Boundary Line AR Display Using Only a Smartphone! Surveying Revolution with RTK Centimeter-Level Accuracy

Contents

• Challenges in Conventional Boundary Confirmation

• Technology to Display Boundary Lines in AR with a Smartphone

• Use Cases for Boundary Line AR Display

• Benefits Brought by AR Surveying

• Conclusion: The Future Opened by Simple Surveying

• FAQ

Challenges in Conventional Boundary Confirmation

Invisible boundary lines on the ground that appear to float in front of you simply by holding up a smartphone—such a futuristic surveying experience is becoming a reality. This technology has the potential to completely change how surveying work is done. However, prior to the arrival of this innovative technology, various problems were pointed out in the field of boundary confirmation. First, boundary markers (stakes) are often hard to find because they are buried by vegetation or soil, and it is not uncommon for old stakes to be damaged or missing. Because boundary lines themselves are not visible on site, even if their positions are known from drawings, it is difficult to intuitively grasp “where exactly one’s land begins and ends” on the actual ground. Even if surveying professionals such as land and house investigators or local government staff can understand the positions from survey maps, it is not easy for landowners or neighboring landholders to read the drawings. Even when boundary locations are explained on site, people often can’t visualize them and say, “I don’t know whether my land extends beyond here,” which frequently leads to differences in perception with neighboring owners.

These visibility and comprehension issues pose major obstacles in consensus-building situations such as boundary inspections or public–private boundary negotiations. When boundary lines remain unclear, stakeholders’ opinions may conflict and, in the worst case, escalate into boundary disputes. Also, on construction sites where property boundaries are unclear, safe working areas cannot be properly secured and construction plans may be affected. Traditionally, during boundary inspections, surveyors have responded by placing temporary stakes or marking lines on the ground with chalk or rope, but these methods have limits in accuracy and visibility, and it is not easy to share boundary positions in a way that satisfies all parties. In short, the difficulty of “showing” boundary lines has led to lack of understanding on site and delays in reaching agreement.

Technology to Display Boundary Lines in AR with a Smartphone

The key to visualizing these “invisible boundary lines” is the combination of high-precision GNSS positioning and AR display. GNSS (Global Navigation Satellite System) refers to technologies that determine current position by receiving signals from multiple satellites, such as GPS and Japan’s quasi-zenith satellite Michibiki, but the accuracy of typical smartphone-built-in GPS is only on the order of a few meters (a few feet), which is insufficient to identify boundary points. This is where the RTK (Real-Time Kinematic) method comes into play. RTK is a technique that uses correction information broadcast from known reference points to correct satellite positioning errors in real time and achieve centimeter-level positioning (half-inch accuracy). However, until recently, using RTK on site required expensive, bulky dedicated GNSS equipment and antennas.

The recent emergence of LRTK devices has made high-precision positioning much more accessible. LRTK is an ultra-compact GNSS receiver that attaches to a smartphone and turns the phone into a surveying device capable of centimeter-level positioning (half-inch accuracy). It supports services such as the centimeter-level positioning augmentation service (CLAS) provided by Japan’s quasi-zenith satellite system Michibiki and network RTK using electronic reference stations, enabling real-time acquisition of high-precision position information anywhere in the country. With a compact, lightweight design weighing a few hundred grams, it mounts to the back of a smartphone with a dedicated cover or attachment and connects via Bluetooth or Lightning, so it can be used immediately. We have entered an era in which you can achieve professional-level positioning accuracy with a palm-sized device and a single smartphone, without lugging around several-kilogram surveying equipment and setting up tripods.

On the other hand, AR (augmented reality) technology overlays digital information on real-world scenes. Modern smartphones and tablets come standard with advanced AR capabilities, and there are robust platforms (for example, ARKit and ARCore) that can stably display virtual objects even in outdoor spaces. Virtual lines and points can be drawn over the camera view of a smartphone or tablet so that it appears as if actual lines or markers are present there. For boundary line AR display, previously obtained boundary point coordinates and boundary line data are loaded into a smartphone app, which projects those coordinates as lines onto the real-world view through the camera. Crucial to this is precisely matching the smartphone’s current position and orientation to the coordinate system of the boundary data. If GNSS position measurements are inaccurate, the virtual line will be misaligned, but by using an RTK-capable LRTK device, the device position can be determined to centimeter-level (half-inch accuracy), allowing boundary data to be displayed perfectly aligned with the real space. For example, calibrating the smartphone position at a known point on site or linking point cloud data obtained by scanning the surroundings with the smartphone’s built-in LiDAR scanner to the design coordinates can further improve alignment between the current conditions and the boundary data. With such precisely aligned AR, boundary lines remain stably displayed at the correct positions on the ground even when you move the smartphone around.

Use Cases for Boundary Line AR Display

• Use in boundary inspections and boundary confirmation: AR visualization of boundary lines is powerful at boundary confirmation meetings. Where explanations used to rely on boundary stakes or markers like “the boundary is around here,” projecting a virtual boundary line on the smartphone screen allows all stakeholders to share the boundary position at a glance. For example, during an inspection with a neighboring landowner, you can intuitively show “this is the boundary” by looking at the screen together, deepening mutual understanding and smoothing consensus-building. Even if boundary markers have been lost, if you have pre-surveyed and registered the boundary coordinate data in the app, the smartphone can navigate you to that point with centimeter-level (half-inch) accuracy, allowing you to precisely identify boundary points even before restoring stakes.

• Use in placing temporary stakes and planning temporary enclosures: AR is also useful when placing temporary stakes along a boundary or planning the line of a temporary enclosure before construction. If you preload the design drawings or survey results’ boundary line data into the app, virtual stake markers or lines will appear on the smartphone’s AR screen on site, which can be used as references to accurately determine points even in places where physically driving stakes is difficult (for example, on asphalt or bedrock). Tasks that used to require two or more people operating a total station and staff to mark stake positions can now be done by one person marking points sequentially while following AR guidance. As a result, installing temporary stakes along extensive boundaries can be completed quickly, and work in difficult terrain can be performed safely with fewer people.

• Application to public–private boundary negotiations: AR is a reliable tool for negotiations that determine boundaries between public and private land, such as roads or waterways. When local government officers and landowners discuss boundaries on site, drawings alone can leave their images mismatched, but projecting the boundary line onto the ground with AR lets both parties visually share the same positional relationship. This reduces discrepancies such as “the drawing suggests it goes to here, but it feels different on site,” and helps facilitate on-the-spot agreement. Also, the AR boundary line displayed on site can be recorded as photos or videos, which can serve as evidence for later reference in negotiations.

For example, in one mountain forest boundary confirmation, AR display using a smartphone equipped with LRTK was extremely helpful. At a site that previously took more than half a day to find boundary stakes and confirm the boundary line, the team loaded pre-surveyed boundary coordinates into the smartphone and went to the field, and were able to determine the accurate boundary position in minutes. The landowners confirmed the boundary line that appeared on the smartphone screen, and long-standing disagreement about the boundary was resolved on the spot, concluding the inspection amicably. In this way, AR surveying is an effective means of directly resolving on-site problems and shortening working hours. Also, at an urban construction site, projecting the planned temporary enclosure line with smartphone AR before starting work revealed a slight discrepancy between the design and site conditions, and by correcting the placement plan in advance they prevented rework after construction began.

Benefits Brought by AR Surveying

• Improved efficiency and reduced manpower: Surveying with a smartphone + LRTK raises boundary confirmation tasks that used to require two to three people to a level that one person can complete. There is no need to transport and set up heavy equipment; you can simply take out your smartphone when needed and perform measurements or confirmations immediately. RTK provides centimeter-level positioning (half-inch accuracy) comparable to traditional large instruments while greatly reducing personnel and time. For example, even when searching for buried boundary stakes, the coordinate navigation function can guide you to the target point in a short time, significantly shortening the time spent on boundary confirmation. In addition, the introduction cost of LRTK is lower than that of traditional surveying equipment, so multiple staff can each carry their own device and perform surveying and recording whenever they like. As a result, even small offices can handle many projects in parallel and overall site productivity improves. With fewer people required, investigations in difficult terrain can minimize physical entry and increase safety. In some cases, the search for boundary stakes that used to take half a day may be completed in just a few dozen minutes, achieving dramatic efficiency gains.

• Clearer explanations to clients: Showing boundary lines and stake positions with AR has great impact on explanations to landowners and neighbors. Information that was hard to convey with technical drawings and difficult terms becomes immediately understandable when you view virtual lines together on a smartphone screen on site. Ambiguities and misunderstandings can be resolved on the spot, increasing clients’ sense of security and satisfaction. The process of reaching agreement on boundaries also becomes smoother, reducing the time and effort surveyors must spend on explanations.

• Improved recordability and reproducibility of data: By using an LRTK app, data measured on site (coordinate values, photos, notes) can be automatically saved to the cloud in real time. The date and exact positional information of measured boundary points are recorded, preventing errors that come from manual transcription. Once boundary coordinate data are stored in the cloud, they can be reused in the future. When you revisit the same point, simply selecting the recorded coordinates in the app will guide the device to that point within a few centimeters (a few inches). This makes it easy to reproduce exactly the same points even over long periods or when personnel change. You can also review photos of past boundary markers and site notes on the cloud in chronological order, which helps confirm changes in markers over time and prevent oversights. Since survey records can be centrally managed as electronic data, it also provides peace of mind in terms of evidence preservation.

Conclusion: The Future Opened by Simple Surveying

The smartphone surveying method that leverages AR and RTK is likely to play an increasingly important role in the daily work of not only land and house investigators but also municipal staff and construction managers involved in surveying. With the ability to intuitively visualize boundary lines on site, on-site communication and confirmation tasks will become vastly more efficient, and processes that previously required time and effort will proceed much more quickly. For surveying professionals, the barrier to performing small checks and measurements is lowered, enabling flexible responses such as measuring and recording points on site whenever necessary. With a new companion in your pocket—the LRTK attached to your smartphone—a future in which you can handle boundary confirmation and various surveys “anytime, anywhere, immediately” becomes a reality.

These initiatives also align with construction DX efforts such as the i-Construction program promoted by the Ministry of Land, Infrastructure, Transport and Tourism, and are expected to spread as technologies that contribute to site digitalization. By proactively adopting new technologies, professionals involved in surveying can provide faster and more accurate services to clients, improving both their operational efficiency and the quality of deliverables. The surveying field as a whole is entering a transformational period driven by the introduction of digital technologies, and a new work style that blends traditional experience with cutting-edge technology is emerging. The innovative surveying experience of LRTK-enabled boundary line AR display will be a key that greatly changes future workflows and brings new possibilities to the world of surveying. By adding the latest technologies to traditional methods, a next-generation surveying style that balances productivity and customer satisfaction is just around the corner.

FAQ

Q: What is needed to display boundary lines in AR? A: In addition to a smartphone (preferably one with a high-performance camera or built-in LiDAR), you need an RTK-GNSS receiver capable of centimeter-level positioning (for example, an LRTK device) and a surveying app that uses that data for AR display. An internet connection to obtain RTK correction information (or an environment to receive Michibiki’s CLAS) is also required. Furthermore, you need to prepare the coordinate data of the boundary points or lines you want to display in advance and load them into the app.

Q: How accurate are the boundary lines displayed? Are they comparable to conventional surveying instruments? A: By using RTK-GNSS, you can achieve accuracy on the order of a few centimeters (a few inches). This is high precision comparable to conventional total stations and dedicated GNSS equipment. Although slight errors may occur depending on the environment and positioning conditions, the accuracy is entirely adequate for applications such as boundary confirmation and marking stake positions.

Q: What is LRTK? How is it different from RTK? A: RTK is the name of a high-precision positioning technique, and LRTK is a small device (product name) that makes RTK positioning easy to use with a smartphone. By attaching an LRTK receiver to a smartphone, the phone becomes capable of RTK-based centimeter-level positioning and functions as a surveying instrument. In other words, LRTK is a tool that allows you to conveniently use the RTK technique in the field.

Q: Is operation and setup difficult? A: No, the operation is simple. Attach the LRTK device to your smartphone and launch the app; then follow the on-screen instructions to perform measurements and AR display. Initial setup is also straightforward—after configuring reception of GNSS augmentation services and connecting to the smartphone, no special procedures are necessary. Those with surveying expertise should find it intuitive to use.

Q: Can GNSS positioning be used in any environment? What happens in areas with poor signal conditions? A: GNSS positioning that uses satellite signals achieves higher accuracy in open-sky locations. In forests with dense trees or in urban areas with many high-rise buildings, satellite signals may be blocked or reflected, reducing accuracy. Satellite positioning is basically not available underground or indoors. In such environments, it is advisable to perform calibration (position alignment) at known points on site or to combine conventional surveying methods as appropriate. However, thanks to systems such as Japan’s quasi-zenith satellites, positioning in urban areas has become more stable than before, and in many outdoor environments practical accuracy can be obtained.

Q: Will traditional surveying instruments become unnecessary with this smartphone AR surveying? A: While it is expected that smartphone + RTK simple surveying will be able to replace traditional instruments for many uses such as boundary confirmation and stake placement, it does not mean that conventional surveying instruments will become completely unnecessary. For example, tasks that require millimeter-level precision such as establishing control points, or indoor measurements, still call for optical instruments like total stations and conventional methods. However, for purposes such as boundary confirmation, temporary stake placement, and rough as-built checks, smartphone AR surveying will increasingly be sufficient. It is realistic to replace parts of the workflow with AR surveying where efficiency gains are possible while continuing to use conventional instruments as needed.

Q: Does an AR-displayed boundary line serve as official proof? A: The boundary line displayed on a smartphone AR screen itself does not have legal effect. Formal procedures such as survey maps and consent documents from involved parties are required to determine boundaries. However, AR makes it much easier for everyone to visually confirm the boundary at the same location, significantly simplifying the consensus-building process. If you record the AR display with photos or videos, they can be used later as explanatory materials or records of negotiations. Thus, AR display is an extremely effective tool to assist in boundary confirmation.