Introduction to AR Inspections for Surveying Novices: The New Standard for As-Built Inspections

Table of Contents

• What is AR inspection?

• Challenges of traditional as-built inspections

• Use cases for AR inspections

• Benefits of AR inspections

• Key points for introducing AR inspections

• Simple surveying with LRTK

• FAQ

What is AR inspection?

The task of comparing completed structures on a construction site with drawings to confirm “is this really built according to the design?” is an important process that construction management engineers perform routinely. In recent years, however, AR (Augmented Reality) technology has been changing that conventional wisdom. By simply holding up a smartphone or tablet, design drawings and 3D models can be overlaid onto the real scene at full scale, allowing intuitive on-site verification of whether the work matches the plan. This reduces the burden of interpreting drawings and numbers and is easier for less experienced personnel to use. As a result, on-site quality checks become dramatically faster and more reliable, strongly accelerating the DX (digital transformation) of construction management.

As-built inspection is the quality-assurance process in civil engineering and building works that measures and verifies whether completed structures and terrain have been finished in the shapes and dimensions specified by the design drawings. Heights, thicknesses, slopes, and other values are measured at designated survey points during or after construction and compared with design values to determine pass/fail. Traditionally, heights and thicknesses were measured with levels or total stations (TS), and results were taken back to the office for comparison with drawings. This was a time-consuming process because it could not be confirmed on-site immediately. As a next-generation method that addresses these issues, as-built inspection using AR has attracted attention. By applying AR technology to as-built management and digitally “visualizing” construction results on-site for immediate checking, this approach has rapidly moved into practical use in recent years, aided by the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction initiative. The spread of modern smartphones equipped with high-performance cameras and LiDAR sensors has made AR available to everyone in daily use, and now AR is playing an active role in as-built inspections. It is fair to say AR is becoming the new standard for as-built inspection.

Challenges of traditional as-built inspections

As-built inspections are essential for ensuring quality, but traditional methods have many inefficiencies. Here are the representative challenges.

• Time-consuming work: Because staff measured point by point using leveling instruments or TS, projects with large sites or many survey points required enormous time. It was not uncommon for it to take several days to bring measurement results back and compare them with drawings to determine pass/fail.

• Dependence on manpower and skilled technicians: Accurate measurement and evaluation require experienced surveying technicians, and work is often done in pairs. With severe labor shortages and an aging workforce, the burden of ensuring quality with limited personnel has grown.

• High equipment costs: To measure with millimeter-level high precision, specialized equipment such as total stations 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.

• Risk of measurement errors and record mistakes: Manual surveying can accumulate small errors each time, and there is a risk of human error when transcribing values noted on-site into drawings. Discovering typographical errors later may require re-measurement and rework.

• Burden of report preparation: Creating as-built drawings and reports from measurement results and submitting them to clients is also a major burden for field personnel. Time spent organizing photos and plotting on drawings can prevent on-site data from being fully utilized for quality analysis.

• Delayed detection of defects: Even if there are construction mistakes such as insufficient thickness or incorrect slope, these are often not noticed immediately on-site and may be identified only after data are brought back and drawn up—sometimes the following day or later. By the time the issue is discovered, concrete may have hardened or heavy machinery may have left, leading to extra labor and costs for rework.

As described above, traditional as-built inspection methods suffered from a lack of immediacy and heavy burdens in terms of personnel and cost. It goes without saying that a new method capable of grasping as-built conditions in real time, accurately and intuitively, was needed.

Use cases for AR inspections

How can AR technology actually be used on site? By directly “visualizing” the as-built checks that were previously done on drawings as digital information on-site, immediate on-the-spot checks become possible. Specific use cases include:

• Overlaying design data in AR: 3D design data for buildings and civil structures (BIM/CIM models, etc.) can be overlaid on the site view, allowing intuitive on-site confirmation of structure placement and dimensions. You can visually compare via the camera whether columns or walls under construction are off from their design positions. Discrepancies from the expected finished image that are hard to grasp from paper drawings or numeric data alone can be instantly perceived as full-scale visuals in AR.

• Heatmap display of as-built deviations: It is becoming common to compare 3D as-built data (point clouds, etc.) acquired after construction with design data and display deviations as colored heatmaps on-site. A heatmap automatically generated by comparing the design model and as-built point cloud in the cloud can be downloaded to a smartphone and overlaid on the camera view to instantly show which areas are higher or lower than the design. For example, it helps speed up the PDCA cycle by enabling areal evaluation of fill or pavement thickness and immediate correction of defective areas.

• AR visualization of buried objects: The positions of underground structures and pipes can be displayed in AR as if they were transparent, even after backfilling. For example, in sewer pipe work, scanning pipes with a smartphone before burial and saving point cloud data with position information in the cloud allows anyone to understand pipe routes and depths through the smartphone screen after backfilling. This makes it possible to identify buried objects on the spot without marking the surface or carrying drawings, helping prevent construction mistakes and ensuring safety.

• Other applications: Beyond the above, AR can be used to guide heavy equipment operations by displaying construction limits or height references, or to virtually mark concrete placement areas in advance. In training and education, AR-based safety drills and task procedure simulations that recreate the site are gaining attention. Uses continue to expand, but especially “as-built inspection × AR” is a use case that tends to deliver benefits immediately after introduction and is generating high expectations from the field.

Benefits of AR inspections

How do the aforementioned issues get resolved by implementing AR as-built inspections? Main benefits include:

• Real-time verification and rapid rework: Since as-built conditions can be confirmed immediately on-site, there is no time lag from measurement to pass/fail judgment. If defects are found, corrective actions can be taken immediately, minimizing rework. There are dramatic time-saving reports where inspections that used to take half a day were completed in actual work time of 5 minutes. Being able to respond on the spot prevents major later rework and quality troubles.

• Improved efficiency and reduced manpower: With a smartphone and AR, surveying and inspection can be conducted by a single person, dramatically improving team-wide efficiency. Tasks that relied on veteran experience and intuition can be replaced by technology, allowing anyone to manage construction quality efficiently. The ability to reduce manpower while maintaining quality amid chronic labor shortages is a major advantage.

• Cost reduction: It is attractive that you do not need to purchase expensive surveying equipment; introduction can be done with a modest initial investment of a smartphone plus a small device. Reduced rework shortens schedules and lowers labor costs. In many cases it fits within budgets even if a device is issued to each person, making it a cost-effective solution.

• Improved accuracy and reliability: Centimeter-level high-precision positioning with RTK-GNSS and high-resolution point cloud measurements dramatically improve the reliability of as-built data. Measurement values are automatically saved to the cloud and can be output and used in formats that conform to the Ministry of Land, Infrastructure, Transport and Tourism’s as-built management guidelines. As AR use begins to be officially recognized, the reliability of inspection records can be sufficiently ensured.

• Efficient data utilization and record keeping: Measurement data and site photos are saved and shared to the cloud on the spot, eliminating the need to transcribe data into drawings later. Point clouds and coordinate information can be exported in common formats such as CSV, SIMA, or LAS, which are easy to handle in operations and can be smoothly imported into existing CAD or GIS systems. Past data are easy to search and reference in the cloud, greatly improving the efficiency and accuracy of record management compared with paper field books. Because data can be shared with clients and supervisors via the cloud, remote verification of as-built conditions and smooth consensus building are also possible.

• Improved safety: Remote measurement without entering hazardous areas contributes to safety. For example, surveying steep slopes from below using AR to check heights reduces risk. Displaying buried objects in AR also reduces the risk of accidentally damaging pipes or cables during excavation. In this way, AR use brings major benefits not only in operational efficiency but also in site safety.

Key points for introducing AR inspections

When introducing AR inspections, consider the following to maximize benefits.

• Phased implementation and training: While AR-based surveying and inspection are intuitive to operate, it is smoothest to conduct basic operational training and establish usage rules within the company during the initial introduction. Establishing file naming rules for acquired data and sharing procedures in advance prevents confusion during operation. Start with a small trial group, verify accuracy and effectiveness, and then roll out company-wide in stages for success. When using it for the first time, verifying errors at known points and deepening understanding of the equipment is also effective.

• Combining with existing methods and data integration: At the time of introduction, it is reassuring to combine AR with traditional surveying equipment and methods, comparing measurements obtained by LRTK and those from total stations to understand error tendencies. It is also important to test in advance 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 operations, but preparing operational workflows in advance will help avoid confusion on site.)

• Preparation of equipment and environment: Prepare devices and work environments suitable for AR inspections. Ideally, use AR-capable modern smartphones or tablets, preferably models equipped with LiDAR scanners. Large-screen tablets are suitable for checking the details of point clouds. Also ensure access to GNSS correction services such as network RTK for high-precision positioning. It is essential to have design data (drawings or BIM/CIM models) ready so they can be called up on-site immediately.

Attending to these points will help you maximize the effects of introducing AR inspections and ensure smooth on-site adoption.

Simple surveying with LRTK

A solution attracting attention for easily implementing as-built AR inspections is LRTK. LRTK is an innovative technology that turns a smartphone into a centimeter-level precision surveying instrument by attaching a small high-precision RTK-GNSS antenna to the phone. The Real-Time Kinematic (RTK) satellite positioning correction cancels out GPS errors that are normally several meters and reduces them to a few centimeters (a few inches), enabling high-precision surveying with hand-sized equipment. Combined with the LiDAR scanner and high-performance cameras built into modern smartphones, simply scanning the surroundings can acquire 3D point cloud data and complete as-built inspection tasks on the spot such as volume calculations, fill quantity calculations, and buried pipe depth checks. Acquired point clouds and photos are automatically shared to the cloud, allowing real-time confirmation of as-built conditions from the office. No special equipment or complicated setup is required; positioning starts simply by attaching the device to a smartphone and launching the app.

LRTK-based simple surveying is steadily penetrating many sites. Aiming to be a “versatile surveying instrument for one person per device,” this system, combined with its reasonable pricing, is quietly creating a boom at many sites. If you have not yet tried high-precision positioning or AR inspections, consider introducing LRTK now. Once you experience the labor- and cost-saving benefits, you may find it hard to go back to previous methods. Starting as-built management DX with a smartphone will further improve on-site productivity and quality assurance going forward.

FAQ

Q: What is AR inspection? A: It is an as-built inspection method that displays drawings and design data in AR on the real site view, enabling on-the-spot confirmation of whether a completed structure matches the plan. By visualizing traditional as-built inspections done with paper drawings and surveying equipment digitally on smartphones and the like, it enables real-time, intuitive quality checks.

Q: What equipment and preparations are needed to introduce AR inspections? A: Essentially, you need a smartphone or tablet capable of AR display and high-precision positioning, a high-precision GNSS receiver, and a compatible application. For example, attaching an RTK-GNSS receiver such as LRTK to a modern smartphone allows combining centimeter-accuracy position information with AR functions to perform as-built inspections. Additionally, it is essential to prepare design drawings or 3D models (BIM/CIM data, etc.) in advance for on-site verification.

Q: Can measurement accuracy be sufficiently ensured? A: Yes. High-precision GPS (RTK-GNSS) positioning provides accuracy within a few centimeters (a few inches), meeting the measurement precision required for as-built inspections. The GNSS receiver attached to the smartphone receives correction information from reference points to accurately align 3D models and point clouds with site coordinates. Verification conforming to the Ministry of Land, Infrastructure, Transport and Tourism’s guidelines has been conducted, confirming the effectiveness of AR-based as-built inspection methods.

Q: How much does introduction cost? A: Compared to traditional surveying equipment, introduction costs are significantly lower. By utilizing a commercially available modern smartphone and adding a small GNSS device, the initial cost is roughly equivalent to a single high-precision GNSS receiver and is very reasonable. Subscription-based usage plans are also available, allowing low-cost operation for only the needed period. Specific pricing depends on feature configuration, but even if one device is provided per person, the cost-effectiveness is generally favorable.

Q: Can surveying novices handle it? A: Yes. AR inspection is an intuitive method of overlaying digital information on the site view, so it is relatively easy to use even without traditional specialized surveying skills. Because design data is displayed at full scale when you point a smartphone, novices who have difficulty reading drawings can visually grasp deviations in the finished form. Systems like LRTK are simple to operate—measurements and recording can be completed with the push of a button—so anyone can start using them on-site soon after introduction.

Q: On what kinds of sites can AR inspection be used? A: It can be used on any site where as-built verification is required, from civil engineering to building works. AR-based as-built checks are being introduced across a wide range of fields, such as road embankments and pavements, development sites, bridge structures, and building finish inspections. AR technology is also being applied to some quality checks such as rebar placement inspections. Note, however, that outdoor environments where GNSS corrections can be received are preferable for high-precision positioning.

Q: Does it comply with Ministry of Land, Infrastructure, Transport and Tourism standards? A: Yes. Acquired point cloud data and comparison results with drawings can be output and submitted in formats that comply with the ministry’s as-built management guidelines. The latest guidelines even include wording indicating that when as-built measurement results projected on-site via AR are used for pass/fail judgments, submission of traditional as-built management drawings and tables may be omitted in some cases. In this way, the environment for operating AR inspections on-site in compliance with inspection procedures is becoming well established.