Revolutionizing As-built Inspections: How AR Technology Will Change Things

Table of Contents

• What is an as-built inspection?

• Challenges of traditional as-built inspections

• What is AR technology? Digitalization advancing on construction sites

• How will as-built inspections change by applying AR?

• Precise inspections that don’t miss millimeter-level deviations

• Efficiency and real-time inspection work

• Digitalization and reliable recording of as-built data

• Labor reduction through easy surveying anyone can use

• Site DX with remote verification and cloud sharing

• Start the AR revolution with simple surveying using LRTK

• FAQ

What is an as-built inspection?

In construction and civil engineering, an as-built inspection (as-built management) is a quality-control process to verify that the shapes and dimensions of completed structures and terrain have been constructed according to the design drawings. Measurements are taken at specified points—such as pavement or bridge thickness, widths, heights, and slopes of embankments—to check whether the finished work falls within allowable tolerances. As-built inspections are an indispensable step in assuring construction quality, and delivering deliverables (as-built drawings and reports) to the client is also required.

Challenges of traditional as-built inspections

Traditional as-built inspections have often been time-consuming and labor-intensive. Survey technicians measure each point carefully on site using total stations (TS), auto levels, tape measures, and other tools, often requiring multiple personnel. On large sites with many measurement points over wide areas, it is not uncommon for measurements and comparisons with drawings to take several days. The following issues have also been pointed out with conventional methods.

• Dependence on experts: Accurate measurement and judgment require the know-how of experienced surveyors. With chronic labor shortages and an aging workforce, securing sufficient personnel has become difficult. Many surveying tasks still require two-person teams, increasing labor costs and coordination burdens.

• High-cost equipment and adoption hurdles: High-precision TS and RTK-GNSS receivers are indispensable for millimeter-level accuracy, but these specialized instruments entail extremely high initial investments (on the order of several million yen), making adoption difficult for small and medium contractors. Equipment maintenance costs and theft risk cannot be ignored.

• Human error and missed measurements: Manual measurement and recording can lead to human errors such as misreading numbers or incorrect entries. Discovering errors later and having to re-measure on site leads to inefficiencies.

• Delayed detection of problems: Traditionally, data collected on site were taken back to the office for comparison with drawings, so施工 defects could not always be detected immediately. For example, insufficient pavement thickness might not be noticed until the next day or later, by which time concrete may have hardened and repairs will require significant effort.

• Burden of report preparation: Measurement results must be compiled into drawings and reports for submission, and organizing paper-based data and entering figures into drawings takes time and effort. Being tied up with paperwork can prevent effective use of the collected measurement data for construction improvement.

As described above, conventional as-built inspection methods face major challenges of low work efficiency and lack of immediacy. Information obtained on site cannot be immediately linked to quality improvements, causing rework and unnecessary costs. To break this situation, a new approach that enables real-time, intuitive grasping of as-built conditions has been sought.

What is AR technology? Digitalization advancing on construction sites

AR (Augmented Reality) technology is attracting attention as a trump card to solve these issues. AR overlays digital information—such as design drawings and survey data—onto live camera images of the real world. Once a cutting-edge experiment, AR has become usable without expensive dedicated equipment thanks to recent improvements in smartphone and tablet performance. Latest iPhones and iPads are equipped with LiDAR sensors for height measurement and high-performance cameras; combining these with construction-oriented apps has made it realistic to incorporate AR into everyday as-built inspections.

The construction industry as a whole is also undergoing DX (digital transformation), and the introduction of 3D data and ICT technologies on sites is being promoted, typified by the Ministry of Land, Infrastructure, Transport and Tourism’s *i-Construction* initiative. Drone photogrammetry and 3D scanner point-cloud measurements have also become more common, but many sites still feel hurdles from equipment costs and required specialist skills. In that respect, AR technology, which can be used by combining smartphones or tablets with small devices, is expected as a relatively easy-to-adopt, high-impact solution.

How will as-built inspections change by applying AR?

What exactly will change when AR technology is applied to on-site as-built inspections? The key point is that digital information can be visualized and checked on site in real time. Pass/fail judgments that were previously made from numbers on drawings or paper forms can now be made intuitively on location, promising dramatic improvements in both accuracy and efficiency. The following explains specific changes (benefits) AR brings from several perspectives.

Precise inspections that don’t miss millimeter-level deviations

By introducing AR for as-built inspections, even slight construction errors or subtle differences in finish can be detected without being missed. Overlaying design data on camera images makes minor height differences and insufficient thickness visually apparent on site. For example, in road embankment work, scanning the finished terrain with a smartphone and comparing the acquired point-cloud data to the design model allows instant recognition of subtle bumps or slope defects that are difficult to notice with the naked eye. Displaying height deviations as a color-coded heat map makes it immediately clear which points are how many cm higher or lower than the design. As a result, mistakes that might previously have been overlooked based on a veteran’s intuition can be reliably detected and corrected early.

Furthermore, being able to compare drawings and actual conditions side by side drastically improves inspection accuracy. Human errors such as misreading numbers can be reduced, and even unseen buried objects can be verified on AR. For example, if buried pipes are recorded in 3D before backfilling, their positions and depths can be displayed on a smartphone screen even after paving, helping reduce the risk of damage in later processes. The ability to reliably capture minute deviations important to quality directly on site through AR is a major revolution.

Efficiency and real-time inspection work

Introducing AR dramatically improves the efficiency of as-built inspections. Because wide areas can be measured in 3D at once, on-site measurement time is greatly reduced compared with the point-by-point approach of the past. Automated processing of acquired data enables immediate pass/fail judgment and quantity calculations on site, eliminating the need to take data back to the office. For example, using drone photogrammetry or an iPhone LiDAR scan, embankment as-built measurements that used to take half a day can sometimes be completed in a matter of tens of minutes. If pass/fail can be determined on the spot, responsible personnel can perform corrections or rework on the same day, minimizing impact on subsequent work.

In addition, AR’s intuitive visualization is powerful for building consensus with clients and supervising staff. Because the finished condition can be confirmed together on site, all stakeholders can immediately share “which parts need what kind of rework.” Finish quality that is hard to convey with paper drawings or numerical data becomes obvious on the AR screen. Inspection attendance becomes quicker and time spent on explanations and discussions can be reduced. Thus, AR contributes not only to speeding up measurements, but to streamlining the entire inspection process and improving communication.

Digitalization and reliable recording of as-built data

As-built inspections using AR record measurement data and inspection results in digital format from the start. Point-cloud models and photos acquired on site automatically include location coordinates and timestamps, and uploading them to the cloud for team sharing is easy. This eliminates the need to take notes on paper on site and retype them at the office, ensuring reliable data recording and traceability.

Digitized as-built data can be used directly as evidence for quality certification, which is a major advantage. Heat maps and 3D models automatically generated from differences between point-cloud data and the design model serve as highly persuasive attachments to as-built drawings and reports. Forms that used to be created manually over time can now be generated efficiently from digital measurement data. Furthermore, sharing site status and quality remotely via the cloud makes it possible for headquarters or clients to participate in inspections remotely from their offices. Digitizing the as-built management process brings great effects in both increasing the reliability of quality control and reducing workload.

Labor reduction through easy surveying anyone can use

Widespread adoption of AR-based as-built inspections will create an environment where surveying and inspections can be performed even by non-specialists. Tasks that previously required highly skilled surveyors can be carried out by simply taking measurements with a smartphone or tablet, so junior or less experienced site personnel can master the tools with short training. Actual operation is intuitive: select the design data file in a dedicated app and follow the on-screen instructions. Advanced calculations or drawing interpretation do not need to be performed manually, enabling anyone to conduct accurate as-built checks.

This can help address chronic labor shortages. Staff without surveying experience can participate in on-site measurements, enabling more efficient use of human resources compared with the past, when a single veteran had to rush between sites. A “anyone can measure, anyone can inspect” system improves organizational productivity and reduces workload concentration on specific seniors. Even generations unfamiliar with digital devices are often surprised at the ease of AR surveying when they try it, and it can aid cross-generational skill transfer and education. Labor reduction through simple surveying is a major change that contributes to industry-wide work-style reform.

Site DX with remote verification and cloud sharing

AR technology and digital measurement directly support the promotion of on-site DX (digital transformation). As mentioned above, sharing measurement data in the cloud allows remote, real-time confirmation of site conditions, and supervisors or clients can attend inspections without traveling to the site. Demonstration projects by the Ministry of Land, Infrastructure, Transport and Tourism have already begun, where design models are overlaid on a tablet’s AR screen to check as-built conditions, or remote attendance is combined with point-cloud-based surface management. Once guidelines are established, AR as-built inspections could be recognized as an official inspection method.

Moreover, digitally archiving 3D data and inspection histories accumulated on site enables use for construction reviews and future maintenance planning. Recording the completed state in 3D allows accurate understanding of the as-built condition during post-delivery inspections or renovations. Such data-driven construction management provides great value not only for quality assurance and efficiency, but also for accumulating and utilizing site knowledge. With AR plus digital technologies, construction sites are now shifting to a “new normal” that is becoming indispensably convenient.

Start the AR revolution with simple surveying using LRTK

For those who want to try AR but don’t know how to start, simple surveying with LRTK lets you realize on-site AR use in a short time. LRTK (Lightweight RTK) is an ultra-compact, high-precision GNSS receiver device that attaches to a smartphone; by attaching it to a commercial iPhone or iPad, you can obtain centimeter-class high-precision positioning via RTK. Dedicated apps support 3D design data and point-cloud scans, and with prepared electronic drawings (BIM/CIM models or CAD data) and site control point coordinates, you can begin AR-based as-built checks on the spot.

No difficult settings or specialist skills are required—if you can use a smartphone, the operation is intuitive. LRTK simple surveying combines cutting-edge technology with ease of use, becoming a new reliable ally on site. In practice, LRTK simple surveying has demonstrated a horizontal positional error of about 1–2 cm (0.4–0.8 in), achieving positioning accuracy comparable to first-class surveying instruments using only a smartphone. Models displayed on the AR screen align with the real object, allowing reliable detection of centimeter-level (half-inch accuracy) steps and gaps. For critical areas, combining point-cloud measurement data enables millimeter-level (0.04 in) precision verification.

Thus, by using LRTK simple surveying, a single person can easily start DX of as-built inspections. Bringing the latest AR technology and high-precision positioning to the site to achieve “faster, cheaper, and more reliable” inspections is likely to become the new standard. Why not take this opportunity to introduce LRTK simple surveying and invite the wave of the AR revolution that balances quality assurance and efficiency to your site?

FAQ

Q: What is required to introduce AR technology for as-built inspections on site? A: Basically, you can get started with a tablet or smartphone, a high-precision GNSS receiver, and an AR app that supports as-built management. For example, solutions like LRTK that enable centimeter-accuracy positioning by attaching a small GNSS antenna to a commercial iPhone allow handling 3D design data and point-cloud models in a dedicated app. If you prepare design data (BIM/CIM models or electronic delivery drawings) and site control point coordinates in advance, you can begin AR checks on site immediately.

Q: Can the accuracy of AR-based as-built inspections be trusted? A: Yes—combined with high-precision GNSS, sufficiently reliable accuracy can be achieved. Built-in GPS in a normal smartphone has errors on the order of several meters (several ft), but RTK corrections improve this to within several centimeters (several in). In practice, LRTK simple surveying has confirmed horizontal accuracy of about 1–2 cm (0.4–0.8 in), comparable to conventional high-end surveying instruments. With AR displays accurately aligned to real objects, height or gap differences on the order of several centimeters can be reliably detected. For critical parts, verifying with point-cloud measurement data alongside AR display enables millimeter-level (0.04 in) quality verification.

Q: Can AR as-built checks be used for public works inspections? A: Currently AR is not explicitly stated in formal as-built management procedures, but the Ministry of Land, Infrastructure, Transport and Tourism is conducting demonstrations of AR use as part of ICT construction and 3D as-built management, and examples of overlaying design models on tablets to check as-built conditions are increasing. As a new inspection method combined with remote attendance and surface management using point clouds, it is attracting attention; if guidelines are developed, there is a sufficient possibility that AR as-built inspections will become an established official inspection method.

Q: Is AR inspection operation difficult? Can young or inexperienced personnel master it? A: Operation is simple and intuitive, so even those unfamiliar with digital tools can learn quickly. Measurement and AR display can be performed with the same sense as taking photos in a smartphone app, so special surveying skills are unnecessary. You simply select prepared design drawings or models, and follow on-screen instructions on site. Tools with well-designed UIs, such as LRTK simple surveying, guide users through the process so anyone can conduct high-accuracy as-built checks; results are visually displayed, making team information sharing easy.

Q: For what types of construction or sites is as-built AR inspection effective? A: AR is effective in any situation where you want to confirm discrepancies between design and construction results on the spot. For large-scale earthworks such as road or land development, AR heat maps are useful for wide-area height management. For structures like tunnels or dams, cross-sectional clearances and thicknesses can be checked against 3D design models after construction. In building works, you can verify column and wall positions with a BIM model or examine equipment piping clashes in AR. In short, as-built AR inspections are effective in any situation where you need to verify construction results on site; the benefits are particularly great in processes where rework is costly, since AR allows detecting deviations and correcting them immediately.