Every industrial facility exists in two versions simultaneously. One lives in documentation – drawings, schematics, models describing how the object was meant to look. The other exists in reality – with all the changes, modifications, and deformations that have accumulated over years of operation. The documentation describing how an object should look is called Design Intent. The documentation describing how an object actually looks – right now, at this moment – is what we call as-built. It can take the form of a parametric model in AVEVA E3D, a BIM model in Revit, a simpler solid model, or sometimes just a point cloud. As-built is a concept, not a format.
And precisely because as-built is meant to describe reality, the industry has adopted an assumption – a mistaken one – that the more accurate it is, the better.
Equipment manufacturers advertise scanner accuracy at the level of 2-3mm – and designers start assuming that the point cloud, and later the as-built model, must be equally precise. However, the stated accuracy applies to a single scanner station. In the reality of a large industrial facility, where data comes from dozens or hundreds of stations, the overall accuracy of the registered cloud is different. And the accuracy of the as-built model is an entirely different conversation.
Where the myth of the millimetre-precise as-built comes from
High scanner accuracy does not mean that the as-built model should faithfully reproduce every pipe deflection and every foundation settlement. This belief – though widespread – is a mistake that in practice generates models that are useless for further design work.
What an as-built model should actually be
A good as-built model is deliberately simplified wherever precision has no bearing on further work. Pipeline deflections caused by their own weight, minor structural settlements, deviations that don’t affect the functionality of the installation or pose a safety risk – all of this is straightened out in the model. Consciously and intentionally.
The reason is practical: isometrics generated from a pipe with a dozen irregular bends, faithfully reproduced from the point cloud, are in practice useless. No one can use them to design, prefabricate, or order components. A model must be useful – and usefulness requires simplification.
From our experience working with clients in the process industry, we know that the best results come from an approach where the as-built model stays as close as possible to design intent – meaning the design documentation describing how the object was meant to look – with precise representation only in those places where accuracy has real significance for the project.
Where precision really matters
This doesn’t mean that accuracy is unimportant. On the contrary – in specific locations, millimetre precision is absolutely critical.
Prefabrication and tie-ins
Elements prefabricated off-site must fit the actual state of the installation at connection points – so-called tie-ins. Fitting a flange requires precision of up to 5mm. There’s no room for simplification here. However, the general routing of a pipeline between connection points – a tolerance of around 30-50mm is entirely sufficient and doesn’t affect the quality of subsequent design work.
Deformation analysis – a job for the raw point cloud
At 3Deling, we most often carry out settlement and deformation analyses directly on the raw point cloud – it provides a complete, unsimplified picture of the geometry, while the as-built model is, by design, simplified and straightened. Comparing the point cloud with the original design documentation allows for precise measurement of deviations from the ideal state – beam deflections from vertical, twisting of structural elements, floor deflections from a perfect plane.
Why this matters for your budget
The closer an as-built model is to design intent – meaning the design documentation describing how the object was meant to look – and the more deliberately simplified it is, the easier and faster subsequent design work and 2D documentation generation become. This is a principle that, in practice, translates into real time savings at later project stages.
Excessive model accuracy – faithfully reproducing every deflection and every deviation – doesn’t just fail to add value, it actively hinders the work. It generates heavy, difficult-to-handle files, useless isometrics, and additional modelling costs that the client pays for but cannot make use of.
As-Built in construction and industry – different tools, the same goal
As-built modelling is carried out using different standards depending on the sector. In construction and architecture, the BIM standard dominates – models are created in environments such as Revit or OpenBuildings Designer.
In the process industry – refineries, chemical plants, power stations – the standard is intelligent installation models built in systems such as AVEVA E3D, where industry logic, pipeline specifications, and links to technical documentation are built into the model’s structure.
Regardless of the tool, the goal remains the same: to deliver a reliable, useful representation of the object’s actual condition – not the most accurate one possible, but the most functional one.
A good as-built model isn’t one that reproduces reality with millimetre precision at every point. It’s one that delivers precision where it’s needed – and useful simplification everywhere else. This approach has been developed by the 3Deling team based on years of work in the process industry.
Related articles from this series on 3D modelling
This article is part of a series dedicated to 3D modelling in the process industry. If you’re wondering how a mesh model differs from a CAD model and when to reach for which one, check out Not every 3D model is a CAD model – a difference that can cost you. And if you’re facing a decision about what scope of 3D modelling to order and how to match it to your project budget, read Before you order a 3D model – a strategy that saves your budget.
Planning a facility upgrade and want to make sure your model reflects the actual condition of the plant in a way that’s useful for your project? Contact us – our experts will advise you on the optimal scope of as-built survey and modelling.
