The accuracy of as-built documentation methods used in the North American architecture, engineering, and construction (AEC) industry is crucial. Studies show that the industry-average error rate for as-built documents created with traditional methods is 12-15%. Such inaccuracies cause construction teams to waste time; for example, teams performing layout work must correct errors found in as-built documents before they can go ahead and finish the job. Time wasted is money wasted—an especially bitter pill in an industry notorious for running over budget. But this ranks just one reason why many in the AEC industry consider laser scanning a transformative technology. Its rate of accuracy (less than 2% error) alone makes it worthwhile.
Several firms within the AEC sector are using 3D laser scanning technology to enhance the precision and productivity of as-built documentation.
Construction as-built documentation provides a vital record of a structure or building as it was really built. It shows all the variations and changes that—inexorably and invariably—occur between design and construction; it captures reality. If there is a need to know anything about the building or structure after its construction, the as-built documentation is the place to look. It is not just the final drawings that count; it is also how faithful they are to the structure and the precision used to hourly, daily, and weekly log all the details between the first excavation and the last coat of paint.
This all-encompassing manual investigates as-built documentation by means of 3D laser scanning in great detail, down to the most elementary aspects of the subject. Yet, it also delves deep into its more technical aspects, covering fundamental concepts as well as advanced techniques.
If you are an architect, engineer, contractor, facilities manager, or other stakeholder in the construction process, this guide will provide you with the depth of knowledge and insights needed to implement and greatly optimize the use of 3D laser scanning to achieve your as-built documentation requirements.
What is As-Built Documentation?
The documentation in place once a structure or building is built down to the last detail is known as as-built documentation. It encompasses a design’s initial intent but mirrors the construction’s reality. As-built documents capture changed conditions (i.e., deviations from the original design) as a run of construction progresses.
Definition and Purpose
The as-built record serves as the final authority on what exists in the real world. It provides accurate accounts of a structure’s dimensions, materials, systems, and components. It typically includes the following:
- Drawings that are detailed and show precisely where everything in the building goes exactly, with dimensions and configurations.
- Detailed models portraying the physical setup in electronic form.
- Documents that describe deviations from the original design specifications.
- Technical specs of installed systems and components.
- Proof of work that has been done, in the form of photographs.
The fundamental reason for producing as-built documentation is to present a true-to-life depiction of what was actually constructed—that is, a structure as opposed to just a set of working drawings. A reliable reference can be made to a structure depicted in as-builts, should anyone wish to alter, refurbish, or expand the structure several years down the line.
Traditional vs. Modern Approaches
As-built documentation has, in the past, been an immense effort requiring many people to accomplish a myriad of tasks to detail the as-built product. It has been necessary to physically measure, hand draft, revise, and otherwise note a great many things about a product as it is being built. Not only old-time methods of as-built documentation but also many recent methods are too time-consuming and prone to human error to be practical. It is too easy to miss a dimension and too easy to introduce inaccuracies. And when it comes to labor, as-built documentation has been a very labor-intensive task.
As-built documentation today takes full advantage of contemporary reality capture advancements, particularly 3D laser scanning, to create highly accurate digital models of the built environment. Some state-of-the-art methods include: comprehensive point cloud data capture, digital point cloud processing, integration with Building Information Modeling (BIM) workflows, and, most importantly, “the ability to automate the comparison between design intent and as-built conditions” (Braun, 2015). These technologies represent the best in their respective fields. They offer a significant enhancement in both the precision and the speed of the documentation process.
The change from old to new methods has speeded up the work and has also made results much more accurate and much more complete. What once took us several weeks to accomplish can now be done in several days—and with far greater precision and far greater detail too.
Importance in Construction and Facility Management
There are numerous reasons why accurate as-built documentation is vital, several of which are listed below:
Facility management and maintenance: provides the essential information needed for ongoing building operations, maintenance planning, and system troubleshooting. Facility managers make use of accurate as-built documentation to locate building systems, plan maintenance activities, and respond effectively to emergencies.
Renovation and Retrofit Projects: Provides a dependable launching pad for scheming changes to preexisting edifices, minimizing the amount of vast upfront exploration required. Designers—from either the architectural or engineering camp—can plunge ahead with preparations, certain that they understand the precise situation they’re adapting to.
Compliance and Regulations: Shows adherence to building codes, safety standards, and contractual requirements that differ across Canadian provinces and US states. This documentation is often essential for acquiring occupancy permits and for passing inspections.
Liability is decreased when accurate records are kept. That is, records that attest to what was built (and to how it was built), especially when differences from the original plans are noted. If disputes arise, or if some failure occurs, what is called “as-built” documentation will provide the objective evidence necessary to determine just what the conditions were at the time of construction.
Asset Management: Provides assistance in the effective inventory and management of building assets throughout their lifecycle. Organizations can track and manage their physical assets with good documentation. They can perform better in managing assets by using accurate data.
Preserving history: This creates a detailed record of structures that are significant for historical reasons. This is something that is particularly important for buildings that are part of our heritage in the various cities of North America.
Understanding 3D Laser Scanning for As-Built Documentation
Over the past several years, 3D laser scanning has become the go-to method for producing reliable—and even more importantly, precise—”as-built” documentation. And for good reason: the technology is efficient, and it captures so much detail that the “digital twin” it produces closely resembles the real thing. For the uninitiated, here’s a brief overview of how the method works, what the potential pitfalls are, and how best to ensure that your next project reaps its rewards.
What is 3D Laser Scanning?
Three dimensional (3D) light detection and ranging (LiDAR) is a non-invasive, non-destructive means of obtaining precise measurements on the surfaces of physical objects. This is done through the use of a laser, which emits light that travels to the object and back. By measuring the time it takes for the light to return (or the shift it makes in returning) and understanding the light’s interaction with the object’s surface, LiDAR can obtain a nearly perfect representation of the object’s surface.
3D laser scanning in the context of as-built documentation makes a digital record of a building or site with such precision that the existing conditions can only be accurately portrayed to within millimeters. This laser scanned data is then used to produce the as-built drawings, 3D models, and other documentation that forms the basis of as-built verification. Not only is the geometric data accurate, but the color information recorded during the scanning makes for a much more detailed recreation of the environment that was scanned.
The technology gathers millions of data points in mere minutes, and it registers all visible surfaces within range. This means that the main strength of the system is detail—no detail is too small to escape detection. Traditional methods that depend on key point measurement are not even in the same league.
Types of 3D Laser Scanners for As-Built Documentation
Various kinds of 3D laser scanners serve as the backbone of as-built documentation. Each boasts particular benefits that make it ideal for certain applications. They include the following:
Laser scanners that are used in a terrestrial application are set on a tripod, stationary while scanning, and can capture data with very high accuracy. They are best used when detailed and formal documentation of structures like buildings or industrial facilities is needed. By contrast, laser scanning that is used in a mobile application can be mounted on vehicles or mobile platforms, allowing the operator to cover large areas very quickly and scan a great amount of data. Finally, handheld laser scanners allow operators to be even more flexible and free when capturing data in an informal setting or in spaces that are difficult to navigate with larger systems.
Difference Between LiDAR and Other Scanning Technologies
Although “LiDAR” and “laser scanning” are frequently substituted for one another, significant differences exist between LiDAR and other scanning methods such as photogrammetry and structured light. This unit will therefore periodically refer to scanning technologies in general and to laser scanning in particular.
Light Detection and Ranging (LiDAR) employs laser light to measure distances directly and create precise three-dimensional measurements of any environment. It functions consistently in all lighting conditions and offers exceptional accuracy, which makes it ideal for as-built documentation of even the most complex environments.
| Scanner Type | Accuracy | Range | Best Applications | Typical Cost Range (USD) |
|---|---|---|---|---|
| Terrestrial | ±2-6mm | Up to 350m | Detailed building documentation, Industrial facilities | $40,000-$150,000 |
| Mobile | ±10-30mm | 100-200m | Roads, railways, large sites | $30,000-$150,000 |
| Handheld | ±2-15mm | 0.5-5m | Complex interiors, confined spaces | $15,000-$60,000 |
| Aerial (LiDAR) | ±5-15cm | Up to 1km | Large sites, terrain, exterior building documentation | $30,000-$200,000 |
Using photographs from many angles, photogrammetry calculates 3D data. Offering better color and texture capture than other methods, it also requires optimal lighting and can struggle with uniform or highly reflective surfaces. For precise measurements, it’s less accurate than laser scanning but can serve as a suitable adjunct for capturing visual details.
To provide accurate documentation of how something was built, the best current technology is laser scanning. For very large structures or not-so-simple environments, this is far and away the most reliable method for recording precise measurements.
The As-Built Documentation Process Using 3D Laser Scanning
As-built documentation of comprehensive quality can be achieved through the systematized process of 3D laser scanning. This process starts with planning, runs through many stages of careful data extraction and point cloud processing, and ends with the distillation of the necessary bits of information from the resultant accurate documents, which are in turn used to create comprehensive as-built documentation. The documents are said to be of “as-built” quality when they accurately reflect the condition of the building at the moment in time they were created.
Project Planning and Preparation
Successful as-built documentation projects begin with thorough planning. This initial phase encompasses site assessment, setting up control points, and selecting scan positions that secure not just coverage but also the precision necessary to make as-builts useful. The first step in the point cloud processing pipeline might seem a no-brainer: Make sure you have comprehensive coverage and the accurate configuration of the point cloud to start with.
A site assessment should be performed before scanning starts to determine and delineate the area to be documented. The site conditions and any potential challenges that might affect scanning should be identified. Accessibility and safety issues for the scanning crew should be discussed. Any special parts of the site that require more attention should be singled out. Areas that are directly or indirectly lit by sunlight or artificial sources should be evaluated in terms of their potential to interfere with the scanning process.
Reference frameworks are formed by control points for proper alignment of multiple scans. Establishing accuracy is the first step in ensuring that large and complex projects are successful. Control points are references that when used logically help you get your point cloud aligned and scaled to a real-world coordinate system.
To ensure efficiency and thorough coverage, plan the best scan positions in advance. A well-planned strategy will cut down on setups and ensure that everything is covered, which will save time in the field and improve the quality of the final product.
Field Data Capture
The digitization of the physical environment occurs during the field data capture phase. To obtain high-quality data, it is essential to have the proper setup of the scanners at each position. This phase aims to create a complete and detailed point cloud data set, with adjacent scans having sufficient overlap. The image capture during the field data capture phase has a direct effect on the quality and accuracy of the resultant point cloud data.
Even across multiple scan positions, reliable results stem from consistent, methodical setup procedures. The setup is a direct determinant of the final point cloud’s quality. The setup’s direct impact on the point cloud means that comprehensive, accurate capture is all the more essential. If the goal is complete as-built documentation, then what one “captures” in the field ought to be as close to exhaustive as is required for the mind to conceive of it as part of the built environment. Any missing areas will incur some accounting “difficulties” or “impossibilities” later on.
Point Cloud Registration and Processing
Aligning several scans into a single coordinate system (aligned in a single point cloud) is point cloud registration. It is very similar to a human eye’s ability to take in different angular views of an object and combine those into a single unified object perception. Just as one eye might see a little more or less of an object in a cross-sectional shape, so, too, can different line-of-sight perspectives from different scans allow for a registration process that yields a more complete volumetric shape from the point cloud in the end.
There are many ways to register point clouds, with the common methods being target-based registration, cloud-to-cloud registration, and registration with survey control. The best method to use depends on the project’s requirements, what resources are available, and the conditions at the site.
After registration, point clouds usually need to be processed to make them suitable for modeling and analysis. The processing generally involves several steps: cleaning and filtering to eliminate noise and undesirable data, and extracting features to find specific elements within the point cloud. Point clouds generally contain much more data than they need to—and excess data can hide the features you do want to see—so they need to be trimmed down to just the parts that are (or should be) visible.
Model Creation and Documentation Delivery
Transmuting point cloud data into functional 3D models is a vital precursor to producing anything like as-built documentation that one could reasonably consider valuable. There are several ways to perform that transmutation, which architects might variously call direct modeling, semi-automated modeling, or, in the best of worlds, fully automated modeling. The way that you perform this critical operation depends on your project requirements, the tools you have or can get, and the copiousness that you have to play with in the built environment.
To obtain the utmost value, as-built models can be melded with Building Information Modeling (BIM) workflows. This integration transforms geometric documentation into an information-rich digital asset that supports ongoing building operations and future projects. A BIM model derived from accurate point cloud data provides a reliable foundation for facility management, renovations, and other building lifecycle activities.
The last step is to prepare the as-built documentation and deliver it in formats that meet client needs and industry standards. These formats may include point cloud data, 2D CAD drawings, 3D models, PDF reports, web-based viewers, or experiences in virtual/augmented reality.
Key Benefits of 3D Laser Scanning for As-Built Documentation
The acceptance of 3D laser scanning for as-built documentation offers many essential benefits over traditional documentation methods. Capture technologies play a major role in improving the precision and efficiency of as-built documentation.
Improved Accuracy and Reduced Human Error
3D laser scanning significantly improves the accuracy of as-built documentation through precise measurement capabilities.
Today’s scanners are accurate to within 2-3mm. This is much better than the accuracy you can get with a manual measurement method. The technology captures millions of data points rather than selective measurements. Direct digital capture removes the risk of manual recording mistakes. The standardized capture process means that there is much less variability between operators.
This enhanced accuracy means more reliable documentation that backs up decision-making in remodeling and future interventions. Accurate as-built documentation reduces the likelihood of costly surprises when remodeling or modifying existing structures.
Time and Cost Efficiency
Even with the upfront costs in equipment and training, 3D laser scanning proves a net benefit in time and cost. It allows for rapid field data capture, with the potential for up to an 80% reduction in the time necessary to be on-site. It massively cuts down on the number of workers needed on-site to get the job done. It allows for the work to be done in single-site visits, with many jobs needing only one crew. And it allows for the work to be done in parallel, with no need for staging or rework.
These efficiencies take on great importance in large or intricate projects where conventional documentation might consume vast amounts of time and resources. The payoff usually increases with the size and complexity of the project.
Comprehensive Data Capture
In contrast to measurement techniques that are limited to sampling, 3D laser scanning measures everything in the environment. It acquires full geometric detail, all contextual information, and even condition of the systems around the thing being measured.
Every surface that can be seen is recorded, not just chosen spots. The technology captures spatial relationships between all building elements and documents actual conditions including deformations, wear, and damage. It captures mechanical, electrical, and plumbing systems in context and documents site conditions and adjacent structures.
This extensive acquisition guarantees that data will be accessible for any subsequent necessity—even ones that might not have been foreseen when the original documentation was prepared. The point cloud transforms into a thoroughly digital equivalent that can be unfailingly resorted to at various times and for sundry different reasons during the building’s lifespan.
Digital Twin Creation from As-Built Documentation
The creation of digital twins—comprehensive digital replicas of physical assets used for monitoring, analysis, and simulation—is one of the most powerful applications of 3D laser scanning when it comes to as-built documentation.
In the context of the built environment, a digital twin is more than just a 3D model—it’s an information-rich, dynamic representation that can reflect the current state of the physical asset, update based on real-time data, and support simulation and analysis, providing insights into performance and maintenance needs and facilitating decision-making throughout the asset lifecycle.
The convergence of the physical and digital worlds is represented by digital twins, and this opens up entirely new ways to manage and to optimize assets. They facilitate not only the observation and the analysis of how buildings perform but also the optimization of that performance—without any sort of physical intervention.
There are five typical levels of sophistication at which digital twins may be implemented. These levels are usually categorized as follows:
- Fundamental Digital Model: A 3D static representation of real-world physical forms.
- Model with embedded metadata and attributes: 3D model with enhanced information
- Smart Digital Twin: An all-inclusive BIM model enriched with data.
- Digital Twin: Connected to real-time data from sensors and IoT devices.
- A digital twin that is autonomous, enhanced by AI for analysis and decision-making.
The majority of present implementations exist at levels 2-3. The organizations that are at the forefront of this technology have mostly begun to implement level 4 capabilities. Level 5 is the future direction of this technology. In this level, digital twins are expected to be capable of optimizing building performance in an autonomous fashion and predicting maintenance needs. Most current implementations exist at levels 2-3. Leading organizations begin to implement level 4. The future is level 5.
Creating a Digital Twin from Point Cloud Data
Producing a digital twin from point cloud data requires several important steps:
- Capturing Reality: Utilizing 3D laser scanning to create a complete point cloud of the actual asset.
- Point Cloud Processing: Aligning, purifying, and perfecting the point cloud data.
- The creation of a model: Turning the point cloud into a parametric 3D model.
- Integrating data: Enhancing model components with extra data and semantics.
- Linking to the systems within the building, the connections to sensors, and establishing other data sources.
- Implementing the Platform: Using a platform that enables visualization, analysis, and collaboration to deploy the digital twin.
In different industries, digital twins are used to improve operations. For instance, in the manufacturing and oil & gas sectors, notable cases like reactors and cokers significantly benefit from this advanced technology.
Creating a digital twin can cost between $10,000 to $50,000 for a small building and up to $500,000 or more for a large facility, mainly because the size and sophistication of these assets tend to call for the same levels of detail and implementational savvy that make a good digital twin really good. The payoff comes in improved operational efficiency, reduced maintenance costs, increased lifespans for these assets, and enhanced decision-making capabilities.
FAQ Section
What does “as built” mean?
“As built” refers to the actual physical state of a building, structure, or system as it was constructed, installed, or fabricated, when compared to how it was meant to be built according to the original design. The term recognizes that construction work often requires adjustments to be made in the field, that changes to the design are also sometimes necessary, and that both kinds of adjustments and some others that might not fit those two categories are often mandatory to achieve the kind of final built environment.
What is an as-built report?
A comprehensive document that details the actual constructed state of a building, structure, or system forms the basis of an as-built report. This report includes narrative description, deviation documentation, dimensional data, visual documentation, compliance verification, and reference information.
What is the difference between as-built and design documents?
Design documents serve as instructions for what should be built, while as-built documents record what was actually built. This includes all deviations from the design, field adjustments, and modifications made during construction. At many points in the process, the project team makes decisions that could have a significant impact on the design or the cost of construction.
What is point cloud processing?
Point cloud processing refers to the series of operations performed on raw point cloud data to transform it into usable information for analysis, modeling, or visualization. This process typically includes registration, cleaning, filtering, segmentation, classification, feature extraction, meshing or modeling, and analysis.
What is the difference between LiDAR and point cloud?
LiDAR is a technology or method that uses laser light to measure distances, while a point cloud is the data output or result produced by LiDAR or other 3D capture technologies. In simple terms, LiDAR is the technology used to capture data, while a point cloud is the resulting dataset.
What are the stages of creating a digital twin?
Creating a digital twin involves several stages: data acquisition through reality capture technology, data processing and integration, information enhancement with metadata and attributes, system connection with sensors and IoT devices, and implementation and training for stakeholders.
What is verification in construction?
Construction verification is the systematic process of confirming that the built environment conforms to design specifications, quality standards, regulatory requirements, and contractual obligations. It involves dimensional verification, material verification, system verification, regulatory compliance, quality verification, and documentation verification.
What is included in architectural documentation?
Architectural documentation includes drawings (plans, elevations, sections, details), specifications, schedules, models, renderings, calculations, and reports that describe the design intent for a building or structure.
For as-built architectural documentation, it includes accurate records of the actual constructed conditions, including any deviations from the original design.
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Conclusion
3D laser scanning provides a revolutionary method of capturing, recording, and using information about the built environment. We have evolved from using traditional manual methods of as-built documentation to employing advanced 3D laser scanning techniques.
Increasingly, not just an advantage but a necessity—the as-built documentation of 3D laser scanning is modern construction and facility management across North America. Organizations that embrace this technology and these methodologies render themselves prepared for success in an evolving industry.
