Just hold up the drawings? How AR inspection makes as-built checks this simple

What if you could check the finished work on the spot simply by holding up paper drawings or a tablet at the site? Traditionally, as-built inspections required measuring dimensions with tapes or surveying instruments and later cross-checking them with drawings back at the office, but with the power of AR (augmented reality) technology those checks become astonishingly easy. In recent years, the construction and civil engineering fields have focused on “AR inspections” using smartphones and tablets, enabling intuitive, real-time verification of whether construction matches the design. This article explains what AR inspection is, how it differs from traditional methods, its benefits, and concrete use cases. Finally, we introduce a solution anyone can start with easily — simplified surveying using LRTK — and propose it as a first step toward DX of as-built checks.

Table of contents

• What is AR inspection

• Traditional as-built inspection and its challenges

• How AR inspection changes the field

• Benefits of AR inspection

• Start AR inspection with simplified surveying using LRTK

• FAQ

What is AR inspection

AR inspection is a new method of performing as-built verification at construction sites using augmented reality technology. Concretely, it overlays digital information such as design drawings or 3D models onto actual structures or terrain through the camera of a smartphone or tablet. Because the lines or models on the drawings appear to float on the real site, it is easy to intuitively grasp misalignments between the constructed object and the design.

For example, projecting design height and slope lines onto a paved surface with AR after paving lets you immediately judge whether the finish falls within tolerance. You can also hold up a smartphone before concrete pouring to check whether rebar placement matches the drawings, or compare the positions of walls or columns under construction with AR models to verify alignment. Tasks that used to require taking field measurements and later reconciling them with paper drawings can be done on the spot with AR, enabling inspection on-site in real time.

What makes AR inspection possible is recent advances in smartphone and tablet performance and positioning technologies. In addition to built-in cameras and gyroscopes, some models include LiDAR scanners, allowing stable recognition of physical space and reliable overlay of digital data. By combining these with high-precision GNSS (satellite positioning) receivers, you can align drawing data exactly to the site coordinate system. In other words, it is becoming possible to perform as-built inspection and surveying with just a smartphone, and AR inspection is putting that into practice.

Traditional as-built inspection and its challenges

First, let’s review the traditional procedures for as-built inspection (confirmation of post-construction shape and dimensions) and organize the challenges. In public works and similar projects, as-built management results directly affect quality acceptance, so strict measurement and record-keeping have long been required. But the process carried several inefficiencies and burdens that site staff all recognized.

• Time-consuming and labor-intensive: Measurements typically required two people using total stations (TS), auto levels, tape measures, etc., to painstakingly measure heights and thicknesses at each point. For wide areas or many measurement points, the work could take several days. Because measured values were noted, taken back to the office, and then compared with drawings to determine acceptance, there was often a time lag before problems were discovered, causing rework.

• Dependence on personnel and skilled technicians: Accurate as-built inspection required experienced surveyors. With labor shortages and aging technicians, it isn’t easy to assign enough personnel to each site. High-precision measurement especially needs specialized know-how, leading to knowledge concentration where “only this person can do it.”

• High equipment costs: Millimeter-level accuracy requires high-performance TS or RTK-GNSS receivers and other dedicated equipment, and initial investment can reach millions of yen. For small and medium contractors this is a high hurdle, and costs for transportation, maintenance, and theft risk add further burden.

• Risk of errors and record mistakes: Manual surveying can accumulate cumulative errors, gradually skewing measured values from reality. Transcribing field notes to drawings also carries human error risk. If such mistakes go unnoticed in reporting, they can become serious quality problems and are a constant worry for site staff.

• Burden of report preparation: Measurement results must be compiled into as-built drawings, photo logs, and other reports. Organizing tables and photos with measured values is time-consuming and a major burden amid busy site management.

• Delayed problem discovery leading to rework: In the traditional flow, issues weren’t always apparent on-site; sometimes defects were noticed only after producing drawings later. For example, if a pavement thickness fell short of the standard and was only discovered the next day, the pavement may already have set, making rework costly and time-consuming. This lack of real-time capability led to missed defects and delayed corrections.

Given these challenges, sites increasingly asked, “Can we verify as-built conditions more quickly and efficiently?” With labor shortages and workstyle reforms, expectations for new technologies to reduce labor and improve productivity grew. One such solution that emerged was the use of AR technology described above.

How AR inspection changes the field

Incorporating AR into as-built inspection enables visualization and immediate checks on-site that overturn conventional assumptions. By overlaying checks previously done on paper or a computer screen onto the real world, the following use cases have emerged.

• On-the-spot overlay of design data: 3D design models (BIM/CIM) or 2D drawing data for buildings, bridges, roads, etc., can be displayed in real time over live camera footage. For example, you can AR-display a planned structure model on an empty lot to confirm position before construction, or compare a pillar under construction with its design position on the spot. Misalignments that were hard to grasp with paper drawings or traditional surveying become immediately obvious in space through AR.

• As-built difference heat maps: Efforts are underway to compare as-built 3D point cloud data or models acquired after construction with design data in the cloud and visualize deviations as color-coded heat maps. If you download such a heat map to your smartphone and overlay it via the camera, you can instantly see where the site is higher or lower than the design. In practice, some paving sites scanned the road surface, detected thickness-short areas on the spot, and performed additional paving or trimming the same day, achieving zero rework. Visualizing deviations with AR enables running PDCA on-site within the same day.

• See-through verification of buried objects: Things that become invisible after installation, like underground pipes or cables, can be “seen through” with AR. For example, in sewer pipe works, 3D scans of pipes saved to the cloud before backfilling let anyone hold up a smartphone after backfill and instantly know the route and depth of underground pipes. This can eliminate the need for post-installation marking and allows future maintenance to avoid excavation at the wrong spot using AR. Visualizing the invisible is a unique advantage of AR inspection.

• Efficient checks over wide or hazardous areas: For steep slopes or large-scale earthworks, using terrain models acquired by drones or LiDAR enables safe and rapid as-built management. Scanning slopes before and after work and comparing them can calculate volumes of collapse or fill in minutes. Displaying that data with AR allows all workers to share dangerous areas or verify anchor positions. Inspections that were difficult over wide areas or at height can be performed reliably and safely by combining AR with 3D data.

Thus, as-built management × AR is being applied in many on-site scenarios. It not only improves efficiency but also helps discover previously unseen issues early to raise quality, and smooths information sharing among stakeholders. Next, let’s summarize the concrete benefits AR inspection provides.

Benefits of AR inspection

Introducing AR into as-built checks produces many benefits that traditional methods could not provide. Key points are summarized below.

• Discover problems on the spot: You can immediately detect construction defects or deviations from the design and take corrective measures right away. For example, AR can color-code areas with insufficient pavement thickness immediately after construction so additional paving can be done the same day. Real-time inspection minimizes rework and reduces the risk of leaving quality defects unaddressed.

• Shorter work time and labor savings: Point-by-point measurements are replaced by intuitive checks where you simply hold up a smartphone or tablet. Because you can view a wide area at once, inspections that used to take days are dramatically accelerated. One person can measure and verify, reducing staffing needs and saving labor.

• Anyone can do it without relying on skills: AR app operation is simple; following on-screen prompts completes the inspection. Even inexperienced workers can handle measurements and checks, preventing knowledge concentration and serving as a countermeasure to labor shortages.

• Cost reduction: AR using smartphones or tablets eliminates the need to newly purchase expensive TS or dedicated GNSS equipment. By combining existing mobile devices with relatively inexpensive GNSS receivers, you can build a positioning environment with centimeter-level accuracy (cm level accuracy (half-inch accuracy)). Transportation and maintenance costs are also reduced, leading to overall cost savings.

• Improved accuracy and reliability: Combining high-precision positioning techniques such as GNSS RTK corrections yields positioning accuracy in the range of a few centimeters in plane and elevation, consistent with public coordinate systems. Comparing digital data reduces human errors and eliminates concerns about missing records. Proper operation can achieve more reliable as-built verification than traditional methods.

• Efficient recording and reporting: Screenshots of AR views and difference heat map images can be used directly in reports, creating more intuitive and understandable documents than numerical-only reports. Data stored in the cloud makes later rechecks by different personnel easy. Ministry of Land, Infrastructure, Transport and Tourism field demonstrations confirmed that AR could simplify submitted documents, so AR is expected to reduce the burden of record-keeping.

• Improved consensus-building and communication: AR visualization is effective for information sharing among site staff and with clients. Viewing completion images and inspection results together on a tablet reduces miscommunication and smooths consensus-building. Sharing on-site AR footage with remote supervisors to obtain instructions is also easy, speeding decision-making.

In summary, AR inspection has the potential to improve both efficiency and quality simultaneously. Of course, actual operation requires attention to precision management and data preparation (addressed in the FAQ), but even accounting for that, the benefits for sites are substantial.

Start AR inspection with simplified surveying using LRTK

Finally, we introduce LRTK as a noteworthy solution for easily and highly accurately implementing AR as-built checks. LRTK is an innovative tool that enables centimeter-class positioning in real time simply by attaching an ultra-compact high-precision GNSS receiver to a smartphone. Surveying work that traditionally required specialized equipment and skilled operators is designed to be completed with one smartphone and one person when using LRTK.

Connect an LRTK device to a smartphone or tablet via Bluetooth and launch the dedicated app, and RTK corrections are applied to satellite positioning signals, enabling position measurement with an accuracy on the order of centimeters (cm level accuracy (half-inch accuracy)). It supports Japan’s Quasi-Zenith Satellite System “Michibiki” centimeter-class augmentation service (CLAS), so even in mountainous sites without mobile communication you can receive corrections directly from satellites and maintain high precision. In other words, even without veteran surveyors, you can perform everything from reference point surveying to as-built inspection by simply holding up a smartphone.

LRTK also integrates seamlessly with AR functions. Using high-precision GNSS position data to accurately overlay design drawings or 3D models on the actual view eliminates cumbersome alignment work. For example, walking a site with a tablet in hand can accurately indicate virtual stake positions or reference lines on the actual ground, allowing you to visually identify targeted points even at a distance. You can also automatically overlay and compare acquired point cloud data with design models in the LRTK cloud, enabling anyone to quickly check whether construction matches the plan without specialized knowledge.

LRTK provides cloud services so that measured and scanned data from the site can be shared instantly. Team members can view site 3D point clouds and measurement point information in real time from the office, reviewing inspection results and issuing instructions remotely. You can perform distance, area, and volume calculations in the cloud, or display geotagged site photos in lists — functioning as a platform that connects the site and the office. This dramatically improves as-built inspection efficiency and smooths team decision-making based on data.

Moreover, LRTK offers features beyond as-built management, such as single-person stake placement navigation (coordinate guidance), instant calculation of fill volumes from LiDAR point clouds, and cloud storage of georeferenced photos. In short, it enables processes that formerly required multiple devices and procedures — surveying, as-built inspection, and record-keeping — to be completed with one iPhone/Android device. Acquired data can be organized and output in formats compliant with the Ministry of Land, Infrastructure, Transport and Tourism’s as-built management procedures, and many construction companies are adopting LRTK to address labor shortages while improving quality.

By using such smartphone surveying + AR systems, anyone can easily perform high-precision AR inspection and overcome many of the traditional constraints in surveying and inspection. Even sites that had to rely on veterans can expect reduced work time, fewer human errors, and enhanced information sharing among stakeholders with a “one device per person” smart surveying tool. These innovations strongly support DX on construction sites and are changing as-built management itself. The key to successful AR inspection is to incorporate these advanced tools and improve productivity across the entire site. Why not start simple checks by “just holding up the drawings” at a familiar site and let the latest technology be your ally?

FAQ

Q: What do I need to start AR inspection? A: Basically, you need an AR-capable smartphone or tablet, a high-precision GNSS receiver to improve measurement accuracy, and an AR surveying app that supports them. The latest iPhone and Android devices have high camera and sensor performance suitable for AR. If centimeter-level accuracy is required, pair a small Bluetooth GNSS rover for RTK positioning (for example, smartphone-mountable LRTK devices). Also prepare design data for comparison (2D drawings or BIM/CIM 3D models) and as-built point cloud data, etc. With these set up you can try AR inspection on-site immediately.

Q: Is AR-based as-built checking accurate enough to trust? A: Yes—when properly operated, high accuracy and reliability can be achieved. Systems using GNSS RTK corrections can realize positioning accuracy on the order of a few centimeters in plane and elevation, which is within the typical accuracy requirements for as-built inspection. AR difference visualizations, such as heat maps, can provide quantitative visual information like “which point is how many cm higher/lower.” However, ensuring accuracy requires aligning with site reference points beforehand and, where necessary, verifying key points with traditional methods. Initially comparing AR results with conventional measurements at important points helps build confidence in AR inspection.

Q: Can AR inspection be used at sites without a 3D design model? A: Even without a 3D model, AR can be used with some ingenuity. Some apps overlay 2D CAD drawings in AR to visualize key lines on site. If the final shape is relatively simple, you can mark major dimensions on site before work and then compare them with AR images. However, AR inspection shows its true value with 3D models. More public projects are providing CIM/3D data, so consider requesting 3D data from the client or creating simple models in-house. If your goal is to compare measured point clouds with the design, you can also detect differences in point-cloud processing software without relying on AR display. The purpose is intuitive on-site confirmation, so choose the optimal method according to model availability.

Q: Are AR inspection results recognized as official inspection records? A: Currently, operations that rely solely on AR as the only basis for official inspection are just beginning, but acceptance is gradually growing. The Ministry of Land, Infrastructure, Transport and Tourism conducted field demonstrations in FY2023 and confirmed that AR technology can allow partial omission of as-built documentation. For the time being, conventional records (measurement drawings, photo logs) are often still required in parallel, but as guidelines develop, completing inspections solely with AR may not be far off. It’s important to introduce AR in the field, accumulate evidence and data, and promote understanding among clients through technical proposals so that AR may be widely accepted as official records in the future.

Q: Is specialized training required? Can older site staff handle it? A: Compared with traditional surveying equipment, AR inspection systems are intuitive, but brief training reduces on-site confusion. Learning app operation, basics of RTK positioning, and key cautions in advance enables smooth introduction. There are cases where site supervisors mastered the system after a few hours of training and trial use. Older experienced staff may initially resist, but the best approach is to demonstrate the benefits so they can experience them. Concrete results — for example, inspections that used to take half a day now finishing in 30 minutes, or AR catching mistakes missed on paper — help change attitudes. By blending old and new knowledge and providing support so everyone can use the tools, adoption is feasible. Start with a small pilot area and gradually expand to the whole site to ensure smooth implementation.