Transforming a Smartphone into a Surveying Device:
Construction Site DX Achieved with LRTK Phone

Surveying Challenges on Construction Sites and the Need for DX

Surveying work in civil engineering and construction sites is a crucial process for obtaining accurate location data. However, traditional surveying methods have presented numerous challenges. Manual surveying is prone to cumulative errors and takes a considerable amount of time, placing a significant burden on construction management.

Moreover, the shortage of skilled surveyors and the aging and labor shortage among on-site workers have become more severe, making it a challenge for the entire industry to secure an efficient workforce.

Traditional surveying equipment, such as total stations (TS) and GNSS surveying equipment (RTK-GNSS receivers), while capable of providing high-precision positioning, are expensive to implement and require specialized operating skills. It is generally said that assembling an RTK-based GNSS receiver system requires an investment of at least several million yen, making it difficult for individuals and small businesses to afford.

Additionally, surveying with total stations typically requires two people, which is labor-intensive and time-consuming. In response to these challenges, the construction industry is promoting i-Construction, led by the Ministry of Land, Infrastructure, Transport, and Tourism, and exploring labor-saving and advanced solutions through ICT technology.

This is where the new surveying solution, LRTK Phone, which utilizes smartphones, comes in. This device, which transforms a smartphone into a surveying tool, is affordable, easy to implement, and can achieve centimeter-level positioning without the need for specialized technicians, making it a solution that has garnered attention. In the following sections, we will explore the features of LRTK Phone and the benefits of applying RTK surveying on construction sites.

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What is LRTK Phone? Achieving Centimeter-Level Positioning with a Smartphone

LRTK Phone is an innovative device that enables high-precision GNSS positioning (RTK positioning) by attaching it to a smartphone. Normally, positioning accuracy using the built-in GPS on smartphones is said to have an error of several meters (up to around 10m), but by attaching the LRTK Phone, positioning accuracy down to a few centimeters can be achieved.

RTK (Real-Time Kinematic) is a high-precision real-time positioning technology that uses satellite positioning. It achieves centimeter-level accuracy by utilizing error correction data from a reference station. The LRTK Phone is designed to easily implement this RTK surveying in combination with a smartphone, effectively realizing "smartphone surveying."

In terms of hardware, the LRTK Phone includes a high-sensitivity GNSS antenna, receiver, and battery. It connects to the smartphone via Bluetooth, Wi-Fi, or the 920MHz band for short-range radio communication and is compatible with both Android devices and iPhones.

Once the dedicated LRTK app is installed on the smartphone and connected to the device, RTK positioning can be started immediately. Without needing to worry about complicated settings, the system automatically utilizes signals from GNSS satellites and correction data from reference stations (such as network-based RTK, electronic reference points, and regional services like Himawari) to calculate high-precision positioning. Notably, it supports Japan's quasi-zenith satellite system "Michibiki (QZSS)" and its centimeter-level augmentation service (CLAS).

This allows for centimeter-level positioning even in areas with no mobile coverage or where internet-based RTK correction data cannot be received, such as mountainous areas or disaster sites, by receiving signals from Michibiki. The LRTK Phone is also featured on the official website of the Cabinet Office (Space Development Strategy Promotion Office) and is gaining attention as a Michibiki-compatible product.

The LRTK Phone also offers excellent features on the software side. The LRTK app on the smartphone is equipped with a mechanism that instantly uploads acquired position coordinates and photo data to the cloud, enabling real-time data sharing. By simply pressing the sync button in the app, the coordinates of surveyed points and photos taken on-site can be saved to the cloud, allowing the status of the site to be checked remotely via the internet from the office.

For example, photos taken are automatically tagged with high-precision location data (longitude, latitude, elevation), timestamp, and notes, and can be viewed and shared in a list on the cloud. With the LRTK Phone, optimized in both hardware and software, anyone can easily perform centimeter-level GNSS surveying.

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Accelerating Construction Site DX with LRTK Phone

The introduction of LRTK Phone, a smartphone RTK surveying device, is expected to bring significant changes to surveying tasks on construction sites. First, it enables labor-saving and faster surveying operations. Previously, total station surveying required two people, but with LRTK Phone, a single worker can perform measurements at multiple points quickly.

Unlike optical total stations, which require clear sightlines and heavy equipment setup, RTK surveying with LRTK Phone only requires a space where the satellite signals can be received, making it much easier to handle on-site. Additionally, the data collected is automatically stored digitally, eliminating the need for manual records and reducing errors in recording. For example, by simply walking around the site with the LRTK Phone, anyone can quickly create 3D point cloud data with position coordinates (latitude, longitude, elevation) attached in real-time, without the need for preparation or post-processing.

What used to require specialized contractors and costly software for point cloud data processing can now be done easily, leading to a significant reduction in time.

Second, cost reduction is another key benefit. Instead of purchasing and maintaining expensive surveying equipment or employing specialized technicians, all that’s needed is LRTK Phone and a smartphone, drastically reducing initial investment costs. For example, a typical RTK-GNSS receiver set, including overseas models, can cost several million yen (approximately $20,000–30,000), while a smartphone-attached RTK device is available for around several hundred thousand yen (approximately $2,000–3,000). This makes it much easier to establish a high-precision surveying environment at a low cost. Since smartphones are already widely used, there is no need to purchase additional controllers, and training is relatively easy. With intuitive smartphone app operation, surveying can be completed, making it user-friendly even for on-site staff with limited surveying knowledge, lowering the barriers to training.

Third, real-time construction management through data sharing between the site and the office is the key to DX. Surveying data obtained with LRTK Phone is instantly uploaded to the cloud, enabling remote sharing of data with stakeholders on-site.

Site supervisors and designers can check the as-built data and surveying results in real-time from a remote office and issue instructions if needed. This accelerates decision-making and construction verification, reducing delays in feedback and enabling quick responses to issues. This creates a seamless digital connection between the site and office, realizing the true form of construction DX.

As seen above, LRTK Phone ensures surveying accuracy while greatly improving efficiency in terms of cost, personnel, and time. The ability to instantly share data via the cloud distinguishes it from traditional methods. For example, while traditional methods involved taking point cloud data back to the office and processing it the next day, after introducing LRTK, data is uploaded to the cloud and can be instantly reviewed and analyzed at the office.

This eliminates information transfer delays between the site and office, enabling truly real-time construction and quality management. Instant sharing of surveying data also makes remote site supervision and support easier, paving the way for a new on-site operation model in the DX era.

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Specific Use Cases of LRTK Phone

Simplification of Benchmark Surveying
In civil engineering projects, benchmark surveying (verifying or setting the coordinates of known points) is essential at the start of construction. Traditionally, surveyors performed traverse surveys and static GNSS positioning to establish and measure benchmarks on-site.

With LRTK Phone, benchmark surveying can be performed more easily. For example, by utilizing network-based RTK services or electronic reference point data, it is possible to obtain the public coordinates of any point on-site simply by standing at that point and using smartphone surveying. By registering and sharing the obtained coordinates as a benchmark, subsequent construction surveys can proceed smoothly. Because benchmark positioning can be completed in a short time without the need for multiple days of observation or halting heavy machinery for precise measurements, the preparation time before construction can be significantly reduced. This is especially beneficial for remote or mountainous construction sites, where the ability to determine benchmark coordinates without relying on communication infrastructure, using Michibiki-compatible RTK, provides a significant advantage.

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Real-Time As-Built Management
LRTK Phone is highly effective in as-built management (as-built inspection and as-built surveying) conducted after road construction or structural work. As-built management is the quality control process of verifying whether construction has been carried out according to the design, measuring the completed shape and dimensions. Traditionally, level instruments and total stations (TS) were used to measure as-built conditions, and based on those measurements, decisions and drawing creation were made. With LRTK Phone, as-built measurements can be performed in real-time and digitally.

For example, when checking the thickness of a roadbed or the slope of an embankment, the surveyor can simply walk around with the smartphone and take a few measurements, instantly storing height and slope data in the cloud. On the cloud, these data can be immediately compared with design values, enabling on-site assessment of construction accuracy. If discrepancies are found, corrective actions can be directed before the concrete hardens or before heavy machinery is removed, leading to reduced rework.

Additionally, LRTK Phone, in combination with the smartphone’s camera and LiDAR functions, allows for 3D scanning to capture as-built conditions. Using the LiDAR on an iPhone or iPad Pro, structures and terrain can be scanned and turned into point cloud data with the high-precision positioning information from LRTK, making it easy to perform 3D as-built surveying that would have traditionally required specialized equipment. The point cloud data obtained can be used to calculate volume and area instantly, allowing for the immediate calculation of earthworks, such as embankment and excavation volumes, on-site. Even workers without specialized knowledge can measure distances between two points, areas, or calculate the volume of embankments using the app, greatly improving both the efficiency and accuracy of quality management.

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Cloud Integration and Remote Monitoring on Construction Sites

The integration of LRTK Phone with the cloud is powerful not only for sharing geographic information but also for sharing on-site photos. Photos taken on-site using the smartphone can be tagged with high-precision positioning information obtained by LRTK Phone, and then uploaded directly to the cloud.

This allows for immediate sharing of photos that accurately record "when, where, and under what conditions" in infrastructure inspections or disaster surveys. For example, when inspecting cracks in a bridge, workers can simply take a photo of the crack with their smartphone, and the photo will automatically include latitude, longitude, and height information, which is then stored in the cloud.

Technicians in the office can view the photos and instantly determine the exact location on a map, making it possible to immediately prioritize repairs or issue instructions for additional investigations. In large-scale infrastructure inspections, such as for highways and railways (JR), this method allows the accumulation of records where photos and location data are linked, making it a useful tool for advancing maintenance DX.

Additionally, it becomes easy to remotely monitor the overall progress of the construction site. By listing the surveying data and photo data collected with the LRTK Phone on a cloud dashboard, progress and as-built data for the day can be checked even without being on-site. For instance, in a dam construction project, workers can wear a helmet-mounted LRTK device (LRTK helmet, a product from the same company) and patrol the site, sending real-time trajectory data as it is acquired.

This allows for the tracking of workers' current positions with centimeter-level accuracy while continuously accumulating and sharing the positioning data. Even when workers' hands are occupied, positioning is still possible, helping with safety verification. The collected data can be instantly validated and used for instructions by the office via the cloud. In this way, by utilizing the LRTK series, the site and remote offices are connected through data, enabling accurate on-site supervision and support from any location.

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Summary of Key Benefits from Introducing LRTK Phone
Let's review the benefits gained from introducing the LRTK Phone to construction sites.

• Significant Efficiency Improvements and Labor Reduction in Surveying Tasks: With the ability to perform high-precision surveying easily by a single person, the number of workers required for surveying tasks can be reduced while improving work speed. This reduces the cumulative errors and time losses associated with manual surveying, allowing even with limited personnel to handle more surveying tasks.

• Significant Improvement in the Use of Digital Data: Since survey results are digitally recorded and shared in real-time, there is no need for paper drawings or manual data entry. The acquired data can be directly imported into CAD drawings, BIM/CIM models, and GIS systems, making it easy to utilize the data in later stages of the project. Data flows seamlessly between the site and the office, reducing the reliance on tacit knowledge and personal expertise.

• Achieving a Low-Cost, High-Precision Surveying Environment: By utilizing smartphones, the initial setup cost is reduced, making RTK surveying, which was traditionally expensive, more accessible. The compact and lightweight device is easy to maintain, and its versatility is a key advantage, as it can be used anywhere as long as power is available. As a result, small and medium-sized civil engineering contractors can more easily incorporate high-precision surveying into their daily operations, leading to strengthened competitiveness.

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How to Implement LRTK?

If you are interested in the LRTK Phone, the first step is to request free materials. The official LRTK website offers detailed specifications and case studies. By contacting us through the dedicated form, you can also receive information about pricing and implementation plans. In some cases, you may be able to schedule a demo or request a rental trial, so be sure to experience its on-site usefulness firsthand.

The LRTK Phone, which transforms a smartphone into a high-precision surveying device, is an innovative tool that strongly promotes DX (Digital Transformation) on construction sites. It brings RTK surveying to the field with unparalleled ease, breaking away from traditional norms, and enables the balance of productivity and precision through real-time data usage and labor reduction. Its applications extend beyond surveying tasks, including construction management and infrastructure maintenance, holding great potential for driving workstyle reforms across the entire industry.

With the continued development of GPS/GNSS technology, the widespread adoption of 5G, and the advancement of cloud platforms, smartphone-based surveying solutions like LRTK will continue to evolve. In the future, intuitive on-site measurements combined with AR technology or automatic as-built determination through AI analysis will become more realistic and accessible. To stay ahead of the wave of construction tech, it is crucial to begin digital transformation with the tasks right in front of you.

Introducing the LRTK Phone is an ideal first step in this journey. Now that high-precision positioning is accessible to everyone, why not introduce smart surveying to your site and take the first step toward next-generation construction management?