Construction management is changing! Overlay 3D drawings on-site with absolute-coordinate AR

As digital technology is increasingly used on construction sites, techniques that overlay 3D drawings onto the site using AR (augmented reality) are attracting attention. With tailwinds such as i-Construction promoted by the Ministry of Land, Infrastructure, Transport and Tourism and other construction DX initiatives, expectations for the digitalization of construction sites have risen further. By using AR, a three-dimensional model representing the finished image can be projected in place, which is expected to reduce construction errors and improve the efficiency of progress management. However, there have been several challenges with conventional AR applications. It has been difficult to imagine the finished form from paper drawings alone, and on site many situations still relied on the intuition of experienced personnel.

• Manual alignment (calibration) was required as an initial setup

• The model's displayed position shifts over time and with movement

• Does not adequately meet the accuracy required on civil engineering and construction sites

A key to solving these problems is absolute-coordinate AR that leverages high-precision positioning technology RTK (Real-Time Kinematic). Because RTK allows the device’s position to be corrected at the centimeter level (half-inch accuracy) while displaying 3D models, models can be fixed accurately in place without prior alignment. Even when users move around the site, the models remain properly registered and continuously displayed, enabling stable AR overlays that aid construction management.

In this article, we explain how overlaying 3D drawings using absolute-coordinate AR is transforming construction management, and present real-world use cases and key points for implementation.

⒈ What does it mean to overlay 3D drawings using absolute-coordinate AR? ⒉ Overview and benefits of 3D drawing overlay with absolute-coordinate AR ⒊ Practical use cases for AR overlay of 3D drawings ⒋ Challenges and countermeasures in implementation ⒌ The future of AR applications on construction sites ⒍ Summary ⒎ FAQ

What does it mean to overlay 3D drawings using absolute-coordinate AR?

With conventional AR technology, it was necessary to place markers or perform manual alignment (reference alignment) each time to overlay drawings and models on-site. This approach caused problems such as 3D models drifting over time and alignment being time-consuming.

On the other hand, Absolute-coordinate AR is a method of performing AR displays based on a predefined coordinate system (for example, public coordinate systems used in surveying). By enhancing GNSS (satellite positioning) with RTK (ordinary GPS has errors of several meters (several ft), but RTK can reduce them to a few centimeters (a few in)), and by determining the device’s position to centimeter-level (half-inch accuracy), a digital 3D model can be anchored to the correct position in physical space. As a result, without performing calibration work, the model is always displayed at a position that matches the real object, and the model remains in place even when the user moves. Absolute-coordinate AR has made it possible to overlay 3D drawings on-site without error.

Benefits of Absolute-Coordinate AR for Construction Management

Absolute-coordinate AR brings the following advantages to construction management sites.

• Reduction of construction errors: Because drawing data can be projected and checked directly on site, dimensional mistakes and positional offsets can be detected and prevented in advance. This suppresses rework and reduces quality defects, preventing redo work and additional costs.

• Streamlining of progress and quality control: By comparing the as-built condition of structures on site with a 3D model, progress and finish accuracy can be grasped immediately. Not only can records be kept by surveying and photographs, but intuitive on-the-spot inspection and correction are possible, making schedule management smoother. It also reduces the need for site supervisors to run around for sequential checks, easing the burden of management tasks.

• Facilitating consensus building: AR visualization is effective for communication with clients and site staff. Because it allows sharing the completed image and demonstrating design intent on the spot, explanations and meetings become faster and troubles caused by mismatched understanding decrease. For example, during a site walkthrough the owner (client) can confirm while viewing the actual work, which tends to provide greater reassurance.

• Strengthening safety management: Since AR can visualize hidden hazards and construction risks in advance, it contributes to accident prevention. For example, knowing the location of buried pipes reduces the risk of accidental damage, demonstrating effectiveness for safety.

• Labor-saving for surveying and layout work: Because reference lines and design models can be displayed in AR, the effort of layout and setting-out work traditionally performed by experienced surveyors can be reduced. Workers can follow digital guides, shortening work time and lessening personnel burden. As a result, this also leads to reduced workload for surveyors and lower labor costs.

Use Cases for AR Overlays of 3D Drawings

So, in what specific situations can AR overlay of 3D drawings be used? Below are the main examples.

• Pre-construction design checks: Before construction begins, display the 3D design model on site in AR to confirm whether the work can be carried out as designed. For example, you can verify in advance whether a building’s placement and height fit the surroundings, and if there are problems you can modify the plan before construction. This helps nip potential construction errors in the bud.

• Accuracy checks during construction: At intermediate stages of the work, check in real time whether the structure under construction matches the design data. Compare the positions of formwork and the placement of steel members with the AR model, and if there is any deviation, correct it immediately. For example, before concrete pouring you can compare the design model with the on-site formwork and correct positional or height errors on the spot. Because corrections can be made immediately, rework is minimized.

• Infrastructure inspection and maintenance: For completed bridges, roads, and similar structures, overlay past inspection data and 3D models on site to visually grasp deterioration and displacement. You can compare aging changes at a glance, aiding repair planning and safety management. Tasks that used to involve comparing drawings and photos become immediately clear with AR.

• Location confirmation of underground utilities: Visualize underground pipes and cables in AR to prevent accidental damage during excavation. By projecting the positions of buried objects obtained from trial excavations or the pipeline routes from drawings onto the site, workers can accurately identify unseen obstacles. Excavation can proceed with greater confidence and improved safety.

• Sharing the finished image: Present exterior landscaping or post-renovation images to owners and stakeholders using AR. By overlaying the anticipated 3D model on the actual site or interior, stakeholders can experience the finished product realistically, increasing the persuasive power of proposals and meetings. This smooths consensus building and makes it easier to propose plan changes.

Challenges and Countermeasures during Implementation

There are several challenges to consider when introducing AR overlays. However, these can be overcome with appropriate measures.

• Preparing high-precision positioning: Absolute-coordinate AR requires an RTK-based positioning environment. However, high-precision GNSS receivers that can be attached to smartphones have become widespread, allowing centimeter-level accuracy (half-inch accuracy) to be obtained easily even without dedicated equipment.

• Preparing 3D design data: AR displays require 3D models or digitized drawing data. Recently, the use of BIM/CIM has advanced, and three-dimensional data have been prepared in many projects. Even when only 2D drawings exist, it may be possible to handle the situation by creating a simple 3D model or scaling on site. Note that the design model's coordinate system needs to be aligned with the site's survey coordinates, but this is easily handled by recent CAD/BIM software.

• Training of field staff: Staff may feel unsettled by new technologies, but if they are familiar with smartphone operation, it's not difficult. Intuitive UIs are designed so that anyone can master them with a short training session. In fact, there are comments that "it was easier than traditional surveying equipment," and adoption on site is progressing smoothly.

• Concerns about implementation costs: You may worry that state-of-the-art systems are expensive. However, implementing AR overlays on a smartphone basis can be introduced relatively inexpensively compared with traditional surveying equipment. Above all, considering the reduction in rework due to fewer construction mistakes, benefits exceeding the cost can be expected.

The Future of AR Use on Construction Sites

The use of AR in the construction industry is expected to expand further in the future. Currently the main use is on tablets and smartphones, but workers may eventually wear dust- and waterproof AR glasses (eyeglass-type devices) and be able to check AR information hands-free while working. The information displayed in AR will also be diverse; in addition to design models, measured data from sensors and AI-generated detection results will be provided in real time. For example, AI could check rebar placement from camera footage and highlight on the spot areas that differ from the design. A future in which the entire construction site's "digital twin" is shared in real time can also be envisioned.

Furthermore, in the construction industry—where chronic labor shortages and the need to respond to work-style reforms are pressing issues—AR can become a trump card for reducing labor and passing on technical skills. Because drawing information packed with veterans’ know-how can be shared on site by anyone, even less experienced workers will be able to carry out tasks without mistakes. The proactive use of such digital technologies contributes to productivity improvements and is also expected to serve as a countermeasure to the so-called “2024 problem.” In the near future, AR-based on-site overlays of 3D drawings may cease to be special advanced cases and instead become an everyday sight.

That said, you don't have to wait for that future — solutions already usable in the field have appeared. The LRTK introduced next is one of the tools that quickly delivers the benefits of such absolute-coordinate AR.

Make AR overlays easy with simple surveying using LRTK

The solution that makes such absolute-coordinate AR easy to deploy on site is LRTK. LRTK consists of a high-precision RTK-GNSS receiver and an AR app for smartphones, and by simply attaching a dedicated device to a smartphone anyone can achieve centimeter-level positioning and AR display. If design data is pre-registered to the LRTK cloud, it can also be instantly called up from the on-site app and displayed in AR. Unlike other AR systems, there is no need to set up markers or perform complex initial calibration; you can bring it to the site and immediately project 3D drawings.

LRTK is one of the few smartphone-compatible absolute-coordinate AR tools available domestically, and it is designed so that even people without surveying expertise can use it. The compact, lightweight device can be carried in a pouch and operated intuitively with one hand, dramatically improving the efficiency of on-site surveying and verification tasks. It is also the latest technology compatible with the Ministry of Land, Infrastructure, Transport and Tourism's i-Construction (ICT construction) initiative, and is already being introduced at various civil engineering and construction sites.

Translation target:

• AR display with RTK positioning achieving centimeter-level accuracy (cm level accuracy (half-inch accuracy))

• No complicated on-site alignment required

• Supports a wide range of applications such as construction management, surveying, and inspections

• Cloud integration enables smooth data sharing

Thanks to the above features, using LRTK will significantly advance on-site management—traditionally reliant on experience and intuition—toward data-driven visualization.

For example, in bank protection works, overlaying the design model on the embankment under construction to check the as-built (final shape) contributed to speeding up as-built management and preventing rework. In road construction, displaying the planned road shape on site with AR and confirming the finish in advance has led to improved efficiency of final inspections.

Furthermore, the high-precision data obtained through simplified surveying using LRTK can be shared internally as is or used for electronic delivery. By directly linking digital systems with the field, the quality and speed of construction management will improve dramatically. Please leverage cutting-edge AR technology to help boost on-site productivity.

Summary

The technology that overlays 3D drawings onto construction sites with AR is poised to bring a major transformation to construction management. High-precision model display using absolute-coordinate AR is beginning to reduce errors and streamline operations, and some sites have already reported improvements in safety and productivity compared with conventional methods. A future in which AR technology is commonplace is just around the corner. As adoption continues to grow, incorporating these technologies early will directly enhance competitiveness. Be sure to take advantage of easy solutions like LRTK and experience cutting-edge AR construction management on your own sites. Take the step you can now toward the construction sites of the future.

FAQ

Q: What is absolute-coordinate AR?

A: Absolute-coordinate AR is an AR technology that displays virtual models based on a common reference coordinate system. Whereas conventional AR places objects relative to the camera image, absolute-coordinate AR aligns 3D models with actual latitude, longitude, and altitude. Once placed, a model remains at its real-world position and does not drift as users move or time passes.

Q: What is required to overlay 3D drawings in AR?

A: Basically, you need devices such as smartphones or tablets that combine a high-performance GNSS receiver (RTK-capable) and 3D design data for overlay display. Specifically, prepare a GNSS terminal (or correction information service) capable of centimeter-level positioning (half-inch accuracy), a smartphone to run the AR app, and the design's 3D model data (or CAD drawing data). With these in place, you can achieve on-site AR displays that faithfully reproduce the design model.

Q: How accurate is AR overlay?

A: When positioning with RTK, errors are generally within a few centimeters (a few in). Under good conditions, horizontal position accuracy of 2–3 cm (0.8–1.2 in) and vertical accuracy of less than 5 cm (<2.0 in) can be expected, which is a marked contrast to ordinary standalone positioning, which has errors of several meters (several ft). However, note that GNSS signal reception can be affected by the surrounding environment; nevertheless, this level of accuracy is sufficient for routine construction quality control.

Q: Do I need any specialized knowledge or special skills?

A: No. The AR overlay system is designed to be intuitive so that anyone on site can use it. If you can operate a smartphone or tablet at a basic level, you simply follow the on-screen prompts to display the model. It can be mastered with a short training session, and no complex surveying calculations or programming knowledge are required. Because it is far easier to understand than traditional drawing checks, it should be easy to adopt on site.

Q: Can it be used indoors or in tunnels where GNSS does not reach?

A: Because satellite signals cannot be received indoors or inside tunnels, AR based on absolute coordinates using RTK is difficult to use as-is. However, techniques are being researched that install AR markers (printed markers) corresponding to reference points surveyed in advance and recognize them with a camera to achieve similarly high-precision alignment. Currently use is mainly outdoors, but in the future AR overlays will be usable in all kinds of environments.

Q: Is the benefit worth the implementation cost?

A: Introducing absolute-coordinate AR provides benefits such as reduced construction errors and improved work efficiency. In particular, a method that combines a smartphone and a compact GNSS receiver keeps initial investment low and is less expensive than conventional large surveying equipment. Considering the costs saved by preventing rework and shortening construction schedules, it can be regarded as a sufficiently cost-effective technology.

Q: Can I use it without design data for a 3D model?

A: Yes, even without a 3D model, AR overlays can be used to a limited extent. For example, in LRTK it is possible to project 2D CAD drawings (plans) directly onto the site. However, to examine things three-dimensionally it is desirable to prepare a 3D model, even a simple one, and as needed existing drawings can be converted to 3D, or photogrammetry or laser scanning can be used to obtain a current point cloud and model it.

Q: Can it be used at sites without an Internet connection?

A: RTK positioning requires receiving correction information and, in many cases, connects to a network RTK service via cellular communications. Therefore, in principle an environment in which the site can connect to the Internet (cellular) is required. However, in mountain areas or other locations outside coverage, it is possible to achieve high-precision positioning even without network coverage by installing your own base station in advance and transmitting correction data by radio.