Mythbusters: Separating Fact from Fiction in Subsea 3D Data Capture
3D photogrammetry has become one of the most widely discussed tools in subsea inspection and dimensional inspection — and for good reason. It offers a flexible, cost-effective and highly accurate method of capturing 3D data in environments where traditional technologies can struggle, take too long or delivery uncertain results.
As adoption has grown however, so have the misconceptions. We often hear statements that sound definitive but don’t reflect how modern photogrammetry actually works in the field. In some cases, these myths lead to unnecessary limitations; in others, they prevent operators from choosing a solution that could significantly improve data quality, reduce time offshore, and cut costs and schedule during activities which rely on the accuracy of that 3D data.
At Viewport3, we’ve helped our customers achieve first-time-fits for their retro-fit engineering scopes on more than 30 occasions, obtained Lloyd’s Register approval for our 3D scanning accuracy and even scanned a hair-line crack in a bilge keel – all as a result of the many years we’ve spent delivering engineering-grade photogrammetry in some of the most challenging subsea environments. We don’t treat photogrammetry as a scanning product, but as a method of delivering Engineering Grade Dimensional Assurance, which is the structured acquisition, validation, and reporting of dimensional data to a defined and demonstrable level of accuracy, suitable for supporting crucial engineering evaluations and classification-related decision making.
Below, we break down six of the biggest misconceptions and share the reality behind them.
Myth 1: “Photogrammetry doesn’t work in low-visibility conditions.”
Reality: While poor visibility can affect image quality and increase the time required to collect valuable data, it certainly doesn’t rule photogrammetry out. What matters is control, light management, and image density — not crystal-clear conditions. In many turbid water scenarios, laser and sonar systems will struggle before photogrammetry does, and by adding advanced lighting techniques, photogrammetry is only stopped in its tracks when visibility is close to zero.
With the right planning and technique, high-accuracy 3D models are achievable in challenging conditions that many assume are off-limits, and when the visibility begins to drop, photogrammetry is usually the ‘last man standing’.
With the right planning and technique, high-accuracy 3D models are achievable in challenging conditions that many assume are off-limits. The following link details a 3D data collection project in 6m of turbid water in the Dutch Sector: LINK
Myth 2: “Photogrammetry needs multiple cameras – one camera isn’t enough.”
Reality: A single camera is usually the best approach for technical 3D data work-scopes. The only benefit offered by stereo systems that a single-camera cannot match is the built-in / automated scaling capability, but due to the inherent compromises and with many other scaling options available, we don’t use them for analysis which engineers will base their decisions on, or for regulatory reporting.
Modern subsea photogrammetry relies on methodical capture, consistent technique and robust processing — not on the number of lenses. One calibrated digital stills camera, deployed within a structured workflow, will deliver sub-millimetric accuracy when executed correctly, reducing complexity, cost and mobilisation time, and avoiding the technical compromises sometimes associated with stereo-camera systems.
So yes, the stereo systems do have more lenses – but no amount of video will match the quality and reliability of a high-end digital stills camera.
Our published list of case studies contains many example of high-end photogrammetry, with every single instance of photogrammetry being completed using a single, high-end digital stills camera: LINK
Myth 3: “You need to hire expensive, specialised equipment to get usable results.”
Reality: Many people confuse 3D photogrammetry with ‘one-size-fits-all’ 3D scanning systems.
In truth, photogrammetry’s power and flexibility is best realised through capability and technique, not high-cost hardware. With the right workflow, even compact subsea cameras can produce engineering-grade 3D outputs. In multiple emergency scenarios, Viewport3 have helped customers use the ROV’s existing flight camera to solve important, time-sensitive (if elementary) challenges. The results were of course compromised, but nonetheless comparable to what you might expect from some ‘plug-and-play’ systems.
The following case-study provides some detail on an instance where Viewport3 determined the requirement for a methanol spool repair clamp without the need for any personnel or equipment. The results were of course compromised, but nonetheless comparable to what you might expect froma some ‘plug-and-play’ systems: LINK
Myth 4: “Photogrammetry only works for large, clear, simple structures.”
Reality: Quite the opposite.
Some of the strongest use cases for 3D photogrammetry are actually complex geometries, tight spaces, intricate mooring links to the highest possible accuracy, or areas where laser scanning is impractical. For very large capture areas, we have often advised clients that a hybrid ‘data-fusion’ approach — combining the coverage speed of sonar with the resolution of photogrammetry — better serves the engineering objective and improves efficiency, by producing a ‘base’ 3D model collected by acoustic methods, which has 3D photogrammetry elements overlayed – the best of both worlds. You will of course be familiar with aerial photogrammetry outputs that cover large areas, but this is enabled by daylight, which is not something that will come to your aid during subsea operations.
Photogrammetry thrives where traditional measurement tools struggle.
The following case-study details the project associated with Viewport3’s North Sea accuracy record of 62 microns, which allowed propagation monitoring at a very small scale. The project was completed with a single (and quite old) 10MP digital stills camera: LINK
Myth 5: “Photogrammetry isn’t accurate enough for engineering decisions.”
Reality: When done properly, subsea photogrammetry provides millimetric and sub-millimetric accuracy, suitable for metrology, anomaly propagation, wear measurement and more. Through demonstrable detail and validated measurement workflows, 3D photogrammetry supports engineering grade evaluation. Accuracy must be demonstrated, verified and understood within defined limits — not assumed.
At Viewport3, we have completed dozens of projects whereby our 3D data was used as a basis for ‘wrap-around’ design, leading to the client’s retrofit part fitting at the first time of asking. We believe that this ‘real-world’ validation of our accuracy levels speaks volumes – if we’d be even 1% incorrect, the parts simply wouldn’t have fitted.
During Lloyd’s Register RITS classification trials, Viewport3 demonstrated a maximum error of 0.05mm (0.03%) prior to approving us to measure mooring links via 3D data.
The key phrase is “done properly” — with a controlled workflow, dedicated processing, and a knowledgeable team, accuracy is a reason to choose photogrammetry, not discount it.
The following case-study details our very first retro-fit engineering scope – following an 80% vessel-time saving during the resulting installation, we were soon award further 2 similar scopes by the same client: LINK
Myth 6: “Photogrammetry doesn’t work with legacy or low-quality data.”
Reality: Viewport3 has used legacy images and video to reconstruct 3D geometry on many occasions, successfully answering high-importance technical questions for our clients.
While fundamentally poor or incomplete data cannot be corrected, existing material often contains more usable information than first assumed. Through structured processing and careful analysis, we work to maximise the value of every viable pixel.
In practice, around 60% of legacy enquiries we assess result in the client’s question being answered. The remaining 40% typically involve insufficient coverage or data that falls below the minimum quality threshold.
Legacy imagery is often the only available record of an event, condition, or installation state. When recollection is not possible, the ability to extract structured and viable analysis from existing material becomes especially valuable. Viewport3 has also been instructed as an expert in a legal case between two multi-national companies, where imagery dating back to 2007 was used to reconstruct geometry in support of court proceedings.
Where the alternative is vessel remobilisation or unresolved technical uncertainty, successful legacy reconstruction can deliver substantial operational and financial value.
Using these techniques, we have (amongst other solutions):
- Confirmed XMT geometry to support spool installation
- Measured riser clamp liner slippage
- Verified ROV interface dimensions during failed override installation attempts
In each case, this avoided unnecessary expenditure and repeat mobilisation.
An overview of some previous legacy data projects can be found on the following case study: LINK
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If dimensional uncertainty is costing vessel days or creating engineering risk, we help teams replace assumptions with verifiable data.
This is why we don’t treat photogrammetry as a scanning product, but as a method of providing Engineering Grade Dimensional Assurance — data you can trust to make engineering decisions, even years later.
