Point Clouds and AR—All in One! Expanding Surveying Possibilities with the Latest Compact Surveying Instrument LRTK

In recent years, miniaturization of equipment and innovations in digital technology have progressed at surveying and construction sites, and efficient work using compact surveying instruments has been attracting attention. Facing challenges such as labor shortages and the aging of technicians, on-site DX (digital transformation) is accelerating, and there is demand for smart surveying solutions that anyone can use. Born from this background is the latest compact surveying instrument LRTK, a device that can handle everything from point cloud measurement to AR display with this one device. In this article, starting with the evolution and background of compact surveying instruments, we will explain in detail the features and principles of this LRTK, specific application scenarios, and the value it brings to users in various roles. Finally, we introduce the benefits of simplified surveying brought by LRTK and provide tips for considering its introduction to the field.

Evolution and Background of Compact Surveying Instruments

Once, surveying typically involved optical surveying instruments mounted on tripods and large GNSS receivers. Specialized survey technicians would travel to sites as a team, carrying heavy equipment to perform precise measurements, which required a great deal of time and manpower. However, in recent years, dramatic advances in satellite positioning technologies such as GPS and GLONASS and in sensor technology have rapidly miniaturized and enhanced the performance of surveying instruments. In particular, the emergence and development of the real-time kinematic (RTK) method have made centimeter-level high-precision positioning possible even with handheld receivers.

Moreover, the construction industry is facing a serious decline and aging of experienced surveyors, along with worsening labor shortages. For that reason, there has been a strong demand for systems that allow surveys to be carried out quickly by a single person without relying on specialists as before. At the same time, site digitization (on-site DX), represented by initiatives such as the Ministry of Land, Infrastructure, Transport and Tourism's *i-Construction*, is advancing the use of 3D data and the adoption of ICT technologies. Advanced technologies such as photogrammetry using drones and point-cloud measurement with 3D laser scanners have also emerged, but these can present high barriers in terms of equipment costs and specialized skills. Enter the new generation of surveying tools that achieve high-precision positioning and 3D measurement by combining smartphones with small devices. LRTK is a prime example of this and is expected to be a key item supporting on-site DX.

What is LRTK?

LRTK is a pocket-sized, all-purpose surveying instrument that attaches to a smartphone. Developed by a startup originating from the Tokyo Institute of Technology, it weighs just 165 grams and is housed in a very compact body about 1 cm (0.4 in) thick. Within this small body are a high-precision GNSS antenna, an RTK-GNSS receiver, and a battery, and simply integrating it with a smartphone enables centimeter-level positioning (cm level accuracy (half-inch accuracy)). It can be attached to a dedicated smartphone case with one touch, and, if needed, by attaching a monopod (pole) you can point at ground points like conventional surveying instruments to obtain precise positions. Yet the device’s price is markedly lower than that of traditional expensive surveying instruments, making it realistic to introduce one device per person and carry it on a constant basis.

LRTK operates in conjunction with a smartphone app and offers a wide range of functions, from positioning to point cloud scanning, layout (positioning) and navigation, and even photography and AR (augmented reality) simulation. For example, with a single button press you can record the current position’s coordinates (latitude, longitude, height), and conversions to the plane rectangular coordinate system and calculations of geoid height are performed automatically. You can also name measurement points and add notes and upload them instantly to the cloud, allowing real-time data sharing with colleagues in the office. LRTK is an all-in-one solution filled with the features you’d wish for on site, giving the impression that your smartphone truly transforms into a high-precision surveying instrument.

Principle of the Point Cloud Acquisition Function

One major reason LRTK is attracting attention is that it makes point cloud data acquisition by smartphone easy, and moreover can assign accurate positioning coordinates to it. Traditionally, obtaining the 3D shape of a site required expensive terrestrial laser scanners or photogrammetry from drone aerial photography. However, in recent years smartphone models equipped with LiDAR (Lidar: high-speed laser range measurement) sensors have appeared, allowing easy acquisition of surrounding point clouds. However, LiDAR scans performed with a standard smartphone alone do not attach positioning coordinates (map coordinates) to the acquired point clouds, so there has been the issue that the resulting point cloud model's corresponding real-world position and scale are unknown. There is also the problem that scanning while walking around gradually distorts the point cloud.

This is where LRTK comes into play. By combining a smartphone’s LiDAR function with RTK high-precision positioning, anyone can easily obtain georeferenced 3D point clouds. Because LRTK is constantly capturing its own position at centimeter-level accuracy (half-inch accuracy), scanning while walking with a smartphone does not cause positional shifts or distortions in the point cloud. For example, you can scan the shape of an excavated embankment and calculate its volume on-site, or later measure the dimensions of a structure by taking the distance between any two points—these tasks can be performed instantly. The acquired point cloud data can be uploaded directly to the cloud and displayed and inspected in 3D in a browser, allowing stakeholders to share it without specialized point cloud processing software. You no longer need to carry heavy laser scanners or laptops—the era has arrived when, with nothing more than an LRTK in your pocket, you can record a site in 3D with sufficient accuracy.

On-site Navigation Using AR Display

Another innovative feature of LRTK is AR (augmented reality)-based site navigation. Because virtual objects based on blueprints and survey data can be overlaid onto the real-world view on a smartphone screen, it enables intuitive on-site verification and instructions. Thanks to RTK’s high-precision self-positioning, the displayed AR aligns precisely with the actual coordinates, providing a stable experience that does not drift even as the user moves.

Specifically, by using LRTK, the following AR navigation can be realized:

• Support for staking and layout marking: Display points and lines on the ground in AR based on design drawings, visually indicating stake positions and reference lines. Site personnel can mark while confirming exact positions through a smartphone screen, significantly streamlining the traditional process of setting out positions with surveying instruments. Even on slopes or other locations where direct surveying is difficult in remote areas, virtual stakes can be "driven" in AR to record and share positions.

• Boundary verification and visualization of design extents: If property boundary lines and construction area limits are preregistered, those lines can be displayed in AR on site for confirmation. Invisible boundary lines become visible on the screen, helping prevent encroachment onto neighboring properties and aiding in the search for boundary markers. You can also overlay building layouts and heights from the design drawings onto the actual site to check harmony with the surrounding environment during the planning stage.

• Pre-construction checks and consensus building: By displaying planned 3D models (such as BIM/CIM data) in AR over the existing terrain, you can share the completed image and check for interferences before work begins. For example, projecting planned models of fill or structures onto the site allows all stakeholders to experience on the spot what the finished result will look like—something difficult to grasp from drawings alone. Explanations to clients and nearby residents become more persuasive, facilitating smoother consensus building.

In this way, LRTK's AR functionality is also highly useful as an on-site communication tool. Because it can recreate spatial representations on-site that are difficult to convey with paper drawings or numerical data alone, it helps prevent mistakes and reduce rework.

Use Cases Fusing RTK Positioning with Point Clouds and AR

The fusion of high-precision positioning enabled by LRTK with point cloud and AR technologies is creating a wide range of unprecedented use cases. Here we introduce some representative examples.

• Utilization for as-built management: In as-built management for civil engineering works, it is necessary to verify that the completed terrain and structures match the design. With LRTK, you can 3D-scan the site immediately after construction to acquire as-built point cloud data, overlay it with the design model, and compare shapes and dimensions. Because it can automatically calculate volumetric differences in the cloud, calculating fill and excavation volumes can be performed quickly. As-built checks that traditionally required the surveying team to revisit the site can now be completed on the spot by the responsible person, contributing to improved efficiency and accuracy of inspection tasks.

• Disaster Response and Emergency Surveying: At disaster sites caused by earthquakes or heavy rain, such as landslides, it is required to rapidly and safely grasp the situation. LRTK is small and easy to carry, so it can be taken on foot into steep terrain in affected areas. Furthermore, it supports correction signals (CLAS) broadcast from Japan's positioning satellite 'Michibiki', allowing it to maintain centimeter-level accuracy (half-inch accuracy) without relying on the Internet, even in mountainous areas outside of communication coverage. On site, you can scan collapsed areas to measure the extent of damage and the volume of soil, and record the locations of critical points with photos, speeding up the planning of recovery operations and the preparation of reports. Dangerous places that cannot be approached physically can also be measured non-contact using LRTK's target positioning function (a function that captures distant objects with a camera to measure coordinates). This enables acquisition of necessary data while reducing the risk of secondary disasters, making it a powerful tool for disaster response.

• Surveying Education and Technology Transfer: In the surveying field, training young personnel and transferring skills are challenges, and LRTK helps address them. Because it is an intuitive smartphone-based surveying instrument, beginners and students can handle it easily and learn the basics of spatial measurement while enjoying the process. AR features visualize survey points and reference lines, making it easier to grasp coordinate systems and survey outputs, thereby enhancing educational effectiveness. In addition, field staff who were previously unaccustomed to handling surveying equipment can more readily participate in surveying tasks by using LRTK. Its cost performance is such that each person can have a device, so multiple units can be introduced for training and used in practical exercises. As a result, it realizes sites anyone can measure, promoting both individual skill improvement and operational efficiency simultaneously.

Value for surveying beginners, site representatives, surveyors, and municipal employees

LRTK provides a range of benefits to users regardless of their role. Let's look at its value for each type of user.

• Surveying beginners: Even beginners with little specialized knowledge or experience can perform surveys simply by following the smartphone app’s easy-to-understand UI and guidance. Difficult coordinate system settings and complex calculations are automated, minimizing operational errors. Because visual feedback via AR is available, the measured results can be intuitively understood on the spot. Without being confused by difficult technical terms, first-time surveying can become a successful experience.

• Site agents (construction managers): For those responsible for construction sites, LRTK becomes a powerful support tool. Tasks such as staking out and as-built verification, which previously required the cooperation of a surveyor, can now be carried out by the site agent themselves in a short time. For example, before concrete placement they can scan with LRTK to immediately confirm whether the ground has been leveled to the design elevation. Interruptions to work due to waiting for surveying are reduced, preventing schedule losses. Furthermore, if acquired data is shared via the cloud, designers or clients in remote locations can share information in real time, speeding up decision-making.

• Professional surveyors such as land and house surveyors: For professional surveyors and land and house surveyors, LRTK is also a powerful means to streamline daily operations. With high-precision single-point positioning and various data output functions, boundary surveys and land acquisition survey field records can be compiled digitally and concisely. Coordinate data required for drafting drawings and preparing reports can be obtained on site immediately, reducing post-processing effort. Also, because the equipment is compact and maneuverable, it is convenient for small, confined sites that a surveyor can enter alone and for residential land surveys. By using AR to show boundary lines and building layouts to clients while explaining, it can also be used as a communication tool to facilitate consensus-building. LRTK can appeal to clients who are receptive to cutting-edge technology and provide added-value services that differentiate you from competitors.

• Municipal government staff: LRTK is useful for administrative staff responsible for managing roads and parks and for conducting on-site surveys during disasters. Without requesting a specialized surveying department, they can go to the site themselves to measure dimensions and positions and plot them on a map on the spot. For example, for small-scale surveys such as measuring locations of road damage or confirming the positions of illegal structures, same-day response is possible, contributing to faster administrative services. In disaster response, recording damage as 3D data and sending it to the head office to assist recovery planning is another possible use. Because even with limited personnel they can achieve real-time situational awareness on site, this can also lead to improved quality of services for residents.

Cloud integration, report output, photo positioning, and other features

LRTK demonstrates its true value when the hardware device, smartphone app, and cloud service work together. The acquired positioning data, point clouds, and photos are uploaded with a single tap—automatically uploaded to the cloud—and can be viewed and downloaded instantly from an office PC. Issuing a shareable URL makes it easy to share data with clients and partner companies, and they can check the latest survey results from a browser without logging in. This eliminates the hassle of exchanging files via USB drives or email, making information sharing faster and more reliable.

The LRTK app also has the ability to output positioning results in CSV or PDF formats, allowing survey report generation to be completed on-site. Because necessary information such as date and time, coordinate system, and surveying conditions is automatically recorded, it also prevents recording errors in the field. Compared to the days when entries were handwritten in paper field notebooks, the efficiency and accuracy of data organization are dramatically improved.

As a unique feature, there is the aforementioned subject positioning (photo positioning). This is a function that uses a smartphone camera to measure the position coordinates of a target object located at a distance. For example, even for high bridge girders out of reach or points on steep slopes with poor footing, if you capture and photograph the target through a smartphone from a safe location, you can calculate and record the object's latitude, longitude, and height. This capability becomes possible by LRTK accurately determining the device's position and orientation and by estimating distance via LiDAR and image analysis, and it is highly effective for surveying locations that cannot be approached directly.

Furthermore, LRTK also supports 3D model generation by photogrammetry (photogrammetry), enabling the creation of high-precision point cloud models from multiple photos taken with a smartphone. Extensive terrain that LiDAR scans cannot fully cover can be automatically converted into 3D simply by taking photos and uploading them to the cloud, allowing you to grasp the overall picture. Because these diverse functions are integrated, it can truly be described as a versatile surveying system condensed into a compact device.

Conclusion: The surveying possibilities opened up by LRTK

The compact surveying instrument LRTK, which overturns conventional wisdom, is a new-era tool that benefits everyone from surveying professionals to beginners. By combining high-precision RTK positioning with point cloud and AR technologies in a single device, tasks that were previously abandoned due to time or cost constraints can now be carried out easily. For example, LRTK is useful in every on-site scenario, from daily dimension checks in construction management and rapid documentation of sites requiring emergency response to preparing explanatory materials for residents.

Simplified surveying's benefits are, above all, "speed," "convenience," and "accuracy." By adopting LRTK, you can measure with your own hands whenever needed, share immediately, and move straight to the next action. This directly improves on-site productivity and will become the driving force that enables you to continue delivering high-quality results even amid labor shortages. If you feel there are challenges with surveying work at your site, why not consider introducing this latest compact surveying instrument, LRTK? It will surely become a reliable partner that greatly expands the possibilities of surveying.