Table of Contents

• Introduction

• Surveying Challenges and the Need for Smartphone Surveying

• What Is LRTK Phone?

• Features and Functions of LRTK Phone

• On-site Benefits Brought by LRTK Phone

• Conclusion: A New Era of Surveying Opened by Smartphones

• FAQ

Introduction

Surveying work is indispensable on construction sites. However, traditional surveying required specialized technicians and expensive dedicated equipment, so it was not something anyone on site could perform immediately. Recently, however, easy surveying techniques that utilize smartphones have been attracting attention. In particular, the "LRTK Phone" is a groundbreaking device that turns a smartphone into a surveying instrument capable of centimeter-level high-precision positioning (cm level accuracy (half-inch accuracy)). This article introduces the appeal and benefits of high-precision surveying using LRTK Phone for site workers and construction companies with no prior surveying experience.

Surveying Challenges and the Need for Smartphone Surveying

The construction industry faces issues such as a shortage of experienced surveyors and the need to improve productivity. Traditional surveying often involves setting up large equipment like transits or GNSS receivers and sometimes requires two or more people, which takes time and costs. Summarizing survey results into drawings or data and sharing them with stakeholders also requires specialized knowledge. Against this backdrop, initiatives like the Ministry of Land, Infrastructure, Transport and Tourism’s *i-Construction* have increased the demand for digitalization and ICT utilization on sites. Smartphone surveying, which combines smartphones with cutting-edge technologies, is expected to be a solution.

LRTK Phone was developed as a next-generation surveying solution to meet these needs. Based on the concept that a smartphone becomes a surveying instrument, it is designed so anyone can easily obtain high-precision positioning and survey data.

What Is LRTK Phone?

LRTK Phone is a compact RTK-GNSS receiver device that attaches to a smartphone (mainly iPhone and iPad). Just by attaching it like a phone case, you can raise a smartphone’s GPS—which normally has errors of several meters—to centimeter-level (cm level accuracy (half-inch accuracy)). It weighs about 125 g and is compact, with a thickness of only about 13 mm (0.51 in). The antenna and battery are integrated, so there are no troublesome cables or external power supplies on site.

When combined with the dedicated LRTK app, a single smartphone functions as a versatile surveying instrument. In addition to acquiring high-precision position coordinates, you can intuitively perform various surveying and measurement tasks such as 3D scanning, stakeout guidance, and projecting design data using AR (augmented reality). LRTK Phone was developed by a startup originating from Tokyo Institute of Technology and is attracting attention as an innovative technology supporting DX (digital transformation) on construction sites.

Features and Functions of LRTK Phone

• Quick attachment and immediate surveying: LRTK Phone is easy to attach to your smartphone and requires no special setup. Take it to the site, attach it to your phone, and you can start positioning immediately. You can hold the phone in one hand, place the device at the point you want to measure, and tap the app button to perform surveying. Even without complicated operations or specialized knowledge, you can obtain accurate latitude, longitude, and elevation with a one-touch action.

• Centimeter-level high-precision positioning: The biggest feature is its high positioning accuracy. LRTK Phone supports the RTK (real-time kinematic) method, dramatically reducing positioning errors. It also supports the augmentation signal (CLAS) provided by Japan’s Quasi-Zenith Satellite System “Michibiki,” enabling high-precision positioning even in mountainous areas or infrastructure sites outside network coverage. Achieving centimeter-level positioning, which previously required GNSS receivers and base stations costing millions of yen, with just a smartphone and LRTK Phone is revolutionary. In actual tests, standalone positioning achieved horizontal accuracy of about 10–20 mm (0.39–0.79 in), and averaging multiple measurements yielded accuracies of about 5–10 mm (0.20–0.39 in), matching professional surveying instruments.

• Various surveying modes (single-point and continuous positioning): The LRTK app offers various positioning modes tailored to site needs. For example, in single-point positioning, you simply place the device at the point to be measured and press a button to record its coordinates. Point names and timestamps are recorded automatically, and you can add notes. In continuous positioning mode, you can acquire position data continuously while walking and measure surrounding terrain sequentially. By measuring multiple points at regular intervals or arranging measurement points along a line or surface, you can capture cross-sections or plan shapes of terrain.

• 3D point cloud scanning: By combining the smartphone’s camera or LiDAR sensor (on compatible models), you can easily perform 3D measurements on site. With LRTK Phone, you always know your position to centimeter-level (cm level accuracy (half-inch accuracy)) while walking with the phone, allowing you to obtain surrounding structures and terrain as a 3D point cloud. Normally, smartphone-only scans can produce distortion when moving long distances and lack absolute (global) coordinates. However, with LRTK Phone, every acquired point cloud is tied to global geodetic coordinates, so multiple scan datasets can be integrated without misalignment. For example, for a road section of about 50–60 m (164.0–196.9 ft), a worker can walk from one end to the other while scanning to generate a high-accuracy terrain point cloud model aligned with the design coordinate system. From such point cloud data, you can calculate the distance between any two points or the volume of embankment/excavation on the spot. Tasks that previously required dedicated 3D laser scanners or drones can now be completed with just a smartphone.

• Stakeout and position guidance: LRTK Phone also serves as a tool to indicate positions, not just measure them. Traditionally, staking out coordinates from design drawings required surveyors to go to the site and set positions with surveying instruments. The LRTK app includes a coordinate guidance function that displays arrows and guides on the smartphone screen toward specified target coordinates. Users simply follow the guidance to find the target point with centimeter-level accuracy. This allows less experienced personnel to perform staking tasks. Also, for locations that are hard to approach, such as steep slopes or areas beyond obstacles, AR technology can display a virtual stake at the point, enabling safe and efficient stakeout.

• On-site projection of design data with AR: LRTK Phone integrates with AR functions to overlay 3D design data or previously acquired point cloud data onto the site view. For example, if you upload a 3D model of a planned structure (such as a retaining wall or embankment) to the LRTK cloud, you can project that model at full scale through your smartphone on site and compare it with the surrounding terrain. Typical smartphone AR requires placing markers or manual scale adjustments, but with LRTK you don’t need such steps. Because your position is always known at high precision, you get AR that doesn’t drift while walking. This makes it easy for clients and contractors to share a completed-image on site and instantly spot discrepancies between the design and current conditions.

• Photogrammetry and record keeping: On-site surveys often require taking photos for records. With LRTK Phone, the smartphone’s orientation (bearing) and the shooting position coordinates are automatically recorded when a photo is taken. The photos are later plotted on maps or point cloud data with their capture locations, so you can instantly see where and in what direction a photo was taken. This makes it easy to reproduce photos from the same location and angle, useful for comparing changes over time in infrastructure inspections or for pre- and post-construction records.

• Cloud integration and data sharing: All data acquired with the LRTK app can be uploaded to the dedicated LRTK cloud with one tap. office staff can immediately view positioning points and point cloud data shared from the field on a web browser map or 3D viewer. No special PC software installation is required; you can perform distance, area, and volume measurements in the cloud, and check differences by overlaying point cloud data with design models (displayed as an as-built heatmap). Coordinate data acquired on site can be exported in CSV or CAD formats for smooth integration into traditional drawing workflows.

• Compact, lightweight, and easy to carry: LRTK Phone is a pocket-sized device, so workers can carry it around the site at all times. The convenience of pulling it out and measuring whenever needed is a major advantage for daily construction management. Tasks that would normally require calling a surveying team—such as quick as-built checks, interim inspections, or locating buried objects—can be handled on the spot by site staff. If everyone on site has one surveying tool per person, the way work is conducted will change dramatically.

• Intuitive operation anyone can use: Unlike specialized surveying instruments, LRTK runs on a smartphone app with an intuitive user interface. Start/stop buttons and functions are clearly iconized, so first-time users can operate it without confusion. Even without surveying expertise, the app automatically performs coordinate transformations (such as converting to plane rectangular coordinates or calculating geoid heights) and data processing, so users don’t need to worry about complicated steps. The ease of “measure when you want, view when you want” spreads ICT usage beyond skilled technicians to other site staff.

On-site Benefits Brought by LRTK Phone

Introducing LRTK Phone brings various benefits to construction sites.

• Improved productivity: Reducing waiting times for surveying and enabling immediate measurements when needed smooths workflows. For example, as-built management previously outsourced to external surveyors can be performed on site by in-house staff, reducing delays in the schedule. Real-time data sharing eliminates communication losses between field and office.

• Cost reduction: Instead of procuring multiple expensive total stations or GNSS surveying units, deploying multiple relatively affordable LRTK Phones allows many staff to measure simultaneously while keeping initial costs down. Reducing outsourced surveying also lowers labor and outsourcing costs. Early detection and correction reduce rework and associated costs.

• Addressing personnel shortages: With the aging and shortage of surveyors, LRTK Phone enables non-specialist workers to take on parts of surveying tasks. This reduces dependence on skilled personnel and alleviates bottlenecks caused by labor shortages. For training new staff, starting with smartphone surveying helps them get accustomed to field measurement and expands the pool of future survey professionals.

• Improved safety: Surveying in hazardous locations (such as on roads or steep slopes) can be performed quickly and safely with LRTK Phone. Remote scanning and AR projection allow site conditions to be assessed without workers entering dangerous areas. Displaying stakeout positions in AR prevents incorrect installations and contributes to maintaining safety and quality.

• Enhanced quality control: Using LRTK Phone, as-built data can be digitally recorded sequentially. Comparing with the design model allows color-coded checks of construction accuracy, and accumulating fixed-point observation data enables tracking changes over time, enhancing quality control. Replacing paper records and verbal handovers with data-driven management reduces mistakes and oversights.

• Promoting on-site DX: LRTK Phone embodies digital transformation on site. From surveying to recording, verification, and sharing, everything can be completed digitally, transforming previously analog workflows. It supports outcomes required by the Ministry of Land, Infrastructure, Transport and Tourism’s "ICT earthwork" and as-built management guidelines, streamlining the preparation of deliverables for clients. For companies aiming to advance on-site DX, LRTK Phone is an ideal first step.

Conclusion: A New Era of Surveying Opened by Smartphones

With LRTK Phone, the era in which a smartphone becomes a surveying instrument has become a reality. Even site workers with no surveying experience can intuitively operate a smartphone to perform centimeter-level positioning and data measurement. It contributes not only to productivity improvement, safety management, and quality assurance on construction sites, but also ensures that each person working on site can benefit from digital technology.

Traditionally, surveying was left entirely to specialists, but LRTK Phone has made it accessible. In the near future, smartphones may become as common a surveying tool on construction sites as hammers and shovels. Take this opportunity to experience simple surveying that you can start easily with LRTK Phone. The world of high-precision surveying that opens up with just a smartphone will change common practice on site.

FAQ

Q: Do I need any special qualifications or knowledge to use LRTK Phone? A: No, no special qualifications are required. Basic operations are completed within the smartphone app, and you can position and measure by simply pressing a button. The app automatically handles coordinate transformations and data processing so that even users without surveying expertise can operate it intuitively.

Q: What equipment or preparations are required? A: All you need is the LRTK Phone device and a compatible smartphone (currently iPhone or iPad iOS devices). LRTK Phone is provided as a dedicated cover or attachment for smartphones and is easy to install. Once you install the dedicated app, you can start positioning immediately. Network-based RTK requires a communications environment, but by utilizing Michibiki CLAS, positioning is possible even outside network coverage.

Q: Is the positioning accuracy really centimeter-level? A: Yes, under appropriate conditions centimeter-level accuracy can be achieved. In open outdoor environments with good satellite visibility, horizontal positions are typically within about 1–2 cm (0.4–0.8 in), and vertical errors are on the order of a few centimeters. However, obtaining high accuracy requires good satellite reception and radio conditions. Accuracy may degrade in areas with building shadows or dense vegetation, but even in those cases it is significantly more accurate than ordinary smartphone GPS.

Q: Can it be used indoors or in tunnels? A: Since it relies on satellite positioning, direct positioning is not possible indoors, underground, or in tunnels where satellite signals cannot reach. However, by using reference points obtained near entrances for relative positioning, or combining with AR technology to estimate indoor positions, you can still find creative ways to use it. Currently, outdoor use is the main focus, but future technological advances may enable simple indoor positioning.

Q: How are data stored and shared? A: Positioning data and point clouds are saved on the smartphone and can be uploaded to the LRTK cloud for storage and sharing as needed. Data uploaded to the cloud can be viewed in a web browser from a PC and shared with stakeholders. Coordinate data can be exported in CSV or DXF formats for use in your company’s CAD software or GIS systems. Local data management without using the cloud is also possible to match internal rules.

Q: Is LRTK Phone expensive? A: LRTK Phone is offered at a price point that is more accessible than traditional surveying equipment. For exact pricing, please contact the provider, but it generally offers better cost performance compared to purchasing multiple devices for each surveying function, as it provides all necessary functions in one unit. Considering reduced outsourcing and productivity gains, it can be a worthwhile investment.

Q: What about durability and battery life? A: LRTK Phone is designed to be robust for field use. It operates reliably under light rain, wind, and dust typical of construction sites, offering durability suitable for daily on-site use. The battery is built-in and supports several hours of continuous use on a full charge (depending on usage). For long workdays, you can operate while charging with a mobile battery, so it can support a full day of surveying tasks.

Q: Will it be available for Android devices in the future? A: Currently, LRTK Phone is available for iOS devices, but future Android support is being considered depending on user demand. Technically, high-precision positioning is possible on Android smartphones, so development to expand supported devices may proceed. Please check official sources for the latest compatibility information.