Freeing Yourself from Paper Drawings: Start Digital Construction Management with AR As-Built Inspections

Table of Contents

• What is AR as-built inspection

• Benefits of AR as-built inspection

• Keys to successfully implementing AR as-built inspection on site

• Use cases of AR as-built inspection

• Challenges and countermeasures for AR as-built inspection adoption

• Simple surveying and AR as-built inspection enabled by LRTK

• Frequently asked questions

What is AR as-built inspection

Traditionally, as-built inspections in civil engineering and construction have commonly been performed using paper design drawings together with surveying instruments such as total stations (TS) and levels. The usual workflow is to measure the height and thickness of structures and terrain at points on site, then return to the office and compare those measurements with the drawings to determine whether the work conforms to the design. However, this method tends to introduce time lags between measurement and discovery of problems, causing rework. Accurate inspection and judgment also require experienced surveyors, and many tasks are done in two-person teams, making the process inefficient amid labor shortages and an aging workforce. Carrying paper drawings and checking detailed numbers is a substantial burden, and on-site personnel have long asked, “Isn’t there an easier way to confirm as-built conditions?”

Recently, AR (Augmented Reality) technology has attracted attention as a trump card for solving these issues. AR overlays three-dimensional digital information (models or drawing data) onto live images of the real world. With improvements in smartphone and tablet performance, AR can now be used in everyday construction management without special equipment. Modern smartphones and tablets often include high-performance cameras and LiDAR sensors, and combining these sensors with dedicated AR apps allows intuitive as-built inspections on site. Instead of tracing numbers on paper plans, design data can be superimposed on the actual view, enabling site personnel to “visualize” the finished condition on the spot. As digitalization and DX advance across the construction industry, driven by initiatives like the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction (https://www.mlit.go.jp/tec/i-construction/), AR as-built inspection is increasingly expected to liberate sites from paper drawings and simultaneously improve efficiency and quality.

Benefits of AR as-built inspection

Introducing AR technology to as-built inspections yields many benefits that conventional methods could not provide. Key advantages include:

• Detect issues in real time: Construction defects or deviations from the design can be identified immediately on site, allowing instant corrective action. For example, in paving work, if you color-code areas on AR to indicate insufficient pavement thickness or incorrect slopes right after paving, additional work or corrections can be made the same day. Because the PDCA cycle can be closed on the same day for each inspection, rework is minimized and deterioration in quality due to postponed fixes is prevented.

• Reduce work time and labor: Inspection tasks that measured points one by one with paper drawings and surveying instruments are replaced by intuitively checking the whole by holding up a digital model in AR. Because a wide area can be visualized at once, inspections that used to take days can be greatly accelerated. Also, measurement and verification can be completed by a single person, reducing personnel coordination and labor.

• Address labor shortages: Site personnel themselves can check as-built conditions without relying on specialist surveyors or veteran technicians. AR app operation is simple, and anyone can complete survey tasks by following on-screen guidance. Because special skills are not required, AR prevents knowledge from becoming siloed and enables less experienced staff to conduct measurements and inspections.

• Cost reduction: AR using smartphones or tablets eliminates the need to newly purchase expensive TS or precision GNSS surveying equipment. Conventional surveying gear can require initial investments of several million yen in some cases, but recently it has become possible to set up a centimeter-level positioning environment at low cost by combining existing mobile devices with relatively inexpensive GNSS receivers. Maintenance and transport costs of equipment to the site can also be reduced.

• Improved accuracy and reliability: AR reduces the risk of human measurement errors and transcription mistakes. There is no need to copy numbers written on-site, and digital data can be compared directly, eliminating human error. Furthermore, when combined with high-precision positioning technologies such as RTK-GNSS, measurements can be at centimeter-level precision (cm level accuracy (half-inch accuracy)) in a public coordinate system, enabling more reliable as-built verification than before.

• Streamlined recording and reporting: AR enables inspection results to be recorded and shared as intuitive visuals. For example, attaching screenshots of the AR screen or differential heatmap images to inspection reports makes them far easier to understand than traditional reports that list numbers. In fact, Ministry of Land, Infrastructure, Transport and Tourism field demonstrations have confirmed that AR can simplify submission documents such as as-built drawings. Because history is retained as digital data, later verification is easy and reporting workload is reduced.

• Improved consensus-building and communication: AR visualization helps information sharing both inside and outside the construction site. For example, showing the client the completed image or as-built condition overlaid on the real object via a tablet makes explanations during inspection visits smoother. Visualizing as-built data on AR reduces discrepancies in understanding with the client and makes it easier to reach agreement on corrective areas on the spot. Reports also indicate that AR is beginning to be used not only for construction management but also for pre-construction resident briefings and meetings with subcontractors, contributing to smoother communication inside and outside the site.

Keys to successfully implementing AR as-built inspection on site

Even convenient AR as-built inspection requires several measures to become established and produce results on site. Addressing the following points during introduction will help integrate AR smoothly into on-site operations.

• Ensure high-precision alignment: Accurate alignment of digital information with the real world is essential for overlaying AR correctly. In large sites or long structures, slight positional shifts can cause significant errors. Use RTK positioning via GNSS or calibration using known points to always align the model and real space at centimeter-level (cm level accuracy (half-inch accuracy)). RTK-capable AR systems can project models in the correct location without placing physical markers in advance, enabling stable AR display that does not drift as you walk around.

• Prepare 3D design data: Performing AR as-built inspections requires 3D models of the design drawings (BIM/CIM data, etc.). If 3D data are not included in the contract documents, prepare comparable digital data by creating a simple model from 2D drawings or by LiDAR-scanning the existing conditions to obtain point cloud data. The Ministry’s push for CIM (Construction Information Modeling) is increasing the practice of creating 3D data from the design stage. As models become easier to obtain for many projects, it is important to get your organization used to handling 3D data early.

• Integrate into operational workflows: To make AR inspections part of standard site operations rather than a one-off demonstration, clearly define “when, who, and at what timing” to use AR. For example, incorporate steps such as “use AR for reinforcement inspection before concrete placement” or “confirm finish with AR at embankment completion” into construction plans and checklists. Also decide in advance how to record and reflect AR verification results in reports. For instance, set up a system that automatically appends date/time and location to AR screenshots and saves them to the cloud for use as inspection evidence. Embedding AR into existing quality control workflows helps it become an everyday tool for everyone on site.

• Train site staff: Eliminating resistance to new technology requires that site staff understand how to use AR and its benefits. Initially, have tech-savvy personnel lead small-scale AR inspections. Demonstrating actual use so staff can feel “anyone can measure by following on-screen instructions” is crucial. Modern AR apps are intuitive and can be learned in short training sessions without specialized knowledge. Share operation procedures through in-house training and on-the-job training, and present success stories so veterans also see the benefits, promoting smooth acceptance.

• Phased introduction and verification: Instead of rolling out AR across all sites and processes at once, start experimentally on a few sites or specific processes and verify effects and issues. For example, try AR measurements alongside conventional measurements in one zone, and collect data on efficiency improvements and reduction in missed defects compared to the traditional method. Sharing objective results (e.g., labor savings of ○% or reduction of △ defect corrections) makes it easier to gain acceptance from staff and management. Begin small to accumulate know-how, improve issues (such as device handling and accuracy verification procedures), and then scale company-wide. Preparing manuals and checklists based on demonstration data will smooth future deployment.

• Use cloud services: Cloud services that link with AR apps can automatically save and share measurement data, point cloud models, and photos captured on site. This enables real-time information sharing between the site and office and allows remote team members to check the as-built status shown on an AR screen. With everyone able to view and comment on the latest data in the cloud, instructions for corrections and requests for additional investigations can be issued quickly. Since data are accumulated in time series, they can be referenced in future projects or serve as evidence if problems arise. When introducing AR, leverage cloud connectivity as much as possible to centralize data management and facilitate smooth information sharing.

Use cases of AR as-built inspection

In practice, AR as-built inspections are beginning to be applied in various on-site scenarios. Here are some representative use cases.

• Confirming positions of rebar and structures: AR is effective for checking rebar placement before concrete placement and for verifying positional shifts of structures during construction. For example, instead of measuring with a scale while looking at paper drawings to check whether column rebar is misaligned, you can display a 3D rebar layout in AR on site to confirm counts and spacing. Overlaying the design model on the actual object makes subtle differences visible, enabling progress while maintaining accuracy. There are reports that early AR verification reduced rework and material waste.

• Pavement thickness and slope inspection: In road paving, combining AR with point cloud measurement enables wide-area as-built evaluation in a surface manner. Immediately after paving, you can scan the pavement with a smartphone LiDAR to obtain a dense point cloud, overlay it with the design 3D data, and generate a color-coded as-built heatmap on site. You can instantly determine whether pavement thickness across the entire section is within design tolerances and detect unevenness or insufficient thickness without omission. Because you can directly measure longitudinal slope and width on the acquired point cloud, inspections can be completed safely and quickly, and some sites have achieved zero rework later.

• Confirming buried utilities and hidden items: AR can “see through” and confirm objects such as pipes and cables buried underground that cannot be visually inspected after construction. For example, in sewer pipe works, scanning pipes in 3D before burial and saving accurate position and depth point cloud data to the cloud allows anyone to perceive underground pipe routes and depths later simply by pointing a smartphone. This eliminates the traditional need for marking buried positions and makes future maintenance excavations easier by avoiding buried items via AR display. The ability to visualize what cannot be seen is another major advantage of AR as-built inspection.

• Using slope and terrain models: For steep slope works or large-scale earthworks, combining 3D scanning and AR for as-built management enhances safety and efficiency. For example, scanning slopes with drones or LiDAR before construction to obtain a baseline terrain model and rescanning after construction (or after a disaster) allows immediate calculation of collapse areas or changes in embankment volume. Earthwork volume calculations that used to take days can be completed in minutes on site, aiding rapid recovery planning and as-built evaluation. Overlaying slope point cloud models in AR on the actual view enables all workers to intuitively share dangerous areas and anchor reinforcement locations. Combining 3D terrain and structural data with AR displays makes it possible to safely and reliably manage wide-area and high-elevation as-built conditions and detect deformations that were previously difficult to observe.

Challenges and countermeasures for AR as-built inspection adoption

AR-based as-built inspection offers many benefits, but there are points to consider when introducing and operating it on site. Below are major challenges and countermeasures.

• Concerns about accuracy: There are common concerns such as “Can AR really measure accurately?” Indeed, incorrect alignment prevents correct judgments, so accuracy management is a key issue. Countermeasures include combining GNSS RTK corrections and strict calibration with known points to minimize misalignment between digital models and the real world. Integrating GNSS rovers with AR allows you to spatially align design data perfectly with as-built conditions. Properly operated, various demonstrations have confirmed that inspections can be performed with measurement accuracy comparable to traditional surveying (errors within a few centimeters (cm level accuracy (half-inch accuracy))) for both horizontal and vertical. In the early stages of introduction, it is advisable to use conventional verification at key points in parallel to validate errors.

• Effort to prepare digital data: AR requires digital design information such as 3D models or point cloud data, and preparing these can be time-consuming. While some small- to medium-scale projects lack 3D data, you can LiDAR-scan the site to obtain as-built point clouds that serve as an impromptu 3D model. There are also apps that display simplified models of main lines and surfaces in AR if only 2D drawings are available. National guidelines are encouraging the shift to as-built management using 3D measurement technologies, so digital data will become increasingly available. Once models and point clouds are prepared, they also help subsequent process management and future maintenance, so view data preparation as an investment for the future.

• Adapting devices to site environments: Physical issues related to using smart devices on site must be addressed. For example, screens become hard to see and batteries drain quickly in hot, sunny weather, and devices need protection in rainy conditions. Countermeasures include sunshades for tablets, carrying mobile batteries, and using waterproof cases or splash covers. In dusty sites, clean the camera and sensor areas frequently. If holding a tablet for long periods is strenuous, use a neck-hanging holster to reduce burden. By adopting accessories and operating methods suited to site conditions, you can create an environment where devices can perform optimally and maximize AR benefits.

• Resistance from site staff: Psychological barriers to new technology cannot be ignored. Experienced veterans especially may prefer traditional manual methods. The most effective remedy is letting them experience AR and feel its benefits. For example, sharing concrete outcomes such as an inspection that used to take half a day now taking 30 minutes with AR, or catching previously missed rebar errors on the spot, can change attitudes. Tools like LRTK, which enable “anyone to survey easily alone,” often convert tasks that required two people into single-person operations and are welcomed on site. Start with younger employees using the tools and let their positive experiences spread; resistance will gradually diminish.

• Introduction cost and ROI: Introducing new equipment and software involves cost, but AR can reuse existing smartphones or tablets, so initial hardware investment is relatively low. Instead of buying expensive dedicated surveying machines, you typically need only GNSS receivers and software subscription fees, making it easy to get started. Considering quantitative benefits such as reduced rework and labor cost savings, ROI can be realized relatively quickly. If cost-effectiveness is a concern, introduce AR on a limited basis and demonstrate visible outcomes (e.g., labor reduced by ○%, defect corrections decreased by △ cases) to build an ROI case. Demonstrable results help persuade management and clients for further investment.

• Applicability to official inspections: Currently, guidelines may require conducting traditional measurements and document creation in parallel for as-built management. Some inspectors are cautious about accepting digital checks on a tablet alone for approval. However, the Ministry has already confirmed the effectiveness of using AR in as-built inspection field demonstrations, and AR-based labor-saving methods are expected to be incorporated into guidelines. Even now, using software that can automatically generate as-built documents from point clouds and photos obtained by AR can produce deliverables equivalent to manual work, so in practice AR measurement alone can be sufficient. It is important to explain AR-derived results appropriately to clients and inspectors to gain their understanding. For instance, showing an AR heatmap indicating “this location is ◯ cm higher/lower than the design” during an inspection provides more persuasive evidence than a table of numbers. As understanding of AR grows gradually in both public and private sectors, early adoption and accumulation of know-how will provide future advantages.

Simple surveying and AR as-built inspection enabled by LRTK

One solution attracting attention for making AR as-built inspection easier and more precise is “LRTK.” LRTK is a cutting-edge tool that achieves centimeter-level positioning by RTK (Real-Time Kinematic) simply by attaching a small high-precision GNSS receiver to a smartphone. It is a next-generation system that allows surveying work, which used to require specialized equipment and skilled operators, to be completed by one person. LRTK supports the CLAS augmentation signals of Michibiki—the Quasi-Zenith Satellite System in Japan—as well as network RTK, maintaining high precision even in mountainous areas outside communication coverage. In short, even without veteran surveyors on site, a smartphone alone can handle everything from reference-point surveying to as-built verification.

LRTK also integrates seamlessly with AR functions. Using high-precision GNSS position data, 2D/3D design data can be overlaid on site with perfect alignment, eliminating the cumbersome alignment work and preventing model drift. For example, simply walking the site with a tablet can accurately indicate virtual pile-driving positions from the design model on the actual ground. Target coordinates can be visually recognized instantly even from distant points, supporting efficient pile-driving operations. It is also possible to automatically overlay the acquired as-built point cloud with the design model in LRTK’s cloud and perform differential comparisons to check “whether construction conforms to the design” on the spot.

LRTK provides a cloud platform where various data measured and scanned on site are synchronized to the cloud in real time. Team members can immediately view 3D point clouds and measured-point information from office PCs and collaborate with remote specialists while verifying data. One-click operations such as measuring distances, areas, and volumes on the cloud or linking photos with geolocation for list display are available. This enables collaboration that transcends the boundaries between site and office and dramatically improves as-built inspection efficiency.

In addition to as-built management, LRTK offers diverse features such as a “coordinate navigation” function enabling one-person pile-positioning, a function to calculate embankment volumes from LiDAR-scanned point clouds, and cloud sharing of high-precision geotagged photos. In other words, LRTK is designed to let a single smartphone handle the whole sequence from surveying to verification, recording, and as-built inspection—tasks that formerly required multiple devices and personnel. Data obtained on site can be organized and output in formats compliant with the Ministry of Land, Infrastructure, Transport and Tourism’s as-built management specifications, and many construction companies have already adopted LRTK to achieve both labor savings and quality improvement.

Using a smartphone-surveying + AR system like LRTK makes high-precision as-built inspection easy and breaks various constraints related to surveying and inspection. Even on sites suffering labor shortages, “one device per person” smart surveying tools combined with AR can shorten work time, suppress human error, and improve communication. These technological innovations strongly support DX (digital transformation) in construction sites and are fundamentally changing as-built management. The key to successful AR as-built inspection is to incorporate such advanced tools effectively to improve overall site productivity. Take advantage of the latest technology to free your site from paper drawings and take the first step toward digital construction management.

Frequently asked questions

Q: What is needed to start AR as-built inspection? A: Basically, you need a smartphone or tablet capable of AR display, a GNSS receiver to improve positioning accuracy, and an AR surveying app that supports those devices. Modern iOS/Android devices have high-performance cameras and sensors suitable for AR. If centimeter-level precision is required, combine a small Bluetooth GNSS rover to perform RTK positioning (examples include LRTK devices that can attach to a smartphone). Also prepare the design-side 3D model data or as-built point cloud data for comparison. With these set up, you can immediately try AR as-built inspection on site.

Q: Can the accuracy of AR as-built inspection be trusted? A: Yes—if operated properly, AR can provide high accuracy and reliability. Systems using GNSS RTK corrections can achieve positioning accuracy on the order of a few centimeters in both horizontal and vertical dimensions, which falls within the typical error tolerances required for as-built verification. Even when checking differences in AR, heatmap displays and similar tools provide quantitative information such as “which point is how many centimeters higher/lower.” The important points are to properly align site reference points with the AR space in advance and to verify key points with conventional methods when necessary. With these precautions, AR inspection results can be trusted with sufficient justification.

Q: Can I confirm as-built conditions with AR at sites that don’t have 3D design models? A: Yes—AR can be used even without 3D models with some ingenuity. For example, apps exist that overlay 2D drawing data (DXF, etc.) in AR space so main lines and positions can be visualized on site. If the finished shape is relatively simple, you can also mark key dimensions on site before construction and overlay design information on photos in AR as a simple workaround. However, AR’s true value is best realized with 3D models. Increasingly, public works are creating 3D CIM models. Request data from the client or create a simple model internally—prepare 3D data as much as possible. If you only need to detect differences by comparing measured point cloud data with the design drawings, doing so in point cloud processing software without AR is also effective. The goal is to “intuitively confirm on site,” so choose the method that best fits whether a model exists.

Q: Can AR as-built inspection results be used for official inspections? A: Currently, using AR alone as the official record is still in early stages, but acceptance is gradually growing. The Ministry conducted field demonstrations in FY2023 and confirmed that AR technology can allow omission of some as-built document submissions. While many cases still require submission of traditional records (survey drawings or photo albums), submitting AR-verified content as supporting materials can help inspectors understand the results. For instance, displaying an AR heatmap that shows “this location is ◯ cm higher/lower than the design” during inspection is more immediately understandable than a list of numbers. In the future, AR data itself may be accepted as official deliverables, but for now it is prudent to use AR as corroborating evidence and perform traditional measurements when necessary.

Q: I’m worried whether everyone on site can master this technology. A: AR construction support tools are becoming increasingly user-friendly, and basic operations are not very difficult. Many adopting companies report that staff from junior to veteran can use AR after short training. If concerns remain, begin with demonstrations by staff already comfortable with the tools so others can observe and try. People become receptive when they see benefits firsthand—when they realize “it’s definitely faster” and “it’s convenient,” resistance fades. Recent AR apps also offer Japanese language support and good customer service, making assistance readily available when needed. Site ICT and DX will only accelerate, so steadily create an environment where everyone can use the tools.

Q: Is it necessary to use dedicated AR glasses? A: At present, smartphones and tablets are perfectly practical. AR-capable smart glasses (transparent goggles) are emerging, but they are very expensive and may be difficult to use with hard hats. Smartphones and tablets can be used on site in dustproof/waterproof cases and operated intuitively via touch. Device screen resolution and processing power improve year by year, so visibility and speed on handheld devices are already adequate for practical use. If glasses become lightweight and affordable in the future, their use may expand, but for now handheld devices are the most realistic and cost-effective option. Start with familiar smartphone AR, and consider future device expansion as needed.