The On-Site Revolution Begins! How Absolute-Coordinate AR Is Shaping the Future of 3D Drawing Display

Table of Contents

⒈ Challenges of conventional AR technologies ⒉ High-precision alignment with absolute-coordinate AR enabled by RTK ⒊ Use cases for overlaying 3D drawings in AR ⒋ The future of absolute-coordinate AR accelerating on-site digital transformation ⒌ Starting on-site AR with simplified surveying using LRTK ⒍ FAQ

In recent years, the technology of overlaying 3D drawings with AR on construction and civil engineering sites has rapidly gained attention. AR (augmented reality) is a technology that overlays digital information onto real-world scenes through smartphones and tablets. Because it allows the finished image that could previously only be seen in drawings or CAD 3D models to be intuitively grasped by superimposing it onto the actual site view, many benefits are expected, including prevention of construction errors, smoother consensus-building among stakeholders, and improved work efficiency. In particular, if three-dimensional design data (BIM/CIM models, etc.) can be displayed on site as-is, it can be widely used from pre-construction planning simulations to progress checks during construction and verification after completion, and thus has attracted significant attention from civil construction managers, design personnel, survey technicians, and municipal employees and others in all roles involved in surveying work.

However, conventional AR technologies have faced challenges in alignment accuracy and the amount of effort required, creating barriers to full-scale use in the construction sector, where high precision is demanded. In this article we organize those challenges of conventional AR and explain how RTK-GNSS-based absolute-coordinate AR can transform the field as a solution. We also discuss specific use cases for AR overlays and future prospects, and finally introduce a solution that allows anyone to easily deploy high-precision AR on site: simple surveying with LRTK.

Challenges of Conventional AR Technologies

Many AR apps for smartphones and tablets currently display virtual objects by capturing the surroundings with the device’s camera and sensors while tracking the device’s movement. However, this traditional AR has several problems when used on construction sites.

• Manual alignment required：When overlaying 3D models onto the real world, initial calibration work was required at each site, such as placing and scanning QR code markers or manually positioning the model to known reference points. Performing alignment at every site each time is a major burden.

• Model misalignment：Typical smartphone GPS positioning accuracy is only on the order of a few meters, and AR apps display virtual models based on the device’s relative movement（relative coordinates）, so when moving over a wide area small errors accumulate and the displayed position shifts. A model that had been correctly placed would often come to diverge from the real object over time or with walking.

• Insufficient accuracy：On civil engineering and construction sites, positional errors on the order of a few centimeters can be problematic. However, general AR has difficulty achieving that level of high accuracy, and there was the issue that it is essentially unusable in situations that require millimeter-level precision.

As described above, conventional AR technology alone can sometimes fail to fully meet the accuracy and stability required on construction sites, and even when 3D models are overlaid they could only be used as rough guides. In response to this, a new approach called absolute-coordinate AR, which will be introduced next, has emerged.

High-precision alignment using absolute-coordinate AR enabled by RTK

Absolute Coordinate AR is an AR technology that places virtual models based on absolute positional information such as geodetic coordinates used in surveying and coordinates of known reference points. The key to realizing this is high-precision positioning using RTK-GNSS (real-time kinematic satellite positioning).

By using RTK-GNSS, GPS positioning errors that are normally on the order of several meters (several ft) can be reduced to a very small range of a few centimeters (a few in). By employing a dedicated high-precision GNSS receiver and correction signals from a base station, centimeter-level positioning (half-inch accuracy) becomes possible even on smartphones. By integrating this RTK-based position information into AR apps, the displayed positions of 3D models can be aligned to the absolute coordinates specified on the design drawings.

As a result, pre-calibration is no longer necessary. Once the model's position in absolute coordinates is set, you can bring a device to the site and immediately display the virtual model there. You can start overlaying 3D drawings without tedious alignment work. Also, because the model is fixed to real-world coordinates, the model stays in the correct place even when the user moves. For example, when you approach the planned bridge-pier location, a life-size bridge-pier model will appear to rise up from the empty ground at the exact position and height, so that the real and the virtual align perfectly.

In this way, using absolute-coordinate AR makes it possible to overlay 3D models with high accuracy even over wide areas. What was previously difficult—the accurate projection of 3D models across an entire site—becomes a reality, promising dramatic efficiency gains in construction management and surveying. The main advantages are as follows.

• Elimination of position drift: Because positioning errors are minimized by high-precision GNSS, models will not move on their own or gradually drift. Even with long-duration or long-distance use, the AR display remains stable and does not deviate from the initial position.

• Anyone can place accurately: Because it is based on absolute coordinates, workers no longer need to make manual fine adjustments. No special marker placement or specialized knowledge is required, and as long as you have a device, anyone can make the model appear in the correct position.

• Reduced on-site rework: Because work proceeds with virtual models positioned as designed, you can prevent mistakes discovered later like "the position was wrong." As a result, this leads to a reduction in redo work (rework) and improved quality.

Use Cases for Overlaying 3D Drawings in AR

Now, let's look at a few representative scenarios that show how absolute-coordinate AR's "3D drawing overlay" can actually be useful on-site.

Pre-construction planning simulation and design check

Before construction begins, displaying design-stage 3D models on site in AR to simulate the plan can be used for pre-checks. For example, in road construction, you can overlay 3D models of the planned road or bridge onto the site’s terrain to confirm whether they fit as designed. Because interferences with the terrain or inconsistencies with the surrounding environment that were not noticed on drawings can be intuitively grasped, this is effective for identifying risks before construction.

Traditionally, meetings with stakeholders were held based on two-dimensional drawings, but with AR you can check the finished image on-site together with the client and on-site staff. Because everyone can discuss while looking at the same anticipated finished image, it also has the effect of eliminating gaps in understanding and streamlining consensus-building.

• Prevention of incorrect construction: Detect discrepancies between the design and on-site conditions at an early stage, reducing the risk of proceeding with work in the wrong location.

• Sharing among stakeholders: By sharing a full-scale model of the finished project on site, align the client’s and contractor’s expectations and streamline explanations and approval processes.

• Consideration of plan revisions: By viewing the model in AR, if problems are found you can consider design changes or countermeasures before construction. This contributes to planning with fewer reworks.

Progress monitoring and quality control during construction

Even during construction, AR-based overlays of 3D drawings are highly effective. On-site, you can align the design model with structures and temporary works that are still under construction and confirm progress and accuracy in real time.

For example, before pouring concrete, you can display the as-designed final model in AR over the assembled rebar and formwork. This lets you immediately determine whether the rebar positions and formwork heights match the design model. If there is any deviation, you can correct it before pouring. This allows you to address issues much earlier than discovering mistakes like "the height was wrong" or "the position was off" after pouring, thereby reducing rework.

Similarly, even at a stage where construction has progressed to some extent, you can overlay the final model on top of the structure being built to check the as-built condition. You can confirm on-site via AR whether the as-built (the finished product) matches the design's dimensions and positions, and if there are any discrepancies you can correct them immediately to ensure quality. Because supervisors and inspectors can view the AR imagery together to point out and verify issues, on-site communication loss is prevented and consensus on corrective actions is reached smoothly.

• Early detection of construction errors: Misalignments that used to be discovered after completion or after waiting for survey results can be detected instantly during work with AR display.

• Immediate quality verification: Because the finished result can be compared to the model as work progresses, you can verify in real time whether it meets quality standards.

• Efficient supervision and inspection: It reduces the time spent comparing drawings and the actual site, and because all stakeholders on site can share the same information in AR, communicating issues and confirming corrections is more efficient.

Post-Completion Verification and Infrastructure Maintenance and Management

Overlaying using absolute-coordinate AR can also be applied to post-construction inspections and the maintenance management of infrastructure facilities. For example, at completion, by displaying the design-phase 3D model in AR over the finished structure and performing as-built verification, you can intuitively check whether the final deliverable conforms to the design. Inspections of critical structures still require detailed measurements, but by using AR to get an overall view you can proceed with confirmation work more efficiently.

In routine infrastructure inspections, overlaying past inspection data and design drawings onto the current structure with AR allows you to visually grasp changes over time. For example, during a bridge inspection, projecting previous crack locations with AR and comparing them to the present makes it easy to confirm the progression of cracks. In road excavation work, displaying maps of buried pipes and cables on-site with AR and visualizing unseen underground buried objects can also prevent accidents that would accidentally damage lifelines.

• Rapid verification of as-built conditions: At completion, you can check differences from the design while viewing the entire site in AR, streamlining inspection tasks.

• Visualization of changes over time: By overlaying inspection history onto the actual asset, the progression of deterioration and repair history becomes immediately apparent, aiding appropriate maintenance management.

• Locating underground utilities: Pipes and cables that are normally unseen can be shown in AR, helping ensure safer construction and maintenance.

Improving Efficiency and Reducing Labor in Surveying Operations

Overlaying 3D drawings with AR also streamlines surveying and measurement work on-site. With high-precision absolute-coordinate AR, simple surveying and dimensional checks can be performed on the spot without using dedicated surveying equipment.

For example, at a construction site, when you want to check whether the elevation at a given point matches the design, you conventionally had to set up surveying instruments such as a level or a total station and take measurements. However, with an RTK-enabled AR app, you can simply hold up a smartphone and compare the design model’s height reference with the current ground or structures. By combining the device’s tilt sensor and LiDAR capability, you can also measure elevation differences from the ground surface, so you can instantly measure heights and positions with a reasonable degree of accuracy. This reduces the number of times you need to call a surveying team for minor checks and expands the range of checks site personnel can perform themselves.

Furthermore, by performing stake driving and marking using the design positions displayed in AR as a guide, simplification of surveying (positioning) work can also be expected. Even inexperienced workers only need to make marks to match the positions shown in the AR, allowing survey points to be set quickly while avoiding dependence on specific individuals.

• On-site dimension verification: By using the overlaid model as a ruler to visually measure differences from the current condition, you can perform quick self-checks.

• Reduced effort for surveying tasks: In situations where simple measurements suffice, expensive surveying instruments are not required, saving personnel and time.

• Positioning support: By referencing the positions indicated by AR, even non-experts can carry out highly accurate positioning work, leading to overall productivity improvements.

The Future of Absolute-Coordinate AR That Accelerates On-site Digital Transformation (DX)

The overlaying of 3D drawings using absolute-coordinate AR is bringing about a change that could truly be called "an on-site revolution". Even within the momentum of the Japanese government–promoted *i-Construction* and the drive for construction DX, high-precision construction management and surveying methods that leverage AR+RTK are beginning to become the new standard. So how will on-site AR utilization evolve from here?

First, as a technical challenge, there is the need to cope with environments where GNSS (satellite positioning) is difficult to use. Under elevated structures, inside tunnels, or in dense urban areas surrounded by tall buildings, satellite signals can be blocked or reflected, causing high-precision positioning by RTK to become unstable. To maintain AR accuracy in such environments, measures such as calibrating in advance at known reference points on site or supplementing with local positioning systems (total stations or simple beacons, etc.) will be future challenges. There are also device-related issues when using smartphones outdoors. For example, screens can be hard to see in direct sunlight, and devices can become hot and operate unstably. These problems are also points that must be addressed to enable wide deployment in the field.

On the other hand, advances in technology are gradually addressing these issues. In particular, on the device side, companies are advancing development of AR glasses and MR headsets. Going forward, instead of holding a smartphone, people will wear helmet-integrated smart glasses and be able to use hands-free AR displays. Work efficiency should further improve—for example, workers will be able to check projected 3D drawings even while carrying heavy objects. GNSS positioning environments are also improving year by year due to an increase in satellites and enhancement of augmentation signals. In Japan, a centimeter-level augmentation service using the Quasi-Zenith Satellite System has been commercialized (cm-level, half-inch accuracy), and high-precision positioning in mountainous areas and urban areas has become more stable than before. Furthermore, with the spread of 5G and the development of cloud services, we can look forward to a future in which multiple people can share location data and video captured on site in real time and synchronize the same AR space with remote specialists to verify work.

The future of 3D drawing display enabled by absolute-coordinate AR is not merely a story about a novel gadget; it has the potential to transform the way work is done on site itself. As drawings and surveying become digitized, this technology brings scientific grounding and efficiency to site management that has until now relied on human intuition and experience. As hardware and software infrastructure further develop, new work styles such as paperless construction, where carrying drawings becomes unnecessary, and remote construction management, which enables understanding and directing sites from a distance, will become increasingly realistic.

Getting Started with On-site AR Using LRTK for Simple Surveying

Finally, as a solution to easily use these absolute-coordinate AR technologies on-site, we introduce LRTK. LRTK is a smartphone-compatible absolute-coordinate AR system that leverages high-precision RTK-GNSS. By attaching a dedicated compact GNSS receiver to a smartphone and launching the supported app, anyone can immediately display AR with centimeter-level accuracy. No complex setup or cumbersome initial calibration is required, and once you arrive on site you can immediately overlay the design model in place.

With this LRTK, high-precision on-site verification that previously required a specialized surveying team can now be performed on the spot by construction managers and designers themselves. It can be applied to a wide range of uses such as construction management, surveying, and infrastructure inspection, and it supports data sharing via the cloud, making it easy to review information recorded in the field while in the office. The LRTK series also supports the Ministry of Land, Infrastructure, Transport and Tourism's i-Construction initiative, making it a practical solution that strongly supports the construction industry's DX (digital transformation).

From major construction companies to local governments, LRTK is already being introduced at a wide range of sites. Please experience absolute-coordinate AR — a "revolution on the job site" — at your workplace as well. Cumbersome surveying and as-built inspections become astonishingly simple, allowing you to step into the next stage of site management.

FAQ

Q: What do you need to overlay 3D drawings in AR? A: Basically, you need the 3D design data and a smartphone or tablet capable of running the corresponding AR app. To achieve higher, construction-site–level accuracy, GPS correction devices or an RTK-capable GNSS receiver are ideal. For example, if you use a high-precision positioning device such as an LRTK that can be attached to a smartphone, you can display the model with an accuracy of several centimeters (several in).

Q: What is the positioning accuracy of absolute-coordinate AR? A: When using RTK-GNSS, the theoretical error is on the order of 1-2 cm (0.4-0.8 in). However, since it depends on satellite reception and the environment, in practical use it is reasonable to expect accuracy on the order of several centimeters to several tens of centimeters (several inches to several tens of inches). Even so, this is far more accurate than standard GPS, which has errors of several meters (several ft), and it is suitable for use in many construction management and surveying tasks.

Q: Can people without specialized knowledge use AR overlay technology? A: Yes, they can. The operation of AR apps is intuitive, and by following the on-screen guidance while looking at a smartphone screen, you can display models. Even with absolute-coordinate AR, the cumbersome calibration procedures that used to be necessary are no longer required, so there are fewer headaches in initial device setup. It is designed so that field personnel can begin using it after a short training.

Q: What happens in places where GNSS cannot be used, such as inside tunnels or in densely built urban areas? A: Unfortunately, in environments where positioning from satellites cannot be obtained, the accuracy of absolute-coordinate AR also degrades. In such cases, auxiliary measures are necessary, such as performing manual corrections using local control points on site or aligning the model by using surrounding landmark structures. Recent advances include research into integrating with local positioning systems that can be used indoors and estimating position by matching with pre-scanned point cloud data, and it is expected that AR overlays will become possible in a wider variety of environments in the future.

Q: Does displaying 3D drawings in AR require expensive dedicated equipment? A: No. In the past, special equipment or headsets were sometimes necessary, but today high-precision AR can be achieved with a combination of commercially available smartphones and small GNSS receivers. For example, LRTK is one such solution that can be used with familiar devices. Because you can get started with handheld devices without using special head-mounted displays, the barrier to initial adoption has been greatly reduced.