Surveying Sites Are Evolving! 3D Drawing Display Technology Using Absolute-Coordinate AR

Table of Contents

⒈ What is Absolute Coordinate AR? ⒉ On-site use cases and benefits ⒊ Preparations and technologies required for deployment ⒋ Simplified surveying using LRTK ⒌ FAQ

In recent years, the use of AR (augmented reality) technology has been advancing at construction and surveying sites. By overlaying 3D design drawings onto the real-world landscape via smartphones and tablets, verification of construction locations and as-built checks can be performed intuitively. This technology, particularly highlighted as 3D drawing AR overlay, enables on-site visualization of design information to reduce surveying errors and is expected to improve work efficiency. Such new initiatives are steadily spreading across job sites.

However, in conventional AR, projected positions in the real world tend to drift over time or as users move, and accurate overlay requires cumbersome calibration (alignment) each time. The new technology that solves these issues is called absolute-coordinate AR. In this article, we will explain in detail how absolute-coordinate AR works, its benefits, and the innovations it brings to surveying operations. Now, let's go step by step to see exactly what kind of technology absolute-coordinate AR is.

What is absolute-coordinate AR?

First, regarding the display of drawings on a worksite using AR, let's outline the differences between conventional techniques and absolute-coordinate AR. In conventional AR, the common approach has been to project markers into the camera view or manually calibrate to local reference points (manual calibration), then overlay a 3D model on top. However, this approach had several issues.

• Alignment required every time：Each time you visit the site, you must align the model using reference markers or known points, which is time-consuming.

• Model drift：Even after placement, over time or due to camera shake the AR model gradually drifts away from its actual position.

• Insufficient accuracy：The accuracy of smartphone-built-in GPS is low at around 5-10 m (16.4-32.8 ft), and it falls far short of the cm level accuracy (half-inch accuracy) required by civil engineering surveying.

Because of these problems, conventional AR overlays, though appealing in concept, were often insufficiently accurate for practical use.

On the other hand, absolute-coordinate AR is an AR technology that, as the name implies, places 3D models based on absolute coordinates on the Earth. The key is the use of the high-precision positioning technology called RTK (Real-Time Kinematic). By using RTK-GNSS, even smartphones can obtain position information with an error of several centimeters (a few in), and by incorporating this into AR display, models can be fixed at the exact positions in real space. Specifically, it has the following features.

• No calibration required: With RTK-enabled absolute-coordinate AR, there is no need to place markers or perform alignment on site beforehand. Models are automatically displayed in the correct positions according to the coordinates included in the design data.

• Models do not shift: Even if a user walks around the site and views from different points, once displayed the model always remains in the correct position and orientation. Because AR objects do not float or move relative to the ground when you move, it can be used with confidence.

• Supports high-precision surveying: RTK achieves planar positioning accuracy of several centimeters (a few in) and vertical accuracy within about 10–20 cm (about 3.9–7.9 in). It eliminates the conventional meter-scale errors of several meters (about 6.6–16.4 ft), reaching a level usable for high-precision surveying tasks such as batter boards and stake setting.

In other words, with absolute-coordinate AR, it becomes possible to continuously display the design model "as is" on site. As long as the coordinates are aligned, simply holding up a tablet will make the drawing lines and structural models blend into the real-world scene at true scale, and their positions won't drift even when the user moves or changes viewpoint. This stable AR overlay enables intuitive and accurate plan verification even in the field.

On-site Use Cases and Benefits

1. Pre-construction Design Verification and Pile-driving Guidance

If design drawings and 3D models are displayed on site in AR before work begins, you can detect planning-stage discrepancies in advance. For example, in bridge and road construction you can project the design model onto the site before starting work to confirm whether it fits the planned position and elevation. Compared with the traditional method of comparing paper drawings on site, verifying at true scale is more intuitive and reliable. AR also proves powerful for guiding pile-driving locations. Because virtual piles or markings can be displayed in AR based on the design coordinates, workers can install piles at the exact locations by following the on-screen guidance. Even inexperienced staff can identify their positions without hesitation thanks to the markers visible through the device, enabling pile driving with small errors even without a surveyor on site. Furthermore, if the client and the entire team share the finished image in AR before construction starts, it reduces misunderstandings and smooths consensus building.

2. Progress management and as-built checks during construction

AR overlays are also useful during the construction process. At intermediate stages of work, they allow on-site, immediate confirmation of whether the structure as built is progressing in the correct positions and dimensions specified in the design. For example, before casting concrete, you can compare the formwork positions with the AR-displayed design model to check for any deviations. If errors are found, they can be corrected on the spot, preventing rework later. Also for embankment works and paving, you can compare the finished surface height against the AR design lines to instantly see whether the specified elevation has been achieved. Whereas conventional as-built verification required surveying after completion and cross-checking with drawings, AR enables that as-built management to be completed on-site and in real time. This makes early detection of construction errors and quality assurance easier, and explanations to clients more visual and persuasive. Final inspections and handover become smoother, allowing all stakeholders to agree on the quality control.

3. Infrastructure maintenance and safety measures

Absolute-coordinate AR is also useful for post-construction infrastructure maintenance and safety measures. For example, during routine inspections of roads and bridges, past inspection records and 3D scan data can be overlaid in AR onto current site footage to visualize the progression of deterioration and displacement. Because previous and current states can be directly overlaid and compared, it helps in formulating precise repair plans that account for aging-related changes. In excavation work, position data of underground buried pipes and cables obtained in advance can be displayed on the ground using AR. Since information such as "a gas pipeline runs ahead from here" can be intuitively understood on site, the risk of accidentally damaging lifelines can be greatly reduced. These applications therefore contribute to improved safety and greater efficiency in maintenance operations. Given these benefits, AR use in the infrastructure sector is likely to expand further going forward.

Preparations and technologies required for deployment

So, what is needed to realize on-site overlay of drawings using this kind of absolute-coordinate AR? Broadly speaking, the key points are "data preparation" and "equipment/system preparation."

• Providing digital drawing data: First, prepare the design data you want to display on site in digital form. CAD data (e.g. DWG or DXF) or 3D models from BIM/CIM are desirable when possible; if you only have paper drawings, it is better to convert them to CAD rather than using scanned images. At a minimum, if you can create a georeferenced image (an image with positional information) from a PDF drawing, you can use that for a simple AR display.

• Confirming the coordinate system: Check whether the prepared drawing data corresponds to the actual survey coordinate system. For example, if the data were designed in the Geospatial Information Authority of Japan’s Plane Rectangular Coordinate System or the World Geodetic System (WGS84), they are official absolute coordinates and can be matched to GNSS positioning coordinates more easily without additional corrections. On the other hand, if the drawings were drawn in a site-specific arbitrary coordinate system (local coordinates), you will need to determine the correspondence with field survey values in advance. Specifically, obtain multiple field latitude/longitude points corresponding to known points on the drawing, calculate the translation and rotation amounts, and apply them to the drawing data. This will allow AR display of drawings in a local coordinate system to be aligned with the site’s absolute coordinate system.

• High-precision GNSS and AR-capable terminals: On the hardware side, you need a GNSS receiver that supports the RTK method and a smart device that can connect to it. The GPS built into ordinary smartphones lacks the necessary accuracy, so prepare an RTK receiver capable of centimeter-level positioning (cm level accuracy (half-inch accuracy)). Connect this to a smartphone or tablet and receive correction information from base stations (such as a network of continuously operating reference stations) via the internet to measure high-precision positions even while moving. On the device side, use an app that supports AR display. Recent smartphones and tablets come with AR capabilities (ARKit or ARCore), and when combined with a dedicated app they can overlay 3D models onto the camera view based on the acquired coordinates.

• Positioning environment: High-precision positioning also requires certain environmental conditions. Because signals are received from satellites, it is desirable to use the system in places where the sky is as open as possible. This method is generally unusable in environments where GNSS cannot reach, such as inside tunnels or in dense forests (see the FAQ below). Even so, it can be used in almost all outdoor construction and surveying sites without major issues.

Once the above preparations are complete, all that's left is to launch AR mode on your smartphone on site. The drawing data alignment completes automatically, allowing you to immediately start a 3D drawing AR overlay without complicated setup. Positioning work that used to be done by surveyors setting up tripods and measuring equipment will likely change to simplified surveying where you just hold up a tablet to check.

Simple surveying with LRTK

Finally, as a solution that enables easy on-site use of such absolute-coordinate AR, we introduce LRTK (pronounced L‑R‑T‑K). LRTK is a groundbreaking system that enables centimeter-level positioning (cm level accuracy, half-inch accuracy) simply by attaching a compact RTK receiver to a smartphone. Moreover, because there is no need to set up reference points and adjust positions for each site, models can be displayed with correct coordinates from the start, greatly reducing cumbersome alignment work. A major feature is that it delivers high-precision AR—which previously required dedicated equipment and HMDs costing several million yen—using a handheld smartphone and a compact device. Because it is smartphone-based and portable, operation is simple: users can proceed with on-site tasks just by following the positioning prompts and AR display guidance in the app.

LRTK is not just a positioning instrument; it is also an on-site DX platform that serves as an all-in-one solution for centrally managing acquired point cloud data and drawing information in the cloud. Because a series of tasks—from surveying and construction management to photographic records for reports—can be completed within a single system, data sharing and work efficiency improve dramatically. It also supports construction DX initiatives promoted by the Ministry of Land, Infrastructure, Transport and Tourism, such as i-Construction, and is gaining attention as a tool that contributes to productivity improvements through the latest technologies. Systems that can consistently handle data from surveying through construction and maintenance are rare, making this a distinctive strength of LRTK.

From sites that have actually introduced LRTK, many voices attest to the effectiveness of simplified surveying, such as "even a newcomer could lay out stakes just by following the on-screen instructions" and "we were able to carry out construction according to the drawings, reducing rework." If you want to try incorporating absolute-coordinate AR at your sites, be sure to check LRTK's official information. Cutting-edge AR technology will update standard practices at surveying sites and evolve your operations to the next stage.

FAQ

Q1. The only drawing data I have are paper documents or PDFs. Is AR overlay still possible?

A. Yes, it is possible. However, I recommend taking the extra step to digitize the data. Even if you only have PDF drawings, converting them into CAD data such as DXF/DWG with CAD software will allow them to be displayed in AR as line data. If that’s difficult, you can also import the PDF as an image and place it to match site coordinates (georeferencing). That said, obtaining the original design CAD data is still the most reliable option. Because LRTK supports various drawing formats such as DXF and LandXML, preparing digital drawing data as much as possible will make overlays go smoothly.

Q2. Can smartphone AR displays really achieve accuracy to within a few centimeters? Is it okay to use them for surveying?

A. If RTK positioning is working properly, planar position errors will be within ± a few centimeters (± a few inches). This level of accuracy is comparable to conventional total-station surveying and is fully adequate for practical use. However, note that in smartphone AR, device tilt tends to cause vertical offsets of a few centimeters (a few inches). Slight errors in projected height can especially occur for more distant objects. Therefore, careful verification is required for perfect height alignment, but the errors are not at a level that would impede tasks such as stakeout or setting out the positions of structures, and the accuracy can be considered reliably sufficient for on-site use.

Q3. Can it be used in locations where GNSS cannot reach, such as indoors or in tunnels?

A. In environments where GNSS reception is basically unavailable, absolute-coordinate AR using RTK cannot be used as-is. However, LRTK is equipped with a mode that, for short periods, continues to estimate position using inertial navigation. For example, when entering a tunnel you can continue to be positioned autonomously by the smartphone’s built-in sensors for a while. However, since errors gradually accumulate with travel distance, over long sections you need to periodically return to an RTK reference point on the surface or place correction markers such as QR codes along the route. In short, you cannot expect the same high accuracy as outdoors, but with some ingenuity it is possible to perform a certain degree of AR overlay in GNSS-denied areas for short periods.

Q4. What makes it superior to other companies' high-precision AR systems?

A. Conventional high-precision AR typically required investing heavily in dedicated head-mounted displays and surveying equipment. In contrast, LRTK substitutes with commercial smartphones and compact GNSS receivers, which makes the initial deployment barrier considerably lower. Because it is a smartphone-app-based system, functionality can be extended easily through updates, and it provides cross-functional features such as point cloud measurement and photo management all-in-one. In short, the major difference is that it can be started in a low-cost yet multifunctional way. Of course, other dedicated equipment may be more appropriate depending on the application, but for most construction sites, a convenient and comprehensive solution like LRTK is likely the most efficient.

Q5. Isn't the operation difficult? Can elderly or novice workers on site handle it effectively?

A. LRTK can be operated with an intuitive smartphone app and is usable without any special expertise. On site you simply follow the instructions on the tablet screen, so many have reported that even workers unfamiliar with IT could handle it almost like a game. Of course, it’s reassuring to understand the principles of high-precision positioning, but for basic use even newcomers can become effective in a short time. LRTK also covers that knowledge through its support site and manuals, so learning alongside operation helps you gain proficiency even faster.

Q6. What should we start with when introducing LRTK?

A. As a first step, we recommend obtaining the LRTK smartphone app and trying its basic features with a trial account. Even with just your smartphone or tablet, you can experience AR visualization and point-cloud viewing using sample 3D data in the cloud. To fully try high-precision field positioning you need a dedicated RTK terminal, but rentals and demo requests are available, so it’s a good idea to contact them casually at first. When introducing it, set goals for which of your company’s business processes you want to use it in (e.g., accuracy control for pile driving, improving the efficiency of as-built verification), and plan data preparation and operational workflows accordingly — this will be effective. With support from the LRTK team, trial it at small sites and gradually expand the scope of application to smoothly establish it in the field. Start by trying the app — that will be the first step toward on-site DX.