30
Survey Sensors Hydrofest 2014 Ross Leitch Project Surveyor

Hydrofest 2014 - · PDF fileHydrofest 2014 . Ross Leitch . ... • Inertial Navigation Systems ... Inertial Navigation Systems • N positioning system on it’s ownot a

  • Upload
    vodung

  • View
    221

  • Download
    4

Embed Size (px)

Citation preview

Survey Sensors Hydrofest 2014

Ross Leitch Project Surveyor

NAUTRONIX MARINE TECHNOLOGY SOLUTIONS www.nautronix.com

• Satellite Positioning – Only provides position of antenna

• Acoustic Positioning – Only provides position of transponder

relative to transceiver

• How do we connect the two? – Offsets – Sensors

• Offsets – Provide a relative physical distance

between all sensors/systems and a Central Reference Point

• Sensors – Measure movement relative to the

Central Reference Point

VESSELS & VEHICLES

NAUTRONIX MARINE TECHNOLOGY SOLUTIONS www.nautronix.com

Construction Vessels

NAUTRONIX MARINE TECHNOLOGY SOLUTIONS www.nautronix.com

ROV – Remote Operated Vehicle

NAUTRONIX MARINE TECHNOLOGY SOLUTIONS www.nautronix.com

ROTV – Remote Operated Towed Vehicle

NAUTRONIX MARINE TECHNOLOGY SOLUTIONS www.nautronix.com

AUV – Autonomous Underwater Vehicle

SURVEY SENSORS

NAUTRONIX MARINE TECHNOLOGY SOLUTIONS www.nautronix.com

Survey Sensors • Positioning Systems

– Surface Positioning – Acoustic Positioning

• Attitude Systems – Gyro Compass – Motion Reference Unit

• SVP – Sound Velocity Probe • Inertial Navigation Systems • Doppler Velocity Log • Depth Sensor • Cross-Profilers, Singlebeam & Multibeam Echo sounders • Pipetracker • Side Scan Sonar

NAUTRONIX MARINE TECHNOLOGY SOLUTIONS www.nautronix.com

• Gyros always output True North but we generally present Grid North

• Determine heading/bearing relative to ‘True’ North

• Different types available – Mechanical – older style, spinning parts – Ring Laser (RLG) or Fibre Optic (FOG) – uses light

and mirrors (no magic though) – GPS – calculated between two antennas – not

subsea suitable! • Accuracy is Typically 0.1+°sec lat (secant

latitude) • The gyro corrects the offsets between all the

different sensors so if it’s wrong, so are the positions!

Gyro Compass

NAUTRONIX MARINE TECHNOLOGY SOLUTIONS www.nautronix.com

MRU – Motion Reference Unit • Measures the motion of Vessels &

ROVs in 3 axes – Pitch – Roll – Heave

• Many modern Gyros have MRU functionality built in

• Essential to correct for accurate subsea positioning

NAUTRONIX MARINE TECHNOLOGY SOLUTIONS www.nautronix.com

GPS

USBL

ROV

ROV

Heading error Pitch or Roll error

NAUTRONIX MARINE TECHNOLOGY SOLUTIONS www.nautronix.com

Sound Velocity • Sound Velocity is required for the majority of subsea sensors

• SV probe measures: Sound Velocity, Pressure, Temperature & Conductivity.

• SV probe calculates: Salinity, Density & Sound Velocity.

• SV profile required to: – predict ray trace

– compute ranges from TOF

– Distance = Speed x Time

Time – Time of Flight

Speed – Sound Velocity Profile

→ Calculate Distance

• North Sea = 1490m/s, Greenland = 1455m/s – 2 way TOF 3.273s → NS = 2438.385m, Gr = 2381.108m

NAUTRONIX MARINE TECHNOLOGY SOLUTIONS www.nautronix.com

Sound Velocity

Salinity Density

VOS

Temp

NAUTRONIX MARINE TECHNOLOGY SOLUTIONS www.nautronix.com

Inertial Navigation Systems

• Not a positioning system on it’s own • Aid to position • Increases position update & relative

accuracy • Provides low cost/high accuracy

positioning • Vessel INS & ROV INS • Absolute accuracy is limited to host

positioning system

NAUTRONIX MARINE TECHNOLOGY SOLUTIONS www.nautronix.com

Doppler Velocity Log • Relative measuring device – smoothes ROV position • Based on Doppler effect – apparent change in frequency due to

motion • 4 beams reflected from seabed

NAUTRONIX MARINE TECHNOLOGY SOLUTIONS www.nautronix.com

Depth Sensors • Depth Sensor combined with altimeter • Quartz Crystal vibrating under pressure • Pressure output (PSI, Bar etc) • Conversion to depth uses

– Gravity (changes depending on latitude) – Density of local seawater – Atmospheric pressure

• Accuracy - typically 0.01% FSR (Full Scale Range) e.g. 0.07m for 700m sensor

NAUTRONIX MARINE TECHNOLOGY SOLUTIONS www.nautronix.com

Bathymetry • “Sounding” originates from Old English meaning “the sea” or “to swim”

and does not imply the use of sound pulses • Historically a sounding line (leadline) would be used which provided

− Depth − Seabed Information

• The combination of accurate positioning and accurate depth allows the generation of bathymetry charts and seabed terrain models

• Acoustic systems allow data to be collected quickly and efficiently

• Echosounders − Singlebeam − Multibeam

NAUTRONIX MARINE TECHNOLOGY SOLUTIONS www.nautronix.com

Bathymetry – Singlebeam Echosounders • Generation of acoustic pulse from source • Pulse time of flight timed to calculate range to target (typically the

seabed) • Most vessels, small and large, have an echosounder

NAUTRONIX MARINE TECHNOLOGY SOLUTIONS www.nautronix.com

Cross profilers / Multibeam Echosounders • Hull Mounted & ROV Mounted • Scanning the surface of the seabed to determine

depth points relative to ROV/vessel • High frequency sonar • MBES Swathe ~ 120 beams • What’s the difference between scanning sonar

and MBES? • Mechanically moving single beam vs.

simultaneous multiple beams • Data density • Price!

NAUTRONIX MARINE TECHNOLOGY SOLUTIONS www.nautronix.com

Cross profilers / Multibeam Echosounders

NAUTRONIX MARINE TECHNOLOGY SOLUTIONS www.nautronix.com

NAUTRONIX MARINE TECHNOLOGY SOLUTIONS www.nautronix.com

Cross profilers / Multibeam Echosounders

NAUTRONIX MARINE TECHNOLOGY SOLUTIONS www.nautronix.com

Bathymetry – Multibeam Echosounder (MBE)

NAUTRONIX MARINE TECHNOLOGY SOLUTIONS www.nautronix.com

TSS Pipetracker • Highly sophisticated metal detector! • Active Pulse Induction system (440) • Passive tone system (350) • Target Scaling (Calibration)

NAUTRONIX MARINE TECHNOLOGY SOLUTIONS www.nautronix.com

Side Scan Sonar • Imaging the surface of the seabed to identify objects,

pipelines etc. • High frequency sonar • Sometimes towed… • What’s the difference between SSS and MBE?

– SSS looks sideways, perpendicular to direction of ROV travel – Very wide data coverage for SSS – SSS data gap under ROV – No depth data determined from SSS – Data shows intensity of reflection rather than depth

Free span

Rock dump

NAUTRONIX MARINE TECHNOLOGY SOLUTIONS www.nautronix.com

Seabed Imaging – Sidescan Sonar

NAUTRONIX MARINE TECHNOLOGY SOLUTIONS www.nautronix.com

Geotechnical Survey (Brief overview) •Additional sensors − Sub-bottom information can also be

gathered using additional sensors • Sub-bottom profiler

−Fish, ROV or AUV mounted −Can identify layers within the seabed

• Magnetometer − Used to identify features with a

magnetic return such as submerged metal structures or rock formations with a magnetic signature

NAUTRONIX MARINE TECHNOLOGY SOLUTIONS www.nautronix.com

Survey Navigation Packages • Three main survey suites

– EIVA / NaviPac – Quincy – Starfix.Nav, .Seis, .NG

• All survey software does the following

– Interfaces to survey sensors – Logs data – Defines objects or “vehicles” for sensors to be referenced to – Takes WGS84 (GPS) positions and converts to local ellipsoid and grid – Displays objects on a screen including background graphics and vehicles

• Problem - As data density and data collection speed increases so

does the need for fast update rates and accurate time stamping of data • Prime example is multibeam echosounder and AUV data.

NAUTRONIX MARINE TECHNOLOGY SOLUTIONS www.nautronix.com

Summary

• To compute an accurate position for a ROV or object we need: – Satellite Positioning – Acoustic Positioning – Offsets – Sensors

• Any Questions?