AR As-Built Inspections Useful for Municipal Staff Too: Realizing Labor Savings in Inspection Work

Table of Contents

• What is AR as-built inspection?

• Challenges of conventional as-built inspections

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

• Benefits of introducing AR as-built inspection

• Points to consider when introducing

• Simple surveying realized with LRTK

• FAQ

What is AR as-built inspection?

In infrastructure works such as road construction, riverbank protection, land development grading, and pipe burial, confirming that the completed structures match the design—known as as-built inspection (as-built management)—is indispensable. This is routine work for field engineers in charge of construction management and municipal staff on the client side, but a new as-built inspection method using AR (Augmented Reality) technology has recently been overturning that conventional wisdom. By simply pointing a smartphone or tablet camera, design drawings and 3D models can be overlaid onto the real scene at actual scale, allowing intuitive on-site verification of whether the construction has been completed as planned. Introducing AR as-built inspection dramatically improves the speed and reliability of on-site quality checks, achieving labor savings and greater efficiency in inspection work.

As-built inspection is a quality assurance process in civil engineering and building works that measures and confirms whether the completed terrain and structures’ shapes and dimensions match the design. During construction or after completion, heights, thicknesses, and slopes are measured at specified survey points, and deviations from design values are checked to make pass/fail judgments. Traditionally, numbers at each point were measured using levels, total stations (TS), tape measures, etc., and the recorded results were taken back to the office for checking on drawings. Because this method cannot be judged immediately on-site and requires time and effort, a time lag often occurs until inspection completion. Measurement and inspection work has also relied heavily on the intuition and manual work of experienced technicians, and with chronic labor shortages and an aging workforce, labor savings and efficiency have become major challenges.

Against this backdrop, AR as-built inspection has emerged. This method applies AR technology to as-built management by overlaying 3D design data and measurement data onto the camera view on a smartphone or tablet, directly visualizing digital information on-site to confirm as-built status. Inspections that were previously done on paper drawings or numeric data can now be performed by overlaying the data onto the actual object, enabling real-time and intuitive quality checks so that anyone—not just veterans—can reliably judge the completion. Especially when combined with high-precision GNSS (satellite positioning), the models and measured values displayed in AR can be aligned with the real object within an error range of several centimeters (several in). Attaching an RTK-GNSS receiver to a smartphone enables centimeter-level positioning (inch-level positioning), allowing models and reality to be overlaid with almost no offset. Recent iPhones and iPads also include built-in LiDAR sensors, and applications comparing high-density point cloud data (current 3D scans) acquired with these sensors to design data in AR are advancing. The Ministry of Land, Infrastructure, Transport and Tourism (MLIT) is also promoting enhanced and more efficient inspections through 3D measurement and AR under its “i-Construction” initiative, and AR as-built inspection is attracting strong expectations as a solution that can simultaneously improve on-site productivity and quality.

Challenges of conventional as-built inspections

As-built inspection is essential for ensuring quality, but traditional methods carried various inefficiencies. The main challenges are summarized below.

• Long work hours: Because staff measured each survey point painstakingly with levels or TS, large sites or many survey points could require enormous time. It was not uncommon for the process of compiling measurement results on drawings and judging pass/fail to take several days.

• Dependence on manpower and skilled technicians: Accurate measurement and evaluation require experienced technicians such as surveyors, and two-person teams are often required. With severe labor shortages and an aging technical workforce, the burden of ensuring quality with limited personnel has grown year by year.

• High equipment costs: Millimeter-level high-precision measurements require dedicated equipment such as TS or RTK-GNSS receivers, and introducing such high-precision surveying instruments requires initial investments on the order of several million yen, making it a high hurdle for small companies and municipalities. Maintenance costs and theft risk are additional concerns.

• Measurement errors and recording mistakes: Manual surveying inevitably accumulates slight errors each time, and human error can creep in when transcribing field notes to drawings. There is always a risk that errors will be noticed later, requiring re-measurement and rework.

• Time-consuming report creation: Creating as-built drawings and reports based on measurement results and submitting them to the client is also a major burden for field staff. Organizing photos and plotting on drawings takes time, and in some cases the data collected on-site cannot be fully utilized for quality analysis.

• Delayed detection of defects: Even if there are construction defects such as insufficient thickness or incorrect slope, they may not be noticed immediately on-site, and problems are often discovered the next day or later after taking data back and plotting it. Delayed corrective action can lead to unnecessary work and costs if, for example, concrete has already set or heavy equipment has been removed.

As described above, traditional as-built management methods suffered from a lack of immediacy and heavy burdens in terms of personnel and cost. There was no doubt that a new method capable of accurately and intuitively grasping as-built conditions in real time was needed.

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

So how can AR technology actually be used on site? By overlaying digital information to directly “visualize” as-built conditions on-site rather than checking on drawings, immediate checks can be performed. The following use cases illustrate this.

• Overlaying design models in AR: 3D design data (BIM/CIM models, etc.) of buildings and civil structures can be overlaid onto site video to instantly and intuitively confirm the placement and dimensions of structures. It is also possible to compare through the camera whether columns or walls during construction have shifted from their design positions. Discrepancies from the expected finished appearance, which are difficult to grasp from paper drawings or numeric data alone, can be immediately understood as life-size visuals in AR.

• Heatmap display of as-built deviations: Use cases are emerging in which 3D as-built data (point clouds, etc.) acquired after construction are compared with design models and displayed as color-coded heatmaps indicating deviations. If an error heatmap automatically generated by comparing design data and as-built point clouds in the cloud is downloaded to a smartphone and overlaid on the camera view, it is immediately obvious which areas are higher or lower than the design. For example, this helps quickly evaluate embankment height or pavement thickness across a surface and immediately correct defective areas, accelerating the PDCA cycle.

• Visualization of buried objects in AR: The positions of buried structures or pipes can be displayed as if seen through the ground even after backfilling. For example, in sewer pipe work, scanning pipes with a smartphone before burial and saving the georeferenced point cloud data in the cloud allows the pipe alignment and depth to be checked through the smartphone screen even after backfilling. Without marking the surface or carrying drawings, the location of buried objects can be quickly identified on-site, helping to prevent construction mistakes and ensure safety.

• Other applications: AR can also guide work by displaying construction areas and height criteria for heavy equipment operation, or virtually mark concrete pouring locations in advance. In training, AR reproductions of sites are drawing attention as safety drills and procedure training tools. While applications will continue to expand, as-built management × AR is particularly expected to deliver immediate results from initial introduction and is gaining strong interest from the field.

Benefits of introducing AR as-built inspection

How do the above challenges get resolved by introducing AR as-built inspection? Major benefits include the following.

• Real-time confirmation and rapid rework: With on-site confirmation of as-built conditions, the time lag from measurement to pass/fail judgment disappears. If defects are found, corrective measures can be taken immediately, minimizing rework. For example, there are reported cases where measurement and drawing checks that used to take half a day were completed in about five minutes.

• Increased efficiency and labor savings: With just a smartphone and AR, one person can perform surveying and inspection, dramatically improving team efficiency. Tasks that relied on veteran experience and intuition can be replaced by technology, enabling anyone to perform efficient, high-quality construction management. This is a major advantage for sites suffering from chronic labor shortages, allowing labor savings without sacrificing quality.

• Cost reduction: Because expensive surveying equipment is not required, introduction can be achieved with a relatively small initial investment using smartphones and compact GNSS devices. Additional benefits include shortened schedules and reduced labor costs from decreased rework. In many cases, equipping each person with a device can fit within budget, making this a cost-effective solution.

• Improved accuracy and reliability: Centimeter-level positioning (inch-level positioning) with RTK-GNSS and high-resolution point cloud measurement dramatically increase the reliability of as-built data. Measurement data is automatically saved to the cloud and can be output and submitted in formats compliant with MLIT as-built management procedures. As AR use has begun to be officially recognized, the reliability of AR-based inspection materials is becoming well assured.

• Efficient data utilization and recordkeeping: Measurement data and site photos are saved and shared to the cloud on the spot, eliminating the need to transcribe into drawings later. Acquired point clouds and coordinate information can be output in common formats such as CSV, SIMA, and LAS and smoothly imported into existing CAD or GIS systems. Past data is easily searchable and viewable in the cloud, greatly improving the efficiency and accuracy of record management compared to paper field notebooks.

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

Points to consider when introducing

When newly introducing AR as-built inspection, consider the following to maximize its benefits.

• Phased introduction and internal training: Although AR-based surveying and inspection operations are intuitive, it is smoothest to provide basic operation training and establish operational rules within the organization during the initial phase. Establishing file naming rules for acquired data and sharing procedures in advance prevents confusion during operation. Start with a small pilot team to verify accuracy and effectiveness, then roll out company-wide in stages. When using for the first time, verifying errors against known reference points helps deepen understanding of the equipment.

• Combination with existing methods and data integration: At the start, it is reassuring to use existing surveying equipment and methods in combination, comparing results obtained by smartphone surveying (LRTK, etc.) with TS measurements 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 traditional workflows, but organizing operational flows beforehand will help prevent confusion on site.

• Provision of compatible devices: Prepare sufficiently high-performance smart devices to run AR apps and point cloud measurement smoothly. Generally, the latest-generation iPhone/iPad or high-end Android devices are recommended, as older models may not support AR processing or LiDAR scanning or may run slowly. Large-screen tablets are suitable for checking point cloud details, so use them as appropriate for the task.

Simple surveying realized with LRTK

A solution attracting attention for easily implementing AR as-built inspection is LRTK. LRTK is an innovative technology that transforms a smartphone into a surveying instrument with centimeter-level accuracy (inch-level accuracy) by attaching a small high-precision RTK-GNSS antenna to the smartphone. Real-time kinematic (RTK) satellite positioning corrections reduce typical GPS errors of several meters down to a few centimeters, enabling high-precision surveying with palm-sized equipment. Combined with the LiDAR scanner and high-performance cameras built into the latest smartphones, scanning the surroundings can acquire 3D point cloud data that allows on-the-spot volume calculations, embankment quantity measurements, and buried pipe depth checks. Acquired point clouds and photos are automatically shared to the cloud, enabling real-time confirmation of on-site as-built conditions from the office. No specialized equipment or complicated setup is required—the simplicity of mounting the device on a smartphone and launching an app to start positioning is a major feature.

This LRTK-based simple surveying system is currently spreading across many construction sites. Aiming to be a “versatile surveying instrument for one person,” the system’s ease of use and high-precision positioning have been well received, quietly creating a boom at many sites. If you have not yet experienced positioning with high-precision GNSS or AR as-built inspection, this is a good opportunity to introduce LRTK. Once you feel the labor-saving and efficiency benefits, you may never return to the old methods. Starting as-built management DX from a smartphone will further improve on-site productivity and quality assurance.

For product details or questions about introduction, please feel free to [contact us](https://www.lefixea.com/contact-lrtk). Advance your site to next-generation construction management with LRTK’s 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 over the actual site scene to confirm on-site whether completed structures match the plan. By visualizing as-built inspection digitally on a smartphone—work that was previously done with paper drawings and surveying instruments—it enables real-time and intuitive quality confirmation.

Q: What equipment and preparations are required for introduction? A: Basically, you need a smartphone or tablet that supports AR display and high-precision positioning, a GNSS receiver capable of centimeter-level positioning, and a compatible application. For example, attaching an RTK-GNSS device like LRTK to a modern iPhone or Android device enables as-built inspection by combining centimeter accuracy and AR functions. In addition, preparing digitalized design data such as drawings or BIM/CIM models is essential.

Q: Is measurement accuracy sufficient? A: Yes. With high-precision GPS (RTK-GNSS) positioning, errors are within a few centimeters (within a few in), meeting the measurement accuracy required for as-built management. A GNSS receiver attached to the smartphone receives correction information based on reference points and accurately overlays 3D models and point clouds to match site coordinates. Validation consistent with MLIT procedures has been conducted, confirming the effectiveness of AR-based as-built inspection methods.

Q: How much does introduction cost? A: Introduction costs are much lower compared to conventional surveying equipment. By leveraging commercial smartphones and adding a small GNSS device, initial costs are very reasonable, equivalent to that of one high-precision GNSS receiver. Subscription plans are also available instead of purchase, allowing low-cost operation for the necessary period. Specific pricing depends on feature sets, but deploying a one-device-per-person setup is often cost-effective.

Q: Does it comply with MLIT standards? A: Yes. Acquired point cloud data and comparison results with design drawings can be output and submitted in formats that comply with MLIT’s as-built management procedures. In fact, MLIT’s procedures state that “when as-built measurement results projected on-site by AR are used for pass/fail judgments, submission of conventional as-built management reports may be unnecessary,” and AR-based as-built management methods are increasingly being officially recognized. Thus, introducing AR inspections on-site can be operated without issues in inspection and certification procedures.