Reducing On-Site Burden with AR As-Built Inspection: A Game Changer for Workstyle Reform

Table of Contents

• What is AR as-built inspection

• Challenges of conventional as-built inspection

• Benefit 1: Precise as-built inspection that doesn’t miss millimeter-level deviations

• Benefit 2: Dramatic improvement in inspection efficiency and consensus building

• Benefit 3: Digitization of as-built records for assured quality

• Benefit 4: Labor savings through simplified surveying anyone can use

• Benefit 5: On-site DX through remote supervision and cloud sharing

• AR as-built inspection realized with LRTK simplified surveying

• FAQ

What is AR as-built inspection

As-built inspection (as-built management) is a quality control process in civil engineering and construction that measures and verifies whether completed structures or developed land conform to the shapes and dimensions shown in the design drawings. It is especially important in public works because the as-built inspection results are often a condition for acceptance by the client. Traditionally, as-built inspections have been conducted on-site using tape measures, staffs (survey rods), levels, total stations (TS), etc., to measure dimensions and elevations, and then returning to the office to compare and judge against design values. However, manual measurements are labor- and time-intensive to cover wide areas, and because measurement points must be limited, there is a risk of overlooking subtle deviations.

A new approach gaining attention to solve these issues is AR as-built inspection. By leveraging AR (augmented reality) technology to overlay 3D design data and drawing information onto the camera view of a smartphone or tablet, it allows intuitive on-site confirmation of differences between the real object and the design. Combined with high-precision RTK-GNSS (satellite positioning), it is possible to align the digital model and the actual object with errors within a few centimeters (a few in). For example, if the design lines or shapes are displayed in AR over the post-construction terrain or structure, you can immediately tell whether the finish is within tolerances. Some of the latest smartphones include LiDAR (light detection and ranging) sensors, which enable advanced uses such as comparing point cloud data (3D scans of the as-built condition) with design data and color-coding deviations. AR as-built inspection enables even less experienced engineers to make intuitive quality judgments on-site without relying on seasoned professionals’ “gut feeling and experience.” Because defects can be detected on the spot, early correction reduces rework and helps shorten construction schedules.

The Ministry of Land, Infrastructure, Transport and Tourism is also promoting the use of 3D surveying data and AR technology as part of productivity improvement measures on construction sites, exemplified by “i-Construction.” In 2024, a notice was issued to contracting agencies nationwide to actively trial new inspection methods that use 3D models and AR without being bound by existing standards. With this tailwind, AR as-built inspection is attracting growing expectations as a digital solution that simultaneously improves on-site efficiency and quality.

Challenges of conventional as-built inspection

Conventional methods for verifying as-built conditions come with a large on-site burden. The main challenges include the following:

• Time-consuming and labor-intensive: It is necessary to carefully measure each measurement point using surveying instruments or tape measures, note the results, and later compare them with drawings. When the work area is large or there are many measurement points, measurement and recording alone can take several days.

• Reliance on experienced personnel: Accurate measurement and evaluation require experienced survey technicians. In some cases, two-person teams are necessary, but chronic labor shortages and an aging workforce make it difficult to always secure skilled staff on-site.

• Expensive equipment required: Verifying design-to-actual errors to the millimeter level requires dedicated high-precision TS or GNSS receivers, which are very expensive and pose a high barrier to adoption for small and medium contractors. Maintenance costs and theft risks also become burdens.

• Risk of human error: Mistakes such as transcription errors from hand-written notes or later data entry are common. Cases of forgetting to take photos or discovering unmeasured spots later also occur. Omissions or mistakes require returning to the site to redo work.

• Delayed problem discovery: Because measured values are brought back to the office for comparison with drawings, defects cannot always be detected on the spot and may be found too late. For example, if a concrete slab thickness is insufficient and this is only discovered during a later inspection, the placed concrete may already have hardened, potentially leading to major rework.

• Massive paperwork: Results of as-built management must be compiled into drawings and forms and submitted to the client. Traditionally, preparing these documents also consumes significant time and effort, posing a large burden on field technicians.

Thus, conventional as-built inspection methods are inherently inefficient, increasing the risk of overlooked quality issues and workload. The current construction industry is calling for workstyle reform and ICT utilization, and the introduction of new digital technologies is considered essential to solve these problems.

Benefit 1: Precise as-built inspection that doesn’t miss millimeter-level deviations

One of the biggest merits of AR as-built inspection is the ability to detect slight construction errors and finish deviations in real time. By overlaying design model lines and shapes on the camera image, differences such as a few centimeters (a few in) of step or shortage that are difficult to notice with the naked eye can be spotted at a glance. Especially when AR displays are accurately aligned in space using high-precision GNSS, design-to-actual differences can be checked to the millimeter level (≈0.04 in). For example, errors that were easily missed before—such as pavement thickness being a few millimeters thinner or a structure’s height being several centimeters (several in) lower than specified—are visualized in AR as deviations, so they are not overlooked. For critical areas, combining on-site LiDAR-scanned point cloud data with design data enables even more precise verification. Using AR as-built inspection in this way reliably exposes fine defects on-site, improving construction quality and reducing rework.

Benefit 2: Dramatic improvement in inspection efficiency and consensus building

AR as-built inspection dramatically improves work efficiency. Inspection work that used to measure one point at a time can now confirm a wide area at once just by surveying the site through the device screen. Compared with conventional methods that measure multiple points and cross-check with drawings, you can check as-built conditions collectively in a short time, significantly reducing the days and manpower required for inspections. Since pass/fail judgment can be completed on-site, there is no need to return to the office for reanalysis, and if problems are found they can be corrected the same day. As a result, it contributes to reduction of long working hours and shortening of construction schedules.

Visualizing inspection results with AR also helps build consensus among stakeholders. For example, showing the client or inspector on a tablet that “this point is ○ cm lower than the design line” alongside the actual video lets them understand the situation at a glance. Subtle deviations that were hard to convey with numbers or reports alone can be objectively backed up by AR visuals, enabling quick decision-making. Since even non-veterans can intuitively grasp the situation, information sharing and meetings within the team become smoother, reducing communication losses across the site.

Benefit 3: Digitization of as-built records for assured quality

Using AR technology digitizes the record-keeping work of as-built management and makes quality evidence more reliable. Traditionally, measurement results had to be handwritten, site photos organized, and reports created, but with AR as-built inspection, measurement data and comparison results remain in digital form. Coordinates of measured points and sectional differences confirmed are automatically recorded in the dedicated app, and screenshots or point cloud data can be saved as needed. This prevents missing records and transcription errors, and greatly streamlines downstream document preparation.

Also, because data can be stored and shared electronically, it leaves highly objective evidence of as-built conditions. For example, AR images with color-coded deviation displays or 3D point clouds showing inspection results are useful for reporting to clients and for future maintenance materials. Managing data digitally rather than on paper makes search and reuse easier and improves traceability. Introducing AR as-built inspection leads to paperless quality control processes and enables presentation of convincing digital evidence during audits and inspections.

Benefit 4: Labor savings through simplified surveying anyone can use

The measurement systems supporting AR as-built inspection are very simple and designed to be usable without specialized skills. Tasks for verifying as-built conditions that once required highly skilled surveyors can now be performed by one person using just a smartphone, a compact GNSS receiver, and a dedicated app. Following an intuitive UI, users simply point the device and press a button to capture coordinates and perform AR-based checks, enabling high-accuracy inspections even by non-veterans. Young engineers with limited surveying experience can start using the system on-site immediately, increasing flexibility in staffing and helping to alleviate labor shortages.

AR as-built inspection also greatly reduces the transport and setup of large equipment previously required. With only a smartphone and a pocket-sized GNSS receiver, there is no need to carry heavy tripods or long staffs across the site. Time spent by multiple people setting up and packing away instruments is saved, allowing efficient inspection with limited personnel. By leveraging such simplified surveying tools, AR as-built inspection enables anyone to easily perform on-site surveying and inspection, delivering significant overall labor savings.

Benefit 5: On-site DX through remote supervision and cloud sharing

AR as-built inspection also offers major advantages by enabling cloud-based data handling. Measurement data and AR-visualized deviation information acquired on-site can be uploaded to the cloud and shared immediately with stakeholders inside and outside the company. Supervisors or specialist technicians located in remote offices can review on-site as-built data via the cloud, enabling remote supervision and advice. This allows appropriate instructions to be issued without the responsible person having to visit every site, reducing travel time and making it easier to manage multiple sites simultaneously.

Promoting data sharing and remote utilization directly contributes to digital transformation (DX) of construction sites. Moving away from conventional site management that relied on paper documents and verbal reports, it becomes possible to make objective, real-time decisions based on digital data. Accumulated as-built data on the cloud becomes an information asset for the entire project, with potential uses such as referencing in other sections or applying statistical analysis. Creating an environment where data is active regardless of location or time can dramatically change how work is done on-site. AR as-built inspection is a tool that powerfully supports this transition to smart construction.

AR as-built inspection realized with LRTK simplified surveying

To fully leverage the effects of AR as-built inspection introduced above, a supporting system for positioning and data processing is indispensable. Recently, simplified surveying solutions have emerged that combine a smartphone with a compact GNSS receiver, enabling anyone to easily perform centimeter-class positioning and point cloud scanning and conduct AR as-built checks. A representative example is the LRTK system developed by a venture originating from Tokyo Institute of Technology. It consists of a pocket-sized RTK-GNSS device that can be attached to an iPhone and a dedicated app, transforming the site into a smart construction environment where surveying and inspection can be completed with just a smartphone. It provides an all-in-one set of functions for intuitive operation by technicians without special qualifications or long training, enabling immediate implementation of high-precision positioning, point cloud measurement, and AR-based as-built inspection.

With such tools, AR as-built inspection—which used to have high adoption barriers—becomes something anyone can incorporate into daily operations. Because the sequence of measuring, recording, comparing, and sharing is seamlessly completed within a single app, even small or understaffed sites can realize digital construction management. LRTK is already being introduced at construction sites nationwide, dramatically streamlining as-built management that used to take much time. Even those who “want to try AR as-built inspection but don’t know where to start” can begin on-site application in a short time using LRTK. By combining the advantages of cutting-edge technology with ease of use, LRTK offers a pathway to next-generation as-built management.

FAQ

Q: Can the accuracy of AR-based as-built inspection be trusted? A: When AR is combined with high-precision RTK-GNSS, positional errors can be suppressed to the order of a few centimeters (a few in). Ordinary smartphone GPS can have errors of several meters (several ft), but by using real-time correction information, self-positioning can achieve survey-grade accuracy. AR displays also align with the real object sufficiently that steps of a few centimeters (a few in) can be reliably detected. If the smartphone’s gyroscope and compass are properly calibrated, orientation accuracy is also practically acceptable. In key cases, combining LiDAR-acquired point clouds can enable checking of differences down to the millimeter level (≈0.04 in).

Q: What is needed to perform AR as-built inspection on-site? A: Basically, a smartphone or tablet, an RTK-capable GNSS receiver, and a dedicated app are sufficient. Prepare digital data such as design drawings or BIM/CIM models in advance and load them into the device app. If the GNSS receiver can receive correction information over the Internet (e.g., Ntrip services), centimeter-level positioning is possible without setting up your own base station. Outdoors within a communication area, correction services can be used via the smartphone.

Q: Can AR as-built inspection be used in tunnels or indoors where GNSS cannot be received? A: Pure GNSS positioning cannot be used in environments without sky visibility. However, workarounds are possible. For example, in a tunnel you can use GNSS positioning obtained near the entrance as a starting point and apply relative corrections to known control points inside the tunnel (previously surveyed reference points) to align AR displays to that reference. Indoors, similar methods can be used by placing markers at building reference positions and overlaying AR models from those anchor points. Cases also exist where camera pose is estimated using QR codes or feature-point markers to perform AR coordinate alignment.

Q: How much does it cost to introduce AR as-built inspection? A: It can be started at a much lower cost than purchasing dedicated large surveying instruments. Many people already have smartphones or tablets, and compact GNSS receivers are relatively inexpensive compared with total stations. Apps and cloud services available on a subscription basis can keep initial costs low. Above all, the benefits from reduced work time and lower labor costs are significant, so from a total perspective the return on investment is expected to exceed the initial outlay.

Q: Can people who are unfamiliar with IT or machinery use it? Is special skill required? A: Basic operation is not difficult; you simply follow the app guidance. For systems like LRTK, you just hold the antenna-equipped smartphone at the position to be measured and press a button to record coordinates, and overlaying AR can be done by selecting the design data from the menu. However, initial familiarity with device handling and calibration procedures is helpful, so brief pre-training is recommended. With continued use, users pick up the nuances and the tool becomes something that any field staff can routinely use.

Q: What types of works and sites can benefit from AR as-built inspection? A: It can be applied to any situation where as-built conditions need to be verified, from civil works to building construction. For roadworks, it can check subbase or pavement thickness, width, and elevation; for land development, slope gradients and fill heights; for structural works, component installation positions; and it can record buried pipes or cable installations before backfilling. In short, AR as-built inspection is effective wherever discrepancies between design and as-built need to be verified. It is a technology that can contribute to efficiency and sophistication of quality control across disciplines.