Clear at a Glance with AR Boundary Lines! Achieving Centimeter-Level Surveying with a Smartphone + RTK

Table of Contents

• The importance and challenges of visualizing boundary lines

• Achieving centimeter-level positioning with a smartphone + RTK

• How AR visualizes boundary lines

• Main use cases for AR boundary-line display 4.1 AR use in boundary inspections and stake restoration 4.2 AR use in temporary stake placement and temporary fencing planning 4.3 AR use in public–private boundary consultations 4.4 Safety management on construction sites using boundary lines

• Benefits of AR boundary-line display

• Easy high-precision surveying with LRTK

• FAQ

The importance and challenges of visualizing boundary lines

If you can visualize land boundary lines that are invisible on the ground on the spot, everyone involved can intuitively understand locations, which brings great advantages in surveying and construction sites. AR display of boundary lines that lets you visually confirm “how far my property extends” is expected to smooth boundary checks and on-site inspections and help prevent disputes before they occur.

Traditionally, showing boundary lines on site required surveyors to drive temporary stakes or draw lines on the ground with chalk. However, boundary markers are often hidden by vegetation or soil, or old stakes may be missing, so sharing accurate boundary positions is not easy. Even if the locations are known on drawings, non-experts such as landowners or neighbors may find it hard to picture “this is the boundary from here to here” when told verbally, and may be left wondering “where exactly does my land begin?” As a result, differing perceptions of boundaries can lead to conflicts of opinion and even disputes between neighbors.

If boundary lines remain unclear, it can also prevent securing a correct safe working area and interfere with construction planning. For example, when excavating near a site boundary in land development, not knowing the boundary line on site risks excavating beyond the property line into neighboring land. The importance of showing boundary lines on site in a way that everyone can immediately understand is therefore very high from the perspectives of safety management and reaching agreements.

Achieving centimeter-level positioning with a smartphone + RTK

To show boundary lines accurately, you first need to measure your current position with high precision. However, the GPS built into typical smartphones has errors of about several meters (several ft), making it unusable for boundary-point-level precision. What is attracting attention is high-precision GNSS surveying using the RTK (real-time kinematic) method. RTK uses correction data from a known reference base station to correct satellite positioning errors in real time, achieving dramatically higher accuracy on the order of several centimeters (cm level accuracy (half-inch accuracy)).

Traditionally, performing RTK surveying on site required expensive, large dedicated GNSS receivers and antennas mounted on tripods and labor by specialized technicians. But recent technological advances have produced ultra-compact RTK-GNSS receivers that connect to smartphones. This makes centimeter-class positioning possible with a smartphone for anyone. While ordinary smartphone GPS produces errors of several meters (several ft), using RTK allows horizontal positions of ±1–2 cm (±0.4–0.8 in) and vertical positions within ±a few cm (±a few in), achieving accuracy comparable to professional equipment.

In Japan, by using the centimeter-level positioning augmentation service (CLAS) from the domestic QZSS satellite “Michibiki,” high-precision positioning is possible even in mountainous areas out of mobile coverage without an internet connection. Also, using network RTK services that support the Ntrip method allows real-time retrieval of correction information from the nationwide network of reference stations, providing stable accuracy even in urban areas.

Ultra-compact RTK receivers are lightweight at around a few hundred grams and can be attached to the back of a smartphone and connected via Bluetooth or cable for immediate use. You no longer need to carry surveying equipment weighing several kg around the site; a palm-sized device and a single smartphone can now provide professional-grade positioning. The emergence of smartphone + RTK high-precision positioning technology forms the foundation that supports on-site visualization of boundary lines.

How AR visualizes boundary lines

AR (augmented reality) is the technology that overlays digital information onto the real scenery captured by a smartphone or tablet camera. AR boundary-line display is realized using this technology. Boundary point coordinates and boundary-line data obtained in advance from survey maps or design drawings are loaded into a dedicated app, and when you point your smartphone camera on site, the boundary lines and points that should be invisible appear on the screen as virtual lines and markers.

The key here is aligning the coordinates of the digital data with the smartphone’s current position and orientation. In conventional smartphone AR, GPS and electronic compass errors cause display positions to drift from reality, making precise overlay difficult. But if RTK-enabled high-precision positioning keeps the smartphone’s position measured to the centimeter level (cm level accuracy (half-inch accuracy)), the AR boundary lines will be displayed nearly perfectly aligned with the actual ground. Even if the user walks around, the virtual lines won’t float off; they remain fixed in the correct locations.

If needed, you can further reduce discrepancies between real space and data coordinates by calibrating the app’s coordinates at known points on site or using the LiDAR scanner on newer smartphones to scan the surroundings and link terrain data to boundary coordinates. By linking the current position obtained from high-precision GNSS with the boundary positions on survey data, you can visualize “invisible boundary lines” on site. Displaying virtual boundary lines through the smartphone screen lets everyone directly see and share boundary relationships that previously could only be imagined.

Main use cases for AR boundary-line display

• AR use in boundary inspections and stake restoration: AR display is powerful for on-site boundary confirmation with neighboring landowners and for restoring lost boundary stakes. Previously, people had to hold drawings and explain verbally “the boundary is around here,” indicating with temporary stakes or markers, but showing virtual boundary lines on a smartphone screen lets all stakeholders share the exact same positions at a glance. Even if boundary markers are missing, if you register the pre-calculated boundary coordinates in the app, the smartphone can navigate to those points with centimeter-level positioning and indicate the exact locations, allowing identification of boundary points before driving new stakes.

• AR use in temporary stake placement and temporary fencing planning: AR is also useful when placing temporary stakes along property boundaries or setting temporary fencing lines before construction. If you preload the boundary line data, the smartphone screen will show virtual stake position markers and lines on site, which you can use as guides to determine precise points. Even where the ground is asphalt and stakes are hard to drive, you can mark locations guided by AR. Tasks that previously required multiple people using transits or total stations can be done by a single person following on-screen guidance, enabling wide-area stake placement to be completed in a short time.

• AR use in public–private boundary consultations: Visualizing boundaries with AR is effective during public–private boundary negotiations that define the boundaries between public land such as roads or waterways and private land. Drawings alone can lead to mismatched mental images between officials and landowners, but projecting the boundary line onto the ground with AR lets both parties discuss while looking at the same thing. This reduces perception gaps such as “the drawing says it should be here, but it looks different on site” and helps form agreements on the spot. Virtual boundary lines displayed on site can also be recorded as photos or videos and used later as evidence of the consultation.

• Safety management on construction sites using boundary lines: If boundary lines are unclear during construction, heavy machinery may accidentally cross the boundary into adjacent land or mistakenly cut down neighboring trees. Keeping boundary lines continuously visible with AR makes work-area limits immediately obvious, preventing construction mistakes that cross boundaries. For example, when slope areas on the neighbor’s side must be left intact during land development, displaying the boundary line and setback lines in AR lets operators work with safety in mind. Replacing physical stakes and ropes with digital boundary-line displays reduces the need for people to enter hazardous areas.

Benefits of AR boundary-line display

Visualizing boundary lines in AR brings significant benefits to on-site efficiency, safety, and communication. The main advantages are summarized below.

• Improved work efficiency and reduced manpower: Surveying using a smartphone + RTK allows boundary confirmation and stake-setting tasks that previously required two to three people to be completed by one person. You can take out your smartphone to measure and confirm immediately when needed, eliminating the transport and setup of heavy equipment. This greatly reduces personnel and time while delivering accuracy comparable to traditional large surveying instruments. If multiple staff each perform measurements on their own smartphones, small teams can handle many projects in parallel, improving overall productivity. Surveying in difficult-to-access places requires minimal entry, which also enhances safety.

• Smoother agreement formation and clearer explanations: Being able to “show” boundary lines and stake positions on site with AR makes explanations to landowners and neighbors much easier to understand. Information that was hard to convey with technical drawings or jargon becomes immediately obvious when you check the virtual lines together on a smartphone screen. This makes it easier to resolve questions or misunderstandings on the spot, increasing clients’ peace of mind and satisfaction. Smoother sharing of boundary perception shortens the process of reaching agreement during inspections and consultations and reduces the risk of disputes or troubles.

• Improved recordability and reproducibility of survey data: With smartphone RTK-compatible surveying apps, coordinates, photos, and notes collected on site are stored directly in the cloud. The exact positions and timestamps of measured boundary points are recorded, preventing the need to re-enter handwritten notes and reducing errors. Boundary coordinate data saved in the cloud can be reused in the future, and when revisiting a site years later, the recorded data can guide you back to the same point with centimeter-level precision (cm level accuracy (half-inch accuracy)). Because past survey results can be easily reproduced, it is easier to transfer responsibility for boundary points between staff, increasing the long-term reliability of survey records.

Easy high-precision surveying with LRTK

One solution that combines the latest smartphones and RTK technology to provide high-precision surveying is LRTK. LRTK is a small RTK-GNSS receiver that attaches to a smartphone, turning the phone into a centimeter-precision surveying device. It includes a dedicated app and cloud services, offering an all-in-one solution from positioning to data management and AR boundary-line display.

With LRTK, you can easily realize the AR boundary-line display and centimeter-class positioning discussed above with a single smartphone. Initial setup and operation are simple, and the system is designed so that people without surveying expertise can learn to use it after a short training session. On sites where it has been introduced, its mobility—“anytime, anywhere, immediately”—has been well received. Because the upfront cost is lower than that of dedicated equipment, small offices can also start high-precision surveying easily.

The unprecedented experience of AR boundary-line display can be executed on site with LRTK without complicated settings. Bring a smartphone and LRTK to the site, select the reference points or boundary data in the app, and the line will appear on the screen for immediate boundary confirmation. Measured point coordinates are saved in the cloud, making it easy to later reflect them in CAD drawings in the office or revisit and verify the same location on another day.

Using such smartphone + RTK solutions dramatically streamlines surveying tasks that used to require time and manpower. Try incorporating simple surveying with LRTK to experience on site the clarity of AR boundary-line display and the accuracy of centimeter-level positioning (cm level accuracy (half-inch accuracy)).

FAQ

Q: Can a smartphone-based RTK survey really achieve centimeter-level accuracy? A: Yes. Depending on environmental conditions, RTK can provide smartphones with horizontal accuracy of about ±1–2 cm (±0.4–0.8 in) and vertical accuracy on the order of ±a few cm (±a few in). Considering that normal GPS positioning has errors of several meters (several ft), this is a dramatic improvement. Using high-precision GNSS-compatible smartphone devices and appropriate correction information can achieve positioning accuracy comparable to traditional surveying instruments.

Q: What equipment and preparations are required to use RTK positioning and AR display on site? A: Basically, you need a smartphone-compatible receiver that supports high-precision GNSS (for example, a device like LRTK) and a way to receive the correction information output by that receiver. Correction information can be obtained via network RTK services using mobile communication networks or via Michibiki (QZSS) CLAS signals. Also, preparing boundary point coordinate data in advance and loading it into the app will enable smooth AR display on site. No special large equipment or surveying specialists are required—once you have a smartphone, a small receiver, and the data, you are ready.

Q: Is high-precision positioning and AR display possible in locations without internet access, such as remote mountainous areas? A: Yes. In Japan, using Michibiki’s CLAS (centimeter-level positioning augmentation service) allows you to obtain centimeter-level accuracy in real time even in mountainous areas or remote islands without mobile coverage. Alternatively, if you set up your own base station beforehand and transmit correction information via radio, you can create a local RTK environment and achieve high-precision positioning offline. In short, even in sites where network connectivity is difficult, you can realize high-precision smartphone positioning and AR boundary-line display by using satellite augmentation signals or local base stations.

Q: If only old survey maps exist and the coordinate system is unclear, can AR still display the boundary lines? A: Yes, it can be handled. However, you will need to align coordinates at known points in advance. For example, perform RTK surveying on remaining known boundary markers on site, compare those measured values with the coordinates on the old drawings, and correct any offsets. By transforming the boundary data into the current public coordinate system in this way, the AR display can project lines in the correct positions. Although national cadastral mapping and cadastral survey progress have led to the land registry maps being updated with global geodetic coordinates, even if only old drawings are available, AR visualization is possible by adjusting coordinates based on a few survey reference points.

Q: Is operating smartphone-based AR surveying difficult? A: The operation is relatively simple and does not require extensive technical training. By following the on-screen instructions in a dedicated app, even first-time users can get the hang of it in a short time. Products like LRTK have intuitive user interfaces designed to smoothly handle tasks from starting positioning to saving data and switching to AR display. Even users unfamiliar with smartphones can use the system on site after brief training. If questions arise after starting use, robust support systems and manuals are typically available to ensure confident operation.