Solving “AR display drift is a problem”! The new on-site standard: LRTK

Table of Contents

• Causes and challenges of AR display drift

• Traditional countermeasures for AR display drift

• What is the new on-site standard “LRTK”?

• “Drift-free” AR display realized by LRTK

• New possibilities for simple surveying with LRTK

• Conclusion

• FAQ

Causes and challenges of AR display drift

Against the backdrop of initiatives such as i-Construction promoted by the Ministry of Land, Infrastructure, Transport and Tourism, AR (augmented reality) technology is increasingly expected to be used in construction and civil engineering sites. It can become a powerful tool to support on-site work. By overlaying 3D models of drawings or construction procedures onto real-world scenes via smartphones, tablets, or smart glasses, teams can intuitively share the completed image or give instructions on site. However, when actually trying to use AR on site, many encounter the problem that “the AR display is misaligned.” This phenomenon is a common concern among many field personnel who have tried using AR.

Why does AR display drift occur? The main causes include the following:

• Device positioning errors: The typical smartphone GPS has errors on the order of several meters (several m (several ft)), and that alone can cause virtual objects to be offset from real objects.

• Device heading/pose errors: Errors in the electronic compass or drift in gyroscope sensors can cause the displayed orientation to be off, resulting in incorrect placement of models.

• Environment-induced instability in AR tracking: AR apps estimate their position by detecting feature points from the camera image, but in feature-poor, monotonous scenes, dark areas, or on glass surfaces, tracking becomes unstable and models can gradually drift or jump.

• Initial alignment errors: When placing a model in AR, the initial alignment is sometimes done manually; even a small misalignment at this stage causes overall inconsistency. On large sites, a slight angular or positional offset can become a large error at a distance.

• Drift over time: Accumulated sensor error or environmental changes can cause AR displays to slowly drift over time.

Because of these factors, the 3D AR models that have been displayed can end up inconsistent with real-world positions (the so-called “drift”), and on-site teams may come to shun AR as “unreliable after all.” For example, if a position indicated by AR for “drill a hole here” is actually off by tens of centimeters (tens of cm (several in)), there is a risk of drilling in the wrong place. In the end, workers may re-measure with tapes or string lines, making the use of AR pointless. In recent years, devices with LiDAR sensors and VPS (Visual Positioning Service) technologies have appeared, but there remain challenges to achieving stable, high-precision alignment across wide job sites.

Traditional countermeasures for AR display drift

To eliminate AR display drift, various on-site measures have been taken so far. Let’s look at some representative countermeasures.

• Installing markers or QR codes: Preplacing AR markers (image markers) or QR codes on site and using the camera to read them as a reference position. This is simple but impractical for wide areas because markers must be placed everywhere. Outdoors, markers can peel off or get dirty from wind and rain, making stable operation difficult.

• Manual alignment using landmarks: Comparing clear on-site landmarks (e.g., building corners or points on existing structures) with the AR model and adjusting by eye. This can provide some correction, but accuracy is limited and depends on the operator’s intuition. Achieving consistent precision every time is difficult and results may vary between workers.

• Resetting alignment repeatedly: Whenever the model seems to drift, re-aligning (resetting) the model at the current location. This fixes things temporarily but interrupts work and is inefficient. It does not address the root cause, so repeated resets become a hassle and can defeat the purpose.

• Pre-surveying and aligning data: Measuring site control points with surveying instruments and aligning the digital model to those coordinates. This improves accuracy but requires specialist surveying work and is time-consuming. It also requires personnel with expertise, and coordinate transformation mistakes can still leave residual misalignment.

These countermeasures each incur cost and effort, often undermining AR’s original benefit of being quick and real-time on site. As a result, many field personnel have half resigned themselves to “there’s nothing to do about AR drift.”

What is the new on-site standard “LRTK”?

Enter LRTK. LRTK (pronounced “el-ar-tee-kay”) is a new solution developed to fundamentally solve the positioning drift problem when using AR on site. Now called the new on-site standard, LRTK takes a different approach from conventional methods to realize AR that “does not drift.”

Its greatest feature is the fusion of positioning technology and AR technology. LRTK uses high-precision satellite positioning (RTK: Real Time Kinematic) to determine the position of devices like smartphones to centimeter-level accuracy (cm level accuracy (half-inch accuracy)). Because device coordinates are known with precision orders of magnitude better than typical GPS, a reliable basis is established for overlaying digital data at the correct positions in physical space.

Additionally, LRTK includes a mechanism to register and share site-specific coordinate systems (local coordinates) in the cloud. By aligning drawings and 3D models to that coordinate system, the AR display on site overlaps at the correct position and scale as in the plans. In other words, because both the data side and the physical space share the same “reference,” AR can be displayed without the need for manual alignment.

Using an LRTK-dedicated smartphone app, you can call up drawing or model data uploaded to the cloud and overlay it on site. No complicated operations are required: simply stand on site and start the app, and the model is displayed accurately relative to your position.

LRTK is already being used in various sites, such as accurately checking the positions of pile foundations and checking finished lines for river bank protection work. As long as the drawing data is prepared, it can be accurately projected on site, expanding use cases to construction quality control and locating buried objects. Furthermore, since site information can be shared in real time with the office via the LRTK cloud, it is possible to check site conditions or give instructions remotely.

Main features of LRTK include:

• Centimeter-class positioning using satellite positioning (leveraging RTK technology) — centimeter-level accuracy (cm level accuracy (half-inch accuracy))

• Accurate data alignment via registration of site-specific coordinate systems (compatible with existing drawing coordinates)

• Sharing and use of drawings and model data through the cloud (always obtain the latest data)

• Intuitive and simple operation via a dedicated app (no complex settings required)

“Drift-free” AR display realized by LRTK

Now let’s see concretely how using LRTK solves AR display drift. As mentioned above, LRTK accurately corrects device position and pose and ensures model data matches site coordinates. Therefore, when you start the app on site, a building design 3D model, for example, will be displayed at the planned construction site with perfect alignment. Complicated alignment work is entirely unnecessary, and you can literally experience “drift-free AR.”

Previously, when the work area expanded, it was necessary to re-align at distant locations, but with LRTK you can maintain high-precision AR display consistently from one end of the site to the other. Even in scenes where AR tracking usually struggles—such as at night or in feature-poor locations—LRTK’s accurate coordinates support the system and suppress the risk of large model drift. The expectation of more stable AR display in dark outdoor settings or reflective environments is a major reassurance.

This enables smooth workflows such as walking around the site to review the design model from various angles or displaying the same model at multiple spots to check progress. With AR drift resolved, AR becomes a practical tool rather than a mere demo. For example, in design-phase image sharing, you can show clients the completed image overlaid on the actual scenery to eliminate misunderstandings and prevent rework. For on-site quality checks, you can visually compare the current state to the drawing data to quickly detect mistakes or oversights. In one road construction case, overlaying design drawings in AR with LRTK revealed the need to relocate piping that had not been noticed beforehand, allowing plan corrections and coordination with stakeholders before construction began. In this way, drift-free AR helps discover issues early and prevent rework. Reporting and sharing with stakeholders also become much smoother because you can show the AR view on site—“this will be constructed here like this”—instead of relying on paper drawings.

Moreover, if multiple people each view the same model with LRTK-enabled devices, everyone shares the same scene consistent with the real world, making on-site meetings more intuitive.

New possibilities for simple surveying with LRTK

LRTK’s strength is not limited to making AR displays accurate. By leveraging high-precision positioning information, new possibilities open up for simple on-site surveying.

Traditionally, accurate staking out and dimensional checks at construction sites required specialized surveying instruments (such as total stations) and multiple personnel. With LRTK, however, measurements close to surveying work can be performed by one person with only a smartphone and a compact GNSS receiver (satellite positioning antenna).

For example, the following can be achieved with LRTK:

• Guidance for pile driving and stakeout: Based on coordinates set in the LRTK app, AR displays or navigation can indicate on site “the installation position for ○○ is here.” Following this, a single person can precisely identify points without having to search with a tape or stakeout drawings.

• On-the-spot verification and measurement of as-built conditions: The position of completed structures or constructed parts can be checked against design coordinates. For example, you can easily measure the as-built position of installed anchors on site with LRTK to confirm conformity with the drawings.

• Photo records linked with location data: With LRTK you can take photos saved to the cloud with position and orientation information. This makes it immediately clear “which point and in which direction the photo was taken,” smoothing later report preparation and comparative review.

• 3D scanning and volume calculation: Using LiDAR-equipped smartphones or photogrammetry to capture point cloud data of the site, you can automatically calculate earthwork volumes for fills and excavations. Tasks that previously required outsourcing (such as as-built management and volume calculation) can be performed quickly on site with LRTK.

Thus, LRTK simplifies measuring and verifying on site even for non-surveying specialists, contributing to more efficient and labor-saving construction work.

Conclusion

The problem of AR display drift was difficult to solve fundamentally with conventional technologies. However, the emergence of LRTK is changing the situation. Drift-free AR supported by high-precision positioning is a reliable ally for on-site DX (digital transformation) and has the potential to radically innovate construction management and coordination.

As the phrase “the new on-site standard” suggests, accurate AR display and simple surveying using LRTK may soon become commonplace on sites. The era of being troubled by AR drift is coming to an end. By leveraging LRTK, we will enter a time when anyone can easily and accurately “visualize” the site. If you are struggling with on-site AR use, consider trying the new experience offered by LRTK.

FAQ

Q: Why does AR display drift on site? A: AR display drift mainly results from device positioning accuracy and environmental influences. Smartphone GPS errors and sensor errors can offset position and heading, and in environments where the camera cannot easily capture feature points, the AR system’s self-positioning becomes unstable, causing models to fail to match reality.

Q: Can’t I prevent AR drift by using markers? A: Markers or QR codes can be effective to some extent, but they are difficult to use consistently across wide outdoor sites. They are only effective within the areas where markers can be installed and require the camera to read them each time. LRTK’s major difference is that it maintains high-precision alignment across the entire site without relying on markers.

Q: Do I need special equipment or expertise to use LRTK? A: Basically, you can use LRTK with a smartphone (or tablet) and a small GNSS receiver that supports RTK. The dedicated app is designed for intuitive use, so specialist surveying knowledge is not necessary. Initial setup and registering coordinate systems require some familiarity, but typical site staff can master it with a short training period.

Q: What kind of positioning accuracy does LRTK offer? A: Depending on conditions, it generally provides accuracy on the order of a few centimeters. Whereas normal GPS has errors of several meters, LRTK achieves precision that is a fraction of that. In open areas with good satellite reception, you can expect a level of reproducibility where measuring the same point repeatedly yields virtually the same coordinates. However, accuracy can decline in areas where satellite signals are obstructed, such as under elevated structures or under tree cover, though it still maintains higher accuracy than conventional GPS.

Q: What kinds of sites or applications can LRTK be used for? A: In addition to construction and civil engineering sites, LRTK is expected to be useful for equipment maintenance, agriculture, surveying, and any outdoor situation where position information is handled. Whenever you need to link drawings to the actual site—checking design data on site, considering the placement of structures, or recording/inspecting buried objects—LRTK can be effective.

Q: How long does it take to prepare for LRTK implementation? A: You first register the site’s reference coordinates, but if reference point coordinates are already known, setup can be done quickly. For example, measuring and registering about three known points from the drawings on site can be completed in under an hour with practice. Once the coordinate system is registered, you simply start the app on site and can immediately use AR.

Q: What types of drawing data can be displayed in AR? A: LRTK supports common 3D model data used in BIM/CIM (such as OBJ and IFC) and 2D drawing data (such as DXF/DWG). If these design data are uploaded to the LRTK cloud, the app can call them up and display them in AR on site. Point cloud data and aerial photos can also be overlaid, allowing various information to be visualized at once. In short, LRTK’s strength is that almost any digital information can be visualized on site in AR.

Q: Can LRTK be used indoors? A: Because LRTK uses GPS satellites for high-precision positioning, it is primarily intended for outdoor use. It is difficult to ensure accuracy inside buildings or underground where GPS signals are not available. However, by using reference points measured outdoors near the building, relative indoor positioning can sometimes be inferred, so there are cases where it can be applied to some indoor positioning tasks with ingenuity. As indoor positioning technologies advance and integrate, the scope for indoor use will likely expand.