Effective even at municipal sites! On-site 3D drawing visualization technology using absolute-coordinate AR

In recent years, the use of AR (augmented reality) technology has rapidly advanced in the construction and civil engineering fields. By holding up a smartphone or tablet, this technology overlays design drawings or models—3D drawings—onto the real-world view, allowing digital information to be intuitively checked on site. Because the completed image can be shared on the spot, it is expected to have a major effect in preventing construction errors and improving work efficiency. Also, since spatial information that is hard to understand from drawings can be visualized on site, it smooths the process of building consensus among stakeholders and helps reduce rework caused by communication loss. Recently, driven by the Ministry of Land, Infrastructure, Transport and Tourism’s *i-Construction* initiative and the trend toward on-site DX (digital transformation), the use of such AR is spreading not only among large general contractors but also to small and medium contractors, clients, and municipalities.

However, displaying a 3D model so that it exactly matches the real-world position across a large site requires high positioning accuracy. General smartphone GPS has errors on the order of several m (several ft), so it is insufficient for aligning large structures in AR. The method attracting attention is called absolute-coordinate AR. This technique performs AR rendering based on absolute coordinates such as latitude and longitude obtained by satellite positioning, enabling virtual objects to be overlaid at the correct positions in the real world. In this article, we explain in detail the mechanism and use cases of on-site 3D drawing visualization using absolute-coordinate AR. At the end of the article we also touch on a new simple surveying solution that supports AR—LRTK—and introduce how anyone can easily implement high-precision AR.

Table of contents

⒈ What it means to overlay 3D drawings on site with AR ⒉ Technical elements that enable absolute-coordinate AR ⒊ AR use that shines in pre-construction simulation ⒋ Effects of on-site visualization that promote consensus building ⒌ Applications to construction management and heavy equipment operation ⒍ Use in as-built verification and infrastructure maintenance ⒎ Toward AR technology everyone can use: future prospects ⒏ FAQ

What it means to overlay 3D drawings on site with AR

First, what does “overlaying 3D drawings on site with AR” mean? As the name implies, it refers to displaying design data (3D models and drawings) of a construction project over the actual site scenery using augmented reality (AR). For example, showing a completed building model through a smartphone on an empty lot where the building has not yet been constructed, or indicating the route of pipes buried underground as if they are visible through the ground. Because the completed image, which used to be viewable only on paper drawings or as CG on a computer, can now be overlaid on the actual site at full scale, very realistic checks become possible.

With this technology, one can intuitively verify before construction whether “things will fit as planned” or “there will be no interference with the surrounding environment.” During construction, it is also possible to compare the design model and the current state on the spot to check for deviations, preventing mistakes and rework. Compared with imagining drawings mentally, it is far easier to understand, and it allows information sharing in a way that is easy to understand for everyone, from on-site personnel to clients and nearby residents.

Technical elements that enable absolute-coordinate AR

To accurately overlay 3D models on site with AR, it is necessary to combine several cutting-edge technologies. The main technical elements to note are as follows.

• High-performance smart devices and AR apps: As a convenient platform for use on site, high-performance smartphones and tablets such as iPhone and iPad have become prominent in recent years. Using dedicated AR apps, these devices can load design data, render 3D graphics, and perform alignment calculations in real time. They are portable enough for outdoor sites and ideal for displaying models on the spot.

• Environmental sensing with LiDAR scanners: Some of the latest smartphones (and some tablets) are equipped with light-based ranging sensors called LiDAR. Scanning the surroundings with LiDAR makes it possible to quickly acquire terrain and structure shapes as point cloud data. When used in AR, this allows virtual 3D models to be naturally placed on the real ground and enables realistic occlusion where models are hidden behind real objects. The acquired point cloud can also be used to record as-built (post-construction) shapes, allowing digital comparison of changes before and after construction.

• Spatial tracking by AR platforms (ARKit/ARCore): AR development platforms such as Apple’s ARKit and Android’s ARCore provide VIO (Visual Inertial Odometry) technology that tracks the device’s position and attitude by combining camera images and device sensor information. This enables virtual objects to remain in place even as the user walks around. However, typical smartphone AR uses relative coordinates, so accumulated error increases as the user moves long distances and the model’s position can drift. Also, when aligning the model to reality at the start, placing markers or manual fine-tuning is required, which is cumbersome and has limits for precise placement across large sites.

• High-precision GNSS (RTK) positioning: The key here is acquiring high-precision absolute positions using satellite positioning via RTK-GNSS. GNSS (Global Navigation Satellite System) position data typically has errors of several m (several ft), but the RTK (Real-Time Kinematic) method can reduce errors to several cm (several in) by using correction data from a base station or Japan’s quasi-zenith satellite “Michibiki” providing centimeter-level positioning augmentation service (CLAS). By attaching a compact high-precision GNSS receiver to a smartphone and receiving correction information over the Internet, the device’s current position can be determined in the global geodetic coordinate system with almost no error. Using this, BIM/CIM and other 3D models that have latitude/longitude or plane coordinates can be displayed in AR at the design positions without marker placement or manual adjustment. When a user approaches a specified point, a column or wall model can appear at the precise position on bare ground—this is now feasible in reality. With RTK position correction, the relationship between model and real object remains stable even as the user walks around the site, enabling high-precision AR overlay across wide areas.

By combining these technologies, it becomes possible for anyone to realize “visualizing a 3D design model over its actual designed position with just a single smartphone.” Previously, QR-code markers had to be attached or models manually adjusted to known points on site, but the method incorporating high-precision GNSS eliminates such troublesome initial alignment. Simply bringing a device onto the site and launching an app allows immediate AR simulation—an innovation in ease of use. Because horizontal position and elevation can match within several cm (several in), design-to-field comparison can be carried out on typical construction sites without issue, except where millimeter-level precision (mm (in)) is required. Of course, GNSS accuracy can decline under overpasses, inside tunnels, or in dense urban areas where satellite signals are weak, but even then it is operationally viable by, for example, using ARKit tracking locally after one precise alignment point. Today, the configuration of iPhone + LiDAR + ARKit + RTK is making a reliable AR surveying system that provides accuracy in both position and attitude a practical reality.

AR use that shines in pre-construction simulation

Absolute-coordinate AR technologies demonstrate great power in the planning phase before construction begins. By visiting the site before groundbreaking and projecting 3D models of the planned structures and equipment, pre-construction simulation can be easily performed. Even land that appears flat on drawings may reveal subtle elevation differences when models are overlaid in AR, or it may become apparent that there is an impractical interface with adjacent structures. This ability to uncover gaps between the design proposal and site conditions in advance is a major advantage. If issues are found, modifying the plan before construction prevents later rework.

Moreover, displaying phased 3D models or temporary structure layouts corresponding to construction progress in AR helps examine construction procedures and temporary works plans. For example, it is possible to simulate on site whether there is enough space for a crane to swing materials in the yard, or whether multiple machines working simultaneously would interfere with each other’s paths—practical construction planning checks. Visualizing the positions of temporary fences or scaffold installation in AR to check for safety issues is also possible.

Using AR for pre-construction simulation is also powerful for building consensus with clients and local residents. For example, when constructing a new public facility, showing the full-scale completed building at the planned site through a smartphone is more convincing than presenting perspective drawings or models. As discussed later, using AR at residents’ briefings to check “how the building will affect views and sunlight” on site helps alleviate concerns and questions. By leveraging AR from the planning stage, communication loss in the planning process can be reduced so that all stakeholders head into construction sharing the same completed image.

Effects of on-site visualization that promote consensus building

Construction projects involve not only contractors but also clients (often municipalities or companies), designers, and local residents, among other stakeholders. Reaching mutual understanding and agreement often takes time, but on-site visual, AR-based visualization greatly accelerates this consensus-building process.

When explaining on site, showing the tablet or smartphone screen where the “future completed object appears on the spot” enables people without technical knowledge to understand the plan at a glance. For example, in explaining a road widening project, drawing the widths of the finished carriageway and sidewalks on the ground in AR allows stakeholders to literally see and confirm the final form. Things that previously had to be imagined from panel exhibits or drawings can be virtually experienced on the spot with AR, significantly shortening explanation times.

AR is also effective for information sharing with remote stakeholders. If one person shares AR imagery and positional information from the site via the cloud, those in a distant office can grasp the site situation three-dimensionally. In one project, on-site staff streamed tablet AR screens in a web conference so distant clients and designers could review construction steps. As a result, they were able to share the finished image accurately without everyone having to visit the site, enabling smoother discussions. Being able to share the same AR experience remotely not only reduces travel time costs but also supports faster decision-making.

Even after construction or during maintenance, AR helps align perceptions among stakeholders. For example, highlighting deterioration areas with AR markers at a repair site allows the responsible person and their supervisor to discuss on the same screen what and to what extent repairs should be made. Visualizing the locations of underground water and sewage pipes in AR helps everyone accurately understand “what buried items are located where” when planning works. Information that is difficult to convey with text or 2D drawings becomes immediately clear with AR, reducing misunderstandings and contributing to smoother project execution.

Applications to construction management and heavy equipment operation

In actual construction phases, AR overlay displays support various on-site tasks. Especially in civil engineering, efforts to apply AR to heavy equipment operations—such as excavators, bulldozers, and cranes—are attracting attention because AR can provide visual navigation and alerts to operators, improving both safety and work efficiency. Below are specific application examples.

• Guide for excavation and earthwork: Traditionally, heavy equipment operators relied on paper drawings or ground markings to judge “how deep to dig” or “how much to fill.” With AR, a tablet can display the designed finished ground surface or foundation shapes on the ground as glowing outlines or colored planar guides. Operators and signalers can work while referencing these guides to prevent over-excavation or over-filling. For example, when excavation reaches the specified depth, an AR heatmap can show “how many cm are left to the design surface,” enabling accurate target ground heights without relying on experience. This allows high-precision excavation and grading without depending solely on veteran intuition.

• Interference checks between heavy equipment and surrounding environment: When operating large cranes or backhoes, it is essential to constantly watch for collision risks with surrounding buildings or temporary structures. If 3D models of the equipment and work area are pre-overlaid in AR, the swing range of a crane boom or the arm motion of a work vehicle can be visualized. Being able to check “how far movement becomes dangerous” in advance makes it easier to judge safety margins. In one overpass repair project, AR simulation revealed a potential interference between a high-reach vehicle’s arm and the underside of the bridge girder; presenting that image to stakeholders quickly led to a revision of the construction plan. Thus, clearance checks between heavy equipment and structures using AR are effective for eliminating spatial interference risks in advance.

• Safety through visualization of underground utilities: One of the scariest risks at excavation sites is accidentally damaging buried utilities such as gas pipes or power cables. Typically, locations are checked with drawings or trial digs using metal detectors, but AR can visualize underground piping as if through a transparency. If high-precision positional 3D data of buried pipes is available, they can be displayed as colored pipe models overlaid on the actual ground via a smartphone or tablet. Workers can see on the AR screen “what pipe is directly below and at what depth,” helping them avoid excavating too close with heavy equipment. This not only prevents buried utility damage accidents but also greatly reduces the time and effort required for prior checks.

• Construction navigation and future automation: AR is expected to support advanced autonomous operation and remote control of heavy equipment. For example, a worker wearing AR-capable smart glasses could have real-time guidance lines and work instructions displayed in their field of view while guiding equipment. Some ICT construction machines already use GNSS for automatic control, and if human operators can visually confirm finish images or blade cut lines via AR, human-machine collaborative work becomes more intuitive. In the future, site supervisors may monitor and direct multiple autonomous machines remotely through AR. AR will support construction safety and accuracy from the human perspective and will be a key technology for future sites.

Use in as-built verification and infrastructure maintenance

Overlaying 3D models with AR is also useful in inspection after construction and in infrastructure maintenance phases. For as-built verification and quality checks that confirm whether the completed structure matches the design, AR brings revolutionary efficiency. For instance, if you overlay the design model on the finished structure, you can visually grasp differences from the design on site without bringing tape measures or surveying instruments. If a part of the structure appears to protrude from the model on a smartphone or tablet screen, it immediately indicates a construction deviation. Thus, simply comparing the digital model and the real object on site makes it possible to visualize workmanship immediately, drastically shortening inspection time.

The combination of AR and LiDAR scanning is particularly effective for earthwork involving terrain. By overlaying point cloud data (3D measurement data) of as-built shapes acquired with an iPhone and the design 3D model on site, advanced checks such as color-mapped height and shape differences can be performed. Areas where fill height is insufficient or pavement thickness is greater than planned can be highlighted at a glance, greatly streamlining inspections that formerly required matching drawings to measurement values. In one field, an as-built inspection and reporting task that took half a day was completed in just a few minutes using AR.

AR-verified results can also be preserved as digital records. If you record AR display screens as photos or videos, they can be attached to completion inspection reports as convincing evidence. With cloud-linked systems, captured images automatically include position information when saved, making later detailed office analysis or sharing with stakeholders easy. The Ministry of Land, Infrastructure, Transport and Tourism is preparing new as-built management procedures using 3D data, and applying AR + point cloud measurement methods makes it possible to quickly produce 3D models and measurement data aligned with such official standards, ensuring future compliance.

Absolute-coordinate AR is also an innovative solution for infrastructure maintenance. In replacement projects for aging water and sewer pipes or cables, it has often been difficult to know exact locations until trenches are opened. However, if buried facilities are 3D scanned and recorded during construction with a smartphone + RTK, those data can be displayed in AR even after backfilling to accurately reproduce underground installations. Even if drawings are outdated or not updated, digitally saved 3D records provide assurance. Anyone can understand underground conditions just by holding up a smartphone on site, eliminating reliance on the instincts of experienced personnel. For municipal maintenance staff, visualizing buried infrastructure will dramatically improve the efficiency and safety of inspection work.

Toward AR technology everyone can use: future prospects

Absolute-coordinate AR for on-site visualization of 3D drawings is expected to become more widespread and become a standard tool on sites. In future construction sites, the sight of “everyone checking design drawings with AR on their smartphones while working” may become commonplace. To realize this, it is important to make high-precision positioning and 3D data utilization—currently specialized technologies—easier to handle.

In recent years, simple surveying devices and services that make high-precision GNSS and 3D scanning technologies usable by general site technicians have appeared. For example, by attaching a compact RTK-GNSS unit to a smartphone and linking it with a dedicated app, position-setting tasks that previously required surveying expertise can now be completed quickly by anyone. Our company’s offering, LRTK, is one such solution. With LRTK, a single smartphone enables centimeter-level accuracy (half-inch accuracy) positioning and point cloud measurement all-in-one, allowing immediate overlay of 3D models on site without complicated procedures. In other words, simple surveying using LRTK significantly lowers the barrier to using absolute-coordinate AR, and an era is approaching in which not only specialists but also municipal staff and on-site workers can easily master AR technology.

These trends align with the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction initiatives and are likely to accelerate further. If technologies like LRTK are adopted across projects as reliable partners supporting on-site DX, construction productivity and safety will dramatically improve. Absolute-coordinate AR, which seamlessly fuses real-world space and digital design information, can rightly be called a foundational technology for the future of infrastructure management and construction work.

FAQ

Q: What equipment and preparations are required to introduce absolute-coordinate AR? A: Basically, you need a smartphone or tablet that supports AR display, and a GNSS receiver (RTK-capable device) that can provide centimeter-level positioning. Higher-end iPhone and iPad models include LiDAR sensors, which is advantageous. On the software side, you need a dedicated app that can load 3D models for AR display and an environment to use high-precision GNSS correction information (for example, Michibiki’s CLAS or private correction services). Recently, compact RTK receivers that attach to smartphones and come bundled with apps have become available, enabling quick start of high-precision AR without specialized knowledge.

Q: Is AR overlay possible in places where GNSS cannot be used (indoors or inside tunnels)? A: GNSS signals are not available indoors, so centimeter-level RTK positioning is not achievable there. However, partial solutions are possible with ingenuity. For example, you can perform high-precision alignment outdoors near the tunnel entrance and maintain the display inside using the AR platform’s (e.g., ARKit) relative tracking. Another approach is to survey and obtain reference point coordinates inside the tunnel in advance and place markers at those points to align AR models. In any case, by combining GNSS with nearby visual references or markers rather than relying entirely on GNSS, high-precision AR overlay can be realized within limited areas.

Q: Can AR be used at sites that do not have 3D design data? A: Having 3D models is preferable, but AR can still be used without advanced 3D CG. For example, 2D drawing data (plans or piping diagrams) can be displayed as overlays on the ground in AR to check positional relationships. Recent tools can also convert simple 2D drawings into basic 3D models by specifying rise heights. Ideally, BIM/CIM 3D data will be prepared from the design stage, but for small sites or renovation works, LiDAR scanning the existing conditions to obtain point cloud models and overlaying dimensional information can serve as an alternative. It’s best to introduce AR in a way that suits the site’s needs and constraints.

Q: What is LRTK, and how does it differ from conventional surveying equipment? A: LRTK is an integrated high-precision positioning and AR solution that combines a compact RTK-GNSS receiver, a smartphone app, and cloud services. Conventional total stations and GPS surveying equipment required specialized qualifications and experience, but LRTK allows anyone to perform centimeter-level surveying and point cloud scanning simply by attaching the device to a smartphone and operating the app. For example, height differences at different points can be automatically corrected, and acquired data can be saved to the cloud for sharing with stakeholders. In short, LRTK enables one-stop implementation from positioning to AR display, making on-site AR use possible without special equipment or advanced skills.

Q: Is AR-based on-site visualization effective for small municipal projects? A: Yes, it is effective. In fact, municipalities with limited budgets and personnel can gain significant efficiency benefits from AR. For example, for road repairs or park development, sharing the completed image in advance via AR makes resident briefings smoother and helps avoid unnecessary trouble. In small projects, site managers often juggle multiple roles, but AR allows continuous checking of design drawings against the current conditions during work, helping reduce human error. Also, as-built inspections can be conducted instantly with AR, reducing time spent preparing reports. Regardless of scale, the advantage of being able to “intuitively confirm on site” is common, so AR can be highly effective in municipal field operations.