AR Inspection Primer: What Does the Digitalization of As-Built Inspection Mean?

Table of contents

• What is AR inspection?

• Challenges of traditional as-built inspection

• On-site use of AR technology: achieving instant checks

• Benefits of introducing AR inspection

• Points to consider when introducing AR

• Simple surveying realized with LRTK

• FAQ

What is AR inspection?

As-built inspection (as-built management), which verifies on construction sites whether completed structures conform to design drawings, is a routine but critical process for construction management engineers. In recent years, the digitalization of as-built inspection has become a major topic — but what does that specifically mean? A key technology that is changing the conventional reliance on paper drawings and surveying instruments is AR (Augmented Reality). By simply holding a smartphone or tablet on site, design drawings and 3D models can be overlaid on the real scene at full scale, allowing intuitive on-the-spot checks to see whether built elements match the plan. This dramatically improves the speed and certainty of quality checks on site and is attracting attention as a technology that strongly promotes DX (digital transformation) in construction management.

Below we look in detail at the basics of as-built inspection using AR technology (so-called “AR inspection”).

As-built management is a quality assurance process in civil engineering and building works to measure and confirm that completed structures and terrain have the shapes and dimensions specified in the design. During and after construction, measurements such as elevation, thickness, and slope are taken at designated points, and the deviations from design values are checked to determine pass/fail. Traditionally, devices such as levels and total stations were used to measure elevation and thickness, and the measurement data were taken back to the office for comparison against drawings. Naturally, results could not be confirmed on site and the process was time-consuming, but AR-based as-built checks have emerged as a next-generation method to solve these problems. The Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction initiative has also supported this trend, and practical use has rapidly advanced in recent years. The spread of modern smartphones equipped with high-performance cameras and LiDAR sensors has created an environment where AR can be used in daily operations, and AR is now playing an active role in as-built management.

Challenges of traditional as-built inspection

As-built management is indispensable for ensuring quality, but traditional methods involved many inefficiencies. The main challenges are as follows.

• Long working hours: Staff must measure patiently at each survey point using levels or total stations, and when sites are large or survey points numerous this can take an enormous amount of time. It was not uncommon for the process of bringing measurement results back, plotting them on drawings, and judging pass/fail to take several days.

• Dependence on manpower and skilled technicians: Accurate measurement and evaluation require experienced surveyors, and two-person teams are often needed. With serious labor shortages and an aging workforce, ensuring quality with limited personnel has been a heavy burden.

• High equipment costs: Achieving millimeter-level precision requires dedicated instruments such as total stations (TS) or RTK-GNSS receivers, which demand initial investments on the order of several million yen. There are also maintenance costs and theft risks, making adoption difficult for small and medium-sized enterprises.

• Measurement errors and recording mistakes: Manual surveying can accumulate small errors or introduce human error when transcribing field notes into drawings. Discovering misrecords later can require re-measurement and rework.

• Time-consuming report creation: Creating as-built drawings and reports for clients based on measurement results is also a significant burden for site personnel. Time spent organizing photos and plotting points on drawings can prevent on-site data from being fully utilized for quality analysis.

• Delayed discovery of defects: Thickness shortfalls or slope defects may not be noticed immediately and are often detected only after data are taken back and plotted the next day or later. By the time problems are identified, concrete may have hardened or heavy equipment may have been withdrawn, causing additional rework and costs.

As the above shows, traditional as-built management methods suffered from a lack of immediacy and heavy burdens in terms of personnel and cost. There was a clear need for a new method that could provide real-time, accurate, and intuitive understanding of as-built conditions.

On-site use of AR technology: achieving instant checks

So how does on-site as-built checking change when AR is used? By overlaying digital information onto physical space and making what used to be checked on drawings directly “visible” on site, checks can be performed instantly. For example, the following use cases have become possible.

• Design model overlay in AR: 3D design data (BIM/CIM models, etc.) of buildings or civil structures can be overlaid on the site view, enabling intuitive confirmation of placement and dimensions. You can compare via the camera whether columns or walls under construction have shifted from their designed positions. Discrepancies from the completed image that are hard to grasp from paper drawings or numeric data can be instantly understood in AR as life-size visuals.

• Heatmap display of as-built deviations: Efforts have begun to display deviations between measured as-built 3D data (point clouds, etc.) and design data as color-coded heatmaps on site. A heatmap automatically generated by comparing the design model and the as-built point cloud in the cloud can be downloaded to a smartphone and overlaid on the camera view, making it immediately obvious where elevations are higher or lower than designed. This helps rapidly accelerate feedback for correcting issues, such as assessing embankment or pavement thickness over areas and instantly correcting defects.

• Visualization of buried objects in AR: The positions of underground structures and pipes can be displayed as if transparent even after backfilling. For example, in sewer pipe works, if the pipe is scanned with a smartphone before burial and the position-tagged point cloud is saved to the cloud, anyone can later view the pipe’s alignment and depth on a smartphone even after backfilling. This allows immediate identification of buried items without surface markings or carrying drawings, helping prevent construction mistakes and ensuring safety.

• Other applications: AR can also guide operators by displaying construction extents or height criteria during heavy equipment operation, or virtually mark concrete pour locations in advance. In training, AR that reproduces actual sites is gaining attention as a safety drill and procedural training support tool. Applications are expanding each year, and especially the combination of as-built management and AR is expected to deliver quick benefits from introduction, earning strong interest on site.

Benefits of introducing AR inspection

How do the above challenges get resolved by introducing AR inspection? The main benefits are as follows.

• Real-time checks and rapid corrections: Because as-built conditions can be verified immediately on site, the time lag from measurement to pass/fail judgment disappears. If defects are found, corrective measures can be taken instantly, minimizing rework. There are dramatic time-saving cases reported where inspections that used to take half a day were completed in 5 minutes of actual work.

• Increased efficiency and labor savings: With just a smartphone and AR, measurement and inspection can be performed by a single person, dramatically improving team productivity. Tasks that relied on veterans’ experience and intuition can be replaced by technology, enabling anyone to perform stable, high-quality construction management. This ability to combine labor savings with quality assurance is a major advantage amid chronic labor shortages.

• Cost reduction: There is no need to purchase expensive surveying equipment; introduction can be achieved with the affordable initial investment of a smartphone and small devices. Additional benefits include shortened schedules and reduced labor costs from decreased rework. Providing one device per person often fits within budgets, making this a cost-effective solution.

• Improved accuracy and reliability: Centimeter-level positioning (cm level accuracy (half-inch accuracy)) via RTK-GNSS and high-resolution point cloud measurement dramatically increase the reliability of as-built data. Measurement data are automatically saved in the cloud and can be output and utilized in formats compliant with the Ministry of Land, Infrastructure, Transport and Tourism’s as-built management guidelines. As AR use has begun to be officially recognized, the reliability of AR-based inspection documents has become sufficient.

• Streamlined data use and record-keeping: Measurement data and site photos are saved and shared to the cloud on the spot, eliminating the need to transcribe them into drawings later. Acquired point clouds and coordinate information can be exported in common formats such as CSV, SIMA, and LAS and smoothly imported into existing CAD or GIS systems. Past data are easily searchable and referenceable in the cloud, markedly improving the efficiency and accuracy of record management compared to paper field notebooks.

• Improved safety: Remote measurement without entering hazardous areas contributes to safety. For example, even in steep slope surveys, heights can be confirmed from below using AR to reduce risk. AR display of buried items also lowers the risk of damaging pipes or cables during excavation. AR use brings major benefits not only to efficiency but also to site safety.

Points to consider when introducing AR

When newly introducing AR into as-built management, consider the following to maximize effectiveness.

• Phased introduction and internal training: Although AR-based surveying and check operations are intuitive, it is smoothest to conduct basic operation training and establish operational rules within the company during the early stages. Predefining file naming conventions and sharing procedures for acquired data prevents confusion in operation. Start with a small-scale pilot to verify accuracy and effectiveness, then roll out company-wide in stages. When first using the system, verifying errors at control points to deepen understanding of the equipment is also effective.

• Combining with existing methods and data linkage: Initially use AR alongside traditional surveying instruments and methods to cross-check LRTK-derived measurements against total station measurements to understand error trends. It is also important to test in advance whether data exported from the cloud can be smoothly imported into existing CAD software. LRTK supports industry-standard data formats and is highly compatible with existing workflows, but preparing operational flows in advance helps avoid confusion on site.

• Provision of compatible devices: Prepare high-performance devices so AR apps and point cloud measurement run smoothly. Generally, the latest iPhones and iPads and high-end Android devices are recommended. Older models may not support AR processing or LiDAR scanning or may be slow. Large-screen tablets are suitable for detailed point cloud inspection, so use them as appropriate for the task.

Simple surveying realized with LRTK

A notable solution that makes AR as-built checks easy to realize is LRTK. LRTK is an innovative technology that turns a smartphone into a surveying instrument with centimeter-level accuracy (half-inch accuracy) by attaching a small, high-precision RTK-GNSS antenna to the phone. Real-time kinematic (RTK) satellite positioning corrections reduce GPS positioning errors that were originally several meters (several ft) to a few centimeters (a few in), enabling high-precision surveying with palm-sized equipment. Combined with the LiDAR scanner and high-performance camera built into the latest smartphones, you can obtain 3D point cloud data simply by scanning the surroundings, and immediately complete volume calculations, embankment quantity estimations, and buried pipe depth checks on the spot. Acquired point clouds and photos are automatically shared to the cloud, allowing real-time confirmation of site as-built conditions from the office. No special dedicated equipment or complex setup is required — just attach the device to a smartphone and launch the app to start positioning immediately.

LRTK-based simple surveying is spreading across many sites. Aiming to become a “versatile surveying device for one person,” this system, combined with its affordable pricing, has quietly sparked a boom on job sites. If you have not yet tried high-precision positioning or AR checks, why not consider introducing LRTK now? Once you experience the labor and efficiency savings, you may not want to go back to the old ways. Starting as-built management DX with a smartphone will further improve on-site productivity and quality assurance.

If you have questions about the product details or introduction, please feel free to [contact us]. Advance your site to next-generation construction management with LRTK’s simple surveying.

FAQ

Q: What is AR inspection? A: It is a method of overlaying design drawings or 3D models onto the real site using AR to confirm on the spot whether constructed elements conform to the plan. Traditional as-built inspection performed with paper drawings and surveying instruments is digitized and visualized on devices such as smartphones, enabling real-time and intuitive quality checks. Q: What equipment and preparations are required to introduce AR inspection? A: Basically, you need a smartphone or tablet capable of AR display and high-precision positioning, a high-precision GNSS receiver that attaches to the device, and a compatible app. For example, attaching an RTK-GNSS device such as LRTK to a modern smartphone lets you combine centimeter-level positioning with AR functionality for as-built checks. It is also essential to prepare digitized design data in advance, such as design drawings or BIM/CIM models. Q: Is measurement accuracy sufficiently ensured? A: Yes. Positioning via RTK-GNSS provides accuracy within a few centimeters (a few in), which is sufficient for as-built management. A GNSS receiver attached to a smartphone receives correction information based on control points and overlays 3D models and point cloud data accurately in the site coordinate system. The effectiveness of AR-based as-built inspection methods has also been confirmed in verifications that comply with the Ministry of Land, Infrastructure, Transport and Tourism’s guidelines. Q: How much does introduction cost? A: Compared to equipping a full set of traditional surveying instruments, introduction costs are considerably lower. By utilizing a modern commercial smartphone and adding a small, high-precision GNSS receiver, initial costs are roughly equivalent to a single traditional instrument and are extremely reasonable. Subscription options are also available so you can use the system only for the needed period, further reducing costs. Introducing one device per person often yields good cost-effectiveness. Q: Does it comply with the Ministry of Land, Infrastructure, Transport and Tourism’s standards? A: Yes. Acquired point clouds and as-built comparison results can be output and submitted in formats that follow the ministry’s as-built management guidelines. In fact, the guidelines include provisions that, when as-built measurement results projected on site using AR are used for pass/fail judgment, submission of traditional as-built management forms is not required, and AR-based as-built management methods are gaining official recognition. Therefore, you can operate inspections with AR checks without problems. Q: On what kinds of sites can AR inspection be used? A: It can be applied to as-built management across a wide range of civil and building works. For example, in earthworks you can check embankment or subgrade thickness on the spot, and in concrete work you can confirm formwork and rebar positions with AR. It is effective for confirming buried pipes and cables, shape inspections of bridges and tunnels, and more. Applications are expected not only during construction but also at completion inspections and in maintenance-stage inspections. Government-led AR trials have already begun, and industry-wide adoption is progressing. Q: What should be noted when introducing AR inspection? A: There are several points. First, prepare 3D design data such as drawings or BIM/CIM models in advance. During the initial introduction, it is reassuring to verify accuracy and become familiar with operations by combining AR with traditional methods and checking error trends. Also prepare high-performance smartphones or tablets so AR display and point cloud measurement run smoothly, and conduct basic operation training for smooth introduction. Be aware that AR displays may be hard to see in low-visibility conditions such as rain or nighttime, so consider the timing and conditions for measurement.