(Subsea) Keith Vickery Zupt LLC

Transcription

1 (Subsea) Keith Vickery Zupt LLC

2 Offshore subsea infrastructure surveys (pipeline inspection, well, XT, and manifold inspections) are required to ensure compliance with both internal operator, and external regulatory requirements. Survey specifications are defined by the operator, sometimes with input from the integrity engineering community. The work is contracted and executed. The survey contractor deliver to the operators, who in turn usually hand the survey results to Integrity Management (IM) engineering sub contractors.

3 Why do things need to change? More comprehensive deliverables are needed for accurate compliance engineering. Inconsistent survey deliveries for IM are the norm rather than the exception. Missing data, lack of consistency in annotating and hours of video review are required to visualize the asset. High specification instrumentation is too expensive to mob for all surveys It is very expensive to go back to look at specific areas of interest Can we not just turn up the volume with what we have on the ROV?

4 This presentation will discuss a development program funded jointly by DOF Subsea and Zupt, LLC. For this development to be operationally (and commercially) successful we are trying to change the way some surveys are specified and delivered. This is still a development program and should be deployed offshore for initial testing early next year. But has been tested in air more later. The reason we are presenting on this topic early in the development process is to garner as much feedback as possible to ensure the final methods and processes deliver exactly what the community needs. The community is quite crowded: regulators operators (IM/survey/asset management/compliance/gis/?) IM engineering subcontractors Survey contractors

5 This development will deliver spatially correct, ortho-rectified, georeferenced (to the quality of the infield positioning systems) 2D images (ortho-mosaic) and 3D models (3D digital surface model photo rendered) of subsea infrastructure based on precisely positioned, frame grabbed imagery from standard ROV mounted cameras. We hope that this innovation will provide the end user with optimal, high resolution, visual deliverable while satisfying the rigid spatial integrity demands of the surveying community. An end users comment when reviewing the early demonstration data: exactly the deliverable we need for integrity management. The initial focus is pipeline inspection deliverables, out of straightness surveys and standard infield surveys such as flying lead surveys. Many other uses envisaged for in-field precise positioning.

6 Background technology trends Conventional photogrammetry processing v s Structure from Motion Multi-core processing multiple graphics processing units UAV explosion into survey applications Visualization tools (Quadtree, Octree techniques) and how do these fit into the Operators IT regime? The Details Subsea camera calibration Camera selection HD or SD (bit depth level) Illumination correct scene lighting, type of light? Camera latency management through the mux system? Frame grab rate v s mux capacity Positioning accuracy frame to frame The importance of accurate altitude Obtainable accuracy within the images and 3D models

7 Spatially correct The image will have a known relative accuracy. Measurement of distance, angles, and areas will be possible within the deliverable. Ortho-rectified Adjusting the images to represent an accurate representation of the imaged surface. Images are adjusted for topographic relief, lens distortion, camera position and attitude. Georeferenced (to the quality of the infield positioning systems) The deliverable will be positioned absolutely, with known quality (USBL aided INS for example). 2D images Orthomosaic - Orthophoto 2 1/2D models - or 3D models?

8 Technology in the computer vision sector has grown rapidly over the past few years: Camera based high speed automated inspection on production lines Computer generated imagery (CGI) for films License plate tracking Security screening facial recognition software Structure from motion (SFM) simply stated is a capability where 3D volumes (structures) can be generated from overlapping images looks very good but may be spatially incorrect. Photogrammetry has been a mature science for many years but is currently playing catch up to the SFM advances such as optimized algorithms for image stitching and surface generation. The SFM sector seem to be able process large data sets faster processing, but their final image or volume products are not necessarily spatially correct. Vendors in both of these spaces are using multi-core applications as well as multiple graphics processing units (GPU s) to speed these huge data sets.

9 The huge uptake of unmanned airborne vehicles (UAV) in survey applications has enabled brand new vendors into aerial image processing. Many users of this type of data do not want to deal with the rigor of conventional photogrammetry, they just want a mosaicked image, a volume or a very pretty 3D structure of a city block, or a whole city. Trimble s acquisition of Gatewing shows how this new industry is rapidly becoming mainstream. Trimble know their conventional photogrammetry software offerings need to catch up with the new players in this space.

10 Ease of enterprise wide visualization and use is critical for this data! For the concept we propose here to be used throughout the operators organization and within their subcontractors the visualization and access to these large data sets has to be simple. No proprietary formats, specifications or unique visualization tools. We are trying to ensure that our deliverables seamlessly flow into operators GIS and enterprise wide systems. We need help from this community to ensure that we achieve this goal. Google Earth has set expectation standards for the ease in which non experts are now viewing very huge, dense spatial data sets at their desktop. We are seeing these techniques (Quadtree, Octree, Voxel and other) enabled in some industry standard survey software - EIVA, Fledermaus, etc.

11 On the ROV ROV mounted cameras Camera selection HD or SD (color bit depth level?) Subsea camera calibration (repeatability?) Lights correct scene illumination (type of light?) ROV communications (mux) Camera latency management through the mux system? ROV positioning USBL smoothed with inertial navigation Positioning accuracy frame to frame The importance of accurate altitude On the surface Precisely time tagged frame grabbing Frame grab rate v s data storage and distribution Real time mosaic solution

12 Primary lines In Oct 2011 we laid several USBL pole sections onto the DOF Subsea parking lot and collected multiple survey lines over bland parking lot and the pole sections. Tie lines 25 West Tie lines 21 East We then placed some debris onto the pipe and repeated the lines over the pipe. 24 West 23 West 22 West 21 West 22 East 23 East 24 East 25 East

13 System configuration Single HD-SDI camera Positioning radio RTK GPS loosely coupled to navigation grade IMU 100Hz solution Time tagging via Zupt surface TTU synchronized to 1pps Data acquisition PC with frame grabber 18fps grab rate Data acquisition software just time tagging and logging data at this stage no real time mosaic

14 In this case we frame grabbed images at 18 frames per second (overkill but wanted to test the hardware). At the camera height of 1.593m above ground, cross line image width was ~1.520m and the inline width was ~0.850mm. With a HD (1920x1080) camera 1 pixel is <1mm at the ground.

15 The real time mosaic will be the primary online QC tool. Down sampled images with the same positioning solution as the full resolution data set.

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19 Real Time Mosaicking as shown on previous slide Real time solution required to ensure the data that is collected has no holes. This is the first data set that the client will look at. This data will be an automatically generated, down sampled (lower resolution) ortho-rectified mosaic. Geospatially correct delivered as a GeoTIFF. Upgraded deliverable - post processed, single camera plan view, high resolution ortho-rectified image of the complete pipe this will allow correct scaling of any visible artifacts/issues to be detected and scaled. Medium cost deliverable post processed multi-camera view, very high resolution, orthorectified images of the complete pipe projected and viewed from some useful angle to allow for the accurate scaling of free span. Only the areas selected by the integrity engineer will need this level of processing Higher cost deliverable post processed high resolution complete 3D surface model. Replacing the normal bathymetry deliverable from MBES or sonar. 19

20 Data volumes grow exponentially when dealing with high resolution imagery. RAID Hard drive configuration type matters Backup hard drives need very fast access Frame grabber drivers and processing platforms should be defined by frame grabber manufacturers Time tagging is everything (we knew this, but forgot it). Camera imaging sensor configuration matters (bit depth, reputability of optics) Optimizing resolution and acquisition rate for the task can significantly reduce storage requirements Lever arms are critical Image latency and navigation latency is difficult to calculate Altitude is critical to high resolution processing Omega, Phi, Kappa not Heading, pitch, roll No two camera calibrations give the same answers (yet) Understanding final processing data flow at acquisition is critical Test, test, test and test some more. 20

21 We still have to prove these answers but to date we believe the following should be achievable: Frame to frame and over multiple nearby frames (~10m) positioning accuracy will be < 1 pixel Over a radial distance of ~50m relative accuracy will be <10 pixels SD (720x480) HD (1920x1080) pixel dims apx. 1.5mm pixel dims apx. 0.8mm In addition to high resolution IM survey deliverables this should enable: Out of straightness surveys Automated change detection find anomalies/changes automatically within year on year data sets Precise local positioning could this be a metrology survey tool?