How Accurate is a 3D Laser Survey?

A 3D laser survey is the modern technology alternative to traditional-style hand surveying methods. If you are new to this measured surveying process, you may be wondering, how accurate is a laser survey? This is precisely what we’ll set out to address in this post, as well as exploring the many benefits of precision 3D scanning.

What is a 3D laser survey?

Precision 3D scanning uses cutting edge, high-definition laser scanning technology to capture and record millions of discrete data points. The objective is to create a full and spatially accurate 3D depiction of a building or structure. This data forms the basis for production of highly accurate 3D models and/or 2D plans, sections and elevations.

In contrast to the traditional method of producing a measured survey by hand, precision 3D scanning uses LIDAR (Light, Imaging, Detection and Ranging) technology to capture considerable volumes of spatial data in a much shorter timeframe.

In just a few seconds, the 3D laser scanner is able to capture, in high resolution, the building’s interior or exterior features, or whatever is in the direct line-of-sight from its location. But just how accurate is a laser survey, and how do they work?

How does precision 3D scanning work?

When 3D laser technology records the data points within its field of vision, it builds a point-cloud of the building or structure being measured.

Each recorded point within the point-cloud carries information such as X, Y & Z co-ordinates (relative to the scanner position), surface colour and reflective intensity.

A full survey is built up of scans taken in every location that provides line-of-sight to survey features. These individual point clouds are then stitched together with millimetre precision using clever ‘registration’ software to create one homogenous, spatially-accurate point-cloud.

This is then moved and rotated in space using GPS references. The result is a high-definition, geo-referenced point cloud that can be placed in CAD space and segmented and sliced to enable drafting of accurate 2D drawings and 3D modelling.

The advantage of precision 3D scanning over traditional methods is not just the time saving onsite, but the sheer volume of useful information that is captured. By default, the scanner will pick up everything in its line-of-sight, meaning that any information not specifically required at the time of survey will be stored for recall at any time in the future, without the requirement to return to site.

How Accurate is a 3D Laser Survey?

How accurate is a laser survey?

Precision 3D scanning is able to ensure the most detailed and precise data sets are captured. The process goes beyond basic walls, windows and doors to capture data at such a degree of accuracy that you can actually see all the features present in exceptionally high resolution.

From exposed wires to power sockets, from individual bricks to architectural mouldings, there is nothing that will escape the detail of the 3D survey. They can even see in the dark.

So, just how accurate is a laser survey?

By itself, a laser scanner can record individual points to within 0.3mm accuracy (by manufacturers’ figures). However, the accuracy of the final registered point cloud will certainly be somewhat less.

Surface material, environmental factors and ground stability all have an impact on scan accuracy. But the biggest impact on the accuracy of a registered point cloud is the skill and experience of the surveyor, both onsite and in the office.

Anyone can pick up a scanner and scan a building, but point-cloud accuracy is a product of the understanding of the process by which the individual scans are registered together. This relies heavily on the choice of scanner settings and the onsite scan locations, being sympathetic to registration software, and the choice of method and process of registration itself.

Precision 3D scanning

Despite what is commonly thought, there is no software that will produce the most accurate registration without human input. A well-registered point cloud could have a quoted error of a few millimetres. A bad one could have errors of 30mm or more, unfixable due to poor site scanning or registration technique. But that’s just the beginning of the survey process.

The interpretation of that data and production of meaningful drawings adds another layer of potential inaccuracy. It is no arbitrary measure that leads the RICS Code of Measuring Practice to offer ‘Accuracy Bands’ codified by centimetre, and not millimetre accuracy.

This is a true reflection of surveys produced by skilled and experienced survey engineers. Imagine the errors likely in a survey produced by non-skilled operatives! The avoidance of these compounding inaccuracies from site scanning to CAD linework is the reason that survey professionals exist.

Accuracy in construction is hugely important. Being able to identify potential issues before works commence can lead to significant cost savings. And because precision 3D scanning is so fast compared to traditional methods, recording thousands of data points per second, project timescales benefit too.

Precision 3D scanning

Looking for precision 3D scanning in London?

At Callidus Building Surveys Ltd, we offer a unique ‘whole building’ approach to measured surveys. This means that everything from the structure, internal and external features as well as the services of a building are captured, resulting in a considerably detailed, high quality 3D measured survey. This can be used with full peace of mind for anything from structural redevelopment to major renovation, space planning and lease plans.

Founded in 1999, we have many of the UK’s most experienced measured survey experts on our team. As well as having invested in the highest specification, leading edge precision 3D scanning equipment, we also offer the added reassurance of every laser survey being overseen by one of our highly experienced principal surveyors.

All our measured surveys are conducted under the guidance set out by the Royal Institution of Chartered Surveyors (RICS), which forms the framework of best-practice for measured surveys of buildings, utilities or land. 

There is a lot riding on the accuracy of a measured survey, including budgets, timescales and reputation. Looking at how accurate a laser survey is compared to traditional surveying methods, it is clear to see why so many construction industry professionals are now demanding them as their survey of preference.

Whether you’re looking for a basic floor plan or a highly accurate 3D model, you can rely on Callidus for the most detailed and precise data sets to suit your needs.

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This post was written by

Andrew Wilson
Andrew is the Survey Manager and Director at Callidus Building Surveys Ltd.