Visualizing Work Done with AR As-Built Inspection: Grasp Site Progress at a Glance

Table of Contents

• What is AR as-built inspection?

• Challenges with traditional as-built inspection

• Benefit 1: Visualize progress in real time and immediately identify discrepancies

• Benefit 2: Streamline inspection tasks and smooth consensus building

• Benefit 3: Reliable quality proof through digital recording of as-built data

• Benefit 4: Simple surveying anyone can use to supplement labor shortages

• Benefit 5: Promote on-site DX through remote sharing

• AR as-built inspection enabled by LRTK simple surveying

• FAQ

What is AR as-built inspection?

AR as-built inspection is a new method that leverages AR (augmented reality) technology to verify on site whether completed structures or shaped terrain in construction and civil engineering works have been built according to design. In traditional as-built inspection, it was common to measure dimensions at various locations using total stations (TS), levels, tape measures, etc., then take those measurements back to the office to compare with drawings and make a pass/fail decision. This approach creates a time lag between measurement and defect detection on site, often causing rework. Also, measurement and evaluation relied on the experience and intuition of skilled technicians, and with labor shortages and an aging workforce, improving efficiency became a pressing issue.

AR as-built inspection emerged against this backdrop. By simply pointing a smartphone or tablet camera, you can overlay 3D design models and measurement data onto live imagery, allowing direct comparison of the finished form and the current condition on the spot. For example, when checking the as-built condition of a concrete structure, displaying the drawing model in AR over the actual object makes it possible to visually grasp underplacement or shape errors immediately. Even less experienced personnel can intuitively judge acceptability, achieving the visualization that lets you grasp site progress at a glance.

Combined with the latest high-precision GNSS (satellite positioning) technology, it is also possible to align AR models with the real object with errors within a few centimeters (within a few in). Using an RTK-GNSS-capable smartphone enables centimeter-level positioning (inch-level positioning), allowing AR overlays to align with the site without shift. In addition, advanced inspections such as comparing point cloud data (3D scans of the current condition) obtained by LiDAR scanners built into iPhones and iPads with design data and visualizing the differences in color are possible. The Ministry of Land, Infrastructure, Transport and Tourism also encourages 3D measurement and AR use as part of its "i-Construction" promotion measures, and AR as-built inspection is expected to improve both quality control and operational efficiency. In practice, AR as-built inspection is attracting attention as a technology supporting construction DX across major general contractors, small and medium construction companies, surveying technicians, and infrastructure maintenance sites.

Challenges with traditional as-built inspection

To understand the benefits of AR, it is necessary first to outline the problems inherent in traditional as-built inspection methods. The conventional approach had the following issues:

• High effort and time consumption: Using surveying instruments and tape measures to carefully measure each location and record on paper required a long time to complete across a wide construction area. On sites with many measurement points, measurement and drawing comparison could take several days.

• Dependence on skilled personnel: Accurate measurement and judgment required experienced surveyors and technicians, sometimes working in pairs. With labor shortages and veteran workers aging, it became difficult to always secure sufficient personnel.

• Expensive equipment required: Checking errors at millimeter-level precision demanded high-performance total stations and GNSS receivers, specialized surveying equipment that is very expensive and hard for small and medium enterprises to adopt. Maintenance and theft risk of equipment were also burdens.

• Risk of human error: Manual work tended to cause measurement and recording mistakes. Forgetting to measure certain points that are discovered later, necessitating a return trip to remeasure, resulted in inefficiency.

• Delayed defect detection: Even if measurements were taken on site, inspection was done after returning to the office, so defective points tended to be detected late. For example, finding insufficient concrete thickness days later could mean the concrete has already hardened and is difficult to repair.

• Burden of documentation: As-built management requires preparing and submitting drawings and reports based on measurement results. Traditionally, document preparation also required significant time and effort, imposing a large burden on field technicians.

As described above, traditional as-built inspection had inherent inefficiencies and risks of oversight. To achieve real-time and precise as-built checks, the use of new digital technologies was indispensable.

Benefit 1: Visualize progress in real time and immediately identify discrepancies

The greatest advantage of AR as-built inspection is the ability to visualize site progress and deviations from the finished form in real time. By overlaying the design model on camera imagery, subtle height differences or insufficient thickness that are hard to notice with the naked eye are immediately highlighted. Because you can identify differences from the intended finished image on site during construction, you can promptly correct work as needed and prevent rework.

For example, in road embankment work, scanning the finished roadbed with a smartphone LiDAR to obtain point cloud data and overlaying it on the standard design model makes even slight defective spots in elevation immediately obvious. Displaying height excess/deficit with a color-coded heat map makes it intuitive to see "which point is how many cm higher/lower than the design." The result is reliable detection of deviations that even experienced personnel might overlook, leading to early correction of quality defects.

Such visual checks with AR also reduce human errors such as misreading numbers and dramatically improve inspection accuracy. Being able to compare drawings and the actual object visually increases reliability over inspections that rely solely on numbers on paper. Also, objects that will be buried and cannot be visually inspected after completion can be recorded in 3D before covering so their exact position and condition can be confirmed via AR even after backfilling. AR as-built inspection captures even minor deviations on site and prevents variation in progress and quality from occurring. This real-time progress visualization reduces rework and is expected to shorten schedules and lower costs.

Benefit 2: Streamline inspection tasks and smooth consensus building

Using AR dramatically improves the efficiency of the as-built inspection process itself. Because wide areas can be 3D-scanned and digitized at once, it can greatly reduce time compared to measuring point by point as before. Also, software automatically analyzes acquired measurement data and judges differences from design values, reducing manual calculation and checking. There are reports of large-scale earthwork inspections that used to take several days being completed in about half a day thanks to AR.

Furthermore, because inspection results are visualized instantly on site, consensus building between the client (supervisor) and the contractor becomes smoother. Differences are clearly shown on the tablet screen for anyone to see, so "where and to what degree there is an error" can be shared at a glance. This reduces recognition gaps at the inspection site and enables quick agreement on corrective measures for needed areas. AR as-built inspection reduces communication loss between the field and the client and contributes to speeding up the inspection approval process.

Benefit 3: Reliable quality proof through digital recording of as-built data

A major advantage of AR as-built inspection is that site as-built information can be recorded entirely as digital data. Once a structure is 3D-scanned and point cloud data is obtained, omissions in measurement or omissions in capture do not occur, and construction results can be recorded completely. Even if traditionally only important points were selectively measured, 3D data allows you to understand the entire structure down to the smallest detail.

Digital as-built records also provide reliable proof of quality. Acquired point clouds and inspection result data can be saved and submitted as electronic deliverables, serving as more objective evidence than paper documents. If later verification or traceability is required, having detailed 3D records from the time provides reassurance. Digitizing as-built inspection not only increases trust in quality management but also becomes an asset useful for future maintenance and skill transfer. In addition, by using digital data, automatic generation of as-built management charts and omission of submissions become possible, significantly reducing the documentation burden on site personnel.

Benefit 4: Simple surveying anyone can use to supplement labor shortages

Modern AR-capable surveying tools run on smartphones and tablets, so even those unfamiliar with specialized equipment can operate them intuitively. Complicated settings and calculations are automated by the app, so following on-screen instructions allows high-precision positioning and scanning. For example, some smartphone surveying systems perform RTK positioning using an iPhone and a compact GNSS antenna, enabling anyone to acquire data with accuracy of a few centimeters (a few in).

This kind of simple surveying enabled by AR means that even without a seasoned surveying technician on site, as-built data can be acquired and checked with a certain level of accuracy. On labor-short sites, young staff can complete surveying through inspection, greatly contributing to labor savings. As a result, it reduces the burden on valuable veteran technicians and supports skills transfer.

Benefit 5: Promote on-site DX through remote sharing

Combining AR as-built inspection with cloud technology enables on-site DX (digital transformation) that allows site conditions to be grasped remotely. 3D point cloud data and AR footage captured on site can be shared immediately with stakeholders inside and outside the company via the cloud. This makes it possible for technical staff at headquarters to supervise and support progress at multiple sites in real time from the office.

For example, if a field staff uploads a scanned point cloud model or live AR footage from a smartphone to the cloud, remote clients and managers in a distant office can check the as-built status from their desks. They can also annotate that data with comments or issue additional instructions remotely as needed. Being able to attend inspections or meetings without traveling not only reduces time and travel costs, but also allows experts to support multiple sites concurrently.

Moreover, as-built data accumulated in the cloud is always shared as the latest version, eliminating time lags such as "I don't have the latest drawings on hand and can't make a decision." Information is seamlessly linked between field and office, client and contractor, fundamentally transforming construction management workflows. Using AR and data sharing for remote supervision is likely to become a new standard style for future smart construction sites.

AR as-built inspection enabled by LRTK simple surveying

To maximize the benefits described above, it is essential to quickly acquire high-accuracy surveying data on site and enable AR display. The solution that has emerged for this is LRTK simple surveying. LRTK is a cutting-edge AR-compatible RTK-GNSS positioning system provided by Reflexia Co., and can be used simply by attaching a dedicated compact GNSS antenna to an iPhone or iPad. Leveraging familiar smart devices makes it attractive for significantly reducing introduction costs compared to traditional specialized surveying equipment.

A major feature of LRTK is that it eliminates the previously complicated on-site coordinate alignment (setting out) work. With high-precision RTK-GNSS, the smartphone constantly knows its position to centimeter accuracy (inch accuracy), enabling stable AR display that fits 3D models precisely into real space. Even if the user walks around, the model does not float or shift, and it appears as if the actual structure exists in that place.

LRTK also includes a point cloud measurement function that uses the smartphone’s built-in LiDAR sensor and camera, allowing generation of high-precision 3D point cloud models by simply scanning complex-shaped structures with the smartphone. Because acquired point clouds are assigned absolute coordinates derived from RTK-GNSS, you can immediately compare them with design data or perform volume calculations on site. In addition, when recording the coordinates of measured points for later stakeout, LRTK’s coordinate navigation function is powerful. By simply following arrow guidance on the smartphone screen, you are guided to designated coordinate points with errors of only a few centimeters (a few in), allowing one person to perform accurate stakeout.

By using LRTK simple surveying to realize AR display, point cloud acquisition, coordinate guidance, and as-built verification on a single platform, tasks that used to require separate instruments and software are seamlessly connected. Scanned data can be uploaded to the cloud and immediately checked for differences in AR—the entire workflow can be completed with a single smartphone app, accelerating on-site DX. LRTK is being introduced at construction sites nationwide, contributing to faster disaster recovery work and more efficient construction management. Even those who think, "I want to introduce AR as-built inspection but don't know where to start," can begin operation in a short time with LRTK. Combining advanced technology with field-oriented ease of use, LRTK simple surveying will be a reliable ally for future smart construction sites. If interested, please check the LRTK official site product information page or request free materials for details. Consider promoting DX at your site.

FAQ

Q: What kinds of sites or works can AR as-built inspection be used for? A: It can be used in any situation where you want to check the discrepancy between design drawings and as-built conditions. In civil engineering, it is effective not only for new works such as roads, land development, bridges, and tunnels, but also for terrain-related construction such as dam and embankment repairs. In architecture, it can be applied from structural dimension checks to interior finish inspections. It is also useful for regular inspections in infrastructure maintenance and for understanding current conditions in renovation works. In short, AR as-built inspection is generally useful for any project that requires comparison between the finished design (design data) and the current condition.

Q: What is required to introduce AR as-built inspection on site? A: Basically, a tablet or smartphone, a high-precision GNSS receiver, and a dedicated app that supports AR as-built inspection are enough to get started. For example, with a system like LRTK you can attach a compact GNSS antenna to a commercial iPhone to achieve centimeter-level positioning and handle 3D design data and point cloud scans within the dedicated app. Beyond that, having the electronic design drawings (BIM/CIM models, etc.) and the site reference point coordinates prepared allows you to start AR as-built inspection on site immediately.

Q: Is the accuracy of AR-based as-built inspection reliable? A: Yes. When used with high-precision GNSS, AR can achieve accuracy sufficient for reliable inspection. A typical smartphone’s built-in GPS has errors of several meters (several ft), but with RTK corrections the error can be reduced to the order of a few centimeters (a few in). In fact, LRTK simple surveying has confirmed horizontal accuracy of about 1–2 cm (0.4–0.8 in) and vertical accuracy of about 3 cm (1.2 in), comparable to conventional first-class surveying instruments. With AR models and the real object aligned without shift, steps and gaps of a few centimeters (a few in) can be detected reliably. For critical parts, combining point cloud data allows millimeter-level accuracy verification (hundredths of an inch) as well.

Q: Can AR as-built inspection be used for public works as-built management? A: As part of its i-Construction initiative, the Ministry of Land, Infrastructure, Transport and Tourism promotes the spread of ICT construction and 3D as-built management, and demonstrations of AR technology on site are steadily progressing. There have been trial implementations where as-built inspection is performed by overlaying the design model and current condition on a tablet’s AR screen, and cases of AR use in supervision and inspection are increasing. Although AR inspection methods are not yet explicitly stated in official construction management guidelines, a draft guideline for as-built management by point cloud measurement mentions that "if the as-built is confirmed on site by AR, traditional document submission can be omitted." If guidelines are developed in the future, AR as-built inspection may become established as an inspection method for public works.

Q: The operation seems difficult. Can young or inexperienced personnel handle it? A: AR as-built inspection is designed to be easy to understand even without specialized knowledge. Measurements and AR display can be done with the feel of taking photos with a smartphone, so no special surveying skills are required. Field data (drawing models and reference point coordinates) should be prepared in advance, and following the app’s instructions completes the inspection. There are many reports of young employees mastering it after short training, so even those unfamiliar with digital tools can adopt it with confidence.