Surveying with a Smartphone! i-Construction's On-site DX Revolution

In the construction industry, improving on-site productivity through digital technologies has become an urgent task. Among these efforts, [i-Construction（アイ・コンストラクション）](https://www.mlit.go.jp/tec/i-construction/) promoted by the Ministry of Land, Infrastructure, Transport and Tourism is attracting attention as an initiative to drive DX (digital transformation) on construction sites from surveying through construction and management. In particular, in the field of surveying, movements are underway to revolutionize tasks that previously relied on manual labor and specialized equipment by using smartphones and high-precision positioning technologies. The era in which surveying can be done with a single smartphone has arrived, and a revolution in on-site DX is about to take place.

In this article, titled "Surveying with a Smartphone! The On-Site DX Revolution Brought by i-Construction", we explain in detail i-Construction in surveying—from its overview and background to the challenges of conventional methods and the cutting-edge surveying technologies using smartphones × RTK (Real-Time Kinematic). We also introduce the diverse functions achievable with smartphone surveying, such as point cloud scanning, AR features, and cloud sharing, along with the operational transformations and benefits resulting from their adoption. Finally, we touch on the advantages of simplified surveying using a solution called LRTK that enables smartphone surveying, and provide tips for taking the first step toward on-site DX.

Overview and Background of i-Construction (Specialized in Surveying)

Overview of i-Construction: i-Construction (ai-construction) is a productivity improvement project for construction sites launched by the Ministry of Land, Infrastructure, Transport and Tourism in 2016. It refers to efforts to improve the efficiency and sophistication of the entire construction process—from surveying and design to construction, inspection, and maintenance/management—through the comprehensive use of ICT (information and communication technology). The background includes chronic labor shortages in the construction industry and workplace environment issues described as the "3K" (kitsui, kitanai, kiken: tough, dirty, dangerous). In fact, the number of workers in the construction industry peaked at about 6.85 million in the late 1990s and has steadily declined, shrinking to about 4.79 million in 2022. The workforce at sites has also aged, and the shortage of younger workers has become severe. The government has set a goal of improving on-site productivity by 20% by fiscal 2025 through the promotion of i-Construction, and has been advancing measures such as ICT utilization, 3D data standardization, and smoothing of construction schedules.

The Start of Surveying DX: i-Construction has brought particularly large changes to the field of "surveying." Traditionally, topographic surveys carried out manually with total stations and levels have, through the promotion of i-Construction, begun to be replaced by drone aerial surveys and point cloud measurements using 3D laser scanners. The use of 3D surveying, which can measure wide areas in a short time, has enabled the acquisition of terrain and structures as high-density point cloud data and established workflows to apply them to design and construction. For example, flying a drone over an earthwork site in a mountainous area can quickly obtain detailed terrain data for the entire site, allowing height or distance at any desired point to be measured afterward. The introduction of such ICT surveying has realized major efficiency gains and improved accuracy in surveying work, serving as the first step toward on-site DX.

Traditional Surveying Methods and Limitations (Manpower, Accuracy, Project Duration, Safety)

• Dependence on manpower and specialized skills: Traditional surveying has had to rely on professional surveyors and technicians, and the accuracy was determined by the experience and intuition of veteran personnel. Equipment had to be operated by multiple people, and in situations of staff shortages there is the additional problem that surveying work cannot be carried out at all.

• Limitations of Work Time and Efficiency: Because survey points are measured painstakingly one by one on site, it takes an enormous amount of time for large sites or hilly, uneven terrain. Work can also be interrupted by weather, and the more time surveying takes, the greater the impact on the overall construction schedule.

• Challenges of Accuracy and Coverage: Although the accuracy of instruments such as the latest total stations is high, the number of points that can be measured is limited, so there are limits to fully capturing complex terrain and structures. Two-dimensional drawings represented by points and lines risk overlooking fine surface variations, and errors from missed measurements or recording mistakes cannot be eliminated.

• Safety risks: Surveying work in hazardous locations, such as along roadsides and on steep slopes, always carries the risk of accidents and injuries. Carrying heavy equipment while working in scorching heat or extreme cold places a heavy burden on workers, and the harshness of the working environment has been one factor contributing to people leaving the profession.

As described above, conventional methods imposed many constraints on efficiency and safety, creating challenges for improving productivity in the construction industry.

What Is Surveying DX (Definition and Its Relationship with i-Construction)

Surveying DX (digital transformation) refers to introducing digital technologies into surveying operations to fundamentally change work processes. It is not simply about digitizing surveying equipment; rather, it is an initiative to revolutionize surveying efficiency, accuracy, and the way data is used by leveraging 3D measurement technologies, mobile apps, and cloud services. i-Construction's push to ICT-enable construction sites is precisely grounded in this Surveying DX.

Specifically, cases such as automatically processing aerial photogrammetry from drones and point cloud data obtained by laser scanners with software to generate terrain models in a short time have become widespread. Terrain surveys that used to take skilled personnel several days can now be completed in a few hours thanks to DX, and can be recorded and shared as detailed 3D data. In addition, data measured on site are recorded not in paper field notebooks but on tablets and in the cloud, and are immediately shared with the office for analysis and drawing creation. Surveying DX not only speeds up and reduces labor in surveying itself, but because the acquired data can be used seamlessly in subsequent design and construction processes, it directly contributes to improving the productivity of the entire construction project.

Technical Overview and Accuracy of Surveying Using Smartphones with RTK

The recently introduced smartphone × RTK surveying technology has enabled smartphones to be used as high-precision surveying instruments. RTK (Real-Time Kinematic) is a technique that applies correction information from a reference station to GNSS (satellite positioning) data, greatly reducing positioning errors. While the GPS built into a typical smartphone normally has errors on the order of several meters, using RTK reduces the error to a few centimeters. Centimeter-level accuracy that until now could only be achieved with specialized GPS surveying equipment can now be realized with smartphones.

Specifically, by using a small RTK-GNSS receiver that attaches to a smartphone and a dedicated app, it receives base station data (Ntrip) and augmentation signals from satellites over a network to perform real-time corrections. In Japan, the CLAS signal from Michibiki (QZSS) is used, and devices that can perform positioning even outside communication coverage have also appeared. On the smartphone app, high-precision positioning becomes possible within just a few tens of seconds from the start of positioning, enabling not only single-point coordinate measurement but also guidance to arbitrary coordinates (stakeout operations). The accuracy is about 1-3 cm (0.4-1.2 in) for both horizontal and vertical even with immediate (single-epoch) measurements, and averaging the measurements can achieve an error of 1 cm (0.4 in). That this level of accuracy can be easily obtained on a smartphone that fits in a pocket represents a major breakthrough in surveying technology.

Smartphone Surveying Features: Point Cloud Scanning, AR, and Report Output

• Point cloud scanning：You can scan the surrounding environment with a smartphone camera or LiDAR and record it as a multitude of points (a point cloud). With RTK-enabled smartphone surveying, you can easily obtain an absolute-coordinate 3D point cloud in which each point is given global coordinates (latitude, longitude, height). Even complex terrain and structures can be converted into high-precision 3D data simply by holding up the smartphone and walking, allowing you to later measure arbitrary distances, areas, and volumes or perform analyses by comparing with drawings. (Standalone smartphone LiDAR measurements tend to produce distortions in the point cloud when moving around, but by continuously correcting the device position with RTK you can generate point clouds accurately.)

• AR display and layout guidance: You can overlay plans and 3D models on a smartphone screen to visualize the finished form on site as AR (augmented reality). This allows you to confirm at a glance whether work is progressing according to the drawings and to easily share the finished-image with clients. It also includes a position guidance function (assisting stake-driving work) that navigates to specified coordinates using the smartphone’s determined position. Because the smartphone guides you to the point on the plan, even non-experts can accurately perform setting-out and layout marking. Furthermore, by pre-scanning underground buried objects as point clouds and AR-projecting their positions during the next excavation, safe construction that avoids buried pipes and the like becomes possible.

• Automatic Calculations and Report Output：Smartphone surveying apps automatically calculate and organize the necessary information from the acquired data. For example, they can instantly compute cut and fill volumes from a large number of measured points, and display differences between current point cloud data and design data as a color-coded heat map. Measurement results required for as-built management can also be calculated on the spot, and the apps are equipped with functions to automatically generate and output standard reports and drawings (such as cross-sections). A major advantage is that they can greatly reduce tedious manual calculations and the work of creating drawings in CAD.

Worksites Transformed by Easy-to-Use UX, Automation, and Cloud Sharing

What makes smartphone surveying systems outstanding is that their operability and automation mean anyone can use them. Traditional surveying instruments required specialized knowledge to master, but smartphone apps enable measurements and data processing via an intuitive UI. By simply tapping on a map you can record survey points, and with a single button coordinate system conversions and calculations are completed—the app automatically handles all the tedious tasks behind the scenes. As a result, site supervisors, junior staff, and others outside the surveying profession can more easily collect and utilize data, which also helps reduce the burden on experienced personnel.

Furthermore, cloud integration now enables surveying data real-time sharing. With a single tap on a smartphone to upload to the cloud, information can be shared instantly with office staff and project owners. Point clouds and photos measured on site can be reviewed on the spot with supervisors and partner companies, enabling speedy decision-making that allows work to proceed to the next task without rework. In addition, because data is accumulated in the cloud, it can be used as organizational knowledge even after the project is completed. Eliminating the need to hand over paper or USBs and enabling the field and the office to operate as one across geographical boundaries is a major advantage of DX-driven business transformation. Furthermore, it changes the way people work by allowing supervisors and engineers in remote locations to check data on the cloud and provide advice without traveling to the site.

Benefits of Adoption for Municipalities, Site Representatives, and Surveyors

• Local governments (public contracting authorities): For municipalities as project owners, the spread of smartphone surveying offers benefits in both quality and efficiency. If the as-built data submitted by contractors becomes high-precision 3D survey data, the burden of inspections and on-site attendance is reduced. Even during construction, the measurement status on site can be monitored via the cloud, allowing for early instructions to be issued as needed. Also, since 3D point cloud data remains as an asset after completion, it can be utilized for maintenance and future planning. In terms of achieving operational efficiency and improved transparency through the introduction of the latest technology, smartphone surveying can be considered an attractive solution for municipalities.

• Site Representative (Construction Manager): For site construction managers, smartphone surveying will dramatically transform daily operations. Because they can measure current conditions themselves and verify them immediately without requesting a specialized surveying team, work stoppages caused by waiting for surveys are eliminated. For example, they can scan the fill volume of embankments on the spot to identify shortages or excesses and correct them immediately. Discrepancies between drawings and the actual site can also be checked with AR, helping to prevent rework. With form creation and report preparation automated, the burden of complex administrative tasks is reduced, allowing them to concentrate on core construction management duties. As a result, construction schedules can be shortened, quality improved, and trust from clients increased.

• Surveyors (surveying professionals): For professional surveying technicians, the rise of smartphone surveying is not a threat but a helping hand. If teams introduce tools that can be used without extensive seasoned know-how, assistants and younger staff can be entrusted with a certain amount of surveying work. Because small teams can cover many sites, it becomes easier to handle workloads even amid chronic labor shortages. In addition, automated data processing reduces recording errors and streamlines the creation of inspection and delivery drawings, allowing more time to be devoted to the quality control and analysis tasks that should be the primary focus. Exposure to the latest measurement technologies also leads to skill development, and the surveying profession itself evolves into a digitally attractive field. Surveyors who proactively adopt advanced technologies will be able to play a leading role on infrastructure DX sites, where demand will only increase going forward.

LRTK Enabling Smartphone Surveying and the First Step Toward On-site DX

Finally, a concrete way to realize smartphone surveying on site is the use of LRTK. LRTK is a solution consisting of an ultra-compact RTK-capable device that attaches to a smartphone and an app, turning your handheld smartphone into a surveying instrument with centimeter-level accuracy (half-inch accuracy). There is no need to prepare dedicated equipment—the appeal is the ease with which you can start simple surveying immediately with just a smartphone and LRTK. Its compact design with a built-in battery and included antenna makes it easy to carry, and even at sites where network connectivity is difficult, satellite augmentation signals enable high-precision positioning, so it performs effectively anywhere.

In fact, companies are emerging that have implemented LRTK to establish a one-smartphone-per-person surveying system, leading to increased productivity. By introducing smartphone surveying using LRTK, you can immediately enjoy all the benefits discussed in this article. Each smartphone becomes an all-purpose surveying device, enabling an all-in-one solution from point cloud scanning and stakeout guidance to cloud sharing. It is lower cost and easier to deploy than specialized equipment, and because the output data complies with the Ministry of Land, Infrastructure, Transport and Tourism's standards, it can be safely used as official surveying results. You can start using it the day you bring it to the site, and you will likely notice benefits in a short time. It is truly an ideal solution as the first step toward on-site DX.

Why not bring smartphone surveying, which is becoming the new standard in the i-Construction era, to your job sites as well? Let’s start a productivity revolution on your sites with easy surveying DX that leverages LRTK.