Survey of Vessels

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Survey of vessel reference systems, static and dynamic sensor calibration Seabed Mapping and Inspection Lokale kartdager 2008

Editor: Rolf Arne Ueland Speaker:Rolv Johannessen

October 6, 2008

Content
• • • • • • From Blom to Parker Survey of vessel reference systems Use of close range photogrammetry GPS based static calibration of Sensors GPS based dynamic calibration of sensors Experience

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From Blom to Parker
• Blom ASA demerged into mapping and offshore technology divisions, June 2007 • Blom Maritime was renamed Scan Maritime and joined Scan Rope in Scan Subsea ASA • Scan Subsea ASA was acquired by Parker Hannifin 16th of November 2007 • Parker Maritime (new name from Febr. 2008) will continue to supply our services to existing and new clients 3

Experience from survey of vessel sensors
• During 2007 we performed more than 60 Gyro & DGPS calibrations • We surveyed 17 Multibeam echo sounder and sensor installations • Similar work was also performed on Shuttle Tankers and subsea structures • Our clients are Survey vessels, Seismic vessels, Offshore construction vessels and equipment manufacturers 4

Vessel reference systems
• Purpose
• To establish a precise vessel bound coordinate system to position and align all survey sensor

• Requirements
• Better sensors and positioning increase demand for precision in the vessel reference system

• Methods
• Free station survey with total station • Close range photogrammetry for flatness and alignment 5

Survey of vessel sensors - Method
• Total station (TDM5005)
• Combination of teodolite and Electronic Distance Meter

• Close Range Photogrammetry

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Principles of free point survey – Vessel

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Principles of free point survey – Cont • Define points to be surveyed

Deck-points, Helideck, VRS, GPS antennas, Echo sounder, HPR (e.g. HiPap), Artemis, FanBeam (distance meter), Other reference points, Establish reference points and lines for e.g. calibration of ROV gyro. In dock: Draft marks, keel, rudderstock (Aft Perpendicular) and all sensor underside hull

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Principles of free point survey – Cont • Establish station 1

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Principles of free point survey – Cont
• Add Station 2 and observe common fix points

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Principles of free point survey – Cont
• Add Station 3

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Principles of free point survey – Cont
• Add Station 4

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Principles of free point survey – Cont
• Add Station 5……

Continues with stations onboard (and in) the vessel
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Principles of free point survey – Cont
• From each station:
• Measure sensors, permanent fix points and vessel axis alignment points • Direct sights to point • Distance measured to reflective stickers, magnetic targets or prism targets. 14

Reference systems – Calculations
• We calculate all observations into a common 3D coordinate system • Stations are tied together by transformation through common points • We perform an on site data inspection and quality control • Final transformation to a defined vessel axis system and reference plane • Results reported as coordinates and sketches 15

Use of close range Photogrammetry
• Close Range Photogrammetry
• Marking with coded targets and scale bars • Image acquisition, Image analysis • Object reconstruction

• Accuracy factors

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Use of close range Photogrammetry - cont

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Close Range Photogrammetry
• So far performed on • HU Sverdrup, Viktor Hensen, Acergy Viking and Acergy Petrel • Conclusion • Good for flatness control during installation of EM 710 • Good redundancy and documentation of accuracy • Must be tied to the vessel system by the total station measured points • Accuracy and time to perform similar to total station 18

GPS based static calibration of Sensors
• Method
• Based on calculating baseline heading between two GPS antennas

• Equipment and tools
• We use Javad HD2 GPS (plus GLONAS) heading sensor and AttCon software.

• Gyro, DGPS, RGPS other
• Challenges can...
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