Solve labor shortages! Labor-saving construction management realized by AR heat maps

Table of contents

• What is an AR heat map?

• Benefits of AR heat maps

• Steps to create an AR heat map

• Field use cases of AR heat maps

• The future of construction management DX and AR

• Conclusion

• FAQ

Labor shortages have become a serious issue in the construction industry in recent years. The workforce on site is aging, and according to a Ministry of Land, Infrastructure, Transport and Tourism survey, about 35% of construction workers are 55 years old or older while only around 12% are 29 or younger. The looming “2024 problem,” in which many experienced veterans will retire en masse, raises concerns about a future shortage of successors. In addition, reforms to working styles, such as the wider adoption of a five-day workweek, have reduced the amount of time each person can spend on site. Under these circumstances, improving productivity through labor-saving construction management has become an urgent priority.

One promising approach is the use of AR heat maps for modern construction management. An AR heat map visualizes differences between the as-built (actual finish) and the design data using colors, and projects that visualization onto the site using AR (augmented reality) technology so quality can be intuitively checked on the spot. For example, an “as-built management map” that colors areas higher than the design in red, lower in blue, and within tolerance in green can be viewed directly through a smartphone held up at the site. This makes subtle elevation differences that are hard to grasp from drawings or numbers immediately apparent, enabling instant identification of areas that need rework.

This article explains the benefits and concrete uses of AR heat map–based construction management. From labor-saving points that help alleviate workforce shortages to actual field case studies, implementation steps, and answers to common questions, we cover the topic in detail. Let’s explore how to leverage the latest technology to achieve efficient, high-quality construction management with a small workforce.

What is an AR heat map?

An AR heat map is a method that overlays an “as-built heat map”—which shows deviations between the completed structure or terrain and the design model using color coding—onto the site using AR (augmented reality) technology. The as-built heat map itself is a visualization tool for as-built management that has gained attention in recent years: point cloud data or other 3D surveying data acquired after construction are overlaid with the 3D design model, and deviations at each point are expressed with colors such as red, blue, and green. For example, areas higher than the design are shown in red or warm colors, lower areas in blue, and areas within the design tolerance in green. By simply looking at the color differences, you can immediately see which areas are higher or lower than the standard and whether they are within or outside the specifications.

With AR heat maps, these as-built heat map data are displayed in real time overlaid on the camera image of a tablet or smartphone. When you hold up the screen at the site, a translucent color map is superimposed over the terrain or structure in front of you, making areas with large deviations intuitively obvious on the spot. Conventionally, even if you viewed an as-built management map (heat map) on paper or a PC screen, surveying or marking-out work was required to locate the corresponding points on the ground. But AR display automatically aligns the map with the field, allowing immediate on-site instruction and confirmation of “where and how much rework is required.”

This technology is not just a visualization tool; it is also effective as a communication tool on site. Showing the smartphone screen to the client or site supervisor lets anyone understand construction accuracy through color differences and makes it easier to share points requiring correction. Moreover, initiatives such as *i-Construction* promoted by the Ministry of Land, Infrastructure, Transport and Tourism encourage the use of area-based as-built management (heat maps) using 3D survey data, and methods that combine such AR technologies are becoming a new standard. As part of on-site DX (digitalization), AR heat maps are an innovative solution that combines quality control and labor-saving.

Benefits of AR heat maps

Introducing AR heat maps brings many benefits that traditional construction management methods cannot provide. Here are some of the main advantages.

• Intuitive quality assessment: Since the magnitude of deviations is shown by color, anyone on site—from workers to clients—can immediately understand construction accuracy. Subtle elevation differences that are difficult to notice in numeric or written reports can be intuitively grasped with colored visuals. It becomes easy for the whole team to share judgments about quality and points requiring correction.

• Prevention of inspection omissions: High-density 3D measurements like point clouds allow evaluation of entire surfaces, enabling detection of local defects that conventional spot-check measurements might miss. A heat map covering a wide area can identify unevenness or irregularities without omission. As a result, the risk of “only unmeasured locations having defects” can be reduced.

• Rapid feedback: If you scan areas and create heat maps during construction, you can check the as-built status at that time. Early detection and immediate rework of problem areas minimize the rework that would otherwise be consolidated and performed later. The ability to check quality in near real time contributes to shorter schedules and improved as-built accuracy.

• Digital recording and reuse: Heat maps and point cloud data can be stored in the cloud as digital records. You can save detailed “construction history” that paper drawings could not preserve, making it easier to compare past data during future maintenance and perform root-cause analysis. Furthermore, as-built data can be integrated into BIM/CIM models for use in maintenance and report creation, making them valuable information resources even after completion.

• Labor saving and improved safety: Combining wide-area point cloud measurement with automatic analysis significantly reduces the manpower and time required for surveying. High or hazardous areas can be scanned remotely and safely, reducing the need for workers to spend long periods at height. This enables efficient quality management with a small team and makes it feasible to maintain high standards even at sites suffering from labor shortages.

Steps to create an AR heat map

Below is a general flow of steps to actually create and utilize an AR heat map.

• Preparation of design data: First, prepare 3D design data that will serve as the basis for comparison. For civil engineering works, this includes design ground models (TIN data or design surface data), and for structures, it includes BIM/CIM 3D models. The point is to clearly define the “ideal finished shape” in data form. In as-built management, this design model is the standard for pass/fail judgment.

• 3D measurement of the current condition: Next, measure the actual shape after or during construction in 3D. Point cloud measurement using laser scanners, drone photogrammetry, or LiDAR-equipped smartphones has become mainstream. These methods can rapidly capture wide areas and record the current condition as high-density point cloud data for terrain and structures. With the latest smartphones, you can scan the site and obtain point clouds using a dedicated app.

• Generating the heat map: Compare the acquired point cloud data with the design data, automatically calculate deviations, and create a heat map. This differential analysis can be executed with a few clicks in dedicated PC software or cloud services. If the point cloud data include geodetic coordinates (such as World Geodetic System coordinates), alignment with the design data is automatic and smooth. Some software allows you to freely set the heat map grid size and color-coding thresholds, letting you customize accuracy and thresholds according to your purpose.

• On-site verification with AR: Display the generated heat map in AR on the site to check the as-built condition. Loading the heat map data into an AR-compatible smartphone or tablet app overlays it on the camera image. While the device’s GPS and sensors can achieve a certain level of alignment, for higher-precision overlay you can correct the device position with RTK-GNSS for high-accuracy positioning or place markers (targets) on site for referencing. Using equipment capable of centimeter-level positioning (half-inch accuracy) ensures the heat map is displayed precisely and without drift even across a wide site. While viewing that screen, you can mark out nonconforming areas or perform immediate rework.

Field use cases of AR heat maps

AR heat maps are useful across various civil engineering and construction sites. Here are some representative cases.

• Road pavement work: Heat maps are powerful when checking the finished elevation of asphalt or concrete pavement. Traditionally, road height was measured at fixed points to verify flatness and thickness, but with point cloud heat maps you can evaluate the entire pavement surface at a glance. Areas that are too high or too low are color-coded, so you can instantly identify spots that require re-rolling or surface grinding. Revealing problem areas in AR immediately after construction and correcting them on the spot reduces later rework.

• Embankment and land development: Heat maps are well suited for confirming excesses and deficiencies relative to design ground elevations across large sites. If you survey the entire site with a drone or LiDAR, areas of excessive fill exceeding specified heights or areas where soil is lacking and too low will be clearly color-coded. Local mounds or depressions that manual surveying might miss will not be overlooked with a heat map. Field personnel can walk the site with a tablet in hand and efficiently perform additional filling or removal work guided by the color variations shown in AR.

• As-built management of structures: AR heat maps are also used to check the as-built condition of structures such as bridge abutments, retaining walls, and concrete slabs. Previously, heights and tilts were measured at discrete points with spirit levels or total stations, but scanner measurement and heat map analysis enable a surface-based understanding of the entire structure. For example, irregularities (waviness) on concrete walls or excesses/deficiencies in tunnel cross-sections are immediately obvious in a heat map. Overlaying the map on the actual object with AR allows you to instruct where to trim even right after concrete placement, contributing to quality assurance and labor-saving rework.

• As-built inspection and attendance: AR heat maps are effective for as-built inspections by clients and inspectors. Inspectors can visit the site and confirm the heat map created by the contractor in AR, directly grasping the finishing state that would not be evident from a report alone. Colorized visual information makes explanations easy and speeds up communication of issues. The ability to check wide areas quickly improves the efficiency of inspection tasks. It is also useful in enabling objective decisions based on data without relying solely on the experience of veteran technicians.

The future of construction management DX and AR

AR heat maps are one of the technologies that symbolize DX (digital transformation) in the construction industry. Efforts to boost productivity using digital technologies in response to labor shortages have been accelerating year by year. Within the *i-Construction* initiative advocated by the Ministry of Land, Infrastructure, Transport and Tourism, 3D surveying and ICT construction are already entering a stage of wider adoption, and plans are being proposed to incorporate “as-built inspections conducted by projecting as-built management maps (heat maps) onto the site with AR.” In fact, full-scale introduction of AR-based as-built inspections is expected from fiscal 2025 onward, making a new inspection style that does not rely on paper drawings or traditional methods increasingly realistic.

Leading construction companies and progressive municipalities have already begun trials that use AR and VR on site. Examples include displaying a 3D design model in AR at the site for consensus building or confirming as-built conditions during construction. These efforts are all aimed at enabling accurate construction management with fewer people. The emergence of new devices such as AR-capable smart glasses is also on the horizon, and in the future heat maps may be displayed in the wearer’s field of view without having to hold a tablet or smartphone.

In this way, on-site DX technologies including AR heat maps could become the norm at construction sites. For an industry struggling with labor shortages, digitalization is an unavoidable path. By actively adopting new technologies rather than clinging to traditional methods, limited personnel can achieve results beyond what was previously possible. AR heat maps are expected to develop and spread further as a symbolic tool in the near future.

Conclusion

In an industry where labor shortages are intensifying, labor-saving construction management using AR heat maps can be a powerful solution that balances quality and efficiency. Making as-built conditions intuitively understandable for everyone on site, enabling thorough inspection without omissions and rapid rework by a small team, allows more efficient construction management than ever before. Shifting from an era of reliance on paper documents and experience to smart construction management backed by data and technology is essential going forward.

Some may worry that handling advanced 3D measurement and analysis in-house is difficult. However, easy-to-use surveying systems have recently appeared, enabling anyone to perform point cloud measurement and heat map creation without specialized surveying skills. For example, using a system like LRTK—which attaches a small RTK-GNSS receiver to a smartphone—can transform a handheld smartphone into a high-precision 3D scanner, automatically generating as-built heat maps in the cloud from scanned site data. Moreover, the heat map can be displayed in AR on the smartphone for one-stop on-site verification. By using an all-in-one solution that minimizes special surveying equipment and complex manual work, even first-time users can readily implement modern as-built management.

Even amid headwinds from labor shortages, digital technologies can dramatically improve on-site productivity and quality. Take this opportunity to introduce AR heat maps and other new technologies to your sites, and aim for construction management that produces great results with minimal effort.

FAQ

Q: What is an as-built heat map? A: An as-built heat map visualizes the difference between the actual finished shape after construction and the design shape using color coding. By comparing acquired point cloud data with the design model, areas with small deviations are shown in green, large raised areas in red, and dug-down low areas in blue, making quality intuitively apparent through color differences. It is an as-built management tool that enables immediate judgment of construction accuracy.

Q: What equipment and software are needed to create a heat map? A: Basically, you need equipment to perform on-site 3D measurements and software (or a cloud service) to process the data. Point cloud data are acquired using 3D laser scanners, drones, or LiDAR-equipped smartphones, and then compared with the design data in dedicated PC software or cloud systems to generate heat maps. Recently, services have emerged that automatically create heat maps when you upload point clouds and design models to the cloud.

Q: Can I create an as-built heat map with a smartphone? A: Yes. With a modern smartphone (for example, high-end models equipped with LiDAR sensors) combined with a dedicated RTK-GNSS receiver, you can use the phone as a high-precision 3D scanner. Using a dedicated app to acquire point clouds with your phone and uploading them to the cloud lets platforms automatically generate heat maps. For example, using a smartphone surveying system like LRTK allows you to complete point cloud measurement, heat map generation, and AR display on a smartphone without specialized surveying knowledge.

Q: What is required to overlay a heat map on the site in AR? A: AR display requires an AR-capable smartphone or tablet and a dedicated app that can load heat map data. The device’s camera image and sensors overlay a virtual heat map model onto real space, but accurate matching requires precise knowledge of the device’s position and orientation. For high-precision overlays, RTK-GNSS positioning can correct the device position to centimeter-level positioning (half-inch accuracy), or you can set up reference targets on site for alignment. With a compatible system, you can achieve high-precision alignment without relying on standard smartphone GPS, enabling heat maps to display without drift even on large sites.

Q: Are as-built heat maps recognized as official as-built management documentation? A: In recent years, as-built heat maps are increasingly being recognized as an official as-built management method. Guidelines from the Ministry of Land, Infrastructure, Transport and Tourism include area-based as-built management using 3D surveying technologies, and evaluation by heat maps is being trialed and introduced. For example, in earthworks, comprehensive as-built measurement and heat map evaluation are beginning to be required in some cases. Therefore, it is possible to submit 3D as-built data including heat maps as inspection documents, and they are actively used in modern ICT construction sites. However, follow the instructions of the contracting authority and, if necessary, submit heat map diagrams printed on paper or electronic data as requested.