Surveying a Mile Down – xyHt

Previously mentioned: The metrology considered as a mixed model.

A 3D surveying firm provides very comprehensive lidar facts on subsea drill facilities.

This article practically didn’t take place. I first achieved with ADUS DeepOcean in January 2017, when we talked about how they had captured higher-resolution laser facts deep in the ocean off Ghana. Currently, 4 months later on, I am sitting down in the Countrywide Oceanographic Centre in Southampton, United kingdom, though the world’s premier offshore company convention thunders beneath my ft. Striving to nail these guys down has been tough they are chaotic and it is not hard to see why.

With a track record for capturing astonishingly comprehensive, higher-resolution surveys of manmade constructions, shipwrecks, wind turbines, and oil rigs, Amongst the catalogue of functions this firm has captured, DeepOcean claim that they can undertake subsea surveys at any depth. This was unquestionably place to the examination with a job they had been asked to do in Oct 2016, which needed extremely-higher resolution survey facts captured at 1500m beneath the sea.

One of the pipelines captured using the system.

One particular of the pipelines captured utilizing the procedure.

As I figured out from Stuart Leather, director of company advancement, the undertaking needed the acquisition of higher-resolution survey facts of 12 drill heart spots and a complete of 27 metrologies, in h2o depths in between 800m and 1800m (1/2 mile to 1 mile).

It also needed capturing facts to observe and analyse the asset conditions at higher-accuracy for comparison towards the pre-set up metrologies, to check out for pipeline finish termination (PLET) motion. Doing work at this depth, to this amount of accuracy, would set a new benchmark in subsea survey.

The challenge was to survey the subsea sea property with more than enough depth and to the needed accuracy to be equipped to take measurements for engineering functions and to assess motion of constructions. Laser scanning was the clear solution. The capability to obtain 40,000 points­—in a single swathe 5m extended and 2mm wide—to produce a dense metrical level cloud to milli-metric precision would make laser scanning a complicated technological know-how to conquer for this software.

After the technological know-how was preferred, the upcoming conclusion was how to deploy it. There had been two possibilities: either to have out static laser scans from a tripod on the seabed or to have out dynamic laser scanning from a remotely operated vehicle (ROV). There are various lasers on the current market capable of carrying out the do the job, but in this case a laser from 2G Robotics was picked.

How the ROV works with the equipment. Credit: Sonardyne.

How the ROV performs with the products. Credit history: Sonardyne.

Static scanning would involve various repositioning of the scanner on the seabed to form a closed loop. This would have taken a great deal of time, and the top above the seabed to which constructions could have been imaged would have been confined by the over-all top of the survey rig. This top element was very significant as the joining pipes (spools) in between constructions had been vertically extended up to 10m above the seabed.

The dynamic tactic seemed clear, but the technological know-how out there to position the laser on the ROV to the needed accuracy was continue to currently being made. The query: Was it all set and confirmed? What was needed was centimetric positioning of the laser facts from a relocating system. Two organizations had been in the race to give the technological know-how, and Sonardyne was equipped to give the positioning technological know-how within just the undertaking timeframe.

Adus DeepOcean was equipped to incorporate and integrate the laser positioning and ROV to produce the ideal laser facts acquisition solution.

The Process

The products comprised of deep-rated 2G Robotics’ ULS 500 Pro Laser for capture and Sonardyne’s Sprint inertial navigation procedure, SYRINX Doppler Velocity Log (DVL), ROVNAV 6 LBL, and Extremely Shorter Base Line.

The ULS 500 Pro Laser has a depth rating of 4000m and sample price of up to 61440 points/sec, with the laser mounted in a partly forward, angled arrangement to enhance protection of constructions.

The Sonardyne Sprint INS is now in its 3rd iteration and practically half the dimension of the authentic. It provides an AHRS (Mindset Heading Reference Process) and an AAINS (Acoustically Aided Inertial Navigation Process) to 6000m, building it far more than suitable for the job.

All of this provides the ROV with the operational efficiency of a huge-place mobile mapper and the precision of a static procedure.

Structural survey capture.

Structural survey capture.


Compatt 6 transponders had been deployed on the seabed all over the survey place with their approximate relative positions to each and every other, reliably and time-competently decided by DVL/INS dead reckoning. The vehicle then carried out the needed survey of the composition, though the INS, DVL, LBL ranges, depth, and sound velocity had been collected by the Sprint and Fusion computer software. The process does not involve transponder-transponder acoustic line of sight but can use these acoustic baseline measurements when out there.

The facts acquisition was break up into a few phases: huge-place mapping, structural survey, and metrology.

Metrology measurements had been executed with 4 passes and particular geometry to isolate problems.

Publish-processing calibrated transponder positions utilizing a SLAM (Simultaneous Localisation and Mapping) method and optimizes absolute and relative navigation accuracy. The finished navigation facts was then merged with the laser facts to deliver a geo-referenced 3D level cloud.


The tolerances needed by the client had been:

  • +/-10cms on position
  • +/-1 degree on attitude (heading, pitch, and roll)
  • Normal reporting
  • Primary measurements
  • Hub-to-hub horizontal, slope, and top distances
  • Hub pitch and roll (and heading) with respect to spool segment as VCS (Vertical Connector Process)
  • Genuine-globe position, easting, northing, and depth
  • Manifold heading, pitch, and roll
  • PLET heading, pitch, and roll
  • Comparison with authentic metrology
  • Normal metrology drawing c/w complex note


The fantastic news is that the procedure outperformed expectations in actuality it was ground-breaking. Thinking about the depth at which the survey was undertaken, I’m surprised that position was close to 1cm (vertical and horizontal baseline RMS).

This pipeline image shows the quality of the captured data.

This pipeline impression reveals the high quality of the captured facts.

The level clouds had been utilised to derive precise measurements of the constructions by reverse engineering into primitive styles and then into engineering-analysis computer software, without the need of metrics on the precision and accuracy of the survey and metrology measurements.

After the facts was downloaded, it was simple to do the job with as it was now injected with geospatial data all coordinates had been relative to a real-globe coordinate procedure (WGS 1984 UTM 30N). This implies that the facts is all set to use out of the box by not only the engineers but also the geospatial groups.

I place DeepOcean to the examination when I went to their workplaces to glimpse at this facts. Certain more than enough, I opened ArcGIS Pro and imported the 3D level cloud for one of the PLETs, and it arrived in like a aspiration, precisely wherever I predicted it to be.

Also, many thanks to the new slpk structure Esri has made, I uncovered that I could whizz all over this facts and evaluate, discover, and get real-globe coordinates. I have utilised laserscan facts from onshore surveys that are not this fantastic this is a testament to how fantastic the products is and how perfectly the survey was executed.

It is very widespread for the facts to just get place on a disk and get saved, all set to be in comparison together with the upcoming survey, but DeepOcean has manufactured it usable all alongside the chain. I can see great price in currently being equipped to capture this amount of depth in a geospatial structure so that it can be considered about time utilizing the timeline functions in some of the on the net geospatial Website viewer computer software.

This would give electricity to the shoppers to obtain concerns fast without the need of the need for elaborate modeling, and the software would be not only for metrology but right across the subsea asset chain as perfectly, any where offshore that needs frequent checking.

DeepOcean are retaining quiet about what they’ve obtained coming up. If it is anything at all like this, the globe will be viewing. And I can promise, xyHt will have the scoop!

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