Reduce Work Time by 30%! Effects and Examples of AR As-Built Inspections

Table of contents

• Introduction

• What is AR as-built inspection?

• Benefits of AR as-built inspection

• Use case 1: Road paving – Quickly check wide areas with AR heatmaps

• Use case 2: Retaining wall work – Instantly check discrepancies between drawings and constructions with AR

• Use case 3: Earthworks – LiDAR scanning reduced as-built measurement from half a day to 30 minutes

• Simple surveying with LRTK

• FAQ

Introduction

In recent years, the construction industry has been undergoing major changes in construction management methods due to the wave of ICT adoption and DX promotion. However, on-site surveying and as-built verification still require a great deal of time and effort, and labor shortages and the aging of skilled technicians remain serious issues. Moreover, the application of overtime work regulations in 2024 (the so-called “2024 problem”) is looming, increasing the need to carry out construction efficiently with limited personnel.

One promising solution to these challenges is the introduction of augmented reality (AR) technology using smartphones for construction management. In particular, combining AR with RTK positioning (real-time kinematic) using high-precision GNSS receivers that can be attached to smartphones offers the potential to digitally transform as-built management tasks that previously relied on manual labor and experience. By combining RTK’s centimeter-level positioning accuracy (half-inch level) with AR visualization of on-site information, a palm-sized smartphone can become an “all-purpose surveying instrument,” enabling anyone—not just experts—to easily perform site surveying, layout, and verification that construction matches the design.

This article explains how using AR as-built inspection can drastically shorten work time and presents concrete use cases in civil engineering sites such as road paving, retaining walls, and land development (earthworks). Finally, we touch on a new approach called “simple surveying” enabled by AR×RTK, which we hope will help site managers consider efficiency improvements.

What is AR as-built inspection?

“As-built inspection” is the process of confirming that completed constructions have the dimensions and shapes specified in the design. Traditionally, staff used tape measures and leveling rods or observed coordinates with total stations, spending a lot of time verifying the as-built condition.

By contrast, “AR as-built inspection” is a method that uses smartphones or tablets to overlay design data onto the construction site and verify the as-built condition in virtual space. AR technology displays 3D design models, reference lines, measurement data, and more on the camera feed, allowing inspections to be performed as if stepping into the digital drawings while remaining on site.

When combined with high-precision RTK-GNSS, it is possible to align the real world and digital information with errors of only a few centimeters (a few in). This allows intuitive, on-the-spot understanding of deviations between the design positions on drawings and the actual constructions. In other words, without measuring each survey point individually, AR as-built inspection enables immediate checks of “design vs. site differences” through the smartphone screen.

Benefits of AR as-built inspection

Introducing AR as-built inspection brings various benefits to the site. The main advantages are summarized below.

• Significant reduction in work time: The time required for measurement and inspection is drastically reduced. For example, what used to take half a day for as-built surveying was completed in about 30 minutes using AR-enabled smartphone measurement in some cases. Such reductions of 30% or more in work time can be expected. Time spent creating drawings and reports can also be reduced because data is automatically digitized.

• Enabling work by fewer people or solo workers: As-built management tasks once carried out by multiple people can be handled by a single person with a smartphone. Because the system is intuitive and does not require specialized surveying skills, it can be used even at sites with labor shortages. Tasks previously outsourced to surveying contractors can often be completed in-house in a short time, reducing outsourcing costs and scheduling.

• Improved accuracy and consistent inspection quality: High-precision alignment using RTK-GNSS allows inspections to be performed with consistent accuracy regardless of who conducts them. Human errors such as missed measurements and recording mistakes are reduced, enabling reliable quality control without omissions. Immediate detection and correction of deviations after construction help prevent rework and improve finishing accuracy.

• Improved safety: As-built checks can be performed safely from a distance even on unstable slopes or areas where heavy machinery is operating. Reducing the number of measurements in inherently hazardous locations contributes to site staff safety. Eliminating the need for assistants also reduces the risk of human error in busy site conditions.

• Easier consensus building and smoother communication: AR-visualized information is powerful for explaining matters to clients and inspectors. Completed shapes that were hard to convey with drawings and numbers are instantly clear when displayed on-site with AR. Discussions on design changes and on-site inspections become smoother, shortening the time required for consensus. Sharing the AR screen in online meetings enables remote participants to view and instruct on the site, improving efficiency through remote presence.

• Streamlined digital records and reporting: AR solutions automatically record measurement results digitally and allow cloud-based sharing and analysis. Generation of as-built management charts (heatmaps), point cloud data, and comparison with design data can be done at the push of a button, greatly streamlining previously time-consuming report creation. Real-time data accumulation aids progress tracking and retrospective review.

Use case 1: Road paving – Quickly check wide areas with AR heatmaps

For wide paved surfaces such as roads and parking lots, it is necessary to verify that finished elevations and slopes fall within specified ranges as part of as-built inspection. Traditionally, many elevation points were measured along reference points or long straightedges and wires were used to check surface irregularities. However, point-based measurements can miss issues, and covering wide areas requires significant effort.

AR technology allows quick assessment of such paved surfaces at a glance. Specifically, a colored heatmap showing deviations from the design elevation is displayed in AR over the finished pavement. By pointing a smartphone or tablet, you can immediately see which areas are higher or lower than the design by color. Green or blue indicates compliance with the design, while red indicates a deviation above or below the standard.

Thanks to the visualized heatmap, you can grasp the finishing status of a wide area in a short time. For example, at one paving site that introduced AR as-built inspection, the conventional labor- and time-intensive flatness checks were completed instantly with AR, allowing even minor deviations to be corrected without being overlooked. This achieved both efficiency and improved accuracy in inspection, and explaining the as-built condition to clients became straightforward—seeing is believing.

Use case 2: Retaining wall work – Instantly check discrepancies between drawings and constructions with AR

For structures such as retaining walls and bridges, as-built inspections verify whether the location and dimensions of the completed structure match the design drawings. Traditionally, distances and elevations were measured at key points and compared repeatedly with drawing values. Curved retaining walls and structures composed of many components, in particular, required tremendous effort to check as a whole.

AR as-built inspection significantly streamlines inspection of such structures. When a 3D design model or layout displayed on a smartphone is overlaid on the actual structure, it becomes immediately apparent whether the shape and position match the design. For example, when checking the placement of retaining wall blocks, displaying the design reference line or block placement diagram in AR allows instant confirmation of what used to be scale-based measurements. If part of the structure is misaligned, the discrepancy between the virtual model and the real object is obvious on the spot, enabling immediate detection and correction.

At one site, AR was used for rebar arrangement inspection of a reinforced concrete structure. By displaying the rebar layout in AR and comparing it with the actual rebar on site, shortages or overcrowding in the number and spacing of bars could be confirmed immediately. Previously, manual measurement and counting were required, but AR enabled both labor savings and reliable inspection.

As shown here, AR as-built inspection, which allows real-time comparison of drawing information and the actual object, provides the greatest benefit for complex structures. It not only reduces inspection time but also prevents oversights and misunderstandings, raising the level of quality control.

Use case 3: Earthworks – LiDAR scanning reduced as-built measurement from half a day to 30 minutes

In earthworks such as land development and excavation, surveying the finished terrain to calculate fill and cut volumes is essential for as-built management. Traditionally, surveying teams observed many detailed points on site, then produced drawings and calculated volumes from that data, which could take more than half a day for large sites. Recently, drone photogrammetry has also been used, but flight planning and image processing require time.

AR technology has proven highly effective for as-built surveying in earthworks as well. A construction company in Gifu Prefecture trialed AR point cloud measurement on a small earthworks site using a smartphone/tablet. By attaching a high-precision GNSS unit (LRTK) to a LiDAR-equipped tablet (such as an iPad) and walking the site, they acquired terrain data for an excavation area of about 150 m² in approximately 15 minutes. A 3D point cloud model was then automatically generated in the cloud, and comparison with the design cross-section and volume calculation were completed in less than 30 minutes.

This shortened a process that once took more than half a day with drone photogrammetry to about 30 minutes of actual on-site work. Since the acquired point cloud data is tagged with high-precision coordinates from RTK, no adjustment to fit reference points in the office is necessary. Moreover, the generated point cloud model is produced in a format compliant with the Ministry of Land, Infrastructure, Transport and Tourism’s as-built management guidelines, making it usable as inspection deliverables. Because as-built evaluation and quantity calculation are completed immediately after acquisition on site, construction management decisions can be made the same day.

As this case demonstrates, AR-based as-built measurement dramatically improves the speed and productivity of civil engineering work. The ability to obtain detailed 3D data quickly makes it easy to increase the frequency of routine progress management and inspections. Measurements can be taken and results confirmed whenever needed, reducing waste and unevenness in construction and contributing to shorter schedules and cost savings.

Simple surveying with LRTK

As described above, AR as-built inspection greatly contributes to site efficiency and quality improvement. Nonetheless, some may worry that introducing such advanced technology in-house is challenging. This is where the new approach called “simple surveying” draws attention. Simple surveying is a concept that enables anyone to perform as-built surveying and layout easily by combining a smartphone, a compact GNSS receiver, and a dedicated app.

For example, LRTK is a solution that, when attached to a smartphone, enables centimeter-level positioning (half-inch level) and integrates AR display with point cloud measurement. The acquired data can be output in formats that conform to the Ministry of Land, Infrastructure, Transport and Tourism’s as-built management guidelines, making it suitable as official deliverables. LRTK also supports the ministry’s i-Construction initiative, lowering the barrier to bringing advanced ICT technology to the site. In sites lacking experienced surveyors, LRTK enables new staff to immediately contribute to surveying and as-built management.

The compact, smartphone-based equipment is easy to carry, and AR display remains accurate even when moving around large sites. From heatmap-based as-built checks and point cloud scanning to stakeout guidance and visualization of buried objects, LRTK covers a wide range of measurement needs. It is truly a “surveying instrument in the palm of your hand” and can be the trump card for on-site DX.

For more detailed information and case studies, please also refer to the [LRTK official site](https://www.lrtk.lefixea.com/). Demos and implementation consultations are available upon inquiry. Why not leverage cutting-edge AR simple surveying technology to take your sites to the next stage?

FAQ

Q1. Do I need special equipment or advanced knowledge to introduce AR technology on site? A. No. You can get started without particularly expensive equipment or specialist knowledge. For example, solutions that come as a kit of a small GNSS receiver that attaches to a smartphone and a dedicated app (such as LRTK) allow anyone with a smartphone to intuitively use AR on site. Operation is simple, and in most cases users can be proficient after a few hours of training. Compared to conventional surveying instruments, the equipment is easier to carry, so it can be used on site whenever needed.

Q2. Can smartphone AR display really align positions accurately? A. If you correct the smartphone positioning with RTK-GNSS, you can overlay virtual design data onto the real world with errors of a few centimeters (a few in). Standard smartphone built-in GPS has errors of about 5–10 m, but RTK dramatically improves positioning accuracy, bringing the design and on-site positions to a level where discrepancies are scarcely noticeable. In actual construction sites, it has been confirmed that AR models and real objects align almost perfectly, providing accuracy sufficient for as-built inspections.

Q3. Is AR as-built verification possible in places where satellite positioning is unstable or indoors? A. In environments where GPS signals from satellites are difficult to receive—such as dense urban canyons or under trees—high-precision RTK positioning becomes difficult. In such environments, errors may temporarily increase or positioning may be interrupted. However, if you perform an initial alignment (calibration) in an open area, you can continue short tasks using the smartphone’s built-in sensors and camera markers as supplementary aids. On the other hand, in tunnels or fully indoor locations where satellite signals are completely blocked, AR as-built inspection is currently difficult (future technological advances are expected). Note that LRTK supports Japan’s quasi-zenith satellite Michibiki (CLAS signal), so in some mountainous or remote areas where communication is limited, positioning is still possible as long as satellites are visible, making it adaptable to a relatively wide range of environments.

Q4. Is there any benefit to introducing AR for small sites or short-term projects? A. Yes, absolutely. AR’s benefits are often greatest for small projects with limited personnel, where a single person can perform surveying and as-built management. Tasks that previously required an external surveyor can often be completed quickly by in-house staff using AR, reducing outsourcing costs and wait times. Even on short-term projects, using AR for daily progress checks and as-built inspections allows rapid situation assessment and record-keeping. These daily practices contribute to final quality assurance and schedule shortening, making AR effective on projects of all sizes.

Q5. Is it possible to use AR glasses (smart glasses) instead of a smartphone? A. There are cases that use see-through AR glasses or helmet-mounted displays. However, dedicated glasses are expensive, and narrow fields of view and operational difficulties make their widespread use on sites challenging. In contrast, using smartphones or tablets allows many people to use familiar devices, keeping introduction costs relatively low. LRTK is designed as a smartphone-based solution that balances GNSS-backed accuracy with the convenience of smartphone AR. It is realistic to start with familiar smartphone AR and consider other devices as needed.

Q6. What kind of design data is required to use AR as-built inspection? A. A 3D BIM/CIM model is ideal, but AR can also be used with only 2D drawing data. Many AR solutions can import design DXF data or coordinate information to project reference lines and necessary as-built control points on site. With LRTK, you can upload not only 3D models but also 2D plans and alignment data to display boundaries and elevation references on site. In short, AR technology is flexible and can effectively use available design information even without complete 3D data, allowing phased implementation while gradually improving data preparation.