Paperless Sites! AR Heatmaps Pioneering Construction Management DX

Table of Contents

• What is an AR heatmap?

• Conventional as-built management methods and their challenges

• DX and paperless initiatives advancing in the construction industry

• Benefits AR heatmaps bring to the site

• Use cases for AR heatmaps (pavement, embankments, slopes, structures)

• Technologies and tools required to implement AR heatmaps

• Simple surveying with LRTK

• Conclusion

• FAQ

What is an AR heatmap?

An AR heatmap is a method that overlays an “as-built management chart (heatmap)”—which color-codes the differences between the finished structure or terrain (the actual as-built) and the design data—onto the site view using AR (augmented reality) technology. Through a smartphone or tablet screen, you can simultaneously compare design drawings or 3D models with the actual completed work and intuitively verify on the spot whether the as-built conforms to the plan. For example, areas that are higher than designed are shown in red and areas that are lower in blue over the site video, allowing you to grasp variations in construction accuracy at a glance. Compared with verifying while squinting at paper drawings, this makes checks far easier to understand and speeds up on-site quality inspections.

Conventional as-built management methods and their challenges

In civil and construction works, as-built management is used to confirm whether the finished shape matches the design. However, conventional as-built management methods involved significant effort and time and had various issues. Typically, survey instruments such as levels or total stations (TS) and scales are used; personnel measure heights and thicknesses at each survey point, note them down, and then verify by comparing them with drawings back at the office. Such analog work depended heavily on experienced technicians and lacked efficiency and immediacy. With labor shortages and an aging technical workforce, completing these tasks with limited personnel was a major burden.

The main challenges pointed out with traditional as-built management can be summarized as follows:

• Long working hours: On large sites or projects with many survey points, the conventional method of measuring each point manually takes a great deal of time. It is not uncommon for it to take several days from taking measurements to compiling results on drawings and checking errors.

• Dependence on manpower and skilled technicians: Surveying and as-built evaluation require experienced surveying technicians, and measurements are often done in pairs. With chronic labor shortages, it has been difficult to secure sufficient personnel each time.

• High equipment costs: High-precision surveying requires expensive instruments such as total stations or RTK-GNSS receivers, making initial investment a major hurdle. For small and medium-sized contractors, the cost burden of acquiring and maintaining equipment was a big concern.

• Measurement errors and recording mistakes: Manual measurement workflows risk accumulating small errors each time and introducing human error when transcribing noted values to drawings. Discovering recording mistakes later can lead to the extra work of re-measurement.

• Time-consuming report preparation: Creating as-built drawings and reports based on measurements and submitting them to the client is also a burden on site staff. Time spent organizing photos of survey points and plotting them on drawings can leave insufficient time for the essential task of quality analysis.

• Delay in defect detection: Even if there are deficiencies such as insufficient thickness or incorrect slopes, they are often not noticed immediately on site; instead, they are found after bringing data back and converting it into drawings the next day or later. When problems are discovered, concrete may already have set or heavy equipment may have been removed, incurring additional costs to redo work.

Thus, conventional as-built management was full of inefficiencies and lacked immediacy, imposing significant human and cost burdens. For example, for buried pipe works, a complex process was required: survey pipe positions and photograph them before backfilling, then later create CAD drawings. Such procedures take time to grasp and record site conditions, and the hard-won data often ends up as mere attachments to reports and is not fully utilized. There was a pressing need for a new method that enables accurate and intuitive real-time as-built understanding on site.

DX and paperless initiatives advancing in the construction industry

Against this backdrop, the construction industry as a whole is accelerating initiatives to improve productivity through DX (digital transformation) and to move toward a paperless environment. Since around 2016, the Ministry of Land, Infrastructure, Transport and Tourism has promoted a policy called *i-Construction*, encouraging the adoption of ICT technologies in surveying and construction management across the industry. Smart construction using digital technologies—such as 3D surveying by drones and machine guidance/machine control for construction equipment—is gradually spreading. In as-built management, a shift from traditional layout and level surveying to 3D measurement technology has emerged, and the ministry formulated the “Guidelines for as-built management using 3D measurement technology (draft)” and has been applying them to construction sites nationwide. In March 2025 (Reiwa 7), the inspection and supervision guidelines for as-built management across work types such as earthworks (including embankments), pavement, slopes, and structures were revised simultaneously, and as-built management using digital measurement has been standardized in earnest.

The new guidelines recommend high-precision area measurements of as-builts using RTK-GNSS, ground-based or UAV laser scanners, photogrammetry, etc., and automated pass/fail judgments by comparing to design data. Advanced inspection methods, such as overlaying acquired 3D point cloud data on the design model for difference analysis and visualizing the current condition with a color-coded heatmap, have been officially recognized. Another notable point is the on-site use of AR technology. In recent years, device performance—smartphones and tablets—has improved dramatically, bringing AR from an experimental stage to practical use in day-to-day construction management. Using modern mobile devices equipped with high-performance cameras and LiDAR sensors, dedicated apps can overlay design models and measured as-built data on-site, allowing intuitive on-site verification of as-builts.

The government is also positive about adopting new technologies; in FY2024, a notice stated that “if a contractor proposes simplification/efficiency of inspections using 3D models or AR, active trials in place of conventional standards will be encouraged.” Some wording even indicates that “if as-built measurement results are projected on-site using AR and used for pass/fail judgments, submission of traditional as-built management charts (heatmaps) may be made unnecessary,” suggesting that AR-based as-built management methods are being formally recognized. In other words, using AR heatmaps could mean that inspections can be completed without submitting paper charts. Against this background, AR heatmaps—which simultaneously achieve labor savings and quality improvement on-site—are gathering strong expectations as a key driver of construction management DX.

Benefits AR heatmaps bring to the site

AR heatmaps are a technology that addresses the issues of conventional analog construction management methods and provide significant benefits on site. Here are the main advantages.

• Immediate on-site visualization of quality: Differences in as-builts are color-displayed on the spot, allowing immediate grasp of quality conditions after construction. There is no need to return to the office to compare with drawings, and inspections and corrections can be completed on the same day.

• Improved accuracy through area-based as-built understanding: Localized errors that might be missed by point-sample measurements are visible at a glance in an area-wide heatmap. Being able to overview the entire construction area ensures you can reliably identify portions outside the quality standards.

• Reduction of rework and redo: Problems can be identified immediately on site and corrective actions instructed on the spot, reducing rework discovered later. For example, if insufficient thickness of concrete is detected immediately after placement, additional repairs can be made before hardening, preventing major correction works.

• Labor savings and improved operational efficiency: High-precision AR measurement can be performed by one person, reducing the need for multiple people for surveying. Even if veteran surveyors are scarce, on-site personnel can perform measurement and verification with a smartphone in hand, enabling efficient quality control with limited staff.

• Lower equipment costs: Instead of specialized surveying equipment, relatively low-cost devices such as general-purpose smartphones and compact GNSS receivers can be used. This removes the need for expensive initial investment, making it easier for small sites and companies to adopt the latest technology.

• Streamlined digital recording and reporting: Measurement data and site photos are automatically recorded digitally and can be compared and stored with design data in the cloud. This greatly reduces later transcription or photo pasting tasks and facilitates electronic delivery.

• Improved communication: Because the heatmap is displayed directly on site, both contractors and clients can share the situation at a glance. Instructions to machine operators—such as “where and how much to correct”—are clearly communicated when showing the AR display. Misunderstandings among stakeholders are reduced and consensus building is faster.

• Realizing paperless operations: Using AR heatmaps reduces the need to carry paper drawings and forms. Inspections can be completed with digital data, eliminating the effort to output and distribute traditional paper as-built management charts. Advancing paperless sites reduces the burden of document management and contributes to ecology.

Use cases for AR heatmaps (pavement, embankments, slopes, structures)

In practice, AR heatmaps demonstrate their power across various civil construction sites. Here are representative use scenarios.

• Pavement works: For road pavement, it is necessary to check whether the finished road surface height and smoothness meet specifications. If you 3D-measure the road after paving and display the design height differences as a heatmap, you can instantly find areas with insufficient thickness or surface irregularities. By showing problem areas in AR, targeted additional paving or surface correction can be carried out before the asphalt cools.

• Embankment works: In earthfill works, plane-based evaluation of as-built errors relative to the design surface height and slope is possible. If you confirm the embankment finish on an AR heatmap, areas that are overfilled or underfilled compared to the design are immediately visible by color. Marking defective areas and communicating them to machine operators enables immediate corrective work such as additional fill or trimming.

• Slope works: AR heatmaps are also effective for slope formation and shaping. Scanning the constructed slope and comparing it with the design slope model will show areas deviating from the prescribed gradient or irregularities via color distribution. Early detection and correction of dangerously steep sections or interference points enhances finish stability and safety.

• Structure works: AR can be used for as-built checks on bridges and concrete structures. For example, measuring the top surface elevation after concrete pouring or the tilt of a structure and displaying differences from the design model as a heatmap allows intuitive inspection of finish accuracy. The placement of rebar or bolts can also be checked in a透視-like manner with AR, suggesting applicability for internal as-built inspections of structures.

Additionally, it is possible to display and share the positions of hidden infrastructure such as buried water and sewage pipes using AR. If the pipes are 3D-measured immediately after installation, their precise locations and depths can be known by anyone with AR even after they are covered by pavement, reducing the risk of accidental damage during later excavation and aiding maintenance. The scope of use for AR heatmaps and related digital measurement data is expected to expand further.

Technologies and tools required to implement AR heatmaps

So what is required to implement AR heatmaps on-site? Broadly speaking, two keys are “high-precision as-built measurement technology” and “devices and software for AR display.”

First, means to acquire the as-built data that will form the basis of the heatmap. Traditionally, points were measured manually, but now 3D measurement enables wide-area as-built measurement at once. Specifically, photogrammetry from drone aerial surveys, ground-based or UAV-mounted laser scanners (LiDAR), or surveys using RTK-GNSS are employed. These methods can capture the shape of construction targets as dense point cloud data or 3D models. Recently, smartphones and tablets equipped with built-in LiDAR sensors or cameras can also perform short-range point cloud scans.

The acquired 3D as-built data are analyzed against the design data in the cloud or dedicated software to generate heatmaps. Advanced analysis algorithms automatically compute errors at each point and create color-coded maps without manual calculation, allowing users to generate heatmaps without specialized knowledge.

Next is the technology for AR display. To accurately overlay digital information such as heatmaps onto real space, the device’s position and orientation must be known with high precision. While indoor AR can be handled with markers or image recognition, the GPS accuracy built into smartphones (on the order of several m (several ft)) is insufficient for large outdoor sites. What helps here are high-precision GNSS receivers that can be attached to smartphones or tablets and methods to align coordinates using control points set up on site. By combining centimeter-level positioning data from high-precision GNSS with attitude detection from the device’s gyroscope and accelerometer, digital models and real-world coordinates can be made to match precisely. Additionally, using the device camera feed and LiDAR scans to recognize the surrounding environment enables AR objects to follow and remain aligned with real structures, achieving a seamless overlay.

In short, implementing AR heatmaps requires “equipment to measure as-builts in 3D” and “AR display tools that support high-precision positioning alignment.” Historically these were expensive, specialized instruments, but recently integrated solutions that are easy to operate have appeared. A representative example is the following section on simple surveying with LRTK.

Simple surveying with LRTK

LRTK (pronounced “Eru-Aru-Tii-Kei”) is an innovative solution that enables high-precision positioning simply by attaching a device to a smartphone. By mounting a compact, high-sensitivity GNSS receiver device (LRTK device) on a phone and connecting via Bluetooth, you can boost smartphone GPS—normally subject to errors of several m (several ft)—to errors of just several cm (several in). This is achieved by RTK (Real Time Kinematic) positioning, which improves accuracy by applying correction information transmitted in real time from national or commercial reference stations. In Japan, LRTK also supports the Quasi-Zenith Satellite System “Michibiki” centimeter-level augmentation service (CLAS) (half-inch-level accuracy), enabling stable high-precision positioning even at sites in mountainous areas where reference stations are not nearby.

The smartphone plus LRTK device combination makes it possible for anyone to easily perform high-precision surveying and as-built data collection alone. Without lugging heavy tripods or requiring advanced expertise, you can walk the site with a smartphone in hand and carry out surveying and as-built checks, dramatically improving operational agility. Using an LRTK-enabled app, you can simultaneously acquire point clouds from the phone camera or LiDAR while positioning, upload the data to the cloud, and automatically compare it to the design data. When you take a photo with your smartphone, coordinates, time, and notes for the capture location are automatically recorded, greatly streamlining evidence collection for as-built management.

LRTK devices themselves are very compact and easy to handle, often palm-sized units with built-in batteries and antennas. For example, a smartphone-mounted product called “LRTK Phone” has demonstrated the practicality of surveying while carried all day. The impact of enabling centimeter-level positioning—previously reliant on specialized equipment and technicians—on a single smartphone is profound; it truly upends conventional on-site practices and can be called a game changer. LRTK is already being used across a wide range of sites—civil engineering, construction, surveying, and infrastructure management—including disaster site surveys after the Noto Peninsula earthquake. As a next-generation construction management tool compliant with the Ministry of Land, Infrastructure, Transport and Tourism’s 3D as-built management standards, it is attracting attention and being adopted by small businesses and local governments.

Combining LRTK’s high-precision simple surveying with AR heatmaps dramatically transforms construction management sites. Because you can precisely overlay design data and as-built heatmaps on the actual structures seen on the smartphone screen, inspections previously done in the office with paper drawings can be performed intuitively on site. Quality control speed and reliability improve dramatically, and records can be kept digitally, making a genuinely paperless site a realistic prospect.

Conclusion

AR heatmaps are revolutionizing how quality confirmation is performed in construction management. By visualizing as-built deviations on site, they greatly reduce time loss, personnel shortages, and the risk of errors that were previously common. They align with national i-Construction initiatives and the latest as-built management guidelines, and are expected to embody productivity improvement and paperless operations at the site level through digital technology.

Quality control that once relied on the intuition and experience of veteran technicians is now becoming accessible to anyone who uses tools such as AR and LRTK. Information sharing between clients and contractors also becomes smoother, enabling efficient corrections and consensus building that improve the overall efficiency of projects. “Paperless sites” are no longer a fantasy—technologies like AR heatmaps are making them a reality. Please consider actively adopting the latest solutions to achieve smart site operations through construction management DX.

FAQ

Q: What is an AR heatmap? A: It is a system that projects a heatmap (a color-coded map of differences between design and as-built) onto the site using AR so you can intuitively check as-builts. When you hold up a tablet, differences from the design are color-displayed over the completed structure, enabling visual on-site quality checks.

Q: On what kinds of construction sites can AR heatmaps be used? A: They can be used for checking pavement thickness and finished heights, verifying embankments and slopes, and accuracy management of concrete structures, among many civil and construction works. Essentially, any situation where you need to confirm “is this built according to the design?” can benefit; they can also be applied to confirming the positions of normally hidden elements like buried pipes.

Q: What is required to introduce AR heatmaps? A: First, a method to measure as-builts in 3D (drone surveys, laser scanners, smartphone + LiDAR, etc.). Next, software (including cloud services) to compare measurement data with design data and create heatmaps. Most importantly, you need AR-capable devices and high-precision positioning alignment technology. Smartphones or tablets with high-precision GNSS, or systems like LRTK that attach GNSS receivers to phones, help accurately align digital data with the real world.

Q: Aren’t expensive specialized devices required? A: No, not necessarily. Recently, combining commercially available smartphones or tablets with aftermarket devices can achieve precision comparable to surveying equipment that used to cost millions of yen. Solutions like LRTK can provide an AR heatmap environment at relatively low cost. Additionally, eliminating paper drawings and large-scale photo processing often reduces total costs.

Q: Can AR heatmaps be used for official as-built inspections? A: Yes. The Ministry of Land, Infrastructure, Transport and Tourism promotes efficiency in as-built management through AR, and under the new standards from FY2025, AR-based as-built inspections are being trialed on sites. It has been indicated that when pass/fail judgments are made on AR, submission of paper forms may be omitted. In other words, with appropriate procedures, AR heatmaps can be used as an official inspection method. However, because some cases are still in trial, follow the client’s operational policies and the applicable guidelines when implementing.

Q: Can people without specialized knowledge or skills use it effectively? A: Compared with traditional surveying instruments, AR heatmaps are far more intuitive and easier to use. By following on-screen guides on a smartphone or tablet, people without special qualifications can perform measurement through confirmation single-handedly. Some initial setup and calibration familiarity are required, but they are generally learned much faster than operating conventional total stations. Indeed, young on-site technicians can contribute to quality checks using digital tools, helping to alleviate labor shortages.