Table of Contents

• What is As-built AR Check?

• Challenges of Traditional As-built Management

• On-site Use of AR Technology: Instant Checks through Visualization

• Benefits of Implementing As-built AR Check

• Key Points for Implementation

• Simplified Surveying Achieved with LRTK

• FAQ

What is an as-built AR check?

Comparing as-built structures on a construction site against drawings to check "Is it really built according to the design?" is a routine task for any technician involved in construction management. However, in recent years the technology that is changing this conventional practice is AR (Augmented Reality). By simply holding up a smartphone or tablet, design drawings and 3D models can be overlaid onto the real scene at actual size, allowing you to intuitively verify on the spot whether the constructed elements match the plan. This dramatically improves the speed and certainty of on-site quality checks and strongly supports the DX (digital transformation) of construction management.

そもそも *as-built management* とは、土木・建築工事で完成した構造物や地形がdesigned shapes and dimensions specified in the drawingsに仕上がっているかを測定して確認する品質保証プロセスです。施工途中や完了後に所定の測点で高さ・厚み・勾配などを計測し、設計値との誤差を調べて合否判定を行います。従来はレベルやトータルステーション等を用いて高さや厚みを測り、事務所に持ち帰って図面上で照合するのが一般的でした。その場で確認できず手間と時間がかかる作業でしたが、こうした課題を解決する次世代の手法として注目されているのが as-built AR check です。AR技術を出来形管理に応用し、digitally "visualize" construction results on site and immediately check the as-built statusするこの手法は、国土交通省主導のi-Construction施策の流れも受けて近年一気に実用段階に入ってきました。高性能カメラやLiDARセンサーを搭載した最新のスマホが普及したことで日常業務にARを活用できる環境が整い、今や出来形管理でもARが活躍する時代になったのです。

Challenges of Conventional As-built Management

As-built management is an indispensable process for ensuring quality, but conventional methods have involved many inefficiencies. Below, we outline the main issues.

• Length of work time: Because staff painstakingly measured at each survey point using leveling instruments and total stations, it required enormous time when the site was large or there were many survey points. It was not uncommon for it to take several days from bringing the measurement results back and compiling them into drawings to determine pass/fail.

• Dependence on manpower and skilled technicians: Accurate measurement and evaluation require experienced technicians such as surveyors, and two-person teams are frequently required. With severe labor shortages and an aging technician workforce, ensuring quality with limited personnel became a major burden.

• Expensive equipment costs: To measure with high precision at the millimeter level (0.04 in), specialized equipment such as total stations (TS) and RTK-GNSS receivers are indispensable, but these require an initial investment on the order of several million yen. There are also maintenance costs and theft risks for the equipment, making adoption a high hurdle for small and medium-sized enterprises.

• Measurement errors and recording mistakes: In predominantly manual surveying, small cumulative errors often occur, and there is a risk of human error when transcribing figures noted on site into drawings. There was also a risk that errors would be discovered later, requiring re-measurement and rework.

• Time-consuming report preparation: Preparing as-built drawings and reports based on measurement results and submitting them to the client was also a major burden for site personnel. Time spent organizing photos and plotting on drawings sometimes meant that the data obtained on site could not be fully utilized for quality analysis.

• Delayed discovery of defects: Even when there were construction defects such as insufficient thickness or improper slope, they were often not noticed on site immediately; after bringing the data back and drawing it up, they would become apparent the next day or later. By the time the problem was noticed, the concrete had often already hardened or heavy machinery had been withdrawn, resulting in extra work and costs due to rework.

As described above, conventional as-built management methods were beset by problems such as lack of immediacy and a heavy burden in terms of manpower and costs. It goes without saying that a new approach capable of accurately and intuitively capturing as-built conditions in real time was needed.

On-site Use of AR Technology: Real-time Checks through Visualization

So, how can AR technology actually be used on-site? The as-built verification work that was previously carried out on drawings can be performed by overlaying digital information and directly "visualizing" it on-site, allowing immediate checks to be made on the spot. For example, the following use cases can be cited.

• AR overlay of design models: You can overlay 3D design data for buildings and civil structures (such as BIM/CIM models) onto the site scenery to intuitively check the placement and dimensions of structures on the spot. It is also possible, through the camera, to compare whether columns or walls under construction have shifted from their design positions. Discrepancies with the finished image that are difficult to grasp from paper drawings or numerical data alone can be immediately understood in AR as life-size visuals.

• Heatmap display of as-built deviations: Use is also beginning where 3D as-built data (such as point clouds) acquired after construction are compared with design data and confirmed on-site as a color-coded heatmap showing deviations. If you download a heatmap automatically generated in the cloud by comparing the design model and the as-built point cloud to your smartphone and overlay it on the camera view, it becomes immediately obvious which areas are higher/lower than the design. For example, it is useful for speeding up the PDCA cycle by allowing area-based evaluation of embankment or pavement thickness finishes and immediate correction of defective areas.

• AR visualization of buried utilities: The positions of structures and pipes buried underground can be displayed in AR as if seen through the ground for verification even after backfilling. For example, in sewer pipe work, by scanning the pipe with a smartphone before burial and saving point cloud data with positional information to the cloud, anyone can understand the pipe’s route and depth through the smartphone screen even after backfilling. Because you can immediately identify buried items on-site without marking the ground or carrying drawings as before, it also helps prevent construction mistakes and ensures safety.

• Other applications: Beyond the above, AR can be used to guide operators by displaying construction extents and height references during heavy equipment operation, or to virtually mark concrete pouring locations in advance. In training and education, AR that reproduces the site is also attracting attention as a tool for safety training and for supporting mastery of work procedures. Applications are expanding, but in particular as-built management × AR is being seen by the field as a use case that tends to deliver benefits immediately after introduction.

Benefits of Introducing As-Built AR Checks

How will introducing AR-based as-built checks resolve the above issues? Here are the main benefits.

• Real-time verification and rapid rework: Because as-built conditions can be checked on-site immediately, there is no time lag from measurement to pass/fail judgment. If defects are found, corrective measures can be taken instantly, minimizing rework. There are even reported dramatic time-reduction cases where surveys that used to take half a day to complete are finished in 5 minutes of actual working time.

• Promotion of efficiency and labor-saving: With a smartphone and AR, surveying and inspection can be performed by a single person, dramatically improving the efficiency of the entire team. Tasks that used to rely on veteran experience and intuition can be replaced by technology, enabling anyone to carry out efficient, high-quality construction management. The ability to achieve both labor savings and quality assurance amid chronic labor shortages is a major advantage.

• Cost reduction: There's no need to purchase expensive surveying equipment, and it's attractive that the system can be introduced with an affordable initial investment of a smartphone and compact devices. Furthermore, reductions in rework can shorten schedules and reduce labor costs. In many cases, providing one device per person still fits within budget, making this a cost-effective solution.

• Improved accuracy and reliability: Centimeter-level accuracy (half-inch accuracy) positioning using RTK-GNSS and high-resolution point cloud measurements dramatically increase the reliability of as-built data. Measurements are automatically saved to the cloud and can be output and utilized in a format 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 inspection documents can also be fully ensured.

• Data utilization and streamlined record keeping: Measurement data and site photos are saved and shared to the cloud on the spot, eliminating the need to later transcribe them onto drawings. Point cloud data and coordinate information can be exported to common, business-friendly formats such as CSV, SIMA, and LAS, and can be smoothly imported into existing CAD software and GIS systems. Past data can also be easily searched and referenced in the cloud, significantly improving the efficiency and accuracy of record management compared with paper field notebooks.

• Improved safety: Because measurements can be taken remotely without entering hazardous areas, it also contributes to improving safety. For example, even when surveying steep slopes, using AR from below to check heights can reduce risk. Displaying buried utilities in AR also lowers the risk of accidentally damaging pipes or cables during excavation. In this way, AR use brings major benefits not only to work efficiency but also to on-site safety.

Points to consider when introducing

When introducing a new as-built AR check, it is advisable to keep the following points in mind to maximize its effectiveness.

• Phased introduction and in-house training: AR-based surveying and checking can be operated intuitively, but during the initial rollout it is smoother to conduct basic operation training internally and establish usage rules. Deciding in advance on file naming conventions for acquired data and sharing procedures can prevent confusion during operations. Start with a small pilot group to verify accuracy and effectiveness, then roll out company-wide in stages—that is the key to success. When using the equipment for the first time, measures such as verifying errors at known points to deepen understanding of the devices can also be effective.

• Combining with existing methods and data integration: At the initial stage, use conventional surveying instruments and methods in parallel, and cross-check measurements obtained with LRTK against those from total stations to identify error trends for reassurance. It is also important to pre-test 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 will enable smooth use on site.

• Provisioning compatible devices: To run AR apps and point cloud measurements smoothly, prepare devices with as high performance as possible. Generally, the latest iPhone and 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 also suitable for inspecting point cloud details, so use them according to your needs.

Simple surveying enabled by LRTK

A solution drawing attention for easily enabling such as-built AR checks is LRTK (pronounced "L-R-T-K"). LRTK is an innovative technology that transforms a smartphone into a surveying instrument with centimeter-level accuracy (cm level accuracy (half-inch accuracy)) by attaching a compact, high-precision RTK-GNSS antenna to the smartphone. Using real-time kinematic (RTK) satellite positioning corrections to reduce GPS errors that were typically several meters (several ft) down to just a few centimeters (a few in), anyone can perform high-precision surveying with palm-sized equipment. Combined with the LiDAR scanners and high-performance cameras built into the latest smartphones, simply scanning the surroundings obtains three-dimensional point cloud data, and on-site volume calculations and as-built embankment volume measurement and buried-pipe depth checks can be completed. The acquired point clouds and photo data are automatically shared to the cloud, allowing real-time verification of site as-built conditions from the office. It requires no specialized equipment or complicated setup; positioning starts simply by attaching the device to the smartphone and launching the app.

LRTK-based simplified surveying is currently being adopted at many sites. This system, aimed at being a "one-device-per-person, all-purpose surveying instrument", combined with its affordable pricing, has already sparked a quiet boom at numerous sites. If you have not yet tried high-precision positioning and AR checks, why not consider adopting LRTK now? Once you experience the labor-saving and efficiency benefits, you may find you cannot go back to the old ways. With smartphone-initiated DX for as-built management, on-site productivity and quality assurance will continue to improve.

For questions or consultations about product details or implementation, please feel free to [Contact us]. With LRTK's simple surveying, let's advance your site to next-generation construction management.

FAQ

Q: What is an As-built AR check? A: It is an as-built management method that displays drawings and design data as augmented reality over the actual site, allowing on-the-spot verification of whether the constructed structures match the plans. Whereas as-built inspections were traditionally carried out with paper drawings and surveying instruments, performing them by digitally visualizing that information on smartphones and the like enables real-time, intuitive quality confirmation.

Q: What equipment and preparations are necessary to implement as-built AR checks? A: Basically, you need a smartphone or tablet capable of AR display and positioning, a high-precision positioning device, and a compatible application. For example, attaching an RTK-GNSS receiver such as LRTK to a recent iPhone or Android device allows you to combine centimeter-level position information (cm level accuracy, half-inch accuracy) with AR functionality to perform as-built checks. In addition, preparing digitized design data such as design drawings and BIM/CIM models is indispensable.

Q: Can sufficient measurement accuracy be ensured? A: Yes — positioning with high-precision GPS (RTK-GNSS) can achieve errors within a few centimeters (a few cm; about 1–2 in), so it can meet the measurement accuracy required for as-built control. A GNSS receiver attached to a smartphone receives correction information based on reference points and accurately overlays 3D models and point clouds to site coordinates. In practice, validations conducted in accordance with the Ministry of Land, Infrastructure, Transport and Tourism guidelines have confirmed the effectiveness of AR-based as-built inspection methods.

Q: How much does implementation cost? A: Implementation costs are significantly lower than those of conventional surveying equipment. Because it only requires using a commercially available latest smartphone and adding a small GNSS device, the initial cost is roughly equivalent to one high-precision GPS receiver and is very reasonable. There are also subscription-based usage plans instead of purchase, so it is possible to operate at low cost for only the period you need. Specific pricing depends on the feature configuration, but it can be said that even deploying one device per person offers a sufficiently good cost-effectiveness.

Q: Does this comply with the Ministry of Land, Infrastructure, Transport and Tourism's standards? A: Yes. The acquired point cloud data and the results of matching to drawings can be output and submitted in a format that conforms to the Ministry of Land, Infrastructure, Transport and Tourism's prescribed as-built management guidelines. In fact, the ministry's guidelines include a clause stating, "If the results of as-built measurements are projected on-site using AR and used to make pass/fail determinations, submission of the conventional as-built management forms is not required," and as-built management methods using AR are becoming officially recognized. In this way, the environment is being prepared so that introducing AR checks on-site can be operated during inspections without issue.