Cost-saving AR As-built Inspection: Are Expensive Survey Instruments No Longer Necessary?

Table of Contents

• What is AR as-built inspection?

• Challenges of traditional as-built management

• On-site use of AR technology: immediate checks through visualization

• Benefits of introducing AR as-built inspection

• Points to consider when introducing it

• Simple surveying realized with LRTK

• FAQ

What is AR as-built inspection?

On construction sites, comparing completed structures with drawings to confirm “is this really built according to the design?” is a routine task for construction managers. In recent years, however, this commonplace task has been transformed by AR (Augmented Reality) technology. By simply pointing a smartphone or tablet camera, design drawings or 3D models can be overlaid onto the real scene at full scale, allowing intuitive on-the-spot confirmation of whether the work matches the plan. This dramatically increases the speed and reliability of on-site quality checks and strongly promotes DX (digital transformation) in construction management. With the spread of AR as-built inspection, some even suggest that the expensive surveying instruments once considered essential may “no longer be necessary.” This article explains in detail the effects AR as-built inspection brings to the field and the points to keep in mind when introducing it.

As-built management itself is a quality assurance process in civil engineering and building construction that measures and verifies whether completed structures and terrain conform to design shapes and dimensions. During or after construction, measurements such as heights, thicknesses, and slopes are taken at prescribed survey points, and deviations from design values are checked to determine pass or fail. Traditionally, levels or total stations (TS) were used on site to measure heights and thicknesses, and results were taken back to the office for comparison with drawings before making the verdict. This process could not be confirmed immediately on site and required significant time and effort. AR as-built inspection, which applies AR technology to as-built management to digitally visualize construction results on site for immediate checking, has attracted attention as a next-generation method to solve these issues. Driven in part by the Ministry of Land, Infrastructure, Transport and Tourism’s *i-Construction* initiatives, this approach has rapidly reached practical stages in recent years. The spread of modern smartphones equipped with high-performance cameras and LiDAR sensors has created an environment where AR can be used in daily operations, and AR is now taking an active role in as-built management. Proof-of-concept and implementation are already progressing at construction sites across the country.

Challenges of traditional as-built management

As-built management is essential for ensuring quality, but traditional methods come with many inefficiencies. Here are representative challenges:

• Excessive working hours: Because staff measured each survey point laboriously with level instruments or TS, wide sites or many survey points required enormous time. It was not uncommon for several days to pass between measuring values, compiling them on drawings, and determining pass/fail.

• Dependence on manpower and skilled technicians: Accurate measurement and evaluation require experienced surveyors, and work in pairs is frequently necessary. With serious labor shortages and aging technicians, ensuring quality with limited personnel has been a large burden.

• High equipment investment required: To measure with millimeter-level precision, specialized instruments such as TS or RTK-GNSS receivers are 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 companies.

• Measurement errors and recording mistakes: Manual surveying tends to accumulate slight errors over time, and there is a risk of human error when transcribing field notes onto drawings. Discovering transcription mistakes later can lead to re-measurement or rework.

• Burden of creating reports: Preparing as-built drawings and reports for clients based on measurement results is a major burden for field staff. Time spent organizing photos and plotting on drawings can prevent field-acquired data from being fully utilized for quality analysis.

• Delayed detection of defects: Even when there are construction defects such as insufficient thickness or incorrect slope, they often cannot be noticed immediately and are only discovered after returning to the office and creating drawings the next day or later. By then, concrete may have hardened or heavy equipment may have been removed, causing extra work and cost due to rework.

As shown above, traditional as-built management methods are plagued by a lack of immediacy and heavy burdens in terms of personnel and cost. There was a clear need for a new method that could grasp as-built conditions accurately and intuitively in real time.

On-site use of AR technology: immediate checks through visualization

So how can AR technology be used on actual sites? By overlaying digital information onto the real scene and visualizing as-built conditions directly on site, checks can be made immediately. Here are some use cases:

• AR overlay of design models: 3D design data for buildings and civil structures (BIM/CIM models, etc.) can be overlaid onto the site scenery, enabling intuitive on-the-spot confirmation of layout and dimensions. You can compare through the camera whether columns or walls under construction are offset from design positions. Discrepancies from the finished image that are hard to grasp from paper drawings or numerical data can be instantly understood as full-scale visuals in AR.

• Heatmap display of as-built deviations: On-site verification using color-coded heatmaps of deviations between acquired 3D as-built data (point clouds, etc.) and design data is beginning to be used. If you compare design models and as-built point clouds in the cloud and automatically generate a heatmap, downloading it to a smartphone and overlaying it on the camera feed makes it immediately clear which areas are higher or lower than design. For example, it helps speed up the PDCA cycle by enabling planar evaluation of embankment or pavement thickness and immediate correction of defects.

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

• Other applications: AR can also guide machine operators by displaying construction ranges and elevation criteria during equipment operation, or virtually mark concrete placement areas in advance. In training, AR-based safety drills and work procedure training tools that reproduce job sites are attracting attention. While applications continue to expand, the combination of as-built management and AR is particularly expected to deliver quick benefits immediately after introduction.

Benefits of introducing AR as-built inspection

How do the challenges described earlier get resolved by introducing AR as-built inspection? Here are the main benefits:

• Real-time confirmation and immediate correction: Because as-built conditions can be confirmed immediately on site, the time lag from measurement to pass/fail determination disappears. If a defect is found, corrective action can be taken immediately, minimizing rework. There are reported cases where surveys that used to take half a day were completed in five minutes of actual work.

• Increased efficiency and labor-saving: With a smartphone and AR, surveying and inspection can be conducted by a single person, dramatically improving overall team efficiency. Tasks that relied on veteran experience or intuition can be supplemented by technology, enabling anyone to conduct high-quality construction management efficiently. This ability to combine labor saving with quality assurance is a major advantage in the face of chronic labor shortages.

• Cost reduction: There is no need to purchase expensive surveying instruments; introduction can be done with a modest initial investment of smartphones and small devices. Additional benefits include reduced rework leading to shorter schedules and lower labor costs. In many cases, equipping one device per person fits within budget, making this a highly cost-effective solution.

• Improved accuracy and reliability: Centimeter-level accuracy positioning with RTK-GNSS and high-resolution point cloud measurement greatly enhance the reliability of as-built data. Measurement data is automatically saved in the cloud and can be output and used in formats that comply with the Ministry of Land, Infrastructure, Transport and Tourism’s as-built management guidelines. As AR usage has begun to be officially recognized, the reliability of AR-based inspection documents as formal records is sufficiently assured.

• Better data utilization and record efficiency: Measurement data and site photos are saved and shared to the cloud on the spot, eliminating the need to later transcribe them onto drawings. Point clouds and coordinate data can be exported in common formats such as CSV, SIMA, or LAS, allowing smooth import into existing CAD or GIS systems. Past data is easily searchable and referable in the cloud, dramatically improving the efficiency and accuracy of record management compared to paper notebooks. It also contributes to paperless operations by reducing paper forms.

• Improved safety: Because measurements can be taken remotely without entering hazardous areas, AR contributes to safety. For example, surveying steep slopes from below using AR to confirm heights reduces risk. Displaying buried objects in AR also reduces the risk of accidentally damaging pipes or cables during excavation. Thus, AR brings significant benefits not only in efficiency but also in on-site safety.

In this way, introducing AR as-built inspection delivers results that surpass traditional methods in many areas, not only shortening work time but also reducing costs and improving quality and safety.

Points to consider when introducing it

When introducing AR as-built inspection, consider the following to maximize effectiveness:

• Phased introduction and internal training: Although AR-based surveying and checking are intuitive to operate, carrying out basic operation training and establishing operational rules within the company during initial introduction makes the process smoother. Predefining file naming conventions and sharing procedures for acquired data can prevent confusion in operations. Start with a small pilot group to verify accuracy and effectiveness, then roll out step by step across the company. When using it for the first time, it is effective to verify errors at known points to deepen understanding of the device.

• Co-use with existing methods and data linkage: In the early stages, use conventional surveying instruments alongside AR and compare measurements from LRTK and total stations to understand error tendencies. Also 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 workflows, but organizing the operational flow in advance helps avoid confusion on site.

• Preparing compatible devices: To run AR apps and point cloud measurement comfortably, provide the highest-performance devices possible. Generally, the latest iPhones and iPads and high-end Android devices are recommended. Older models may not support AR processing or LiDAR scanning, or may run slowly. Large-screen tablets are suitable for detailed inspection of point cloud data, so use them according to purpose.

By keeping these points in mind during introduction, you can maximize the benefits of AR as-built inspection.

Simple surveying realized with LRTK

One solution attracting attention for easily implementing AR as-built inspection is LRTK. LRTK is an innovative technology that transforms a smartphone into a centimeter-level surveying instrument by attaching a small high-precision RTK-GNSS antenna to the phone. With real-time kinematic (RTK) satellite positioning corrections, GPS errors that were typically several meters (several ft) can be reduced to several centimeters (several in), allowing high-precision surveying with palm-sized equipment. Combined with LiDAR scanners and high-performance cameras built into modern smartphones, simply scanning the surroundings yields 3D point cloud data that can immediately be used to calculate earthwork volumes, embankment volumes, or check buried-pipe depths on the spot. Acquired point clouds and photos are automatically shared to the cloud, enabling real-time confirmation of site as-built conditions from the office. No specialized equipment or complex setup is required; attaching the device to a smartphone and launching the app starts positioning, offering great ease of use. In short, tasks in as-built management that once relied on expensive specialized surveying equipment can now be completed with just a smartphone and a small device.

LRTK-based simple surveying is quietly spreading across many sites. Aiming to be a “universal surveying instrument, one per person,” this system—together with its affordable pricing—has already sparked a quiet boom on sites. If you have yet to try high-precision positioning or AR checks, consider introducing LRTK now. Once you experience the labor and efficiency benefits, you may not want to return to previous methods. Starting as-built management DX with a smartphone will further improve on-site productivity and quality assurance.

For product details or inquiries about introduction, please feel free to [Contact us]. Advance your site to next-generation construction management with LRTK simple surveying.

FAQ

Q: What is AR as-built inspection? A: It is an as-built management method that displays drawings and design data in AR on the actual site view so you can confirm on the spot whether constructed structures match the plan. Traditionally done with paper drawings and surveying instruments, as-built inspection can now be visualized digitally with smartphones for real-time and intuitive quality checks. It is attracting attention as a next-generation technology that supports on-site quality management DX.

Q: What equipment and preparations are needed to introduce AR as-built inspection? A: Essentially, you need smartphones or tablets capable of AR display and positioning, a high-precision positioning device, and a compatible application. For example, attaching an RTK-GNSS receiver like LRTK to the latest iPhone or Android device combines centimeter-level positioning with AR functionality for as-built inspection. In addition, digital design data such as drawings or BIM/CIM models is indispensable.

Q: Is measurement accuracy sufficient? A: Yes. With high-precision GPS (RTK-GNSS) positioning, accuracy within several centimeters (several in) can be achieved, meeting the measurement precision required for as-built management. A GNSS receiver attached to the smartphone receives correction information based on control points to accurately align 3D models and point clouds with site coordinates. Verifications conforming to the Ministry of Land, Infrastructure, Transport and Tourism’s guidelines have been conducted, confirming the effectiveness of AR-based as-built inspection methods.

Q: How much does introduction cost? A: Introduction costs are significantly lower than traditional surveying instruments. By using commercially available modern smartphones and adding a small GNSS receiver, initial costs are roughly comparable to that of a single high-precision GPS receiver, making it very affordable. Subscription-based usage plans are also available, allowing low-cost operation for only the necessary period. Specific pricing depends on feature sets, but equipping one device per person is often cost-effective.

Q: Does it comply with the Ministry of Land, Infrastructure, Transport and Tourism’s standards? A: Yes. Acquired point cloud data and comparison results with drawings can be output and submitted in formats that conform to the Ministry’s as-built management guidelines. In fact, the guidelines include language such as “If as-built measurement results projected on site with AR are used for pass/fail determination, submission of conventional as-built management forms may be unnecessary,” indicating that AR-based as-built management methods are being officially recognized. Thus, introducing AR checks on site can be operated without issues in inspections.