Visualizing Boundary Lines with AR! A New Surveying Experience for Land and House Surveyors Opened by LRTK

A land boundary that is invisible on the ground can appear on the spot simply by holding up a smartphone――. Such a futuristic surveying experience is becoming a reality now. The combination of AR (augmented reality) technology and high-precision GNSS positioning is bringing innovation to the fieldwork of boundary confirmation and surveying, which are important duties of 土地家屋調査士. This article explains in detail the benefits this new method of visualizing boundary lines with AR brings to the field, its technical background, and actual use cases. Let’s see how the new surveying experience enabled by the groundbreaking LRTK (a smartphone-mountable RTK-GNSS device) is set to change the daily work of land and house surveyors.

On-site issues that become apparent in boundary inspections and boundary negotiations

In situations where boundaries are explained or confirmed in person, various issues have long been pointed out. First, boundary markers (stakes) or landmarks may be buried by vegetation or soil and hard to find, or old pegs may be lost or damaged. Because the boundary line itself is not visible on site, even if it can be identified on a drawing, it is currently difficult to intuitively grasp “from where to where is my land” on the actual ground.

Also, even if 土地家屋調査士 or municipal officials understand the boundary from a survey map, it is not easy for landowners or neighbors to interpret technical drawings. Even when an explanation of the boundary location is given, it can be hard to form a mental image on site, causing confusion such as “I don’t know whether the land beyond here is mine or someone else’s,” and disagreements in perception between neighboring landowners often occur.

Such problems of visibility and comprehension become major obstacles in scenes of consensus building such as boundary inspections and public-private boundary negotiations. If the boundary line remains ambiguous, opinions among stakeholders can clash and, in the worst case, develop into boundary disputes. Also, if site boundaries remain unclear at construction sites, it can be impossible to properly secure safe work areas and construction plans may be affected. Traditionally, at boundary meetings, surveyors have responded by driving temporary stakes or marking lines on the ground with chalk or rope, but those methods have limits in accuracy and visibility, and it is not easy to share boundary positions in a way that satisfies all parties. In other words, the difficulty of “showing” the boundary line has led to lack of understanding and delays in consensus building on site.

Visualizing boundary lines through integration of GNSS, RTK, LRTK, and AR

The combination of GNSS positioning technology and AR display technology solves this problem of boundaries being “invisible.” GNSS (satellite positioning) receives signals from multiple satellites such as GPS and Michibiki to measure one’s position, but the accuracy of typical smartphone-built-in GPS is on the order of an error of several meters (several ft), which is insufficient to identify boundary points. That is where RTK (real-time kinematic) is used. RTK uses correction information from known reference points (base stations) to correct satellite positioning errors in real time and is a technology that achieves positioning accuracy on the order of several centimeters (several in).

Until recently, using RTK in the field required expensive, large dedicated GNSS equipment and antenna installation. The recently introduced LRTK devices have made such high-precision positioning dramatically more accessible. LRTK is an ultra-compact GNSS receiver that attaches to a smartphone and, when used in conjunction with the phone, transforms the device into a surveying instrument capable of centimeter-level positioning. It supports centimeter-class positioning augmentation services provided by Japan’s quasi-zenith satellite “Michibiki” (CLAS) and network-type RTK using electronic reference points (Ntrip), enabling real-time acquisition of high-precision position information anywhere in the country. With a compact, lightweight design weighing a few hundred grams and simply attached to the back of a smartphone with a dedicated cover and connected via Bluetooth or Lightning, it can be used immediately. No longer do surveyors need to carry and set up surveying equipment weighing several kg and mount tripods; a palm-sized device and a single smartphone can now achieve professional-grade accuracy.

On the other hand, AR (augmented reality) technology superimposes digital information on the real scenery. It can display virtual lines or points on the camera feed of a smartphone or tablet so that virtual lines or markers appear to exist there as if they were real. In AR visualization of boundary lines, precomputed boundary point coordinates and boundary line data are loaded into a smartphone app, which then draws lines in the live camera view according to those positions. Crucial here is matching the smartphone’s current position and orientation with the coordinate system of the boundary data. If GNSS position measurements are inaccurate, the virtual line will be off, but by using an LRTK device that supports RTK, the device position can be determined to centimeter precision, allowing boundary data to be displayed perfectly aligned with real-world space. Furthermore, by calibrating the app at known points on site or by linking point cloud data obtained by scanning the surroundings with the smartphone’s built-in LiDAR scanner to the design coordinates, the coordinate systems of the actual conditions and the boundary data can be matched precisely. When this positional alignment is achieved, the AR boundary line remains stably displayed at the correct ground position even as the smartphone is moved.

In other words, by linking the current position obtained with high-precision GNSS (RTK) with the boundary coordinates on the survey data, the “invisible boundary line” can be visualized on site. Land and house surveyors can confirm the boundary line through the smartphone screen as if it were a real object, making it possible to directly “see” and share boundary positions that were previously left to imagination.

Main use cases for AR-based boundary line visualization

• Use in boundary inspections and boundary confirmation: AR boundary display is powerful even at on-site boundary determination meetings. Where explanations used to rely on boundary stakes or landmarks and phrases like “the boundary is around here,” a virtual boundary line displayed on a smartphone screen allows all parties to share the boundary location at a glance. For example, at a joint inspection with an adjacent landowner, both parties can view the screen together and intuitively indicate “this is the boundary here,” deepening mutual understanding and smoothing consensus building. Even if boundary markers have been lost, as long as the precomputed boundary coordinates are registered, the smartphone will navigate to that point with cm level accuracy (half-inch accuracy) and tell you the exact location, making it possible to identify boundary points even before restoring stakes.

• Use for placing temporary stakes and planning temporary enclosures: AR is also useful when placing temporary stakes along boundaries or planning temporary enclosure lines before construction. If design drawings or survey boundary data are registered in the app in advance, virtual stake markers or lines will appear on the smartphone’s AR screen on site. Using these as references allows accurate point identification even in places where physically installing stakes is difficult (for example, on asphalt or bedrock). Tasks that formerly required two or more people with optical surveying instruments and staff can be performed by one person marking off points one after another while following AR guidance. As a result, placing temporary stakes along extensive boundaries can be completed in a short time, and work can be performed safely by a small crew even in poor footing conditions.

• Application to public-private boundary negotiations: AR is a reliable tool for negotiations determining boundaries between government-owned and privately owned land, such as roads and waterways. When municipal officials and landowners discuss boundary positions on site, drawings alone can result in mismatched mental images, but projecting the boundary line onto the ground with AR allows both parties to visually share the same positional relationship. This reduces discrepancies like “on the drawing it should go this far, but it feels different on site” and helps facilitate on-the-spot consensus building. In addition, AR boundary lines displayed on site can be recorded in photos and videos, serving as evidence of the negotiations for later review.

Practical benefits brought by high-precision AR surveying

• Improved efficiency and reduced manpower: Surveying with a smartphone + LRTK elevates boundary confirmation work that traditionally required 2–3 people to a level that can be completed by a single person. There is no need to transport and set up heavy equipment; you can simply take out your smartphone and perform measurements and confirmations immediately. While RTK provides centimeter accuracy comparable to traditional large equipment, it can greatly reduce personnel and time. For example, when searching for previously installed boundary stakes, the coordinate navigation function can lead you to the target point in a short time, greatly shortening the time spent on boundary confirmation. In addition, because LRTK’s introduction cost is lower than that of traditional surveying equipment, multiple staff members can each carry a unit and perform surveying and recording whenever they like. As a result, small offices can handle many cases in parallel and overall site productivity improves. Because the number of people entering the site can be minimized, there is the additional benefit that investigations in areas with poor footing can be conducted with minimal necessary entry, improving safety.

• Clearer explanations for clients: Being able to “show” boundary lines and stake positions with AR is highly effective in explaining to landowners and neighbors. Information that was hard to convey with technical drawings and difficult terminology becomes obvious when the virtual line is confirmed together via the smartphone screen on site. Uncertainties and misunderstandings are easier to resolve on the spot, increasing clients’ peace of mind and satisfaction. The process of obtaining agreement on boundaries is smoother, reducing the time and effort surveyors spend on explanations.

• Improved data recording and reproducibility: Using a dedicated LRTK app, data measured on site (coordinate values, photos, notes) can be automatically saved to the cloud in real time. The date and exact position at which boundary points were measured are securely recorded, preventing errors that might occur when transcribing by hand later. Boundary coordinate data once acquired and stored in the cloud can be reused in the future. When visiting the same point again, simply selecting the recorded coordinates in the app will guide the device to that point within a few centimeters (a few in) of error. This makes it easy to reproduce the exact same point even after long intervals or personnel changes. You can also review photos of boundary markers and site notes taken previously in chronological order on the cloud, helping to check changes to markers over time and prevent oversights. Centralized management of surveying records as electronic data also provides security in terms of evidence preservation.

Conclusion: New possibilities expanding in the daily work of land and house surveyors

The method of simple surveying using AR and LRTK will play an increasingly important role in the daily work of land and house surveyors going forward. With the ability to visualize boundary lines on site, on-site communication and confirmation tasks are dramatically streamlined, and processes that previously required significant time and effort can proceed much more quickly. For surveyors themselves, the hurdle for quick measurement checks is lowered, enabling flexible responses such as measuring and recording points on site whenever needed. With a pocket-sized new partner in the form of LRTK, a daily reality in which one can respond “anytime, anywhere, immediately” from boundary confirmation to various surveys becomes achievable.

By actively adopting new technologies, land and house surveyors can provide clients with faster and more accurate services, improving their operational efficiency and the quality of deliverables. The new experience of displaying boundary lines in AR through simplified surveying with LRTK will be a major key to opening the future of surveyors’ work. By adding the latest technology to traditional methods, a next-generation surveying style that balances productivity and client satisfaction is just around the corner.