. Payloads Typically Required by Commercial Operations: Sidescan Bathymetric mapping Sub-bottom profiling Camera 8

9 GeoSwath Module GeoAcoustics GeoSwath Plus AUV 500kHz cw interferometric sonar Port and starboard transducers ping alternately Sidescan-like pulse, multiple receive staves Max range ~50m to 80m Typical swath width 70m Collects sidescan and bathymetry 9

10 Low Logistics AUV Benefits Vessels of opportunity Easily transported NO specialized LARS Does not require surface vessel contact during operations Operate close to seafloor, pipeline. Lower operational cost Considerations Strategic Power Management Power draw and size of sensors Cleared for Public Release (FAL- 1404) 10 10

11 Ready for Operations Minutes After Arrival On-site 11

12 Fully Co-registered & Geo-referenced Data 12

13 Fully Co-registered & Geo-referenced Data 13

14 Side Scan Mosiac and Bathymetry Image from GeoSwath Data processed and displayed in OIC CleanSweep Boat-mount MBES image 14

15 Alexander Hamilton GeoSwath Mosaic Data processed in OIC CleanSweep 15

16 Harbor Survey 3D Overview Showing Run Lines 16

17 Harbor Survey Bathymetry Grid and Side Scan Mosaic 17 17

18 Survey of jack-up footprints Gavia AUV gathered 500kHz GeoSwath data around an oil rig in the Adriatic showing ocean floor features from previous jack up rig placement and legs of current rig extending from the ocean floor. Data courtesy of GAS Srl. 18

19 Pier Launched Survey 19

20 Position Checks: the FAT Survey Pattern 20

21 GeoSwath Side Scan and Bathymetry 500 khz GeoSwath mounted on Gavia AUV 21

22 1800 khz Marine Sonics at 10m range 22

23 Northrop N3PB Captured with Edgetech /1600 khz High Frequency 23

24 Northrop N3PB Captured with Klein /900 khz High Frequency 24

25 Northrop N3PB Captured with Edgetech /1600 khz Low Frequency 25

26 Position Checks: the Reference Rock 26

27 Position Checks: Multiple Vehicles, Multiple Runs RMS: 2.4m 95%: 4m 27

28 Speed of sound corrections Manual entry Live SOS measurement Sound velocity meter 28

29 Positioning the AUV: Navigation GPS: WAAS / EGNOS GPS as standard -- 5 meter accuracy DGPS optional using WiFi transmitted correction factors meter accuracy -- Veripos ready GPS receiver already in Antenna Tower INS: Kearfott T-24/ TeledyneRDI DVL-aided Inertial Navigation (SEANAV / SEADeViL) Error of ~0.01% distance travelled when in bottom lock, lawnmower pattern survey Improving the Subsea Navigation Solution: Surfacing for GPS fixes USBL Aiding using Directional Acoustic Transponder LBL 29

30 INS/DVL Module Options Kearfott T-24 aided by 1200KHz Teledyne RDI WHN DVL or IxBlue ROVINS154 aided by 1200KHz Teledyne RDI WHN DVL 30

31 INS/DVL Module Specifications T-24 (KI-4092S High Performance IMU): Accelerometer Bias Stability ~50µg Position Accuracy 0.1% Distance Travelled, CEP50, DVL-aided Heading Accuracy 1.0 mils, rms = 0.06 Roll/Pitch Accuracy 0.5 mils, rms = 0.03 ROVINS154: Accelerometer Bias Stability ~80µg (est.) Position Accuracy 0.2% Distance Travelled, CEP50, DVL-aided Heading x secant latitude: 0.05 RMS Roll/Pitch/Yaw accuracy: 0.01 RMS 31

32 Positioning the AUV: Depth. Vehicle depth relative to water surface is found by pressure aiding the INS navigation solution using a high accuracy depth sensor Keller-Druck 33XE sensor: specification 0.01% FS. Errors: pressure-to-depth conversion, density profile, swell effects Relates to water surface: vessel-local tide required With care can achieve uncertainty of 10cm - 20cm in Absolute Pressure Pressure relative to Tare (zero at water surface) is approx. the instrument resolution, equivalent to ~1-2cm 32

33 Position Aiding: Low Logistics Navigation Solutions 33

34 LBL Navigation using SM-976 Transponders All in one transponder and release with burn-wire Can be deployed with no surface expression Positively buoyant, no float needed Unique coded reply to a broadcast ping from Gavia 6000 meter depth rating 18 kg (40 lbs) 34

35 LBL Field Tests: 35

36 Conclusions: Hydrographic surveys are being carried out using low-logistics AUVs The survey results are being used for engineering, dredge and navigation purposes The accuracy of the survey results compare well with boat-mount, ROV and towed platforms, within certain constraints: Navigation aiding is required for longer and deeper work Empirical studies using multiple configurations and multiple vehicles over several months show that the theoretical performance is achieved 36

37 Questions? Dr Thomas Hiller Senior Geophysical Sales and Applications Engineer Teledyne Gavia 37