The Frontline of Surveying DX through i-Construction: Toward an Era of Surveying with a Smartphone

The construction and civil engineering industries face chronic labor shortages and the major challenge of improving productivity. To break this situation, the Ministry of Land, Infrastructure, Transport and Tourism began promoting i-Construction around 2016 as a productivity revolution for construction sites. i-Construction is a national project that uses cutting-edge ICT technologies to digitalize and streamline the entire construction process—from surveying through design, construction, inspection, and maintenance. Among its initiatives, the DX (digital transformation) of surveying is attracting particular attention. Surveying work, which traditionally relied on manual labor and experience, is being dramatically transformed by new technologies such as drones, 3D scanners, and smartphones. The era in which you can survey with just a smartphone is arriving, and this topic sits at the forefront of discussions about on-site DX.

Aims and Background of i-Construction

i-Construction aims to dramatically improve productivity on construction sites through full-scale ICT adoption. The Ministry has set an ambitious target to “increase construction site productivity by 50% compared to traditional levels,” seeking to address labor shortages while creating attractive construction sites. A key to this is transforming the old “3K” workplaces—tough, dirty, and dangerous—into new 3K workplaces where salary, time off, and career prospects are fulfilled. Concretely, this involves using three-dimensional data and automation across all processes—from surveying and design to construction and inspection—to improve efficiency and reduce labor. Dangerous tasks are being replaced by remote operation and automation, pursuing improved safety with the goal of zero fatal accidents. In terms of quality, ICT devices enable accurate, real-time measurement and inspection without relying solely on craftsmen’s experience, preventing rework and standardizing construction quality.

In this way, i-Construction is a national project that seeks to solve structural problems in the construction industry through digital technologies. The introduction of 3D surveying technology is a core element of i-Construction, and the government actively promotes the spread of drone surveying and ICT-based civil engineering. The next section focuses on smartphone-based surveying, which has been rapidly spreading among these digital surveying methods in recent years, explaining how it works and its advantages.

What Is Smartphone Surveying?

Smartphone surveying has recently emerged as a leading technology driving on-site surveying DX. As the name suggests, smartphone surveying uses the capabilities of smartphones and tablets to perform on-site surveying and 3D measurement. For example, the latest iPhones and iPads are equipped with high-performance cameras and LiDAR sensors, and using dedicated apps you can scan surrounding terrain and structures to obtain point cloud data. From the acquired 3D data, you can measure distances and areas on the spot or automatically generate cross-sections and other analyses. Tasks that previously required million-yen-class 3D laser scanners or drones can now be completed with a palm-sized smartphone, which is revolutionary.

The rise of smartphone surveying is driven not only by the aforementioned labor shortages and work-style reforms but also by expectations for digital tools that are easy for younger generations to use. With fewer veteran surveyors, smartphone surveying—allowing one person to take measurements quickly—holds promise as a solution to labor shortages. Intuitive smartphone apps are also easily adopted by digitally native young employees, making them effective for promoting on-site DX and passing on skills.

Government policy has provided additional tailwinds. The Ministry of Land, Infrastructure, Transport and Tourism has actively promoted the use of 3D data at construction sites, and in 2022 revised the As-Built Management Guidelines (draft) to formally incorporate the use of point-cloud surveying apps using smartphones and tablets into its guidance. As a result, smartphone apps that enable high-precision 3D surveying with iPhones and iPads have become practical for professional use, and surveying with a smartphone has become a realistic option even for as-built management in public works. Backed by such policy support, smartphone surveying is spreading rapidly on sites alongside traditional total stations and manual surveying.

With smartphone surveying, site conditions that could not be fully captured by drawings or photos can be entirely recorded and shared as 3D data. Anyone can easily acquire data that combines the accuracy of drawings with the visual clarity of photos, greatly improving the quality and efficiency of construction management. Additionally, since dangerous areas can be measured without people approaching them, the safety benefits are significant. It is truly a next-generation surveying method that supports on-site DX.

RTK Technology That Enables High-Precision Positioning

To use smartphone surveying seriously in professional work, high-precision positioning information is essential. Standard smartphone GPS can have errors on the order of meters, which is insufficient for accurate surveying. Enter RTK (Real-Time Kinematic) positioning technology. RTK exchanges GNSS observation data in real time between a base station (reference point) and a rover (surveying unit), canceling out error factors to achieve centimeter-level accuracy. This reduces typical GPS errors of 5–10 m down to within a few centimeters, providing coordinate positions accurate enough for surveying.

Recently, RTK high-precision positioning has evolved to the point where it is conveniently usable with smartphones. A key factor is the utilization of CLAS (Centimeter-Level Augmentation Service) provided by Japan’s quasi-zenith satellite system “Michibiki.” With a CLAS-compatible GNSS receiver, you can receive correction information directly from satellites without installing a dedicated base station. As a result, even in mountainous areas with no cellular coverage, as long as Michibiki signals are receivable, real-time centimeter-level positioning is possible. As introduced in Cabinet Office publications, this technology is gradually being adopted at local government sites.

Smartphones themselves are becoming increasingly capable, with multi-GNSS support and models that can receive L1+L5 dual-frequency signals appearing on the market. However, standalone smartphone positioning has limits, so in practice it is realistic to use an external RTK receiver that can be paired with the phone to achieve centimeter accuracy. Small RTK-GNSS devices that connect via a smartphone’s Lightning port or Bluetooth can turn an ordinary phone into an ad-hoc surveying instrument. For example, attaching a pocket-sized receiver to a smartphone can make it feasible for one person to perform everything from reference point surveying to point-cloud scanning. There are reports of combining the latest small RTK devices with smartphones to achieve average positioning errors on the order of 5 mm, suggesting that reliance on expensive, fixed GNSS systems is becoming unnecessary for many practical applications.

Thus, the smartphone × RTK combination has revolutionized surveying styles by balancing ease of use with practical accuracy. With centimeter-precision coordinates always displayed on the smartphone screen, you can check as-built deviations on the spot, navigate stakeout positions, and enable real-time construction management. Because Michibiki’s CLAS signals can enable positioning even offline, surveying can continue in situations where communications infrastructure is down, such as immediately after a disaster. There are also cost advantages since expensive dedicated surveying equipment is not required, making adoption easier for small and medium-sized enterprises and local governments, and allowing equipment trials through rental when needed.

Advantages of Smartphone Surveying

Introducing the combination of smartphone + RTK + point-cloud measurement on site brings various advantages not available with traditional methods. Major benefits include:

• High-precision 3D data acquisition: Centimeter-level positioning via RTK combined with point-cloud technology enables digital recording of site geometry with millimeter-to-centimeter accuracy. Small deviations that would be overlooked by visual checks or spot measurements can be detected, improving the quality of as-built management.

• Efficiency and labor savings: Wide areas can be non-contact measured quickly in a single pass, acquiring large amounts of data from one scan. Surveying work that formerly required multiple people and several days can sometimes be completed by a single person in a short time. Volume calculations and drawing generation can be automated, significantly shortening total work time.

• Improved safety: Dangerous areas that workers cannot enter can be measured remotely, ensuring worker safety. Surveys at heights or on slopes can be completed with a single smartphone, potentially eliminating the need for aerial work platforms or fall-prevention equipment.

• Quality control through data: If the entire site is captured as 3D data, comparisons with design models make as-built inspections more efficient. Continuously acquiring surveying data during construction and checking differences reduces rework and improves quality. Recording digitally rather than on paper improves the objectivity and reliability of inspections and reports.

• Easy to master: People familiar with smartphone operation can handle these tools intuitively without specialized surveying knowledge. Training costs are lower, and young personnel can quickly contribute to on-site DX. Even veteran workers who are hesitant about IT may accept smartphone-based workflows more readily.

• Low-cost introduction: Compared to purchasing specialized surveying instruments or large equipment, a setup of smartphone + small device + app can be started relatively inexpensively. Since many sites already issue smartphones, additional investment is small, making adoption easier for small businesses.

Main Use Cases for Smartphone Surveying

Smartphone surveying enables a wide range of applications. Here are several use cases that are particularly useful on site:

• Digitalizing as-built records: Smartphone surveying is powerful for as-built management, where the shape of structures and the ground are recorded at project completion. Traditionally, measurements were taken with tapes or total stations and photos were used for reporting. With smartphone point-cloud scans, the entire finished structure can be saved as high-precision 3D data. For concrete surfaces, even surface irregularities can be measured, and subtle differences from design data won’t be missed. As-built reports can include 3D models as well as numerical values, greatly improving inspection efficiency and persuasiveness.

• Streamlining stakeout and layout work: Smartphone surveying can be applied to essential stakeout/layout tasks in building and civil engineering. Normally, laying out coordinates on site from drawings required multiple workers with surveying knowledge. By attaching an RTK receiver to the smartphone and using an app that guides you to specified coordinates, you can reach the target location by following on-screen arrows. One person can perform stakeout, substantially reducing personnel and time.

• Efficient earthwork volume calculations: Volume calculations for embankment and excavation can be streamlined with smartphone surveying. Previously, pre- and post-construction ground heights were measured at fixed points and cross-sections generated to compute volumes. Scanning the ground surface before and after construction with a smartphone allows software to automatically calculate volumes from the difference between two point clouds. Scanning the entire site in a short time, including subtle surface features, yields more accurate volumes and greater efficiency compared to traditional methods.

• Infrastructure maintenance and monitoring: Smartphone surveying is useful for the maintenance of structures and terrain after construction. For example, when inspecting tunnel walls or bridge bearing areas, scanning targets with a smartphone lets you compare with past point cloud data to understand long-term changes. Annual point cloud surveys of slopes can visualize settlement and deformation, informing priority decisions for repairs. Monitoring based on 3D data provides quantitative, objective information compared to traditional visual inspections.

• Consensus building with AR: A unique application of smartphone surveying is using AR (augmented reality) to visualize design data. By displaying a 3D design model (BIM/CIM data, etc.) on a smartphone or tablet and overlaying it on the real scenery, stakeholders can intuitively share the completed image. For example, AR display of a planned structure on land before development makes explanations to clients and neighboring residents much easier. With RTK-capable smartphone apps, the model can be displayed without positional offset, making it highly useful as an accurate completion preview for consensus building.

Points to Note When Introducing Smartphone Surveying

While smartphone surveying is convenient, there are several points to be aware of during introduction and operation. Below are the main considerations along with current technical limitations.

• LiDAR range and environmental conditions: Built-in smartphone LiDAR measurement range is limited to roughly a 5 m radius, so it’s not ideal for scanning very large sites at once. For large areas, you’ll need to divide the area and perform multiple scans, then merge point clouds later. Under direct sunlight, infrared sensors are prone to noise, and reflective or transmissive materials such as glass or water surfaces are difficult to capture. Rainy conditions also increase the risk of reduced accuracy or equipment failure, so use in rain should generally be avoided.

• Ensuring accuracy and required proficiency: Point-cloud measurement using smartphones requires a certain technique and practice. Moving the device too quickly can cause gaps or distortions in the data, so slow and careful scanning is necessary for stable measurements. Also, standalone smartphone GPS accuracy is coarse (on the order of meters), so RTK augmentation is indispensable for precise positioning. In other words, smartphone-only surveying without RTK is generally difficult to use for as-built inspections, and appropriate equipment configurations should be chosen based on the intended use.

• Data volume and processing environment: High-density point-cloud data produce very large files, which can quickly consume smartphone storage and processing capacity. Long scans or high-detail modes can generate millions of points, and older devices may have apps crash. Care is required for post-acquisition data management and backup, and high-performance PCs or cloud services should be considered for point-cloud editing.

• Battery and equipment management: Continuous use of smartphones and receivers consumes battery rapidly. For long surveying sessions, prepare spare power sources such as mobile battery packs and take charging breaks as needed. Smartphones are precision devices, so pay attention to high temperature, humidity, and impact resistance. When using devices on site, employ waterproof cases and drop-prevention straps, and avoid use in rainy conditions to prevent equipment trouble.

Future Prospects for Smartphone Surveying

The technologies surrounding smartphone surveying are expected to continue evolving. Built-in smartphone LiDAR sensors may see improved range and accuracy in the future, making wider-area scans and finer-detail capture easier. In GNSS, improvements in smartphone chips may enable multi-band support and the use of satellite augmentation signals, potentially allowing standalone smartphones to achieve higher-precision positioning. One day it may be possible to complete surveys with centimeter accuracy using only a smartphone.

At the same time, the adoption of digital surveying across the industry is likely to accelerate. National standards and procedures will be further refined, and construction management methods assuming smartphone surveying may become standardized. On site, 3D data utilization will become routine, and communication will increasingly rely on point clouds and 3D models as well as drawings and photos. For younger technicians, surveying with a smartphone app may become more common than using a total station.

An ideal vision of on-site DX is that each worker carries one smartphone surveying device and anyone can perform surveying immediately when needed. In recent years, ultra-compact GNSS receivers and wearable devices that link with smartphones have emerged, enabling workers to know their real-time positions while working. Looking ahead, combining AR-capable smart glasses with high-precision positioning could enable hands-free measurement and design checks.

In this way, smartphone surveying will continue to advance and spread. The current ability to handle high-precision RTK positioning with smartphones represents a major paradigm shift, and its impact on the productivity revolution (DX) at construction sites is significant. The era of “survey anytime, anywhere, by anyone” is becoming a reality, and smartphone surveying will become indispensable to the future construction industry.

Closing: Start On-Site DX Easily with LRTK for Simple Surveying

Finally, as an easy-to-implement solution for smartphone surveying, we introduce LRTK. LRTK is a compact RTK-GNSS receiver that can be attached to smartphones, turning iPhones and iPads into versatile surveying instruments capable of centimeter-level positioning. Despite weighing only 165 grams and being about 1 cm thick, its compact body can receive multi-frequency GPS/GLONASS and augmentation signals from Japan’s “Michibiki” satellites, achieving positioning accuracy on the order of (horizontal ±1–2 cm; vertical ±3 cm). A dedicated smartphone app and cloud service are provided as a set, offering a variety of on-site DX functions in an all-in-one package, including point-cloud scanning, as-built measurement, volume calculations, and AR-based overlay of design data. For example, scanning a structure with the phone’s camera + LiDAR combined with LRTK’s high-precision position data generates an on-the-spot 3D point cloud model with absolute coordinates. Acquired point clouds and surveyed points can be uploaded to the cloud with one click, and analyses such as comparing with drawing data or measuring distances and areas can be performed in a browser. There is also a feature to display design models on the smartphone in AR without manual alignment, enabling seamless sharing of accurate completion images. Because these rich functions are completed with just a smartphone and an LRTK device, no additional expensive equipment or complex software is required. It is truly an “all-in-one” on-site DX tool that is easy for small and medium-sized businesses and local governments to adopt.

If you are interested in LRTK, please visit the official website for detailed information and case studies. Support systems are in place so that people without surveying expertise can use it, and consultation on introduction is also available. Combining a smartphone with LRTK makes high-precision surveying anytime, anywhere, by anyone possible. Take this opportunity to use the latest tools and move your company’s on-site DX forward. We at LRTK are committed to fully supporting a future in which your sites are safer and more efficient.