Visualizing Cadastral Surveys with Photos and AR! Cloud-Linked LRTK Makes Data Sharing Easy

Table of Contents

• The importance of cadastral surveys and current challenges

• Visualizing boundary lines with photos and AR

• High-precision surveying with GNSS/RTK technology and LRTK

• Easy data sharing via cloud integration

• Benefits of using AR in cadastral surveys

• The future of cadastral surveys enabled by simple surveying with LRTK

• Frequently asked questions

The importance of cadastral surveys and current challenges

A cadastral survey is an important nationwide effort to accurately clarify land boundaries and areas. Municipalities, with landowners present, confirm boundaries and update cadastral maps and registry information based on survey results. It is also an opportunity to correct inaccurate information based on Meiji-era maps to reflect current conditions, and cadastral surveys help establish up-to-date, accurate survey data as social infrastructure.

By conducting cadastral surveys, boundaries can be clarified and land rights relationships properly reflected, which is expected to prevent boundary disputes and make boundary restoration easier in the event of a disaster. Accurate mapping also provides a foundation for secure and smooth land transactions, contributing to regional town planning and infrastructure planning. Despite this importance, as of the end of FY2022 the national progress rate of cadastral surveys was only about 52%, leaving many areas unexamined. Improving productivity is a major challenge to advance wide-area surveys with limited personnel and budgets.

However, several problems are also pointed out in field surveying operations. One of the biggest issues is that the crucial land boundary lines are not visible. When boundary stakes or monuments are hidden by vegetation or lost due to deterioration, it is not easy to accurately determine the boundary position on site. Especially in land that has not been maintained for many years or in wooded areas, boundary markers are often buried and cannot be found.

The invisibility of boundary lines on site also affects consensus-building with landowners and adjacent land users. Although professionals such as land and building surveyors and municipal staff understand boundaries from survey maps, it is not easy for laypeople to visualize “where their land begins and ends” from drawings alone. As a result, confusion such as “I don’t know if this is my land or not” or discrepancies in perception with neighboring landowners tend to occur. If such mismatches arise during boundary confirmation meetings on site, discussions can take a long time and, in the worst case, may escalate into boundary disputes.

Traditionally, surveyors have used temporary stakes or drawn lines with chalk on the ground to indicate boundaries on site. But physical markings have limits: if markers fade or lack sufficient accuracy, it is difficult to share boundaries in a way that satisfies all parties. The difficulty of “showing” boundary lines has led to a lack of understanding and delays in consensus-building in cadastral survey fieldwork.

Visualizing boundary lines with photos and AR

Imagine land boundary lines that are invisible on the ground appearing in the field simply by pointing a smartphone—the measurement method that sounds like the future is becoming reality. Using AR (augmented reality) technology to overlay virtual lines and points on camera images, attempts are being made to “visualize” boundaries that could not be seen before. This method, which overturns conventional wisdom, is poised to bring significant changes to cadastral survey fieldwork.

For example, AR boundary line visualization is powerful in the following situations:

• Boundary attendance: During boundary confirmation meetings with neighboring landowners, displaying a virtual boundary line on a smartphone screen allows everyone involved to share the boundary position at a glance. Content that was difficult to convey with drawings or technical terms can be shown intuitively on site through the screen—“this is the boundary”—deepening mutual understanding and smoothing consensus-building. Even if boundary markers are buried in grass and cannot be found, if the boundary coordinates obtained in advance are registered in the app, the smartphone will navigate to and indicate that point with cm level accuracy (half-inch accuracy), allowing accurate boundary locations to be identified even before stakes are restored.

• Application to temporary stake placement and fencing planning: AR is useful when placing temporary stakes along boundaries or planning temporary fencing along site boundaries before construction. If boundary line coordinates from design drawings or existing survey data are preloaded into the app, virtual stake markers or lines can be displayed on the smartphone screen on site. Using those as references makes it possible to accurately identify points even in places where driving stakes was previously difficult, such as on asphalt pavement or bedrock. Stake layout tasks that previously required two or more people with optical surveying instruments and staff can now be performed by one person marking points sequentially while viewing AR overlays. As a result, temporary stake placement along extensive boundaries can be completed quickly, and work can be done safely with fewer people even in difficult terrain.

• Use in public–private boundary discussions: AR is also a valuable tool in discussions to determine the boundary between public land such as roads and waterways and private land. When municipal staff and landowners discuss boundary positions on site, drawings alone can lead to mismatched images, but projecting the boundary line onto the ground with AR lets both parties visually share the same positional relationships. This reduces discrepancies such as “on the drawing it should extend this far, but it looks different on site” and supports on-the-spot consensus-building. Virtual boundary lines displayed on site can also be recorded as photos or videos. Such records serve as objective evidence when reviewing the discussion later.

In these ways, visualizing boundary lines with photos and AR solves the “invisibility” problem in cadastral surveys and is significantly changing communication on site. Next, let’s look at the technical background supporting this new method.

High-precision surveying with GNSS/RTK technology and LRTK

To display boundary lines accurately with AR, it is necessary to determine the smartphone’s current position with high precision. The built-in GPS in a typical smartphone has errors on the order of several meters, which is insufficient to pinpoint boundary points. The key technology is therefore high-precision positioning using GNSS (Global Navigation Satellite System).

RTK (Real-Time Kinematic) is a method that corrects GNSS positioning errors in real time to achieve centimeter-level accuracy. By receiving correction information sent from known reference stations (base stations) on the smartphone side and correcting signal errors from multiple satellites such as GPS and Japan’s quasi-zenith satellite system “Michibiki,” it is possible to determine positions to within several centimeters (cm level accuracy (half-inch accuracy)). However, until recently, using RTK in the field required expensive, large dedicated GNSS receivers and antennas to be set up.

The recently introduced LRTK devices have made such high-precision positioning much more accessible. LRTK is a small, lightweight high-precision GNSS receiver that can be attached to a smartphone; it mounts to the back of a phone with a dedicated cover and connects via Bluetooth or Lightning, allowing immediate use. Designed compactly at a weight of a few hundred grams, it is easy to carry. Combined with a dedicated app, this device enables real-time centimeter-level positioning anywhere in Japan (supporting centimeter-level positioning augmentation service (CLAS) provided by quasi-zenith satellites, and network RTK via the Ntrip method). The era has arrived in which you can achieve professional-grade positioning accuracy with a palm-sized LRTK and a smartphone without carrying heavy tripods or surveying equipment.

Using the high-precision current position information obtained in this way, AR surveying overlays boundary line data on the smartphone screen. Boundary point coordinates or boundary line data obtained in prior cadastral surveys are loaded into the app in advance; when the smartphone is pointed on site, virtual lines are rendered on the camera image in coordination with the device’s position and orientation. If GNSS positioning is inaccurate, the virtual line will be offset, but by using an RTK-capable LRTK device the device position can be determined to centimeter accuracy (cm level accuracy (half-inch accuracy)), allowing boundary line data to be displayed almost perfectly aligned with the real world. Additional measures such as calibrating position alignment with known points on site or cross-referencing boundary data with point clouds obtained by the smartphone’s built-in LiDAR scanner can further improve positional and orientation accuracy.

The combination of high-precision GNSS and AR has realized the unprecedented experience of “visualizing boundary lines on site.” The next chapter examines how this method improves data sharing.

Easy data sharing via cloud integration

Using the dedicated surveying app for LRTK, survey data collected on site is immediately saved to the cloud, dramatically improving data sharing and record management. Coordinates of boundary points, photos, and notes can be automatically uploaded to the cloud at the time of measurement, eliminating the need to later transcribe into notebooks and preventing associated errors. Since the date, time, and precise location of each measured point are reliably recorded in the cloud, data credibility is also improved.

Once boundary coordinate data are stored in the cloud, they can be reused indefinitely. For example, if the same location is re-surveyed years later, past coordinates saved in the cloud can be called up in the app and selected, and the LRTK device will guide you to that point within a few centimeters (cm level accuracy (half-inch accuracy)). Even if personnel change or a long time has passed, the exact same point can be easily restored. Photos and notes of boundary markers taken on site are also stored in the cloud in chronological order, allowing you to review “what happened to a stake set years ago” or “what condition it was in during a previous survey.” This helps determine whether boundary markers have deteriorated or moved, and prevents past oversights.

Moreover, with data in the cloud, sharing information internally and externally is easy. Because data can be accessed via the Internet whenever needed, there is no time lag between collecting information on site and sharing it at the office. When fieldwork is finished, office colleagues can immediately view the survey results or take over the work. There is no need to hand over paper maps or USB drives, and multiple people can always reference the latest information. Centralized electronic data management reduces the risk of losing survey records and is reassuring from an evidence-preservation standpoint.

Thus, cloud integration has made storing, sharing, and reusing survey data obtained in cadastral surveys much easier. So what concrete benefits does AR technology combined with the cloud bring to cadastral surveys?

Benefits of using AR in cadastral surveys

The new cadastral survey method using AR technology and the cloud offers many advantages for field operations. Specific benefits include the following points.

• Intuitive boundary confirmation and consensus-building: By “showing” boundary lines and marker positions on a smartphone screen, landowners and neighbors can intuitively understand boundaries. Content that was difficult to convey with drawings alone becomes clear at a glance, making it easier to resolve uncertainties or misunderstandings on the spot. As a result, boundary attendance and public–private boundary discussions can more easily align everyone’s perceptions and smooth the process of obtaining agreement.

• Efficiency and labor reduction in surveying work: Surveying with a smartphone plus LRTK elevates tasks that previously required 2–3 people to a level that can be completed by one person. There is no need to transport and set up heavy equipment; you can take out your smartphone and measure or confirm immediately when needed. When searching for previously installed boundary stakes, the coordinate navigation function can get you to the target point quickly. Reducing work time and personnel lets small offices handle many projects in parallel.

• Improved data accuracy and reproducibility: Because survey data are automatically saved to the cloud with accurate timestamps and location information, recording errors are prevented. Once coordinates are obtained they remain in the cloud, so the same points can be reproduced later using that data. The assurance that survey results can be reproduced even after long intervals or staff changes is a major benefit. Digital management including photos and notes of boundary markers prevents information omission and increases the reliability of survey records.

• Enhanced safety: Surveying in difficult terrain such as poorly accessible forests or cliff areas can be done with fewer people, reducing site entries and time spent on site. Eliminating the need to set up large equipment lowers the risk of working in hazardous locations. Reducing the burden of fieldwork itself contributes to worker safety.

• Low-cost adoption and flexible operation: LRTK devices have lower introduction costs compared to traditional dedicated surveying equipment, so multiple staff members can each carry a device to the field. Without competing for equipment, each person can measure and record when needed, increasing operational flexibility. As a result, organizational productivity improves and actively adopting the latest technology provides added value to customers.

The future of cadastral surveys enabled by simple surveying with LRTK

The method of “simple surveying” using a smartphone and LRTK will play an increasingly important role in future cadastral survey fieldwork. With boundary lines now visualizable on site, confirmation tasks and communication become dramatically more efficient, and processes that previously required significant time and effort can proceed rapidly. Surveyors themselves will find it easy to perform quick on-site measurements whenever they want to “just measure and check,” enabling flexible responses by measuring and recording with a smartphone whenever necessary. As long as you carry the new compact companion called LRTK in your pocket, an era in which you can respond to boundary confirmations and various surveys anytime, anywhere, instantly is becoming a reality.

Actively adopting the latest technologies enables surveyors and land and building surveyors to provide faster and more accurate services to clients than before, improving work efficiency and the quality of deliverables. The new experience of AR-displayed boundary lines via simple surveying with LRTK will be a key to opening the future of survey work. Adding the latest technology to traditional methods brings a next-generation cadastral survey style that balances productivity and customer satisfaction right within reach.

Frequently asked questions

Q. What is a cadastral survey? A. A cadastral survey is an investigation conducted mainly by municipalities into land boundaries and areas. Boundaries are confirmed with landowner attendance, and survey results are reflected in maps and registries. Clarifying boundaries is an important initiative that helps prevent future boundary disputes and facilitates smooth land transactions.

Q. Is precise surveying possible with just a smartphone? A. A standalone smartphone’s built-in GPS has errors on the order of several meters, but combining it with an LRTK device enables precise positioning to the centimeter level. By receiving RTK corrections, a smartphone can achieve accuracy comparable to traditional surveying instruments. Field verifications have shown that positioning using LRTK produces results comparable to traditional total station surveying.

Q. Can AR-displayed boundary lines be photographed and used as documentation? A. Yes. Boundary lines and stake positions displayed in AR can be recorded by taking screenshots or photos/videos of the smartphone screen. When explaining agreed boundary positions to third parties later, AR photos allow immediate sharing of the situation. Saving such images as evidence of the discussion can be useful for later verification or in the event of disputes.

Q. What is LRTK? A. LRTK is the name for a small high-precision GNSS receiver device that attaches to and is used with a smartphone. It supports real-time kinematic (RTK) positioning and turns a smartphone into a surveying device capable of centimeter-level positioning. It weighs a few hundred grams, is easy to carry, and connects to a smartphone via Bluetooth or Lightning. This enables easy high-precision surveying.

Q. What is needed to introduce AR surveying? A. First, you need an LRTK device and a compatible smartphone (currently supported on iOS devices). In addition, you need the LRTK dedicated surveying app and a communication environment to receive RTK correction information (Internet connection or reception environment for the quasi-zenith satellite system). Once these preparations are in place, anyone can experience AR-based boundary visualization on site simply by loading the coordinates of the points to be surveyed into the app. The operation is intuitive and does not require difficult specialized knowledge, so surveyors and cadastral professionals can start using it immediately.