On-site Inspections Evolving with AR Construction: Improved Accuracy and Efficiency

Table of Contents

• What are on-site inspections using AR?

• Challenges of traditional on-site inspections

• Accuracy improvements in on-site inspections through AR

• Efficiency improvements in on-site inspections through AR

• Simple surveying enabled by LRTK

• FAQ

What are on-site inspections using AR?

Quality checks and as-built inspections (the work of confirming that finished work matches the design) at construction sites have traditionally been done by comparing drawings with the actual site, measuring dimensions with surveying instruments, and taking the data back to the office for pass/fail determination. This method, in which experienced technicians use paper drawings and tape measures or surveying instruments, requires experience and time and makes it difficult to get immediate results on site. However, in recent years, the technology that is drastically changing this conventional approach to on-site inspection is AR (Augmented Reality) technology.

With the term AR construction being heard more often, AR is making inroads into the construction industry. By displaying drawing data or 3D models overlaid on actual structures through a smartphone or tablet camera, it has become possible to digitally check construction results on site immediately. For example, by simply pointing a smartphone at the scene, you can overlay the expected 3D model onto the real view and intuitively check on the spot whether "columns or walls are displaced from their designed positions" or "finished elevations match the design." Deviations that were difficult to grasp from paper drawings and numbers alone can be visualized in life-size with AR, allowing even less experienced personnel to perceptually grasp differences.

The benefits of applying AR technology to on-site inspections mainly include dramatic improvements in inspection accuracy and efficiency. Below, we first organize the issues with the conventional approach and then look in detail at how AR usage improves accuracy and efficiency. With the momentum of the Ministry of Land, Infrastructure, Transport and Tourism–led “i-Construction” initiative, the digital transformation of construction management using AR has now reached a practical stage. The spread of modern smartphones equipped with high-performance cameras and LiDAR sensors is creating an environment where AR can be incorporated into daily work without special equipment.

Challenges of traditional on-site inspections

On-site as-built verification and quality inspections are indispensable processes, but the traditional methods had the following challenges:

• Long working hours: Staff measured each point painstakingly with levels or total stations and recorded the data. When the site was large or there were many measurement points, this took an enormous amount of time, and it was not uncommon for it to take several days from measuring to taking the results back to the office, comparing them with drawings, and making pass/fail judgments.

• Dependence on manpower and skilled technicians: High-precision measurement and judgment require experienced technicians such as surveyors, and two-person teams were often needed. With serious labor shortages and an aging workforce, ensuring quality with limited personnel became a major burden.

• High equipment costs: To measure with millimeter precision, high-precision surveying equipment such as total stations (TS) and RTK-GNSS receivers is indispensable, but these require 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 measurement is prone to accumulated minor errors and human mistakes when transcribing numbers noted on site into drawings. Discovering recording mistakes later can lead to re-measurement and rework.

• Burden of report creation: Creating drawings and inspection reports based on field measurements and submitting them to the client is also a heavy burden for site personnel. Organizing photos and plotting results on drawings takes time, and collected data is sometimes not fully utilized for quality improvement.

• Delayed discovery of defects: Even if there are construction defects such as insufficient concrete thickness or incorrect slopes, they are often not noticed on the spot; problems are detected only after taking data back and plotting it on drawings the next day or later. When rework becomes necessary, structures may already be completed or heavy machinery removed, causing additional man-hours and costs.

As described above, conventional on-site inspection methods suffered from a lack of immediacy and heavy burdens in terms of personnel and cost. A new method capable of grasping on-site as-built conditions in real time and with high accuracy was required.

Accuracy improvements in on-site inspections through AR

By utilizing AR technology, the accuracy (quality) of on-site inspections improves dramatically. The key point is that digital design information can be visually overlaid on actual construction, making it harder to miss subtle deviations or mistakes.

For example, in road or land development finishing inspections, you can scan the constructed surface with a smartphone LiDAR scanner to obtain 3D point cloud data, and by overlaying that point cloud with the design data in AR, vertical differences of several centimeters (a few inches) can be visualized as a color-coded heatmap. Because you can immediately see which points are how many centimeters higher or lower than the design, small depressions or slope defects that even experienced personnel might have overlooked can be reliably detected and corrected early. This enables inspections that do not miss even millimeter-level errors (millimeter-level errors (~0.04 in)).

Also, visual checks using AR greatly reduce human error compared with traditional methods that rely on the human eye and manual work. Because camera images and drawing information are overlaid and “seen” for judgment, misreading numbers and recording mistakes are reduced, and evaluation against the same standards becomes easier for anyone. AR is also powerful for improving inspection accuracy of buried elements and parts that will be hidden after completion. If underground pipes or rebar locations scanned in advance are displayed as a透視 model in AR, their precise positions can be confirmed even after backfilling. For example, when burying a sewer pipe, if the position and depth are recorded in 3D before burial, you can still understand the pipe’s alignment and depth on the smartphone screen after paving, preventing accidental excavation in later stages. This kind of visualization through AR captures subtle deviations and hidden anomalies that were often overlooked, dramatically improving on-site inspection accuracy.

Efficiency improvements in on-site inspections through AR

AR not only improves accuracy but also transforms the work efficiency (productivity) of on-site inspections. Digital technology can automate and speed up measurement and judgment processes, enabling inspections that are much faster and less labor-intensive than before.

A major efficiency gain is the ability to perform real-time measurement and immediate judgment. Because you can perform 3D measurement over a wide area and automatically analyze the results on site to determine pass/fail, there is no need to measure each point manually and take the numbers back for verification. For example, there are reports that slope finishing inspections that used to take half a day were completed in tens of minutes using drone photogrammetry plus AR judgment, and that pavement thickness checks using smartphone AR produced results within just five minutes from the start of work. By significantly shortening inspection time, you can move to the next stage sooner, directly contributing to shorter schedules and cost reductions.

The effects of reduced manpower and skill leveling should not be overlooked. With just a smartphone and an AR app, one person can perform surveying and inspection, enabling tasks that used to require two-person teams to be handled solo. Tasks that relied on veterans’ intuition and experience are supported by digital tools, allowing anyone to perform inspections efficiently and to a consistent quality standard. This is a major advantage for coping with chronic labor shortages while maintaining or improving inspection capabilities without increasing personnel.

Furthermore, AR improves the efficiency of data recording and reporting. Measurement results and site photos can be saved and shared to the cloud immediately, automatically digitizing the data on site. This reduces the time spent transcribing to drawings or creating reports back in the office, greatly cutting the time spent on record-keeping. Obtained point cloud data and coordinate information can be exported in CSV or CAD-compatible formats, making it easy to import into existing drawing software and construction management systems. Replacing paper field notebooks with cloud data makes searching past data and reuse straightforward, and enables real-time information sharing.

Finally, improved safety also contributes to efficiency gains. Using AR, you can measure and check conditions remotely without climbing dangerous heights or slopes, balancing worker safety with efficiency. For example, survey work on steep slopes can be carried out from a safe distance while confirming heights and slopes via AR display, avoiding unnecessary risk. Visualizing buried elements in AR reduces the risk of accidentally damaging underground pipes or cables during excavation. Fewer accidents and troubles mean fewer unnecessary interruptions and reworks, which ultimately leads to improved productivity across the construction process.

Through the introduction of AR technology, on-site inspections can be performed “faster, with fewer people, and reliably.” Once you experience the benefits in both accuracy and efficiency, you may find it difficult to return to the conventional approach.

Simple surveying enabled by LRTK

That said, some may think, “Doesn’t using AR on site require specialized and expensive equipment?” In fact, there are solutions today that enable these high-precision AR on-site inspections using just one smartphone. This is LRTK (L-R-T-K). LRTK is a revolutionary system that turns a smartphone into a centimeter-class surveying device by attaching a small high-precision GNSS antenna to the phone and using real-time kinematic (RTK) techniques to improve GPS positioning—which normally has errors of several meters—to centimeter-level accuracy. When combined with the LiDAR scanner and high-performance cameras found on the latest iPhones and Android devices, you can obtain high-detail 3D point clouds simply by scanning the surroundings with your phone, and perform volume calculations on the spot, compute as-built earthwork volumes, check the depth of buried pipes, and complete such tasks on site. The acquired positioning data, point clouds, and photos are automatically shared to the cloud, allowing you to monitor site conditions in real time from the office. There is no complicated equipment setup or operation: attach the device to your smartphone, launch the dedicated app, and positioning and AR display start immediately—this ease of use is a major attraction.

This simple surveying with LRTK is currently spreading across many construction and civil engineering sites. Developed with the aim of a “one device per person universal surveying instrument,” this system is a cost-effective solution that lowers initial implementation costs dramatically compared with traditional equipment, and its ease and cost-effectiveness are quietly creating a boom on sites. If you have not yet experienced AR on-site inspections using high-precision GNSS, this is a perfect opportunity to introduce LRTK. Next-generation surveying and inspection starting with a smartphone will raise on-site productivity and quality assurance to unprecedented levels.

FAQ

Q: What exactly do on-site inspections using AR involve? A: It is a method of displaying drawings or 3D models on a smartphone or tablet screen and overlaying them on the actual site images to check whether constructed structures match the design. By comparing finished work with digital information on the spot—something that was previously done with paper drawings and surveying instruments—AR technology dramatically improves accuracy and speed by enabling real-time, intuitive inspections.

Q: What equipment and preparations are required to use AR? A: Basically, you can get started if you have a device capable of AR display and high-precision positioning and a compatible app. Specifically, in addition to a modern smartphone or tablet, you need a centimeter-class GNSS receiver (for example, a smartphone-mounted LRTK device) and a surveying AR application that supports that device. You also need digitalized design data such as drawings or BIM/CIM models for overlay.

Q: Is the measurement accuracy really sufficient? A: Yes—if operated properly, it can sufficiently meet the accuracy required for on-site inspections. By performing corrected positioning with high-precision RTK-GNSS, position errors are generally within a few centimeters. A GNSS receiver attached to the smartphone receives correction information from a reference station and corrects the current location in real time, so the 3D models and point cloud data displayed in AR align with the actual construction with minimal offset. Accuracy verification based on the Ministry of Land, Infrastructure, Transport and Tourism’s as-built management procedures (inspection standards) has also been conducted, and the effectiveness of AR-based as-built inspection methods has been confirmed officially.

Q: How much does implementation cost? A: Compared with traditional high-precision surveying equipment, the implementation cost for AR on-site inspection is substantially lower. By utilizing commercial smartphones or tablets and adding a small GNSS device, the initial cost is far less than procuring a full set of expensive surveying instruments, making it a cost-effective investment. There are also subscription-based plans that allow flexible, low-cost usage for the required period. Specific costs depend on the intended use and the number of units, but the return on investment is becoming achievable even when equipping one device per person.

Q: Are AR-based inspection methods officially recognized? A: Yes. Under the momentum of i-Construction promoted by the Ministry of Land, Infrastructure, Transport and Tourism, inspection methods utilizing AR and 3D data are gradually being formalized. For example, the ministry’s guidelines include language such as “When as-built measurement results are projected on-site using AR and used for pass/fail judgment, submission of conventional as-built management forms may be unnecessary.” In other words, under certain conditions, performing as-built management with AR can eliminate the need to submit previously required paperwork, and AR usage is increasingly being officially recognized. Acquired point cloud data and verification results can be output in formats that conform to the guidelines for submission, so adopting AR for on-site inspections can be integrated into existing inspection workflows without disruption.