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 Implementation ⒋ Simple Surveying with LRTK ⒌ FAQ

Recently, the use of AR (Augmented Reality) technology has been advancing in construction and surveying sites. By overlaying 3D design drawings onto real-world scenes via smartphones or tablets, verification of construction locations and checks of as-built conditions can be performed intuitively. This technology, particularly noted as 3D drawing AR overlay, enables visualization of design information on-site to reduce surveying errors and is expected to improve work efficiency. Such new initiatives are steadily spreading across job sites.

However, conventional AR tends to have the projected positions in the real world drift over time or as users move, and precise overlay requires tedious calibration (positioning) each time. The technology that solves these problems is a new approach called absolute coordinate AR. In this article, we explain in detail how absolute coordinate AR works, its benefits, and the innovations it brings to surveying operations. Now, let’s take a step-by-step look at what exactly absolute coordinate AR technology is.

What is absolute-coordinate AR?

First, let's organize the differences between conventional techniques and absolute-coordinate AR for displaying drawings on site using AR. In conventional AR, the typical approach has been to overlay 3D models by projecting markers into the camera image or by manually calibrating (calibration) to local reference points. However, this method has several issues.

• Requires alignment every time: Whenever you visit the site, you must align the model using reference markers or known points, which is time-consuming.

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

• Insufficient accuracy: The GPS built into smartphones has low accuracy of approximately 5–10 m (16.4–32.8 ft), and is far from the centimeter-level accuracy (cm level accuracy (half-inch accuracy)) required in civil surveying.

Because of these problems, conventional AR overlays, though appealing in concept, were often inadequate in terms of accuracy 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 a high-precision positioning technology called RTK (Real-Time Kinematic). By using RTK-GNSS, even a smartphone can obtain position information with an error of a few centimeters (a few in), and by incorporating this into AR display, models can be fixed to precise positions in the real world. Specifically, it has the following features.

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

• Models do not shift: Even if users walk around the site and view from different points, once displayed the model remains at the correct position and orientation. Because AR objects do not float or move away from the ground when moving, it can be used with confidence.

• Supports high-precision surveying: RTK provides accuracy of a few centimeters (a few in) in horizontal position and within about 10-20 cm (3.9-7.9 in) in the vertical direction. Conventional meter-level errors of several meters (several ft) are eliminated, bringing accuracy to a level that can be used for surveying tasks requiring high precision such as batter boards and stake driving.

In other words, with absolute-coordinate AR, it becomes possible to continuously display the design model "as it is on site". As long as the coordinates are unified, simply holding up a tablet will make the drawing lines and structural models blend into the on-site scenery at actual size, and their positions will not drift even if the user moves and changes viewpoint. This stable AR overlay enables intuitive and accurate drawing verification even at surveying sites.

Examples of On-site Use and Benefits

1. Design Verification Before Construction and Pile-driving Guidance

If you display design drawings or 3D models on-site with AR before starting work, you can detect deviations at the planning stage in advance. For example, in bridge and road construction, you can project the design model onto the site before work begins and verify whether it fits the intended position and elevation. Compared with the traditional method of comparing paper drawings on-site, being able to match at actual scale makes it more intuitive and reliable. AR also proves powerful for pile-driving positioning. Because you can display virtual piles and markings in AR based on design coordinates, workers can drive piles in the correct locations by following on-screen guidance. Even less experienced staff can identify their positions without hesitation thanks to the markers seen through the device, enabling pile-driving with minimal error even without a surveyor on site. Furthermore, if the client and the entire team share the AR visualization of the finished project before construction begins, it reduces misunderstandings and facilitates smoother consensus-building.

2. Progress Management and As-Built Verification During Construction

AR overlays are also useful during the construction process. This is because, at intermediate stages of work, you can instantly verify on site whether the current structure is progressing at the designed position and dimensions. For example, before pouring concrete, you can compare the formwork position with the AR-displayed design model to check for any deviations. If discrepancies are found, they can be corrected on the spot, preventing rework later. For earthworks and paving, you can compare the finished elevation against the AR design lines to instantly ascertain whether the specified height has been reached. Whereas traditional as-built management involved surveying after completion and reconciling with drawings, with AR this can be completed in real time on site. This enables earlier detection of construction errors and easier quality assurance, and provides more visual and persuasive explanations to clients. Final inspections and handovers become smoother, enabling quality control that satisfies all stakeholders.

3. Infrastructure maintenance and safety measures

Absolute-coordinate AR is also useful in post-construction infrastructure maintenance and safety measures. For example, in 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 the previous and current states can be directly overlaid and compared, this helps formulate precise repair plans based on observed long-term changes.

For excavation work, location data of underground buried pipes and cables obtained in advance can be displayed on the ground via AR. Since information such as “a gas pipe runs beyond this point” can be understood intuitively on site, the risk of accidentally damaging lifelines can be greatly reduced by significantly lowering the risk of accidental damage to lifelines. These applications contribute to improved safety and greater efficiency in maintenance operations.

Given these advantages, the use of AR in the infrastructure sector is expected to expand further in the future.

Preparations and technologies required for deployment

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

• デジタル図面データの用意：First, assemble the design data you want to display on site in digital form. If possible, CAD data (e.g., DWG or DXF) or 3D models from BIM/CIM are desirable; if you only have paper drawings, it is better to convert them to CAD rather than rely on scanned images. At a minimum, even from PDF drawings you can create images with position information (georeferenced images) to use for simple AR display.

• 座標系の確認：Confirm that the prepared drawing data corresponds to the actual survey coordinate system. For example, if the data is designed in public absolute coordinates such as the Geospatial Information Authority’s plane rectangular coordinate system or the World Geodetic System (WGS84), it can be matched with GNSS positioning coordinates as is, making additional correction work unnecessary. On the other hand, if the drawings are drawn in site-specific arbitrary coordinates (local coordinates), you need to determine the correspondence with field survey values in advance. Specifically, obtain multiple field latitudes and longitudes corresponding to known points on the drawing and calculate translations and rotations to apply to the drawing data. This allows drawings in a local coordinate system to be displayed in AR aligned with the site’s absolute coordinate system.

• 高精度GNSSとAR対応端末：On the hardware side, you need a GNSS receiver that supports RTK and a smart device that can interface with it. Because built-in smartphone GPS typically lacks the necessary accuracy, provide an RTK receiver capable of centimeter-level positioning (half-inch accuracy). Connect this to a smartphone or tablet and receive correction information from base stations (such as a network of reference stations) via the internet, and you can measure high-precision positions even while moving. On the device side, use an app that supports AR display. Recent smartphones and tablets include AR capabilities (ARKit or ARCore), and combined with a dedicated app they can overlay 3D models onto camera imagery based on the acquired coordinates.

• 測位環境：High-precision positioning also requires certain environmental conditions. Because satellite signals must be received, it is preferable to operate in areas with an open view of the sky. In environments where GNSS cannot reach, such as inside tunnels or dense forests, this method is essentially unusable (see the FAQ below). Even so, it can be used in most outdoor construction and surveying sites without significant issues.

Once those preparations are complete, all that remains is to launch AR mode on your smartphone at the site. The alignment of the drawing data is completed automatically, allowing you to start 3D drawing AR overlay immediately without any complex setup. The positioning work that surveyors traditionally carried out by setting up tripods and measuring instruments will likely shift to simple surveying where you simply hold up a tablet to verify.

Simplified Surveying with LRTK

Finally, as a solution to easily utilize such absolute-coordinate AR on-site, we introduce LRTK. LRTK (pronounced “Eru Aru Tī Kē”) is a groundbreaking system that enables centimeter-level positioning simply by attaching a compact RTK receiver to a smartphone. Moreover, it eliminates the need to set up reference points and perform position adjustments for each site, allowing models to be displayed with correct coordinates from the start and greatly reducing cumbersome alignment work. A major feature is that it realizes high-precision AR—previously requiring specialized equipment and HMDs costing on the order of several million yen—with a handheld smartphone and a compact device. Because it’s smartphone-based and portable by anyone, operation is simple, and field tasks can be carried out just by following the app’s positioning guidance and AR display instructions.

LRTK is not merely a positioning device; it is an on-site DX platform that can centrally manage acquired point cloud data and drawing information in the cloud as an all-in-one solution. Because surveying, construction management, and photographic records for reports can all 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, and this is a distinctive strength of LRTK.

From sites that actually introduced LRTK, there have been many reports attesting to the effectiveness of simplified surveying, such as "Even new staff were able to stake out points simply by following the on-screen instructions" and "Work could be carried out according to the drawings, reducing rework." If you want to adopt absolute-coordinate AR at your company's sites, please check LRTK's official information. Cutting-edge AR technology will update standard practices at surveying sites and elevate your operations to the next stage.

FAQ

Q1. I only have drawing data on paper or in PDF. Is AR overlay still possible?

A. Yes, that's possible. However, I recommend taking the extra step of digitizing the data. Even if you only have PDF drawings, you can convert them to CAD data such as DXF/DWG with CAD software, which allows the line data to be displayed in AR. If that's difficult, you can import the PDF as an image and place it to match site coordinates (georeference). That said, obtaining the original design CAD data is still the most reliable option. LRTK supports various drawing formats such as DXF and LandXML, so preparing digital drawing data whenever possible will make overlaying smoother.

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

A. If RTK positioning is working properly, you will be within ± a few centimeters (± a few in) in horizontal position. This level of accuracy rivals that of conventional total-station surveying and is fully practical. However, note that in smartphone AR the device's tilt tends to cause vertical deviations of a few centimeters (a few in). In particular, more distant objects may exhibit slight errors in projected height. Therefore careful verification is needed for exact height alignment, but the error is not at a level that would prevent use for staking or setting out structures, and it can be considered reliably accurate for field use.

Q3. Can it be used in places where GNSS does not reach, such as indoors or inside tunnels?

A. In environments where GNSS reception is basically impossible, 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 by inertial navigation. For example, after entering a tunnel you can continue to autonomously determine your position for a while using the smartphone’s built-in sensors. However, because errors gradually accumulate with distance traveled, for long stretches you need to periodically reacquire an RTK reference point on the surface or place correction markers such as QR markers along the way. In short, you cannot expect the same high accuracy as outdoors, but with some measures it is possible to perform a certain degree of AR overlay in GNSS-denied areas for short periods.

Q4. What advantages does it have over other companies' high-precision AR systems?

A. Traditionally, high-precision AR typically involved large investments in dedicated head-mounted displays and surveying equipment. By contrast, LRTK replaces those with off-the-shelf smartphones and compact GNSS receivers, which dramatically lowers the initial adoption barrier. Because the system is centered on a smartphone app, feature expansion via updates is straightforward, and it provides cross-functional, all-in-one capabilities such as point cloud measurement and photo management. In short, the main difference is that you can get started at low cost and with rich functionality. Of course, other specialized equipment may be more appropriate for certain applications, but for typical construction sites, a convenient and comprehensive solution like LRTK is likely the most efficient option.

Q5. Isn't it difficult to operate? Can on-site elderly workers and beginners use it effectively?

A. LRTK can be operated via an intuitive smartphone app and is usable even without special expertise. On site, you simply follow the instructions on the tablet screen, so many report that even workers unfamiliar with IT could handle it with a game-like feel. Of course, understanding the principles of high-precision positioning provides extra reassurance, but for basic use, even new hires can become fully effective in a short time. LRTK also provides knowledge support through a support site and manuals, so learning them alongside operation will further accelerate proficiency.

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 functions 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 try high-precision on-site positioning in earnest, a dedicated RTK device is required, but rentals and demo requests are available, so it's a good idea to contact them casually first. When introducing it, set goals for which business processes in your company you want to use it for (e.g., accuracy control for pile driving, improving efficiency of as-built verification), and plan data preparation and operational workflows accordingly. By piloting at small sites with support from the LRTK team and gradually expanding the scope, you can smoothly establish it on-site. Start by trying the app — that will be the first step toward on-site digital transformation.