The Hydrographic Society in Scotland

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James Lambert
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1 The Hydrographic Society in Scotland Workshop Underwater Spoolpiece Metrology Thursday 19th May 2005 Frank Prytz, Blom Maritime Underwater Photogrammetry

2 Agenda Blom Maritime as Photogrammetry explained Some Photogrammetry work done since 2000 Spoolpiece metrology Onshore test Kristin and Snøhvit test Photogrammetry results Kristin and Snøhvit test As seen with the eyes of DeepOcean Lesson learned Acoustics and photogrammetry combined

Snøhvit test Photogrammetry results Kristin and Snøhvit test As seen

3 Blom Maritime AS 47 employees 41 engineers Located in Stavanger Working world wide Office in Stavanger

4 More than 30 years of experience worldwide with industrial metrology and maritime surveying services

5 Photogrammetry under water Blom Maritime AS started using photogrammetry under water in Photogrammetry under water require different combined skills that Blom has in house Photogrammetry specialists Dimensional control specialists Software experience Computer science Electronics Photogrammetry may be described as the science of creating 3D models of objects from images.

Photogrammetry specialists Dimensional control specialists Software experience Computer

6 Photogrammetry principle

7 Fieldwork marking example

8 Advantages Millimetre and sub-millimetre accuracy Reliable results every time Fast mobilization and field work Additional dimensions without new field survey Increased survey possibilities Same accuracy in all axes Can be combined with other methods like acoustics

dimensions without new field survey Increased survey

9 Production line Camera Computer Processing Results

10 Some projects using photogrammetry sub sea

11 Spool-piece test on shore Compared to 52 control points 70 meter (97%) 20 meter (97%) ± ± 10 mm 6 mm Statistics from the photogrammetry software Surveyed route 70 meter (97%) 20 meter (97%) ± ± 12 mm 4 mm Result flanges compared to total station survey Tilt and rotation ± 0.2deg

photogrammetry software Surveyed route 70 meter (97%) 20 meter (97%)

12 Spool piece metrology Preparation on shore if possible Installing and survey of targets Survey of structure and hubs Survey of transponders if used Mobilization at quayside Adaptation of camera system Work offshore Preparing metrology scale bars Placing of scale bars Acquire images Processing and reporting

Mobilization at quayside Adaptation of camera system Work offshore Preparing

13 Spool piece accuracy Error budget Description Distance (mm) Angle (deg) Survey of template HUBs onshore Photogrammetric model (161 images and 708 points) Photogrammetry results of termination head Transformation Temperature effect on scale Total (67 meters at 1 sigma)

14 Photogrammetric model (161 images and 708 points) 4 0.

14 Metrology projects Kristin Snøhvit Template D Snøhvit Plem Image quality 3D model Route length Images used Hours used Images per meters 1,6 6,5 6,4 Hours per meter survey 1,8 t 1,8 t 3,6 t Hours used per image 57 min 16 min 34 min

Hours used 123 95 184 Images per meters 1,6 6,5 6,4 Hours per

15 The next few slides is from a presentation held by DeepOcean at the Geilo conference in Norway this year. Advantages and disadvantages using acoustics Advantages Independent of sighting Known and accepted method Performed by the onboard survey personnel Good accuracy if performed well Disadvantages Relative time demanding offshore A lot of planning and production onshore have to be put into the project to achieve optimal results Vounerable to acoustic noise

by the onboard survey personnel Good accuracy if performed well Disadvantages Relative time demanding offshore A

16 Three tests have been performed where acoustics and photogrammetry were done in parallell. Blom Maritime was subcontractor to DeepOcean. 1 Spool at Kristin and 2 spools at Snøhvit. Both for Statoil. Purpose: Find out if photogrammetry may replace acoustics as a spool metrology tool Factors to be tested: Time and resource used on shore Time and resource used offshore Processing time Result comparison

17 Test experience Preparations onshore: Acoustics Site visit / Planning of method and transponder positions Production of brackets Test of bracket positions / surveying / calibration of brackets and transponders Photogrammetry Surveying of photogrammetry targets Conclution: Photogrammetry approximately 1/3 of the time / cost compared to acoustics.

calibration of brackets and transponders Photogrammetry Surveying of photogrammetry

18 Test experience Time used Offshore Kristin (1 Spool) Acoustics: Photogrammetry: 17/34=0.5 Snøhvit (2 spools) Acoustics: Photogrammetry: 34/98= hours 17 hours 98 hours 34 hours Conclution: Photogrammetry approximately 1/2 of the time/cost compared to acoustics.

5 Snøhvit (2 spools) Acoustics: Photogrammetry: 34/98=0.

19 Results from Kristin N 101 Acoustics Photogrammetry Difference Grid distance 44.36m 44.34m 0.02m Grid bearing º º 0.03º Depth difference m m -0.04m Pitch difference -6.54º -6.42º -0.12º

20 Results from Snøhvit at D Template Acoustics Photogrammetry Difference Grid distance m 36.87m -0.01m Grid bearing º º -0.07º Depth difference m m 0.11m Pitch difference º º -0.07º

87m -0.01m Grid bearing 280.264º 280.336º -0.

21 Results from Snøhvit at PLEM Acoustics Photogrammetry Difference Grid distance 36.39m 36.36m -0.03m Grid bearing º º -0.14º Depth difference m m 0.18m Pitch difference 0.172º -0.84º 1.01º

22 Development and improvements Inclinometer Depth sensor Reduce the time required to final results QC for pitch, roll and relative elevations. Inclinometer and depth sensor mounted on a frame. Use two or more systems. Each system calibrated on shore and calibrated offshore relative to each other. Require little or no extra time offshore and in processing. Coded Targets reduses overall time spent. Used on Snøhvit. Redused time with 65% compared with noncoded targets. If used on Kristin, the prosessing and reporting time would have been reduced from 123 hours to 41 hours.

23 Photogrammetry and LBL Combine the best from the two methods Use results from CRP for LBL QC Use CRP to connect to the objects at each end

Parker Maritime AS. 11. AICON 3D Forum - March 12th 2009. Metrology subsea using AICON's photogrammetry - The timesaver.

Parker Maritime AS. 11. AICON 3D Forum - March 12th 2009. Metrology subsea using AICON's photogrammetry - The timesaver. Parker Maritime AS 11. AICON 3D Forum - March 12th 2009 Metrology subsea using AICON's photogrammetry - The timesaver Frank Prytz March 1, 2009 Parker Maritime AS Agenda - Who we are - What we do - Where