Displaying Drawings on Site with AR: Visualization Enabled by High-Precision Smartphone Surveying

Table of contents

• Digitalization of surveying technology and AR utilization

• Benefits of displaying drawings in AR

• Emergence of high-precision smartphone surveying

• AR display requires centimeter accuracy (cm level accuracy (half-inch accuracy))

• Technologies that support smartphone surveying

• Diverse use cases for AR surveying

• Advantages of simplified surveying

• FAQ

Digitalization of surveying technology and AR utilization

In recent years, technological innovation and digitalization have rapidly advanced in construction and surveying sites. Whereas surveyors once used tripod-mounted total stations or transported large GNSS receivers with a team, the dramatic progress of GPS and sensor technologies now makes it possible to achieve equivalent surveying accuracy with compact devices. In particular, the advent of real-time kinematic (RTK) methods has enabled centimeter-level (cm level accuracy (half-inch accuracy)) high-precision positioning even with palm-sized receivers. Along with this, advanced technologies such as drone photogrammetry and 3D laser scanner point cloud measurement have begun to be introduced on sites.

On the other hand, the industry as a whole is suffering chronic labor shortages and an aging workforce, making it increasingly difficult to rely solely on specialized surveyors as before. With construction DX (digital transformation) efforts led by the Ministry of Land, Infrastructure, Transport and Tourism such as *i-Construction*, demand has grown for smart surveying solutions that anyone can use. Against this backdrop, a new generation of surveying tools combining smartphones and compact GNSS devices—so-called "smartphone surveying"—has emerged. Products like LRTK, which can perform point cloud measurement and AR display on a smartphone, are gathering high expectations as key items supporting on-site DX.

Benefits of displaying drawings in AR

On construction sites, work proceeds based on design drawings, but drawings alone can make it difficult to grasp the completed image or can lead to discrepancies in understanding among stakeholders. For example, a small oversight on a paper drawing can result in a building being constructed beyond the property boundary, or misreading the position of buried pipes can lead to cutting a cable during excavation. AR (augmented reality) is attracting attention as a powerful means to bridge these gaps and improve construction accuracy and safety. By overlaying design drawings or 3D models onto the real-world view seen through a smartphone or tablet camera, it becomes possible to intuitively confirm the "finished state" on site. Also, site boundary lines and underground utilities that are normally invisible can be visualized in AR, allowing necessary information to be grasped at a glance. From site supervisors to craftsmen, clients, and nearby residents, everyone can share the same AR view and visually understand "what will be installed where and how," greatly preventing troubles caused by differences in recognition.

The main advantages gained by overlaying drawings and data onto the site using AR are as follows:

• Completed-image sharing: You can vividly experience the post-construction appearance that is hard to imagine from plan views or sections by aligning it with the actual scenery. The placement and height of structures that are difficult to understand from drawings become immediately clear, helping to accurately share the designer's intent.

• Prevention of construction errors: Because design data and actual conditions can be overlaid and checked in AR, deviations and interferences during construction can be noticed immediately. For example, confirming the formwork positions with AR before concrete placement allows you to correct misaligned areas before work starts. Early correction of errors greatly reduces the risk of rework.

• Safety improvement by visualizing buried objects: The locations of underground gas pipes or communication cables can be identified in advance with AR. Knowing invisible hazards before excavation reduces the risk of accidental damage and directly contributes to safety measures.

• Smoother consensus building: Using AR to explain plans to clients and nearby residents allows sharing of completion images that are hard to convey with drawings alone. This prevents misunderstandings like "the finished appearance is different from what I imagined" and elicits concrete opinions from the planning stage. Being able to confirm the finished image while forming agreement also leads to higher satisfaction after completion.

• Efficiency in surveying and staking-out: If design reference lines and points can be displayed on the ground in AR and marked on the spot, position-setting tasks that traditionally required skilled workers—such as stake driving or string-line setup—can be performed accurately by anyone. This reduces the time spent measuring with tape measures while looking at paper drawings, yielding significant time savings and reduced labor burden.

Emergence of high-precision smartphone surveying

Using a smartphone to perform high-precision surveying would have been unthinkable not long ago. But today, by combining high-performance GNSS receivers with smartphones, the era in which "a smartphone becomes surveying equipment" has arrived. By attaching a dedicated small RTK-GNSS receiver to a smartphone and processing positioning data in an app, centimeter-level (cm level accuracy (half-inch accuracy)) surveying that once required equipment costing millions of yen can be achieved easily.

There are several factors behind the rise of smartphone surveying. Technically, the leap in satellite positioning accuracy due to RTK and device miniaturization are key. Socially, labor shortages demanded a "system that a single person can measure quickly," and the push for on-site DX sought digital surveying tools anyone could use. The answer to these needs was high-precision surveying using a smartphone plus a small GNSS device. For example, the smartphone-integrated small surveying device LRTK Phone can obtain high-precision coordinates anywhere simply by attaching a receiver weighing about 165g and about 1 cm (0.4 in) thick to a smartphone. The idea of "measuring with a smartphone" without relying on costly and complex equipment has begun to transform surveying work.

AR display requires centimeter accuracy (cm level accuracy (half-inch accuracy))

When overlaying drawings or models onto the site with AR, the most important factor is the accuracy of the positioning. If you rely only on a smartphone's standalone GPS or standard AR functions, display positions can have errors ranging from several tens of centimeters to, in some cases, more than 1 m (3.3 ft). That may be acceptable for a rough visual check, but a 50 cm (19.7 in) error is extremely dangerous in tasks that require accuracy such as stake driving or pipe laying. If an AR line is displayed half a meter (0.5 m (1.6 ft)) off from the actual boundary line, you cannot rely on that information for construction.

That is why centimeter-level positioning (cm level accuracy (half-inch accuracy)) is indispensable. By using RTK, a satellite positioning correction technology, a device's position can be tracked to within a few centimeters of error. Connecting a high-precision GNSS receiver to a smartphone for positioning makes it possible to align AR models almost exactly with real-world positions. Because vertical accuracy can also be kept within a few centimeters, you can reproduce a "full-size virtual model" that is trustworthy down to lines projected on the ground and depth displays of buried objects. Improving positioning accuracy turns AR display into a practical tool that sufficiently supports on-site decision-making.

Technologies that support smartphone surveying

Now let's look at the technological elements that make high-precision surveying and AR display on smartphones possible. The main points supporting this field today are as follows.

• RTK-GNSS high-precision positioning: RTK technology adds correction information to satellite positioning and can correct a terminal's position in real time to within a few centimeters of error. This requires setting up base stations or using network correction services, but in Japan infrastructure has progressed through use of the electronic reference point network and augmentation signals from the quasi-zenith satellite "Michibiki" (CLAS). By combining a smartphone with an external RTK-capable GNSS receiver (for example, an LRTK terminal), centimeter accuracy becomes easily attainable.

• AR platforms: Smartphones come with AR platforms such as ARKit (iOS) and ARCore (Android) that provide the foundation for AR display. These systems composite virtual objects into camera images and stabilize the display according to device movement. Combined with coordinates obtained from high-precision positioning, they enable AR rendering that aligns with real-world coordinates.

• Sensors (LiDAR and cameras): Recent smartphones also include LiDAR scanners and high-performance cameras. LiDAR acquires surrounding point cloud data (three-dimensional point sets), and together with camera images can capture spatial information. Using this, you can perform on-the-go 3D scanning of a site and immediately compare results with drawings, or conduct advanced measurements such as measuring distance to a target object in the camera view and deriving its coordinates—so-called photogrammetric/target-based positioning. A smartphone's sensor suite is a major asset for both surveying and AR.

• Dedicated apps and cloud integration: User-friendly dedicated apps are indispensable for smartphone surveying. Apps that guide users through starting positioning, recording data, converting coordinate systems, and loading drawings and AR displays make operation possible without specialized knowledge. Uploading obtained data to the cloud for immediate sharing, or syncing design drawings and point cloud models to devices via the cloud for on-site display, also streamlines networking. This software support is what makes smartphone-based surveying a practical work tool.

Diverse use cases for AR surveying

The fusion of high-precision smartphone surveying and AR technology has generated a wide range of use cases that did not previously exist. Here are some examples.

• Use for as-built verification: AR surveying is powerful for "as-built verification" to check whether post-construction terrain and structures match the design. Immediately after construction, you can walk the site with a smartphone to 3D-scan and acquire point cloud data, then compare it with design data in the cloud to instantly detect shape deficiencies or excesses. For example, by calculating the volume of embankments or excavations right after construction and showing differences from the design model as a heat map, you can quickly identify elevation differences or areas with insufficient thickness. As-built inspections that used to be performed later by experienced surveying teams can now be completed on the spot by site personnel, greatly improving inspection efficiency and accuracy.

• Disaster response and emergency surveying: In emergency sites such as landslides caused by earthquakes or heavy rain, rapid and accurate situational awareness is essential. The smartphone and small GNSS receiver combination is highly portable and can be easily brought on foot into dangerous disaster areas. Even in mountain areas outside of communication coverage, if the system supports CLAS correction signals from Japan's quasi-zenith satellite "Michibiki," centimeter-level accuracy can be maintained without Internet connection, making it effective for surveying isolated sites. On site, you can record locations by photogrammetric measurement (target-based positioning) of collapsed areas from a safe distance and obtain necessary data while ensuring safety. Surveying can be completed by a small team even where heavy machinery cannot enter, enabling quick recovery planning and report preparation.

In addition to these, there are many other scenes where smartphone and AR surveying can be applied. For training young engineers, intuitive AR displays can be used to learn surveying standards and results; in GPS-denied indoor environments, simplified AR staking-out can be performed; and with ingenuity the possibilities expand. High-precision AR surveying will increasingly become an ordinary sight on future sites.

Advantages of simplified surveying

With the latest smartphone surveying tools, you can "measure by yourselves anytime, share immediately, and move on to the next task right away." The biggest benefits this brings to sites are speed, ease, and reliable accuracy.

• Speed: Measurements can be taken immediately when needed and data can be checked and shared on the spot, reducing construction interruptions while waiting for surveying. Frequent as-built checks allow early detection and correction of problems, directly preventing rework and shortening schedules.

• Ease: Compact devices and just a smartphone allow a single person to measure, eliminating the need to transport bulky equipment or gather multiple personnel. Intuitive app operation means anyone can use it, enabling site staff to perform surveying and staking-out without relying on experts. Even sites with labor shortages can adopt digital measurement without strain.

• Accuracy: Centimeter-level positioning ensures that precise position-setting, which previously required skilled technicians, can be reliably performed. With more trustworthy surveying data, quality control accuracy improves and risks such as failing inspections or rework due to positioning errors are reduced. Objective data also strengthens explanations to owners and regulatory bodies.

As described above, introducing simplified surveying tools drives both productivity and quality improvement on site. If your site has challenges with surveying work, consider using a high-precision smartphone surveying system like LRTK. Once you try it, you will be surprised by how easy and accurate it is. Cutting-edge simplified surveying will surely advance your company's on-site visualization and DX significantly.

FAQ

Q: What equipment and preparation are required to display AR on site? A: Basically, AR display itself is possible with a smartphone (or tablet) and a compatible AR app. Recent iPhones and Android devices support standard AR functions, so simple AR overlays can be done without additional equipment. However, high-precision GNSS positioning is essential to overlay drawings and models at exact positions. Therefore, using a high-precision GNSS receiver that can be attached to a smartphone (e.g., LRTK Phone) is recommended. Also, preparing and loading the design drawings and coordinate data for boundaries and buried objects onto the device beforehand, and aligning them to the site coordinate system as needed, will allow smooth AR display start-up.

Q: Can I display AR with only 2D drawing data? A: Yes, it is possible. Even without 3D BIM/CIM models, 2D data like plan drawings are sufficient for AR-based checks. For example, if you only have CAD plans (DXF, etc.) or image files, you can overlay them on the ground on the smartphone screen and render design lines as virtual glowing lines on the ground. You can also place virtual markers or symbols at important points to intuitively check for discrepancies with actual conditions. While 3D models that reproduce column and wall heights are ideal, plan data alone can still leverage AR effectively for understanding positional relationships and interference checks.

Q: What is the positional accuracy of AR display? A: It varies greatly depending on the technology used. A smartphone's built-in GPS or markerless standard AR can produce errors of several tens of centimeters to several meters. That may be fine for rough visualization, but it is insufficient for precise staking-out or boundary confirmation. On the other hand, using RTK-capable GNSS, both horizontal and vertical errors can be kept within a few centimeters, enabling AR overlays with nearly plan-level accuracy. The ability to secure centimeter-level positioning (cm level accuracy (half-inch accuracy)) usable in actual construction is the major difference from traditional approaches.

Q: Is special knowledge or training required? Can site staff operate it? A: No deep skills in CG software or advanced surveying knowledge are necessary. Compatible apps are designed so that anyone can perform positioning and AR display by following on-screen instructions. For example, the LRTK system app guides you from starting positioning to projecting drawings in AR with button operations and visual prompts, allowing even first-time users to operate intuitively. After a short training session, inexperienced site staff can immediately apply it to daily construction management. Enabling staff to "measure and check by themselves" also aids technical succession and human resource development without relying solely on specialized technicians.

Q: Do I need to install markers or reference points beforehand? A: When using GNSS, special marker installation is generally unnecessary. A high-precision GNSS receiver can always determine absolute coordinates, so the device itself serves as a moving reference point and lets you overlay digital models directly at the designated coordinates. However, in indoor environments or under overpasses where GPS signals do not reach, you may need to use plane detection by the smartphone's AR functions (ARKit/ARCore) or pre-installed markers to adjust model positions. In such cases, using easily identifiable feature points—like wall corners or floor markings—as references will improve accuracy. For wide outdoor sites, GNSS-based coordinate alignment is the simplest and most accurate method.