Boundary Lines Clearly Shown in AR! Achieve Centimeter-Level Accuracy Surveying with Smartphone + RTK (half-inch accuracy)

Table of Contents

• The importance and challenges of visualizing boundary lines

• Centimeter-level positioning achievable with smartphone + RTK (half-inch accuracy)

• How AR visualizes boundary lines

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

• Benefits of AR boundary line display

• Easy high-precision surveying starting with LRTK

• FAQ

The importance and challenges of visualizing boundary lines

If boundary lines on the ground that are invisible to the eye can be visualized on site, all stakeholders can intuitively understand locations, which brings great benefits to surveying and construction sites. AR display of boundary lines that lets you actually see “how far your property extends” is expected to smooth boundary confirmation 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 lost, so sharing the exact boundary location is not easy. Even if the boundary is documented on drawings, non-experts such as landowners or neighboring residents may find it hard to visualize “from here to here is the boundary” when told verbally, leading to confusion about “where my land actually begins and ends.” As a result, differences in boundary recognition can lead to conflicts of opinion and even escalate into disputes between neighbors.

If boundary lines remain unclear, it can be impossible to correctly secure safe work areas, disrupting construction plans. For example, during earthworks near the site boundary in land development, not knowing the boundary line on site risks excavating too far and encroaching on adjacent land. The importance of showing the boundary line on site so everyone can see it at a glance is therefore very high from the perspectives of safety management and consensus building.

Centimeter-level positioning achievable with smartphone + RTK (half-inch accuracy)

To accurately indicate a boundary line, you first need to measure your current position with high precision. However, the GPS built into typical smartphones has errors on the order of about 5–10 m (16.4–32.8 ft), making it unusable for boundary-point-level precise positioning. Attention is therefore focusing on high-precision GNSS surveying using the RTK (real-time kinematic) method. RTK uses correction data from a known base station to correct satellite positioning errors in real time, achieving dramatically higher precision on the order of a few centimeters.

Traditionally, performing RTK surveying on site required expensive, bulky dedicated GNSS receivers and antennas mounted on tripods and considerable labor by specialized technicians. In recent years, however, technological advances have produced ultra-compact RTK-GNSS receivers that can be connected to smartphones. This allows anyone to perform centimeter-class positioning with a smartphone easily. While ordinary smartphone GPS yields errors of several meters, using RTK allows horizontal positions to be determined to about ±1–2 cm (±0.4–0.8 in) and vertical positions to within ± a few cm (± a few in), achieving precision comparable to professional equipment.

In Japan, using the QZSS “Michibiki” centimeter-level positioning augmentation service (CLAS) makes it possible to obtain high-precision positioning even in mountain areas or other locations outside cellular coverage without an internet connection. Also, services that support network RTK (Ntrip) allow real-time acquisition of correction information from the nationwide network of continuously operating reference stations, providing stable accuracy even in urban areas.

Ultra-compact RTK receivers weigh on the order of a few hundred grams and are lightweight, attach to the back of a smartphone and connect via Bluetooth or cable, and are ready to use immediately. Gone are the days of carrying survey equipment weighing several kg and running around sites; a palm-sized device and a smartphone can now provide professional-grade positioning. The advent 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 on the real-world scene captured by a smartphone or tablet camera. AR boundary line display is realized using this technology. Boundary point coordinates and line data obtained beforehand from survey maps or design drawings are loaded into a dedicated app, and when the smartphone camera is pointed on site, virtual lines and markers representing boundary lines and points that should be invisible appear on the screen.

The key here is to accurately match the coordinates of the digital data with the smartphone’s current position and orientation. In conventional smartphone AR, GPS and electronic compass errors cause the displayed positions to be offset from reality, making precise overlay difficult. However, if RTK-enabled high-precision positioning keeps the smartphone’s position updated to the centimeter level, the AR boundary lines will overlap the real ground almost perfectly. Even if users walk around, the virtual lines will not appear to float or shift; they remain fixed in the correct locations, which is the crucial point.

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

Main use cases for AR boundary line display

• AR for boundary inspections and stake restoration: AR display is powerful for boundary confirmation meetings with neighboring landowners and for restoring lost boundary stakes. Previously, people would hold drawings and verbally say “the boundary is around here,” marking the area with temporary stakes or markers. If a virtual boundary line is shown on the smartphone screen, all parties can instantly share the same position at a glance. Even if boundary markers are missing, if the boundary coordinates obtained in advance are registered in the app, the smartphone can navigate to those points with centimeter-level accuracy, allowing boundary points to be identified before reinstalling stakes.

• AR for temporary stake placement and temporary fencing planning: AR is very useful when placing temporary stakes along site boundaries or setting temporary fencing lines before construction. If you preload the boundary line data, virtual stake position markers and lines will appear on the smartphone screen on site, letting you accurately determine the points. Even where the ground is asphalt and stakes are hard to drive, you can mark points based on AR markers. Stake layout tasks that traditionally required multiple people using transits or total stations can be completed by a single person following on-screen guidance, enabling rapid placement of stakes over a wide area.

• AR for public–private boundary negotiations: AR boundary visualization is effective in boundary negotiations between public entities and private landowners, such as for roads and waterways. Drawings alone may lead to mismatched images between officials and landowners, but projecting the boundary line onto the ground with AR allows both sides to discuss while looking at the same thing. This reduces recognition gaps like “the drawing says it should be up to here, but it looks different on site” and helps reach agreements on the spot. The virtual boundary lines displayed on site can also be recorded with photos or videos and used as evidence of the negotiation content for later confirmation.

• Safety management on construction sites using boundary lines: If boundary lines are unclear during construction, mistakes such as machines accidentally crossing into adjacent land or mistakenly cutting down a neighbor’s trees can occur. Constantly visualizing boundary lines with AR makes the work-area limits—“do not work beyond here”—instantly obvious, helping prevent construction errors due to boundary crossings. For example, when a slope on the adjacent property must be preserved during land development, showing the boundary line or buffer lines in AR helps operators work with safety in mind. Replacing stakes and ropes with digital boundary lines cuts down on the effort of physically marking the site and 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 labor reduction: Surveying using smartphone + RTK allows boundary confirmation and stake-out tasks that used to require 2–3 people to be completed by a single person. You can take out your smartphone and measure/confirm immediately when needed, without transporting or setting up heavy equipment. This greatly reduces personnel and time while delivering accuracy comparable to conventional large survey instruments. If multiple staff members each perform measurements with their smartphones, small teams can handle many projects in parallel, improving overall productivity. Surveying in rough terrain also requires minimal on-site entry, offering safety advantages.

• Smoother consensus building and clearer explanations: Being able to “show” boundary lines and stake positions on site with AR makes explanations to landowners and neighbors far easier to understand. Information that was hard to convey with technical drawings and jargon becomes obvious when you review virtual lines together through the smartphone screen. On-the-spot questions and misunderstandings can be resolved more easily, increasing client reassurance and acceptance. Smoother sharing of boundary recognition shortens the process of reaching agreements during inspections and negotiations and reduces the risk of disputes or troubles.

• Improved recordability and reproducibility of survey data: Using a smartphone RTK-enabled surveying app saves on-site coordinate data, photos, and notes directly to the cloud. The exact positions and timestamps of measured boundary points are recorded, preventing the need to re-enter handwritten notes and reducing errors. Once boundary coordinate data are stored in the cloud, they can be reused in the future; when revisiting a site years later, you can be guided back to the same point with centimeter-level accuracy simply by recalling the recorded data. Because past survey results are easily reproducible, successor personnel can take over boundary point locations more easily, improving the long-term reliability of survey records.

Easy high-precision surveying starting with LRTK

As a solution that combines the latest smartphones with RTK technology for high-precision surveying, there is LRTK. LRTK is a small RTK-GNSS receiver that attaches to a smartphone and turns the phone into a centimeter-level surveying instrument (half-inch accuracy). It provides an all-in-one package including a dedicated app and cloud services for positioning, data management, and AR boundary line display.

With LRTK, you can easily realize the AR boundary line display and centimeter-class positioning discussed above using just a single smartphone. Initial setup and operation are simple, and the device is designed so that even those without surveying expertise can use it after a short training session. On sites where it has been introduced, its mobility—“anytime, anywhere, immediately”—for surveying and confirmation is highly praised. Because the introduction cost is lower than for dedicated equipment, small offices can also start high-precision surveying easily.

The unprecedented experience of AR boundary line display can be executed on site without complicated settings using LRTK. Bring a smartphone and LRTK to the site, select reference points and boundary data in the app, and the line will be displayed on the screen for immediate boundary confirmation. Coordinates of measured points are saved in the cloud, making it easy to later reflect them in CAD drawings at the office or revisit the same location on a different day for confirmation.

By leveraging such smartphone + RTK solutions, surveying work that used to require substantial time and manpower can be dramatically streamlined. Incorporate easy surveying with LRTK to experience the clarity of AR boundary display and the accuracy of centimeter-level positioning (half-inch accuracy) on site.

FAQ

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

Q: What equipment and preparation are needed 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 over cellular networks or via Michibiki (QZSS) CLAS signals. Also, preparing boundary point coordinate data in advance and loading it into the app enables smooth AR display on site. No special large equipment or surveying specialists are required; a smartphone, a small receiver, and the data are sufficient.

Q: Is high-precision positioning and AR display possible in areas without internet, such as mountainous regions outside cellular coverage? A: Yes. In Japan, using the QZSS Michibiki CLAS (centimeter-level augmentation service) allows you to obtain centimeter-level accuracy in real time without the internet even in mountainous or remote island locations where cellular signals do not reach. Alternatively, if you set up your own base station to provide correction data via local radio, you can create a private RTK environment and achieve high-precision positioning offline. In short, even in sites where network connectivity is difficult, you can realize smartphone-based high-precision positioning and AR boundary display by leveraging satellite augmentation signals or local base stations.

Q: If only old survey maps are available and the coordinate system is unknown, can AR still display the boundary lines? A: Yes, this can be handled, but you need to perform coordinate alignment using known points in advance. For example, you can RTK-survey existing boundary markers on site, compare those measured values with the coordinates on the old drawings, and correct any discrepancies. By transforming the boundary data into the current public coordinate system, the AR display can project lines in the correct locations. Although the land registry maps at local legal affairs bureaus are increasingly being updated with World Geodetic System numeric coordinates, if only old drawings are available, AR visualization is still possible by adjusting coordinates based on a few surveyed reference points.

Q: Is operating AR surveying with a smartphone 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 are designed with intuitive user interfaces that make starting positioning, saving data, and switching to AR display smooth. Even users unfamiliar with smartphones can utilize the system on site after simple training. If questions arise after initial use, robust support and manuals are available to allow continued confident operation.