Introduction

In building and social infrastructure inspections, infrared visual inspection has recently attracted attention as a non-destructive testing method. By visualizing surface temperature with an infrared camera (thermography), it is possible to detect deterioration and anomalies that are difficult to find with the naked eye—such as detached or delaminated exterior tiles, internal moisture, and abnormal heating of electrical equipment—over wide areas in a short time. Inspections can be conducted safely in high or hard-to-reach locations, and the need for scaffolding or hammer sounding tests can be reduced, which is another major benefit. Many building managers, maintenance contractors, and municipalities have begun adopting infrared visual inspection aiming for inspections with “no misses.” However, conventional methods still have issues in recording and locating findings.

This article organizes the principles of infrared visual inspection and the problems of conventional approaches, and explains how linking them with the smart inspection tool “LRTK” achieves higher precision and efficiency. By leveraging digital technologies such as 3D scanning, geotagged photos, AR navigation, and cloud integration, we specifically show how to dramatically improve the accuracy and reproducibility of inspection records and streamline reporting tasks. Finally, we discuss the potential for simple surveying and broader smart inspection applications using LRTK.

What is Infrared Visual Inspection

Infrared visual inspection is a non-destructive testing technique that photographs the surface temperature distribution of the target (such as building exteriors, structural members, or equipment enclosures) with an infrared thermography camera to infer internal anomalies. For example, if an exterior tile is detached from its substrate leaving a void, its daytime heat retention and nighttime cooling will differ from intact areas, causing that surface area to appear anomalously hotter or colder. Likewise, areas where rainwater has penetrated and dampened concrete, missing insulation, or thermal bridges (places where heat leaks through structural members) can be detected as temperature irregularities. For electrical equipment enclosures, loose or deteriorated wiring connections, overheating due to deterioration, and abnormal heating of motors or transformers can be detected via infrared. Because you can visualize invisible defects by “temperature,” infrared visual inspection offers the major advantage of enabling early detection of latent problems that would be missed by visual inspection or sounding.

Moreover, infrared diagnostics are non-contact and non-destructive and can cover wide areas at once, making them time-efficient. High exterior walls can be examined from the ground or a distance simply by pointing a camera, reducing the need for workers to approach and improving safety. The frequency of erecting scaffolding or using elevated work platforms for long periods can be reduced, minimizing impact on building users and the surrounding environment. Inspection results can also be stored as digital images, enabling long-term tracking of degradation trends for each building and serving as materials for repair planning. For these reasons, infrared visual inspection is spreading as a new standard for periodic inspections, contributing to building safety maintenance and asset value preservation.

On the other hand, infrared visual inspection has weaknesses. Results are easily influenced by environmental conditions at the time of shooting (temperature, solar radiation, wind, etc.), so adjusting shooting time and considering weather are essential for accurate diagnosis. There are also operational issues regarding how discovered anomalies are recorded and reported. The next section summarizes the main problems of conventional infrared visual inspection and the issues they cause in the field.

Problems in Conventional Infrared Visual Inspection

In conventional visual inspections using infrared cameras, the following issues have been pointed out:

• Locating and recording anomalies is cumbersome: It is not easy to determine later exactly where an anomaly captured on a thermographic image corresponds on the building. Typically, inspectors manually mark corresponding visible-light photos or drawings, but identifying a location such as “detachment located on the north face of Building XX, center of the 3rd floor, at ○ m from the …” across a large façade with repeating patterns is tedious and prone to recording errors or mistaken placement. Analog methods like photographing a blackboard or note with each shot to record date and location complicate later data organization.

• Risk of missed inspections: When a person conducts an inspection holding an infrared camera and visually scanning, there is inevitably a risk of oversight. For large buildings or bridges, if the shooting coverage isn’t made thorough, some parts may remain uninspected. Low camera resolution at height can miss fine details, and overlaps or gaps in visible coverage can occur. Relying on human intuition and experience for coverage can lead to situations where “one spot was accidentally missed without us noticing.”

• Utilization and reproducibility of recorded data: Even if infrared images and reports are prepared, it is not easy to use that data in the next inspection or quantitatively compare long-term changes. Conventional practice often involved noting anomaly locations only on paper reports or 2D drawings, making it time-consuming for another inspector to relocate the same spot later. Because the data is not linked with coordinate or quantitative information, comparisons such as “how large was the anomaly detected previously” or “which anomalies are newly appearing this time” must rely on subjective judgment. Despite non-destructive inspection, the results could not be fully utilized for long-term maintenance planning.

• Inefficiency in reporting work: Preparing post-inspection reports is also labor-intensive. Organizing a large number of infrared images, plotting each corresponding position on drawings, and creating photo ledgers require significant time and effort. Because field information is taken back to the office and manually compiled, there is a time lag from inspection to report submission, making prompt response to urgent anomalies difficult. Paper records or USB-based data management do not facilitate smooth information sharing among stakeholders, and valuable investigation results may not be fully utilized.

As described above, while infrared visual inspection itself is useful, operational challenges remain, such as “accurate recording of location,” “prevention of missed inspections,” “data reusability,” and “prompt reporting.” How can we solve these issues to achieve “zero misses” in precise inspections? One answer is transitioning to smart inspections that use digital technologies. Particularly noteworthy is the use of the compact device LRTK, which links with smartphones to acquire highly accurate location information.

What is the Smart Inspection Tool “LRTK”

LRTK is an ultra-compact, high-precision positioning device that attaches to and is used with a smartphone. Developed by a startup originating from the Tokyo Institute of Technology, this tool allows you to mount a receiver weighing approximately 150 g and with a thickness of about 1 cm (0.4 in) on your smartphone and achieve centimeter-level positioning accuracy (half-inch accuracy) using real-time kinematic correction technology (RTK) for satellite positioning (GPS, etc.). High-precision positioning that previously required specialized equipment costing millions of yen and skilled operators can now be handled easily with a smartphone + LRTK. Furthermore, LRTK is not just a positioning device; by integrating with various smartphone sensors and apps, it functions as an all-in-one smart inspection platform.

Specifically, using LRTK enables the following functions on a smartphone:

• High-precision position acquisition: Measuring any point on a building or bridge can record latitude, longitude, and height with about 1–2 cm (0.4–0.8 in) error. Ordinary smartphone GPS has an error of around 5 m (16.4 ft), making it unsuitable for precise location identification, but LRTK reduces error to the limit using RTK positioning with correction information. Accurate positioning is possible even on scaffolding or large sites. It also supports Japan’s quasi-zenith satellite high-precision positioning service (CLAS), enabling stable positioning even in areas where communication or satellite reception is unstable, such as mountainous regions or streets of high-rise buildings.

• 3D scanning (point cloud measurement): Combined with a smartphone’s LiDAR sensor or camera, you can acquire surrounding structural shapes as 3D point cloud data. By attaching LRTK-provided position coordinates to each point, the entire acquired point cloud model can be given accurate geographic coordinates. This allows anomalies detected by the infrared camera to be positioned and recorded on a 3D model of the entire building. Storing inspection results that were conventionally managed on flat drawings as a three-dimensional digital model for sharing is a major innovation.

• AR navigation and location guidance: It supports AR (augmented reality) functions that overlay digital information on real-world images through the smartphone screen. For example, AR display can guide a pre-set inspection route or shooting points so that you can巡回 without missing shots even on large structures. Besides preventing missed inspections, you can project markers for recorded anomalies to intuitively locate them on site. Even anomalies in high places can be indicated from a safe distance through the camera, allowing workers to verify locations remotely without approaching hazardous spots.

• Digital recording of photos and notes and cloud sharing: Photos taken with an LRTK-equipped smartphone are automatically tagged with shooting date and positioning coordinates (latitude and longitude). There is no need to photograph a paper note or blackboard; the digital data records “when,” “where,” and “what” at the moment of capture. Data can be uploaded to the cloud with one tap over the network, making it easy to share field inspection results with office stakeholders in real time. Even when multiple people inspect different locations simultaneously, data can be centrally managed in the cloud so everyone can check progress and anomaly details on the spot. Cloud data can be exported in formats such as CSV or drawing-attached reports, greatly reducing the work required to prepare deliverables.

As described above, LRTK combines “high-precision location information,” “3D digitization,” “AR support,” and “cloud integration” to provide an integrated solution that can complete workflows that previously required multiple devices and separate tasks with just one smartphone. Incorporating LRTK into infrared visual inspection dramatically improves inspection accuracy, recordability, and reproducibility. The next section details specific smart inspection methods that link infrared visual inspection with LRTK and the benefits they bring.

3D Scanning for Three-Dimensional Understanding of Anomalies

To record and share deterioration detected by an infrared camera with zero misses, it is effective to capture the entire structure in three dimensions. With LRTK, you can add high-precision position coordinates to point cloud data obtained by a smartphone’s LiDAR or photogrammetry and construct a digital 3D model of a building or equipment.

For example, if you scan the entire façade of a building with smartphone LiDAR, you can obtain an accurate 3D model that includes subtle surface undulations and structural details. Overlaying tile delamination or insulation-deficient areas identified in infrared images allows anomalies to be recorded with three-dimensional coordinates including height. Information such as “a delamination of width ◯ m (◯ ft) located ◯ m (◯ ft) from the center of the north face at the ◯-floor portion” can be plotted as point cloud data on the 3D model, making spatial relationships immediately apparent when reviewing later.

There are also advantages of 3D modeling from the perspective of preventing missed inspections. Since the point cloud is displayed in real time on the smartphone screen during scanning, you can confirm on the spot whether any areas were left unscanned. Even if something is missed, it appears as a missing part in the model, allowing immediate re-checking and additional shooting. Traditionally, managing coverage over wide inspections was difficult for people, but combining digital scanning enables comprehensive inspection of structure surfaces. As a result, not only does this lead to zero misses of anomalies, but having data for areas with no anomalies also provides evidence of “what was inspected and what was healthy.”

Moreover, the obtained high-precision 3D point cloud can be directly used for repair planning and quantity estimation. For example, you can accurately measure the area of detached tiles from the point cloud or visualize the distribution of degradation to prioritize repair work. Tasks that previously required applying a scale to calculate areas can be performed quickly on digital data, shortening lead time from inspection to countermeasure planning.

Geotagged Photos and Subject Positioning for Reliable Records

In LRTK- and smartphone-combined infrared inspections, all captured images are geotagged, eliminating record omissions and location mix-ups. Previously, infrared images and visible-light photos had to be matched to estimate “which part of the building this image corresponds to,” but photos taken with an LRTK-equipped smartphone automatically record latitude and longitude in the file. For example, if you find a crack during a bridge inspection, taking a photo with your smartphone on the spot will record “a crack at this height and orientation on the pier” with one tap. There is no need to spread drawings and mark them by hand; anomalies can be accurately managed in a digital ledger.

Especially in infrastructure inspections, it is common for another person to recheck the same spot later or to monitor progress over several years. With geotagged photographic records, you can re-identify the exact same point with high reproducibility. Comparing aging changes becomes possible not only by overlaying photos but also by quantitative analysis centered on position data. For example, you can determine time-series degradation such as “the crack recorded at X,Y coordinates last time has grown by ○ cm (○ in) this time.”

LRTK also includes a function called subject positioning that uses the camera to measure the position of distant objects. With this, you can obtain position coordinates remotely for anomalies located in inaccessible places. For instance, if an anomaly is detected by infrared in the upper stories of a high-rise, you can record its precise position from the ground by photographing that area with a smartphone, avoiding the need to climb up. This LRTK-linked capability secures data accuracy while reducing dangerous high-altitude work.

Preventing Missed Inspections with AR Navigation

A powerful ally in achieving zero misses is LRTK’s AR navigation function. In building and equipment inspections, less-experienced workers may hesitate about “which route to take to check without gaps.” By pre-setting inspection routes and checkpoints in the LRTK system and visualizing them with AR, anyone can巡回 efficiently and without omissions.

For example, in a building façade inspection, if you display a virtual grid or check markers over the actual wall on the smartphone screen and change their colors sequentially, unshot areas become immediately obvious. You can see in real time that “the ○-floor portion has been inspected, △ floor has not,” supporting gap-free inspection. For large bridges or tunnels, AR guidance makes it easy to manage progress by sections, eliminating human-error-related misses.

AR navigation also improves clarity in reporting. After inspection, when sharing results with stakeholders, you can indicate anomalies not only on 3D models or photos but by projecting them into the real-world view. For example, during an on-site survey, holding up a tablet can show exactly where a defect is hidden in the wall, which is more intuitive and persuasive than oral explanation or drawings alone. When handing over to repair teams, visualizing AR markings ensures that “which parts need repairing” are communicated without omission.

Real-Time Sharing and Reporting Efficiency through Cloud Integration

In smart inspections using LRTK, obtained data is immediately saved and shared to the cloud, greatly narrowing the information gap between the field and the office. Conventionally, there was a time lag before managers or owners could grasp details because photos and notes taken on site had to be compiled into drawings and reports in the office. With cloud integration, infrared images and coordinate data sent from the field can be viewed and checked instantly by remote technicians. If a critical anomaly is found, remote personnel can provide instructions on the spot or decide whether additional investigation is needed, enabling real-time collaboration between the field team and remote support.

Accumulating data in the cloud also enables automation of report generation. Since LRTK ties position and time to captured data, the system can plot anomalies on maps or drawings and auto-generate photo-annotated reports. Inspectors can focus on writing observations and countermeasure proposals, being freed from cumbersome layout adjustments and image placement. Effectively utilizing digitized inspection data can significantly shorten the time spent on reporting, allowing more time for higher-value analyses and proposals.

Cloud-based data management also becomes a long-term asset. If you manage past inspection histories of a building or bridge on the cloud in chronological order, it helps plan the next inspection and predict deterioration. Since accumulated data remains even if personnel change, knowledge transfer is smooth. There is no more hunting through paper files or personal PC photo folders. You can build an inspection data platform where authorized personnel can access necessary information anytime, anywhere.

Effects of Achieving “Zero Misses” with Infrared Visual Inspection + LRTK

As described so far, integrating LRTK into infrared visual inspection yields several effects not possible with conventional methods. Below are the main points summarized.

• Dramatic improvement in location identification accuracy: RTK positioning records anomalies with centimeter precision, clarifying previously ambiguous “which location is defective.” This eliminates the risk of locating the wrong place during subsequent repairs or monitoring.

• Elimination of inspection omissions: 3D scanning and AR navigation enable comprehensive checks even over large areas. By digitally managing coverage instead of relying on human judgment, you can reduce missed inspection sites to zero.

• Improved comprehensiveness and reliability of records: With geotagged photos and point cloud models, complete records including both anomalies and non-anomalous areas are digitized. Keeping records of areas without defects as well as those with defects greatly increases the trustworthiness of inspection results.

• Guaranteed reproducibility and continuity: Data managed in absolute coordinates allows easy re-measurement of the same points in future inspections. Quantitative comparisons of aging changes are possible, facilitating a long-term maintenance PDCA cycle.

• Improved safety: Measurements and verifications can be performed remotely for dangerous high places or confined areas, enhancing worker safety. More accurate data can be obtained while reducing scaffold work and night operations.

• Streamlined reporting work: Data collection, cloud sharing, and report generation are seamlessly connected, reducing labor and speeding up reporting. Results can be shared with stakeholders immediately after inspection, enabling faster decision-making and early consideration of countermeasures.

Thus, smart inspection combining infrared visual inspection with LRTK becomes an ideal method that achieves both highly accurate anomaly detection with zero misses and rapid response through efficient data utilization.

Outlook for Smart Inspections: Possibilities Expanded by LRTK

Although LRTK enhances visual inspections when combined with infrared cameras, its potential does not end there. Originally developed to streamline civil surveying and construction management, LRTK is a platform that can be applied broadly—from simple surveying to integration with various sensor data.

For example, in simple as-built surveys of buildings or sites, you can measure coordinates of required points with an LRTK-equipped smartphone and create drawings without contracting a surveying company. When an anomaly is found during infrared inspection, you can measure adjacent dimensions and clearances on the spot to use as input for repair planning—an integrated inspection + measurement workflow. If one worker can perform both “inspection” and “surveying” with a smartphone, productivity on site will dramatically improve.

LRTK can also be expected to integrate with a variety of inspection technologies beyond infrared. By merging LRTK’s positioning foundation with information from visible-light camera visual inspections and AI image diagnostics, drone aerial inspections, vibration sensors for structural health monitoring, and other sources, you can build a unified facilities management database. In the future, it is likely that position-tagged digital records will become standard for all periodic inspection items and that smart inspections that do not rely on paper reports will become the norm. In that world, pocket-sized LRTK has the potential to become a key device enabling each field technician to carry a precision measuring instrument and a data terminal.

High-precision smart inspections that achieve zero misses are expected to be applied across fields from building façades to social infrastructure and equipment maintenance. The combination of infrared visual inspection and LRTK is just one example. It will be increasingly important to integrate advancing digital technologies into the field to balance the maintenance of safe, secure public assets with improved work efficiency. Toward that goal, let us wisely utilize innovative tools like LRTK and pave the way for the future of inspection.