The Future of Construction Sites: Inspection Processes Transformed by AR As-Built Inspections

Table of Contents

• What is AR as-built inspection?

• Challenges of conventional as-built management

• On-site use of AR technology: immediate checks through visualization

• Benefits of introducing AR as-built inspection

• Points to consider when introducing it

• Simple surveying realized by LRTK

• FAQ

What is AR as-built inspection?

On construction sites, it is routine to conduct "as-built inspections," where completed structures are compared with drawings to confirm they have been built according to design. In recent years, however, this convention has been changing thanks to AR (Augmented Reality) technology. By simply pointing a smartphone or tablet, design drawings and 3D models can be overlaid on the real scene at full scale, allowing intuitive, on-the-spot confirmation of whether the construction matches the plan. Such AR as-built inspections dramatically increase the speed and reliability of on-site quality checks and strongly support the DX (digital transformation) of construction management.

As-built management itself is a quality assurance process in civil engineering and building works that measures and confirms whether completed structures and terrain have been finished to the shapes and dimensions specified in the design drawings. During or after construction, heights, thicknesses, slopes, and other parameters are measured at prescribed points, and deviations from design values are checked to determine pass/fail. Traditionally, heights and thicknesses were measured using levels (surveying instruments) or total stations, and measurement results were taken back to the office for comparison with drawings. Because immediate on-site decisions could not be made, this was a labor- and time-intensive task. As a next-generation method that addresses these challenges, AR as-built inspection has been attracting attention. Applying AR technology to as-built management to digitally "visualize" construction results on site for immediate checks has advanced rapidly in recent years, aided by the Ministry of Land, Infrastructure, Transport and Tourism-led *i-Construction* initiative. The spread of modern smartphones equipped with high-performance cameras and LiDAR sensors has created an environment where AR can be used in daily work, and AR has now become practical for as-built management. Thus, traditional inspection processes are undergoing significant change.

Challenges of conventional as-built management

As-built management is indispensable for ensuring construction quality, but traditional methods have been accompanied by many inefficiencies. Here are the representative challenges.

• Long working hours: Because staff measured each survey point one by one using levels or total stations, vast amounts of time were required for large sites or when there were many survey points. It was not uncommon for measurement results to take several days to be compiled in drawings and judged for pass/fail.

• Dependence on manpower and skilled techniques: Accurate measurement and evaluation require experienced surveyors or technicians, and two-person teams are frequently necessary. With severe labor shortages and an aging workforce, ensuring quality with limited personnel has been a major burden.

• High equipment costs: To measure at millimeter-level high precision, specialized equipment such as total stations (TS) and RTK-GNSS receivers is essential, but these require an initial investment on the order of several million yen. Maintenance costs and theft risk are also high, making adoption very difficult for small and medium-sized companies.

• Measurement errors and recording mistakes: Manual surveying can introduce slight cumulative errors each time, and there is the risk of human error when transcribing numbers from field notes to drawings. Discovering such mistakes later can lead to re-measurement and rework.

• Time-consuming reporting: Creating as-built drawings and reports based on measurement results and submitting them to clients is also a significant burden for field personnel. Time is consumed organizing photos and plotting data on drawings, and in many cases on-site data cannot be fully utilized for quality analysis.

• Delayed discovery of defects: Even if there are construction defects such as insufficient thickness or incorrect slope, they may not be noticed on site immediately; they are often discovered the next day or later after data has been taken back and plotted. By the time the problem is found, concrete may have hardened or heavy machinery may have been removed, resulting in extra labor and costs for rework.

As described above, traditional as-built management methods were plagued by issues such as a lack of immediacy and heavy burdens in terms of personnel and cost. A new method that can capture as-built conditions accurately, intuitively, and in real time was needed.

On-site use of AR technology: immediate checks through visualization

So how can AR technology actually be used on site? By overlaying digital information and directly "visualizing" as-built confirmations on site—work that was previously done on drawings—checks can be made immediately. Examples of possible use cases include the following.

• AR overlay of design models: 3D design data for buildings and civil structures (BIM/CIM models, etc.) can be overlaid on the site scenery to intuitively confirm placement and dimensions on the spot. It is also possible to compare through the camera whether columns or walls during construction have shifted from their design positions. Subtle differences from the expected finished image that are difficult to grasp from paper drawings or numerical data can be understood instantly in life-size visuals on AR.

• Heatmap display of as-built deviations: On-site verification using a heatmap that colors deviations after comparing post-construction 3D as-built data (point clouds, etc.) with design data is beginning to be used. A heatmap automatically generated in the cloud by comparing the design model and as-built point cloud can be downloaded to a smartphone and overlaid on the camera feed, making it immediately obvious which areas are higher or lower than the design. For example, it helps speed up the PDCA cycle by evaluating embankment or pavement thickness across surfaces and immediately correcting defective areas.

• AR visualization of buried assets: The positions of structures or pipes buried underground can be displayed and checked as if viewed through AR even after backfilling. For example, in sewer pipe work, scanning pipes with a smartphone before burial and saving point cloud data with location information to the cloud allows anyone to identify pipe alignment and depth through the smartphone screen even after backfilling. This enables immediate location of buried assets without marking the surface or carrying drawings, helping to prevent construction mistakes and improve safety.

• Other applications: Beyond the above, AR can be used to guide operators by displaying construction extents or height references during heavy equipment operation or to virtually mark concrete placement locations in advance. In training, AR is gaining attention as a safety-training and procedure-familiarization tool that recreates sites. The range of applications is expanding year by year, and in particular as-built management × AR is attracting high expectations from the field as a use case that yields benefits immediately after introduction.

Benefits of introducing AR as-built inspection

How do the challenges of conventional methods get resolved by introducing AR as-built inspection? Here are the main benefits.

• Real-time confirmation and rapid correction: Because as-built conditions can be checked on site immediately, the time lag from measurement to pass/fail judgment is eliminated. If a defect is found, corrective action can be taken at once, minimizing rework. There are reports of dramatic time savings, such as surveys that used to take half a day being completed in an actual working time of 5 minutes.

• Efficiency and labor reduction: With a smartphone and AR, a single person can perform surveying and inspection, drastically improving overall team efficiency. Tasks that previously relied on veteran experience and intuition can be substituted by technology, enabling anyone to manage construction quality efficiently. The ability to achieve both labor savings and quality assurance amid chronic labor shortages is a major advantage.

• Cost reduction: There is no need to acquire expensive surveying equipment; introduction can be achieved with a reasonable initial investment such as a smartphone and a small GNSS device. Effects such as reduced rework leading to shorter schedules and lower labor costs are also expected. In many cases, supplying one device per person to the site stays within budget, making this a highly cost-effective solution.

• Improved accuracy and reliability: Centimeter-level accuracy (half-inch accuracy) positioning by RTK-GNSS and high-resolution point cloud measurement dramatically increase the reliability of as-built data. Measurement values can be automatically saved to the cloud and output/submitted in formats compliant with the Ministry of Land, Infrastructure, Transport and Tourism’s as-built management guidelines. As AR use begins to be officially recognized, the reliability of AR-based inspection documents is adequately ensured.

• Data utilization and streamlined recordkeeping: Measurement data and site photos are saved and shared to the cloud on site, eliminating the need to transcribe later into drawings. Point clouds and coordinate data can be output in common formats that are easy to use in operations, such as CSV, SIMA, and LAS, and can be smoothly imported into existing CAD or GIS systems. Past as-built data can be easily searched and referenced in the cloud, greatly improving recordkeeping efficiency and accuracy compared to paper field notebooks.

• Improved safety: Because measurements can be taken remotely without entering hazardous areas, AR contributes to safety assurance. For example, surveying steep slopes can be done by confirming heights from below using AR, reducing risk. AR display of buried assets also reduces the risk of accidental damage to pipes or cables during excavation. In this way, AR brings significant benefits not only in work efficiency but also in site safety.

Points to consider when introducing it

When introducing AR as-built inspection, consider the following points to maximize effectiveness.

• Phased introduction and internal training: While AR-based surveying and inspection are intuitive, it is smoothest to conduct basic operation training and establish operational rules internally during the early stages of introduction. If file naming conventions and sharing procedures for acquired data are decided in advance, operational confusion can be prevented. A key to success is to pilot with a small group to verify accuracy and effectiveness before rolling out broadly. When using it for the first time, measures such as verifying errors using known control points are also effective for gaining understanding of the equipment.

• Combining with existing methods and data linkage: At the beginning, it is reassuring to operate in combination with traditional surveying equipment and methods, checking error tendencies by comparing measurements obtained by LRTK and those from a total station. 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 has high compatibility with existing operations, but preparing operational workflows in advance will help avoid confusion on site.

• Provision of compatible devices: To run AR apps and point cloud measurement comfortably, provide the most capable devices possible. Generally, the latest iPhone or iPad 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 checking point cloud details, so use them according to the application.

Simple surveying realized by LRTK

One solution attracting attention for easily realizing AR as-built inspection is LRTK. LRTK is an innovative technology that turns a smartphone into a centimeter-level surveying instrument by attaching a small, high-precision RTK-GNSS antenna to the phone. Real-time kinematic (RTK) satellite positioning corrections reduce typical GPS errors of several meters down to a few centimeters (a few inches), enabling high-precision surveying with palm-sized equipment. Combined with the LiDAR scanner and high-performance cameras built into the latest smartphones, you can scan the surroundings to acquire 3D point cloud data and complete on-site volume calculations, embankment quantity measurements, and buried pipe depth checks. Acquired point clouds and photos are automatically shared to the cloud, allowing office staff to check as-built conditions in real time. No specialized equipment or complicated settings are required; positioning starts simply by attaching the device to a smartphone and launching the app.

Simple surveying with LRTK is currently being adopted across many sites. Aiming to be a "universal surveying instrument, one per person," this system, combined with its affordable pricing, has already sparked a quiet boom on many sites. If you have not yet tried high-precision positioning or AR inspection, this is a good opportunity to introduce LRTK. Once you experience the labor- and efficiency-saving benefits, you may find it hard to return to previous methods. By starting as-built management DX with smartphones, on-site productivity and quality assurance will continue to improve. If you have questions or would like information about products or introduction, please feel free to contact us. With LRTK simple surveying, bring your site forward into next-generation construction management.

FAQ

Q: What is AR as-built inspection? A: It is an as-built management method that displays drawings and design data as AR over the real site view and confirms on site if the constructed structures match the plans. By visualizing conventional as-built inspections, which used to be done with paper drawings and surveying instruments, on smartphones and other devices, real-time and intuitive quality confirmation becomes possible.

Q: What equipment and preparations are required to introduce AR as-built inspection? A: Basically, a smartphone or tablet capable of AR display and high-precision positioning, a compatible high-precision GNSS receiver, and a dedicated application are required. For example, attaching an RTK-GNSS device like LRTK to the latest iPhone or Android device enables centimeter-level positioning combined with AR technology for as-built inspections. In addition, having digitized design data such as drawings or BIM/CIM models is essential.

Q: On what types of works and sites can AR as-built inspection be utilized? A: It can be used across a wide range of sites from civil engineering to building construction. It is particularly effective in civil works where dimensional management of as-built conditions is important, such as road construction and river maintenance, and in situations like embankment/cut thickness management and pavement thickness checks. It is also being used for depth and slope checks in buried utilities such as sewer systems, and in construction for positioning foundations and steel frames. AR technology is being applied across construction management, not only for outdoor surveying but also for indoor space as-built checks and equipment installation work.

Q: Is measurement accuracy sufficient? A: Yes. Positioning with high-precision GPS (RTK-GNSS) keeps errors within a few centimeters (a few inches), meeting the measurement accuracy required for as-built management. A GNSS receiver attached to a smartphone receives correction information based on control points and accurately overlays 3D models and point clouds on site coordinates. Validation in accordance with the Ministry of Land, Infrastructure, Transport and Tourism’s guidelines has been conducted, confirming the effectiveness of AR-based as-built inspection methods.

Q: How much does introduction cost? A: Introduction costs are significantly lower than those for traditional surveying equipment. By utilizing a commercially available modern smartphone and adding a small GNSS device, the initial cost is roughly equivalent to one high-precision GPS receiver and is very affordable. Subscription plans are also available instead of purchase, enabling low-cost operation for only the required period. Specific pricing depends on the feature set, but it is generally at a level where supplying one device per person still yields favorable cost-effectiveness.

Q: Does it comply with Ministry of Land, Infrastructure, Transport and Tourism standards? A: Yes. Acquired point cloud data and the results of comparisons with drawings can be output and submitted in formats compliant with the ministry’s as-built management guidelines. In fact, the ministry’s guidelines include language stating that when as-built measurement results are projected on site by AR for pass/fail judgment, submission of conventional as-built management forms may be unnecessary, and AR-based as-built management methods are increasingly being officially recognized. Thus, introducing AR inspections on site can be smoothly integrated into official inspection workflows.