Table of Contents

• [What is an As-Built AR Check](#what-is-an-as-built-ar-check)

• [Conventional As-Built Management Methods and Their Challenges](#conventional-as-built-management-methods-and-their-challenges)

• [How AR×GNSS Enables Real-Time As-Built Verification](#how-ar×gnss-enables-real-time-as-built-verification)

• [Concrete On-Site Workflow Example](#concrete-on-site-workflow-example)

• [Ministry of Land, Infrastructure, Transport and Tourism As-Built Management Guidelines and i-Construction Trends](#ministry-of-land-infrastructure-transport-and-telecom-as-built-management-guidelines-and-i-construction-trends)

• [Benefits of AR As-Built Checks](#benefits-of-ar-as-built-checks)

• [In Closing: How to Easily Start AR As-Built Checks](#in-closing-how-to-easily-start-ar-as-built-checks)

• [FAQ](#faq)

What is an As-Built AR Check

"As-built management" is a crucial process in civil engineering and construction that verifies and records whether completed structures and developed land have been finished to the design's shapes and dimensions. In public works, the results of as-built management are often conditions for inspection approval and handover, making it key to ensuring quality. Traditionally, as-built checks have relied on direct measurement with tape measures, staffs (level rods), and levels, plus photographic documentation, with measurement results compiled into tables and photo albums for reporting. However, manual as-built verification requires substantial labor and time, and because measurement points are limited, there is an undeniable risk of oversights.

In this context, a newly notable on-site verification method is the "As-Built AR Check." This combines AR (Augmented Reality) technology with GNSS positioning to enable real-time as-built verification on site. Through a smartphone or tablet camera, design drawings or 3D model information are overlaid onto the actual construction site, allowing intuitive recognition of discrepancies between the as-built object and the design. For example, projecting the design lines or shapes in AR over the post-construction terrain or structures makes it immediately obvious whether the outcome is within tolerances. What makes this possible is high-precision GNSS (Global Navigation Satellite System) position information combined with smartphone sensor technology. The AR×GNSS combination is driving the digital evolution of as-built management.

Conventional As-Built Management Methods and Their Challenges

First, let’s review how conventional as-built management is carried out and the challenges it faces. In traditional methods, measurements are taken manually at key points of completed structures to confirm and record differences from design values. For roadworks, for example, thickness, width, and height of subgrade and pavement are measured at intervals; for slope works, gradients and lengths are measured and organized into as-built management charts (measurement result lists). However, the conventional approach has drawn many criticisms from the field.

• Labor- and time-intensive: Dimension measurements typically require a team of multiple people, and on large sites the number of measurement points can make this a full-day task. Securing skilled survey technicians is also difficult, making it hard to proceed efficiently within schedules amid labor shortages.

• Lack of coverage leading to oversights: Manual methods limit the number of physically measurable points, so the entire construction area cannot be fully covered. Measuring only a few representative points risks missing locations that deviate from the design. The larger the structure, the more likely subtle unevenness or variability will be missed, leading to last-minute rework when inspectors later note discrepancies with drawings.

• Risk of human error: Busy sites are prone to human mistakes such as forgetting to take photos or record data. For instance, failing to photograph buried items before backfilling can make it impossible to prove the as-built condition later. Mistakes in handwritten measurement notes or data transcription have led to quality problems, placing heavy burdens and anxiety on site personnel.

These challenges have driven a long-standing demand for more efficient and reliable as-built management methods. Especially recently, with labor shortages and work-style reform, there is strong expectation for new technologies to achieve labor reduction and productivity improvements.

How AR×GNSS Enables Real-Time As-Built Verification

A key solution emerging to address these challenges is the fusion of AR technology and high-precision GNSS positioning. By attaching a compact RTK-GNSS receiver to a smartphone and using a dedicated app, anyone can easily obtain centimeter-level positional accuracy (cm level accuracy (half-inch accuracy)). RTK (Real Time Kinematic) GNSS combines satellite positioning with correction information from a reference station to reduce positioning error to within a few centimeters (within a few inches). Where high-cost surveying equipment was once required, precise positioning can now be obtained on a smartphone in real time.

With high-precision self-positioning, spatial comparison with design data becomes possible. By loading BIM/CIM models or drawing data into a dedicated app and aligning them with the site coordinate system, the app can overlay those designs precisely onto the smartphone camera view. For example, the completed shapes or reference lines from design drawings can be displayed in AR over the real scenery seen through the phone. Because GNSS aligns position to world coordinates, the virtual model does not drift relative to reality even as the user walks around. This allows one-to-one comparison of real structures and digital design information to check as-built conformity on site.

Moreover, by using a smartphone’s built-in LiDAR scanner or high-resolution camera, on-site 3D measurement can be performed simultaneously. For instance, scan the area to be verified with a smartphone to obtain point cloud data, then compare that data in the cloud with the design’s 3D model to generate a difference heat map. If the heat map indicating deviations is downloaded to the phone, it can be overlaid in AR onto the actual site. Because the error distribution is projected onto the real scene, it becomes immediately clear which areas are higher or lower than the design, enabling prompt corrective earthwork such as adding fill or excavation. Previously, point cloud processing required creating and submitting heat maps on a plan and then locating the corresponding points on site, but AR now makes it possible to “see it directly on site.”

In short, the AR×GNSS mechanism is transforming the traditional process of measuring and then checking/reporting in the office into real-time on-site verification. Surveying, as-built checking, and photographic documentation can be completed with a single smartphone, and necessary data are immediately shared to the cloud so stakeholders can confirm and decide on next steps on the spot. This is a technological innovation that can dramatically improve site productivity and quality control.

Concrete On-Site Workflow Example

How is an As-Built AR Check actually performed on site? Below is a workflow example for civil engineering work using AR×GNSS for as-built verification.

• Preparation (provide design data): First, prepare the target construction’s drawings and 3D model data in digital form. BIM/CIM models or CAD data typically contain information on the finished shape and reference lines/planes. Load these into the dedicated app and align them with the site coordinate system (survey coordinates). For public works, since fiscal year 2023, BIM/CIM introduction has become the principle in many projects, making digital design data available.

• Equipment setup: Attach an RTK-GNSS receiver to a smartphone or tablet and ensure it can receive GNSS correction information on site. In Japan, QZSS (“Michibiki”) centimeter-level augmentation services (CLAS) and network RTK over the internet make high-precision positioning readily available. Once positioning is stable, activate AR display mode in the app and calibrate heading (compass) if necessary.

• As-built checking operations: To check the height of a developed ground, for example, display a virtual horizontal plane representing the design finish height in AR. The phone screen will show the design height plane overlaid on the site view, allowing the operator to walk around and see whether the actual ground is higher or lower than the virtual plane. Where the virtual plane appears to float above the ground indicates insufficient fill; where it sinks into the ground indicates overfill. Similarly, for roadworks, project the design longitudinal and cross-sectional lines in AR to verify pavement thickness and slope on the spot.

• Real-time instructions and corrections: If discrepancies are revealed by the AR display, share them with workers immediately and carry out corrections promptly. For example, if you see “this point is 5 cm (2.0 in) lower than the design,” you can add soil on the spot. Numeric guides displayed in AR (e.g., “add +5 cm (2.0 in) fill”) or color-coded indicators are intuitively understandable to workers and serve as clearer instructions than words alone. This minimizes rework while advancing construction.

• Data recording and reporting: After inspection, save the check results as data. Photos taken with the smartphone that include coordinates are uploaded to the cloud with position and orientation, and can be reviewed later in the office. If a point cloud scan was performed, some systems can generate as-built heat maps and management tables with one click from that data. These digital files can be organized and submitted as reporting materials to clients.

Through the above flow, AR×GNSS as-built checks allow on-site verification and correction in real time while keeping final records fully digital. Compared with the days of paper field notebooks and tape measures, this workflow is dramatically more efficient.

Ministry of Land, Infrastructure, Transport and Tourism As-Built Management Guidelines and i-Construction Trends

Even though it is advanced technology, the “As-Built AR Check” is not an eccentric departure from existing standards. The Ministry of Land, Infrastructure, Transport and Tourism (MLIT) has been actively promoting ICT utilization in construction management and officially supporting the digitization of as-built management.

As part of the i-Construction initiative, MLIT encourages introduction of BIM/CIM and 3D measurement technologies. In particular, MLIT drafted the "As-Built Management Guidelines Using 3D Measurement Technologies (draft)" and has been standardizing as-built measurement methods using drone photogrammetry and terrestrial laser scanners. Furthermore, in 2022 the as-built management guidelines were revised to formally permit the use of simple mobile devices such as smartphones for as-built measurement in public works. This makes 3D as-built management using smartphones increasingly feasible even for small- and medium-scale sites without expensive dedicated equipment.

In addition, in 2024 MLIT issued a notice on trialing supervision and inspection using digital data on MLIT-managed projects, indicating a new method of “projecting the 3D model created during the construction stage onto the site using AR technology and conducting on-the-spot as-built measurement.” Traditionally, point cloud data were used to create and submit heat maps and then the site was re-measured during field inspections; AR-based on-site confirmation aims to streamline that process. With public and private sectors promoting digital transformation (DX) of construction sites, AR×GNSS as-built checks fit well within this trend.

Moreover, from fiscal year 2023, BIM/CIM application in principle began for all MLIT-managed projects except small-scale ones. As a result, 3D design data will be prepared for many projects, greatly increasing the digital information available for AR. In short, “automation of data linkage” is gaining momentum in the construction industry, and smart construction that does not rely on paper and manual work is beginning to penetrate as-built management practices.

Benefits of AR As-Built Checks

The AR×GNSS as-built checking method offers significant benefits to construction sites. Below are the main advantages.

• Major efficiency gains and labor reduction: Surveying and inspection tasks that used to require two or more people can be completed by a single person, increasing flexibility in personnel allocation. One-person surveying helps address chronic labor shortages and raises overall site productivity. Interruptions caused by waiting for surveying are reduced, allowing immediate measurement and confirmation when needed and smoothing project progress.

• Improved quality through high-density measurement: Point cloud scanning and continuous measurement enable high-density measurement over wide areas, allowing as-built conditions to be understood over surfaces. This reduces the likelihood of missing slight unevenness or dimensional variability and lowers variability in construction quality. The ability to cover the whole site with data provides reassurance in quality management for both clients and contractors.

• Real-time correction and reduced rework: Because verification can occur immediately after construction on site, nonconformities that would otherwise be discovered only at later inspections can be prevented. “Confirm on the spot and correct on the spot” becomes possible, enabling early detection of errors and immediate response that reduce rework and schedule delays, and thereby curb wasted costs.

• Intuitive and easy-to-understand communication: AR-visualized information is more intuitive than reports of text or numbers alone. If everyone on site views the same AR image on their phone, it is instantly clear which locations need what degree of correction. This reduces reliance on experienced intuition, smooths shared understanding and consensus building among craftsmen and supervisors.

• Easy data recording and transfer: Because measurement data and photos are stored and shared digitally, the workload of creating forms and reports is reduced. As-built data centrally managed in the cloud can be used later for maintenance and renovation work. Moreover, skills and site knowledge of experienced personnel are preserved as data, supporting non-personalized knowledge transfer.

• Improved safety: Remote measurement using AR reduces the need to enter hazardous areas. For example, AR markers can be set and guided from a distance for slopes or high places, reducing the need for workers to assume dangerous postures for surveying. Point setting around heavy machinery can also be guided by AR to reduce contact risks. As a result, overall site safety is improved.

As described, AR as-built checks are not merely a novelty; they provide practical benefits directly addressing site challenges. With the construction industry’s aging population and growing labor shortages, AR×GNSS is expected to spread widely as a trump card that balances efficiency and quality.

In Closing: How to Easily Start AR As-Built Checks

AR×GNSS as-built checks used to require specialized equipment and were a leading-edge undertaking. Today, however, easy solutions combining smartphones and compact GNSS receivers are emerging. For example, LRTK, developed by a venture from Tokyo Institute of Technology, is a system consisting of a pocket-sized RTK-GNSS device that can be attached to an iPhone and a dedicated app, transforming the site so that “surveying and inspection can be completed with just a smartphone.” Even general technicians without special training can operate it intuitively and immediately use high-precision positioning, point cloud scanning, and AR-based as-built verification via simple surveying functions.

Such tools make AR as-built checks accessible for everyday practice, lowering previous adoption barriers. With a single smartphone you can measure, record, compare, and share in a seamless workflow, enabling digital construction management even on small sites or with limited personnel. The important thing is to try it on site first. You may be surprised how easily tasks that relied on paper drawings and tape measures can be digitized. AR×GNSS as-built checks are not a special futuristic technology but a practical tool already usable on the job. Why not take this opportunity to start simple smart construction at your site?

FAQ

Q: If I use AR for as-built management, can I trust the accuracy? A: With AR combined with high-precision GNSS (RTK-GNSS), positional accuracy can be secured to within a few centimeters (within a few inches). Regular smartphone GPS has errors on the order of several meters (several ft), but RTK corrections allow self-positioning at a level comparable to survey control points, so AR overlays align with minimal drift. Additionally, properly calibrating the phone’s gyro and compass brings directional accuracy within practical ranges.

Q: What preparations and equipment are needed to display AR on site? A: Essentially, a smartphone/tablet + RTK-capable GNSS receiver + dedicated app will do. Prepare design data (3D models or drawing digital files) in advance and load them into the app. GNSS receivers that receive corrections via the internet are convenient; outdoors with signal access, you can use correction services without maintaining your own base station.

Q: What about environments where GNSS cannot be received, such as tunnels or indoors? A: Pure GNSS positioning cannot be used where the sky view is blocked. In such cases, you can place known points (reference markers) to serve as AR markers or perform alignment using pre-measured reference coordinates. For example, in a tunnel you might use GNSS at the entrance to establish coordinates and then align to interior known points for AR display. Indoors, QR codes or feature-point markers can be used to align AR.

Q: Does introducing AR as-built checks incur significant costs? A: It is considerably lower cost than purchasing large dedicated equipment. Many people already own smartphones, and compact GNSS receivers are much more affordable than traditional surveying gear. Software is often offered as cloud services with flexible licensing for required periods. More importantly, time savings and labor reductions provide strong cost benefits, so the overall return on investment is expected to exceed the initial outlay.

Q: Can anyone quickly become proficient with AR; is special skill required? A: Basic operations are straightforward if you follow the app guidance. For example, with systems like LRTK, you simply point the antenna-equipped phone at the point to be measured and press a button to record coordinates, and AR overlays are selected and applied from the menu. However, some familiarity with equipment handling and calibration procedures is helpful, so a short training beforehand is recommended. With repeated on-site use, users will gain proficiency.