i-Construction era trump card! Achieving DX in civil engineering surveying with LRTK

In recent years, the way of civil engineering surveying at construction and civil works sites has been rapidly changing. In response to issues such as the aging of surveying technicians, labor shortages, and the need to improve productivity, a transformation through digital technology—namely DX (digital transformation)—is being demanded. Among these, “smartphone surveying,” which combines smartphones with high-precision positioning devices, is attracting attention as a groundbreaking solution. Especially following the momentum of the Ministry of Land, Infrastructure, Transport and Tourism’s *i-Construction*, the wave of ICT adoption is sweeping into field surveying. This article explains the necessity of DX in civil engineering surveying and the significance of smartphone surveying, and details how field surveying will change with LRTK, a trump card for the i-Construction era.

Current state of civil engineering surveying and the need for DX

The construction industry faces chronic labor shortages and stagnant productivity. At surveying sites as well, the retirement of veteran technicians and the decline in young entrants have led to a shortage of people who “can do surveying,” making it difficult to maintain traditional arrangements. The conventional two-person surveying approach (one operating the instrument, one holding the rod) is inefficient with limited personnel. In addition, many construction projects must be handled by a small workforce, and under traditional methods the burden on sites only increases.

In response to these issues, the government launched the *i-Construction* initiative around 2016, aimed at fundamentally improving productivity at construction sites. i-Construction is a national project to digitize and streamline the entire construction process—surveying, design, construction, inspection, and maintenance—by utilizing the latest ICT technologies. Central to this is the DX of surveying, and efforts are underway to introduce 3D surveying technologies and automation to achieve both labor savings and improved accuracy. The Ministry of Land, Infrastructure, Transport and Tourism has set a goal to “improve construction site productivity by 50% compared to conventional levels,” and is promoting the adoption of various technologies such as drones, 3D laser scanners, and ICT-equipped construction machinery. In surveying, robotized total stations and labor-saving drone surveying have been explored. However, robotic surveying equipment is expensive and requires skilled operation, and drones are constrained by weather and flight regulations. Now, attention is turning to new technologies that enable surveying to be completed by one person. The realization of “one-person surveying” is precisely the key to compensating for labor shortages and raising site productivity.

Rise of smartphone surveying and compatibility with i-Construction

Against this backdrop, a new method called smartphone or tablet-based “smartphone surveying” has emerged. Modern smartphones are equipped with high-performance cameras, LiDAR sensors, and positioning sensors, and using dedicated apps they can scan site topography and structures to acquire 3D data (point clouds). Tasks that previously required million-yen-class 3D laser scanners and skilled operators are becoming doable with a single palm-sized device. The rise of smartphone surveying is at the forefront of DX in civil engineering surveying.

Part of the appeal of smartphone surveying is that it is a tool that is easy for younger personnel to handle, not just technological progress. Intuitive smartphone app operation is familiar to digital-native generations and can be mastered with short training, allowing surveying tasks to proceed without relying on veteran experience. Even as experienced workers decline amid labor shortages, smartphone surveying expands the potential for young personnel to become immediately effective. It also reduces the burden of carrying heavy surveying equipment and enables non-contact, safe work on dangerous heights or slopes, contributing to reform of working practices at sites.

Policy support has been a tailwind. The Ministry of Land, Infrastructure, Transport and Tourism has strongly promoted the use of 3D data at construction sites, and in 2022 revised the public works “As-Built Management Guidelines (draft)” to explicitly include guidance for using point cloud surveying apps on smartphones and tablets. This means that incorporating smartphone surveying into site inspections and as-built management is formally recognized, and the style of “surveying with a smartphone” has become a realistic option at many sites. In practice, in addition to conventional total stations and manual work, surveying using smartphones and dedicated devices has begun to spread rapidly at sites nationwide. Smartphone surveying enables the entire site, which could not be fully captured by paper drawings or photos, to be recorded and shared as 3D data, dramatically improving the efficiency and quality of construction management. It thus embodies at the field level the “productivity revolution through ICT that anyone can use” that i-Construction aims for.

Transforming smartphones into surveying instruments with RTK technology

For smartphone surveying to be practically used in business, high-precision location information is essential. Built-in smartphone GPS typically has errors of several meters, so it cannot be used as-is for surveying or stakeout work that requires design-level accuracy. The key here is RTK (Real Time Kinematic), a high-precision positioning technology. RTK exchanges satellite signals in real time between a reference station (base) and a moving receiver, correcting error factors to dramatically improve positioning accuracy. GPS errors that are usually around 5-10 m (16.4-32.8 ft) can be reduced to just a few centimeters with RTK.

Recently, environments that allow easy use of RTK positioning on smartphones have been established. A crucial factor is the utilization of Japan’s quasi-zenith satellite system “Michibiki” and its CLAS (centimeter-class positioning augmentation service (cm level accuracy (half-inch accuracy))). GNSS receivers compatible with CLAS can receive centimeter-level correction information directly from satellites without setting up their own base stations. Therefore, even at remote mountain sites or islands out of mobile coverage, as long as satellite signals can be received from the sky, real-time high-precision positioning is possible. The ability to continue positioning even when mobile networks are down immediately after a disaster is a powerful advantage for initial emergency surveys.

Smartphones themselves have been steadily improving, with more models supporting multiple satellite positioning systems and dual-frequency reception. However, achieving centimeter-level accuracy with a smartphone alone has limits, so in practice using an external RTK receiver that can link with the smartphone is realistic. By using a small GNSS terminal that connects via a smartphone port or Bluetooth, the smartphone you always use can instantly transform into a high-precision surveying instrument. For example, by attaching a pocket-sized receiver to a smartphone, one person holding a smartphone could conceivably handle everything from reference point surveying to detailed measurements and point cloud scanning. There are reports of actual cases where the latest small RTK devices paired with smartphones achieved astonishing positioning with an average error of about 5 mm (0.20 in). We have entered an era where sufficient positioning accuracy can be obtained without relying on stationary, expensive GNSS surveying instruments.

The smartphone × RTK combination has innovated surveying styles by balancing portability and accuracy. With centimeter-level current position displayed on the smartphone screen at all times, it becomes possible to check post-construction deviations on the spot, navigate stakeout positions, and perform real-time construction management. The fact that expensive dedicated equipment is not required keeps initial costs down. This makes adoption easier for small and medium-sized enterprises and local governments, and rental options are also readily available, significantly lowering the barrier to acquiring surveying equipment. As a high-precision surveying tool that anyone can use, it aligns with the government’s site DX policy.

Improving as-built management efficiency through point cloud scanning

One major transformation enabled by smartphone surveying is the ability to digitize an entire site as 3D data through point cloud measurement. Using a smartphone’s LiDAR scanner or high-resolution camera, structures and terrain can be scanned in a short time to acquire a collection of many points (point cloud data). When combined with RTK-capable devices, accurate positional coordinate information can be attached to the acquired point clouds. This allows the scanned data to be overlaid on drawing coordinate systems, greatly streamlining current condition assessments and as-built inspections.

For example, where previously a responsible person would measure heights after construction with batter boards or manually take dozens of measurements to create cross-sectional drawings, smartphone point cloud scanning can record a large area of data in a single walkthrough. You can immediately slice the point cloud to measure required cross-sections or automatically calculate volumes of fill and excavation directly on the smartphone. It is groundbreaking that, without bringing expensive 3D laser scanners or dedicated PCs to the site, measurement and analysis can be completed on the spot with only a smartphone and a small GNSS receiver.

Using point clouds for as-built management has the advantage of presenting construction progress and finishes as objective data. Smartphone surveying can digitize entire surfaces rather than measuring only key points, reducing variability and oversights in construction accuracy and ensuring quality control. The acquired 3D data also offers the visual clarity of photographs, which is useful for information sharing with clients and other departments. If point cloud data scanned on site is uploaded to the cloud, stakeholders can check as-built results and compare them against design drawings from the office. This is the digital site inspection that i-Construction aims for, and smartphone point cloud surveying is the practical method to achieve it.

Point cloud surveying also has major safety benefits. Even in steep or collapse-prone areas where people cannot approach, you can grasp conditions by scanning from a safe distance with a smartphone. Survey tasks that used to involve danger can now be completed non-contact, contributing to worker safety and risk reduction. You may worry that the increased data volume will complicate post-processing, but recent smartphone surveying apps can perform automatic processing on site and are equipped with features to instantly calculate required dimensions and volumes from point clouds. This as-built management DX speeds up the process from surveying to reporting and reduces the burden on site supervisors and inspectors.

Visualizing construction sites with AR

Another innovative function brought by smartphone surveying is intuitive site visualization using AR (augmented reality) technology. Virtual objects such as design lines and 3D models can be overlaid on the site imagery shown on a smartphone screen, allowing seamless confirmation of digital data and the actual site. Especially when combined with RTK’s centimeter-level positioning, smartphone AR has achieved high-precision alignment that was previously difficult.

Conventional AR apps required placing markers at the site and reading them with the camera or recognizing planes for initial alignment, and even after alignment the model could drift as the user moved. Low GPS accuracy also made it hard to firmly anchor virtual models in wide outdoor sites, limiting AR to a rough representation. But RTK-enabled smartphone AR allows the smartphone itself to accurately determine its position in a global geodetic coordinate system, enabling AR display based on absolute coordinates. By loading coordinate information from design data into the app in advance and linking it with the smartphone’s current coordinates and heading obtained via RTK, the design model can be displayed precisely over the intended position in the real world. No cumbersome marker calibration is required; simply pointing the smartphone brings up the “structure that should be there” on the screen. The model remains fixed in place even when the user moves to view from different angles, creating the sensation that a completed rendering exists on site.

This AR function can be utilized in various ways for construction management and inspection. For example, in stakeout navigation, displaying a virtual stake at the design stake position in AR allows anyone to perform accurate stakeout without a surveying instrument. Complex piping routes can be projected on the ground or walls in AR for instant verification of discrepancies between drawings and the field. Overlaying the design model on the finished structure enables visual checking of deviations, facilitating early detection of defects. Inspections that once relied on the intuition of experienced craftsmen can be visualized with AR, allowing even younger workers to intuitively judge acceptability. The ability to give visually clear instructions helps reduce communication loss and construction errors.

Remote presence enabled by cloud sharing

The fusion of smartphone surveying and cloud technology also promotes the realization of remote presence. Digitized surveying data can be easily uploaded from the smartphone to the cloud and shared with stakeholders on the spot. This allows the latest site conditions to be synchronized as data between physically separated locations such as the site and the office, or client and contractor.

For example, traditionally, measured results were brought back to the office to prepare reports before submission to superiors or clients, causing time lags and sometimes necessitating re-measurements or additional surveys. By leveraging cloud sharing, data can be shared immediately after measurement, enabling supervisors and inspectors to verify results in real time from the office. If needed, they can issue additional instructions on the spot, and the person in charge can promptly perform supplementary measurements or corrective actions. This reduces rework and drastically shortens communication time.

The Ministry of Land, Infrastructure, Transport and Tourism also promotes process efficiency using remote presence, and cases where inspections are completed by data confirmation without on-site visits are increasing. Smartphone surveying data provides the foundation for such remote presence. If high-precision point clouds and photo-tagged coordinate data obtained on site are shared via the cloud immediately, clients can verify as-built results from the office and point out corrective measures in online meetings while communicating with the site. Reduced travel time and streamlined inspection processes enable limited personnel to cover more sites—good news for municipal maintenance departments struggling with labor shortages. As long as data is collected, veteran technicians can perform checks from the office, making it feasible to send only younger staff to the field.

One-person surveying DX realized by LRTK

Emerging as a solution to fully exploit the potential of smartphone surveying is the LRTK series from Reflexia. LRTK is a system consisting of a small RTK-GNSS receiver that attaches to a smartphone and a dedicated app, turning the smartphone into a versatile surveying instrument with centimeter-level accuracy. The ultra-compact, lightweight receiver houses a battery and a high-sensitivity antenna; simply linking it to a smartphone via Bluetooth or a connector enables easy high-precision positioning. Since it supports Michibiki’s CLAS signal, positioning can continue even outside mobile coverage, demonstrating power in mountainous areas and disaster sites. The LRTK dedicated app fully utilizes the smartphone’s camera and LiDAR, handling single-point positioning, continuous surveying, point cloud scanning, stakeout navigation, and AR-based design overlay all with a single device. It is also equipped with functions to attach photos and notes to positioned points and save them to the cloud, and to instantly calculate distance, area, and volume (earthwork) from acquired data. Location-tagged photos and comments recorded on site can be output as PDF reports with one tap, allowing completion of surveying report preparation on the spot.

Despite its diverse functions, LRTK keeps the introduction hurdle much lower than traditional surveying equipment. You only need to attach a small receiver weighing about 165 g to your smartphone, so there is no need to carry heavy tripods and equipment. You can move nimbly in tight spaces or on slopes, working safely and efficiently. Intuitive smartphone operation means no special expertise is required, allowing those outside surveying specialties to start using it immediately. LRTK is already being adopted at civil engineering, construction, and infrastructure maintenance sites nationwide and offers the accuracy and functions that comply with the ministry’s 3D as-built management guidelines. It is increasingly recognized as the smart surveying tool demanded in the i-Construction era.

The impact of LRTK in realizing a one-person surveying DX is immense. Tasks that previously required a team—surveying and inspection—can be completed by one person using only a smartphone for positioning, inspection, and recording with LRTK. Handling high-precision position information and 3D data in real time creates a seamless flow of measuring, checking, and recording, reducing wasted wait time and rework. Data sharing lowers the barrier between site and office, enabling remote management of multiple sites simultaneously. It allows maintaining output levels despite labor shortages and directly contributes to workstyle reform and productivity improvement.

Smartphone surveying DX aligned with the i-Construction policy promoted by the Ministry of Land, Infrastructure, Transport and Tourism is no longer a future prospect but a current trend. Introducing LRTK as the trump card will let you experience the DX of civil engineering surveying at your site through the latest technology. With a smartphone and LRTK, surveying, as-built management, reporting, and sharing proceed remarkably smartly. Why not start next-generation one-person surveying at your site? LRTK, which changes the conventions of the field, will surely be a powerful ally for improving productivity and streamlining operations.