LRTKで始めるスマホ測量：i-Construction時代の新常識

In recent years, the construction industry has rapidly advanced digitization to improve productivity. One approach attracting attention is "smartphone surveying," which combines smartphones with RTK (real-time kinematic) technology. This method, which can be called the new norm of the i-Construction era, is revolutionary in that it allows anyone to perform high-precision surveying easily. This article explains in detail the benefits and functions of smartphone surveying, the DX effects it brings to the field, and how to introduce it using LRTK.

i-Constructionとは何か（測量の視点から）

i-Construction is a productivity revolution project for the construction industry proposed by the Ministry of Land, Infrastructure, Transport and Tourism in 2016. Its goal is to dramatically improve on-site productivity by introducing ICT (information and communication technology) across the entire construction process, including surveying, design, construction, inspection, and maintenance. The initiative responds to issues such as labor shortages of construction technicians due to a declining birthrate and aging population, and harsh working conditions summarized as “kitanai, kitsui, kiken” (dirty, demanding, dangerous). The government has set a target of improving construction site productivity by 20% by fiscal 2025 through promotion of i-Construction, and is advancing measures such as spreading ICT use and standardizing rules.

One major change i-Construction has brought to surveying is the spread of 3D surveying technologies. Conventional field surveys that took days manually can now measure wide areas at high density in a short time using drone photogrammetry and terrestrial laser scanners. For example, flying a drone over a site to capture images and generating point cloud data (3D survey data) with software allows detailed understanding of terrain and structures. In the i-Construction era, surveying itself is becoming digitalized and automated, dramatically improving efficiency and accuracy.

スマホ測量の登場と現場が抱える課題

Amid the progress of ICT utilization, a newly emerged approach is "smartphone surveying." As the name implies, smartphone surveying uses a smartphone as a surveying instrument, combining dedicated apps and small sensors to perform position measurement and terrain scanning. Smartphones are equipped with high-performance cameras, sensors, and communication functions, making them akin to compact computers. The movement to leverage these familiar devices for surveying is spreading among field practitioners.

Traditional surveying required expensive, specialized instruments such as total stations and GNSS receivers, and operation demanded skilled personnel. Work typically required pairs of workers and time-consuming tasks like compiling survey results into drawings or Excel, consuming manpower and time. Many sites also face shortages of surveying specialists, leaving construction managers to worry that “there aren’t enough people to ask for surveying” or that “calling a specialist for small measurements is inefficient.” In response to these issues, smartphone surveying—which enables immediate measurements with a handheld phone when needed—is expected to become a major on-site aid.

However, standalone smartphone GPS accuracy used to be coarse at the level of several meters, making it insufficient for professional civil engineering surveying as-is. The emergence of technologies that solve this issue has brought smartphone surveying to a practical stage. That approach is incorporating RTK high-precision positioning into smartphones.

RTK測位とスマホ連携で実現する高精度測量

RTK (Real Time Kinematic) is a method that uses GNSS (Global Navigation Satellite System) to perform real-time error correction and achieve centimeter-level positioning accuracy (half-inch accuracy). Regular GPS positioning has errors on the order of meters, but RTK greatly reduces these errors by using correction information from a base station. Until recently, RTK required RTK-compatible surveying equipment and dedicated antennas, but small RTK receiver modules have been developed in recent years that can be used in conjunction with smartphones.

By attaching an external RTK-GNSS receiver to a smartphone and receiving correction data from a reference station over the Internet (using methods such as Ntrip), a smartphone can obtain high-precision position information in real time. In other words, a smartphone can attain accuracy comparable to professional surveying equipment. This enables tasks such as establishing control points and performing detailed surveying with a smartphone, allowing smartphones to be used in scenarios that previously required specialized instruments. With the combination of RTK positioning and smartphones, smartphone surveying has dispelled concerns about accuracy and become a solution suitable for full-scale fieldwork.

スマホ測量で実現できる主な機能

Smartphone surveying offers various functions comparable to traditional surveying instruments. The main functions and their use cases are introduced below.

• 高精度な位置座標測定: Using a smartphone with RTK, you can measure the latitude, longitude, and elevation of any point with centimeter-level accuracy (half-inch accuracy). By placing the device on a point of interest on the ground or structure and pressing a button, the 3D coordinates of the survey point can be recorded. Measured points are automatically converted into the surveying coordinate system (such as a plane rectangular coordinate system), reducing the effort required to create record books.

• 3D点群スキャン: By utilizing a smartphone’s built-in LiDAR scanner or camera, the surrounding environment can be captured as 3D point cloud data. Scanning while correcting position with RTK assigns global coordinates to all acquired points. This makes it possible, for example, to scan the shape of an excavation with a smartphone and calculate earthwork volume on the spot. The ability to acquire high-precision, georeferenced point cloud measurements with only a small, lightweight smartphone is a major advantage for field operations.

• ARによる墨出し・設計照合: AR (augmented reality) functions can overlay design data or drawing positions onto the real world through the smartphone screen. With a smartphone that has high-precision coordinates, a design model can be accurately projected into real space to visualize installation positions of structures or to check for interference with existing structures in advance. This shortens time that used to be spent on traditional staking and layout marking and helps prevent work errors.

• 写真測量と報告書作成: Photos taken with the smartphone camera can automatically have positioning information attached and be saved as photogrammetry data. When you photograph locations required for as-built management, the data will include recorded position and timestamp, reducing later time spent organizing them on drawings. Measurement results and photo data can be automatically formatted into reports, contributing to more efficient report creation and work records.

• クラウド共有とデータ活用: Coordinate and point cloud data acquired by smartphone surveying can be shared in real time via the cloud. If on-site measurements are uploaded to the cloud immediately, office staff can check results instantly from a remote location and stakeholders can share the data. Advanced uses, such as viewing current 3D data together in a cloud-based point cloud viewer and checking differences from design models, are also possible. The ability to link data between the field and the office is a distinctive strength of smartphone surveying.

*スマートフォンに取り付ける小型RTK-GNSS受信機「LRTK」。iPhoneをポケットサイズの高精度測量機に変えることができる。*

測量士・現場代理人・自治体職員にとってのメリット

Introducing smartphone surveying brings significant benefits to people in various roles on site.

• 測量士にとって: Smartphone surveying reduces the burden on surveyors. For simple field checks or as-built inspections, on-site staff can perform measurements themselves using smartphone surveying. This allows surveyors to concentrate on highly specialized tasks such as advanced surveying planning and data analysis. Also, one-person surveying becomes easier, enabling efficient coverage of many sites even amid labor shortages.

• 現場代理人・施工管理者にとって: Site supervisors can measure “whenever they want” using smartphone surveying. For example, they can check excavation depths or embankment heights on the spot and immediately reflect the findings in construction as needed. Removing the need to wait for a specialist team directly shortens schedules and prevents rework. Using AR functions, they can compare the design model with the actual site to check construction accuracy and reduce variability in as-built outcomes. When supervisors themselves can measure and verify data, site management autonomy and accuracy improve dramatically.

• 自治体職員にとって: For municipal staff handling road and park maintenance or disaster damage surveys, smartphone surveying is powerful. Even without specialized surveying instruments, a smartphone and a simple surveying device allow rapid quantification of on-site conditions. For example, staff can measure and photograph a disaster site with a smartphone and share it via the cloud immediately so the main office can grasp the situation in real time and plan responses. As the client, municipalities can also review and verify 3D data submitted by contractors on the cloud, facilitating smooth digital consensus building.

スマホ測量導入がもたらす現場DX効果

Introducing smartphone surveying on site not only streamlines surveying tasks but also becomes a driving force for DX (digital transformation) of construction sites. The main effects are as follows.

• 省力化による生産性向上: Smartphone surveying directly contributes to labor and effort reduction. Surveys that previously required two or more people can be completed by one person, and surveying time can be drastically shortened. Because many sites can perform surveying in parallel, productivity increases dramatically. Equipment transport burdens are also reduced, cutting down preparation and teardown time.

• 手戻り削減と品質向上: By obtaining and utilizing high-precision surveying data at each stage, construction errors and as-built defects can be detected and corrected early. For example, checking the finish with smartphone surveying during construction prevents rework caused by incorrect dimensions after completion. Making decisions based on always-accurate current data also helps standardize and improve construction quality.

• 安全性の向上: Smartphone surveying can reduce risks associated with surveying in hazardous locations. Using drones or poles to measure from a distance and completing surveys quickly minimizes time spent working at heights, on slopes, or on busy roads. Reducing the need to carry heavy surveying equipment also lessens workers’ physical load, offering safety management benefits.

*専用ポール（一脚）にスマホとLRTKを装着して測量している様子。1人で手軽に測量でき、安全性も向上する。*

LRTKを活用したスマホ測量導入の流れ

When starting smartphone surveying, introducing a smartphone surveying solution like LRTK enables smooth deployment. Here is a general flow for introduction using LRTK.

• 機器・アプリの準備: Prepare the smartphone (iPhone or iPad, etc.) to be used for surveying and the LRTK device. LRTK is a small RTK-GNSS receiver that attaches to a smartphone, and compatible cases and mounts are also available. First, attach LRTK to the smartphone and install the dedicated app from the App Store.

• 初期設定と接続: Launch the app and configure the connection settings with the LRTK device. Set up reception of correction information using network RTK (Ntrip method) here as well. By connecting to the nationwide GNSS reference station network (continuously operating reference stations), you can obtain correction data in real time anywhere. When connected correctly, the smartphone screen will display the current position stably with centimeter-level accuracy (half-inch accuracy).

• 測量の実施: Once preparations are complete, perform surveying on site. Take the smartphone (with LRTK attached) to the point you want to measure and tap a button in the app to record a high-precision coordinate. Using a dedicated pole as needed allows accurate measurement of points on the ground, and walking while scanning can acquire 3D point cloud data. The acquired point coordinates and elevations are displayed immediately on the screen, and you can add survey points one after another. The intuitive interface lets even those without surveying expertise operate without hesitation.

• データ活用と共有: After surveying, utilize the acquired data. Data in the app can be exported as CSV or drawing formats, and necessary forms can be automatically generated. Furthermore, uploading from the LRTK app to the cloud enables viewing point cloud data and coordinate lists instantly on an office PC via a web browser. It is also easy to perform applications like comparing with design drawings and past data on the cloud. In this way, data acquired with a smartphone is immediately shared among stakeholders and used for real-time on-site decision-making.

スマホ測量を第一歩に現場DXを推進しよう

Smartphone surveying is an ideal first step for promoting DX on construction sites in the i-Construction era. The LRTK-based approach, in particular, offers a low barrier to entry and rapid improvement effects. You can start simply by attaching a small device to a smartphone you already have, without purchasing expensive dedicated equipment, making it cost-effective. The style of “one surveying device per person in the pocket,” where anyone on site can carry a smartphone surveying device and measure quickly when needed, is spreading as the new norm.

Using LRTK makes surveying dramatically simpler and accelerates data utilization. Replacing paper drawings and experience-based processes with digital data helps eliminate reliance on individuals and enhances transparency of operations. By starting DX with smartphone surveying, you can improve overall site productivity, quality, and safety, and ultimately contribute to workstyle reform across the construction industry. Why not adopt smartphone surveying, which has become the new norm in the i-Construction era, and take the next step at your site?