Zero Construction Errors! Achieve Construction According to Design with Misalignment-Free AR Drawing Overlay

Table of Contents

• The difficulty of building to drawings on site

• What is AR overlay of drawings?

• Problems solved and benefits of AR overlay

• High-precision, non-drifting AR: drawing overlay realized with LRTK

• How to do AR drawing overlay with LRTK and example uses

• LRTK’s simple surveying functions expanded by cm-level positioning (half-inch accuracy)

• Conclusion

The difficulty of building to drawings on site

On construction and civil engineering sites, constructing exactly according to the design drawings is not easy. Site managers and surveyors carry drawings and perform layout staking (setting out) on site, installing batter boards and stakes to indicate reference lines. However, deriving precise positions from two-dimensional drawings amid complex terrain and structures is a nerve-wracking task even for experienced personnel. In large-scale projects especially, the number of items to check becomes enormous, and traditional manual methods relying on human sight and hands reach their limits. Moreover, as long as humans rely on vision and measuring instruments, it is difficult to eliminate human error completely; slight misreads or measurement mistakes can lead to construction errors.

For example, measuring the distance incorrectly from a reference point can shift rebar placement, or confusing vertical reference levels can cause errors in concrete placement height on site. Even if the paper drawing is correct, misunderstandings or communication errors during the process of fitting dimensions to the site can cause rework or reconstruction, directly resulting in delays and cost overruns. To aim for zero construction errors, a new method is needed to bridge the gap between drawing information and on-site work. Recently, attempts to carry drawings on tablets for on-site checks have advanced, but the burden of translating drawing information to the site scale remains. In the context of construction DX initiatives such as the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction,施工支援 using AR technology has attracted attention. Against this background, the AR overlay technology described next is gathering expectations.

What is AR overlay of drawings?

A technology attracting attention for closing this gap is AR overlay of drawings. Using AR (augmented reality) technology, design drawing data is overlaid and displayed on the real-world scene on a smartphone or tablet screen. In other words, when viewing the actual site through the device’s camera, the digital drawing or model appears translucent in the same field of view.

For example, at a road construction site, pointing a smartphone might show the centerline or edges from the design drawn on the ground through the screen. On a building site, foundation and wall layout lines are displayed at full scale in place. Instead of comparing drawings and the site side by side, you can project and visualize the drawing directly onto the site, making it intuitive to understand “what goes where.” Completion images and positional relationships that were hard to grasp on 2D drawings become immediately clear when the drawing is overlapped with the real scenery in AR.

With AR overlay of drawings, the digital system takes over the spatial interpretation work that site personnel used to perform mentally. Even without relying on veteran intuition and experience, anyone on site can visually confirm the design intent. Recently, demonstrations of AR-based construction support have been conducted in various places, and it is also attracting attention as part of digital twin and XR (cross-reality) initiatives.

Problems solved and benefits of AR overlay

So, what specific problems are solved and what benefits are gained by overlaying drawings in AR? Here are the main points from a site perspective.

• Reduction of construction errors and human error: Because design data is visibly displayed on site, positional and dimensional misunderstandings are noticed immediately. If a construction location is off the design line, the deviation is obvious on the AR screen, enabling early correction. This greatly reduces rework caused by memory slips or surveying mistakes and helps prevent quality defects.

• Improved communication and sharing: Drawings displayed in AR are intuitively understandable not only to site staff but also to clients and designers. When a site manager shows a tablet screen to explain, the completed image that is hard to convey with paper drawings becomes easier to share. Also, by recording and sharing AR display screens as photos or videos, remote stakeholders can exchange information from a common viewpoint.

• Simplified work and increased efficiency: Tasks that traditionally required repeatedly checking positions with tape measures or surveying instruments can be verified on the spot with AR. Even without physically marking points, workers can follow digitally displayed guide lines, enabling a single person to work efficiently. As a result, labor-saving and speed improvements are expected even on sites with labor shortages.

• Visual consensus building: AR overlay helps build consensus on site. For example, positions of buried utilities or property boundary lines—normally invisible—can be visualized with AR. When everyone feels they are looking at the same “object”, troubles due to “differences in perception” can be prevented.

• Contribution to skills transfer and education: Less-experienced staff can perform accurate work by following AR guidance, ensuring consistent quality without leaning on veterans’ know-how. Since experienced site senses can be shared digitally, positive effects are expected for skill transfer and human resource development.

In this way, AR overlay of drawings is a powerful ally toward zero construction errors, with the potential to dramatically improve on-site productivity and communication.

High-precision, non-drifting AR: drawing overlay realized with LRTK

To maximize the effects of AR overlay, display accuracy and stability are critically important. If a design drawing in AR is shown tens of centimeters off from the real position, it may cause confusion instead of clarity. However, the GPS accuracy of typical smartphones is coarse—on the order of 5–10 m—and is insufficient for construction applications as is. Also, when displaying AR outdoors across wide spaces without markers, standard approaches rely on a device’s sensors and camera for relative pose tracking, which leads to gradual drifting of the display during extended use.

This is where a high-precision positioning technology called LRTK excels. LRTK is an ultra-compact RTK-GNSS receiver that can be used in conjunction with a smartphone; it corrects satellite positioning errors using the real-time kinematic (RTK) method. By using RTK, positional accuracy improves to several centimeters horizontally and several centimeters vertically (i.e., to the centimeter level). This enables a smartphone to always know its position accurately at the centimeter level (half-inch accuracy), so AR design drawings align precisely with the real world.

LRTK also supports the centimeter-level augmentation service (CLAS) provided by Japan’s Quasi-Zenith Satellite System (QZSS), enabling high-precision positioning even at sites in mountainous areas with limited communications coverage.

With LRTK-based AR, aligning design data is also straightforward. If drawing data already contains latitude/longitude or coordinate system information, there is no need for on-site alignment. For example, if a point on the drawing is known to be at coordinates (X, Y), when the smartphone equipped with LRTK arrives at the same (X, Y), the corresponding element of the design will automatically display at that location. In other words, the drawing and the site are linked with no cumbersome on-site calibration.

Additionally, because LRTK provides consistently high-precision position information, the AR display does not drift even as the user walks around. With conventional AR, virtual object positions may gradually shift as you move, requiring re-calibration. But with LRTK, the user’s absolute position is accurately tracked regardless of movement within the site, so the drawing in AR stays correctly positioned at all times. Put another way, LRTK enables “AR that doesn’t drift even when you walk.”

Another major advantage is that this high-precision AR can be achieved simply by combining a smartphone with a palm-sized LRTK device. There is no need to carry a total station or heavy GNSS equipment; pocketable gear provides cm-accurate positioning anywhere on site. The LRTK terminal itself is about the same size as a smartphone, with a thickness of about 1 cm (0.4 in) and a weight of about 125 g, making it very compact. It can be attached to the back of a smartphone and, being battery-powered, runs for long periods without an external power source.

This significantly lowers the barrier to AR overlay of drawings and makes it easy to incorporate into routine construction management.

How to do AR drawing overlay with LRTK and example uses

Let’s look at the actual flow for displaying drawing data in AR using LRTK. The procedure is simple:

• Data preparation: First, prepare the design and construction drawing data. Obtain the information you want to overlay on site as digital data—2D CAD drawings (DWG/DXF, etc.) or 3D models (BIM/CIM data). Set coordinate systems and scale settings as needed so the drawing data matches real-world survey coordinates.

• Import into the app: Next, import the drawing data into the LRTK’s dedicated app or cloud. If you upload drawings, point clouds, and other project data per project, you only need to sync the data to the smartphone on site to be ready.

• AR display on site: On site, mount the LRTK receiver on the smartphone, select the relevant drawing data in the app, and switch to AR mode. Point the phone’s camera around, and the design lines and models you prepared will be overlaid on the camera image. Thanks to high-precision positioning, the display aligns almost perfectly with the real objects.

• Check and adjust: Compare the AR-displayed drawing with the actual site and confirm construction locations. For example, if the design shows a column at a certain spot but the marked position on site is 10 cm off, the AR display immediately reveals it. Correcting the position on the spot enables construction exactly according to the drawing. Capture screenshots or videos as needed for records and reporting.

With the above steps, even users without specialized surveying skills can intuitively check overlays of drawings. In actual sites, various use cases of LRTK-based AR overlay have been reported.

• As-built confirmation in civil engineering: In roadworks and land development, overlay the design finish shape on the terrain in AR to confirm whether excavation and embankment are within design limits. For instance, in slope-strengthening work on a levee, the planned 3D model of the completed slope can be overlaid on scanned current terrain data so stakeholders can check before construction whether the design slope will be achieved. When deviations are color-coded in AR (e.g., red and blue), it becomes clear at a glance which areas require rework.

• Layout staking in building construction: Using AR overlay for column and wall layout supports layout staking. Virtual guide lines or column position markers generated from drawing data are displayed on floors or structural surfaces in AR, allowing actual components to be placed according to those markers—enabling highly accurate positioning even by workers without instruments. This is especially useful where marking at heights or on scaffolding is difficult; supervisors can give instructions from a safe distance while checking the AR display, improving safety.

• Boundary checks and infrastructure management: AR overlay is powerful for municipal and surveying work. For example, displaying property boundary data in AR allows you to identify exact boundary locations even when boundary monuments are missing. During boundary hearings or pre-survey meetings, stakeholders can discuss while viewing the same AR display, smoothing consensus building. Also, by pre-recording the routes of underground water and sewer pipes and projecting them onto the ground during excavation work, you can help prevent damage to buried utilities.

• Virtual stake placement in hazardous areas: In places where people cannot approach—such as steep slopes or shaft bottoms—AR allows virtual stakes to be “driven” from a safe location. Based on LRTK’s high-precision positioning, virtual stakes can be displayed at specified coordinates, enabling layout staking and as-built confirmation where physical stakes cannot be placed.

As these examples show, LRTK-based AR overlay of drawings can be applied across a wide range of sites from civil engineering and construction to infrastructure maintenance. By directly linking data and the site, you can shift from “intuition-driven construction” to “data-driven construction.”

LRTK’s simple surveying functions expanded by cm-level positioning (half-inch accuracy)

LRTK is not only for AR display of drawings; it also serves as a simple surveying instrument. Centimeter-level positioning means that various on-site measurements and records can be performed quickly and with high precision. Using a dedicated app, simply point the device at the point to be measured and press a button to record that point’s latitude, longitude, and elevation. Recorded points are automatically converted to Japan’s plane rectangular coordinate system or the global geodetic system (WGS84), making it easy to plot them on drawings later or compare them with other GIS data. The system also supports conversion and alignment to arbitrary local site coordinate systems, allowing you to handle data in accordance with existing control points or the drawing’s coordinate system.

With this single-point positioning function, you can, for example, obtain several measured positions of structures on site and immediately compare them with design values for quality control. Tasks that previously required setting up levels or total stations and performing team surveys can be handled by one person with just an LRTK and a smartphone. Measurement results can be uploaded to the cloud and plotted on maps, eliminating the need to transcribe back at the office. On the cloud, data can be viewed and measured without specialized software, smoothing information sharing between site and office.

Furthermore, the LRTK app includes a coordinate guidance (navigation) feature that guides you on screen as you approach a specified coordinate. This makes finding stake locations or equipment installation points specified in the design much easier on site. Even reference points hidden by vegetation or snow can be found by following the device’s direction, giving confidence to less-experienced engineers.

Distance and area measurement functions are also well-equipped, allowing quick on-site measurement of distances between two points or the area of an enclosed region. For example, you can measure the width of an excavation or instantly calculate the area of an irregular parcel without special tools. Additionally, by leveraging an iPhone’s LiDAR scanner, you can perform small-scale terrain or structure 3D scans for volume calculations, supporting as-built control and quantity estimation.

In this way, LRTK functions as a versatile all-in-one tool for the site. From construction checks using AR overlay of drawings to dimensional measurement and as-built recording, a sequence of tasks can be handled seamlessly, maintaining data consistency. Without carrying paper drawings or survey notebooks, everything can be checked and recorded on the smartphone screen—powerfully driving the site’s digital transformation (DX).

Conclusion

The combination of AR overlay of drawings and high-precision positioning technology brings significant benefits to construction sites and is a key to realizing zero construction errors. Such technologies can be powerful tools not only for site managers and surveyors but also for designers and clients. Their usage is expected across many situations, from image sharing in the planning phase to inspection and maintenance after completion. By utilizing solutions like LRTK, anyone can easily achieve construction according to the design drawings, dramatically improving site productivity and safety. Digital supplementation of parts of construction that once relied on craftspeople’s intuition and experience will also help bolster the skills of younger engineers and reduce the burden on veterans.

Why not adopt cutting-edge AR positioning technology on your site and realize “non-drifting construction”? Let’s advance site digitization and jointly aim for a future of zero construction errors. For more information, please visit the [official site](https://lefixea.com).