How to Use LRTK Phone on Site: From Basic Operations to Advanced Techniques

LRTK Phone is a small high-precision GNSS receiver that attaches to a smartphone. A smartphone instantly becomes a versatile surveying instrument with centimeter-level accuracy (half-inch accuracy), dramatically improving positioning work on site. From LRTK beginners to experienced field workers, surveyors, and managers, anyone can easily obtain precise location information and apply it to various measurements and construction management tasks. This article explains how to use LRTK Phone in detail, from basic operations to advanced techniques.

First, we cover the overview and basic usage of LRTK Phone, then introduce advanced site-use functions in sequence, such as AR-based coordinate guidance (layout work), point-cloud scanning with a smartphone for as-built management, and photogrammetric positioning. At the end of the article, you’ll find the benefits of introducing LRTK Phone and an FAQ answering common questions. If you want to streamline surveying and as-built management on site, this article will be a useful reference.

Table of Contents

• What is LRTK Phone?

• Basic operations of LRTK Phone

• AR guidance: coordinate navigation anyone can use

• 3D measurement and as-built management by point-cloud scanning

• Precise site records with photogrammetric positioning

• Benefits of introducing LRTK Phone

• FAQ

What is LRTK Phone?

LRTK Phone is a high-precision RTK-GNSS positioning device used in combination with a smartphone. Despite its compact, lightweight design (approximately 125 g, thickness 13 mm (0.51 in)) and pocketable size, it includes a built-in battery and antenna and functions as a surveying instrument on its own. Attach it to your smartphone with the dedicated attachment, launch the dedicated app, and precision positioning, 3D measurement, and layout (setting out) tasks that previously required specialized equipment become possible.

The key feature is centimeter-level accuracy (half-inch accuracy): by applying RTK (real-time kinematic) corrections using signals from multiple satellites such as GPS and GLONASS, positions can be determined with errors within a few centimeters (within a few inches). In addition to earth coordinates (latitude, longitude, height), plane rectangular coordinate system values and geoid heights are automatically calculated, so even non-surveyors do not need to worry about unfamiliar coordinate transformations. Acquired position data are plotted immediately on the smartphone map screen and can be uploaded to the cloud and shared with one tap.

LRTK Phone is truly a solution that makes the smartphone a universal surveying instrument. For site construction managers and workers, it is a reliable tool that enables precise positioning whenever needed. For professional surveyors, it supports and streamlines routine surveying tasks. From the next chapter, we will look concretely at its basic operations and uses.

Basic operations of LRTK Phone

The basic usage of LRTK Phone is very simple. Below is a summary of the basic procedure to measure a single point on site.

• Attach and prepare the device: Attach the LRTK Phone receiver to your smartphone. A dedicated phone case or holder is provided for one-touch attachment and removal. Power on the device and launch the LRTK app on your phone.

• Set positioning mode: When you start positioning in the app, it will automatically begin acquiring GNSS satellites. For high-precision positioning, connect to a network RTK service (correction information such as Ntrip) or use the LRTK Phone’s support for the QZSS “Michibiki” CLAS signal. When correction reception yields a “Fix” positioning status, you are ready. ※ Even if outside network coverage, CLAS-capable models can apply corrections without communication.

• Measure the point: Move the smartphone to the location you want to measure and tap the app’s “position” button. For example, to record coordinates of a point on the ground, place the included staff or a monopod (optional) at that point, stabilize it, and press the button. The latitude, longitude, and height of that point will be recorded. Date/time and positioning status (RTK Fix/Float, etc.) are saved automatically, and you can name points and add notes.

• Check and save data: Measured coordinates are plotted on the in-app map and numeric data are shown on the screen. If needed, take multiple measurements and average them in the app to improve accuracy (for example: averaging dozens of measurements can approach millimeter-level accuracy). Data are stored on the smartphone and can be reviewed in a list at any time.

• Upload to the cloud: When measurement is complete, synchronize the data to LRTK Cloud with one tap. Once uploaded to the cloud, the site’s positioning results can be viewed immediately from an office PC via a web browser. By issuing a share link, clients and subcontractors can access the data without logging in. On-site recorded coordinate data can also be downloaded as CSV or SIMA formats and imported into CAD software for post-processing.

As described above, basic single-point surveying with LRTK Phone is completed with the intuitive operation of “point the smartphone and press a button.” There is no need to record by hand in paper field books, greatly reducing errors and rework. It is easy enough for beginners to learn in minutes, yet the data obtained rival existing surveying equipment in precision.

AR guidance: coordinate navigation anyone can use

One advanced application of LRTK Phone is the AR guidance function. This displays augmented reality guidance to lead the user to a specified coordinate, greatly simplifying layout tasks such as stake setting and setting out.

For example, when you want to place a stake at a position specified in design plans, traditionally a surveyor would use a total station or measure from known points with a tape measure. With LRTK Phone’s AR guidance, the target point is displayed on the phone’s map or camera view, and you simply follow the on-screen arrows and guides to reach the target. It’s like having the smartphone say, “Dig here” or “Drive the stake here.”

Coordinate guidance does not require difficult操作. Even inexperienced field workers can use it intuitively, finding the target point with centimeter-level accuracy. Buried boundary markers hidden in vegetation or reference points covered by snow can be located using AR markers displayed on the phone screen. Because construction staff without surveying expertise can perform layout themselves, waiting times are reduced and personnel needs can be cut.

AR guidance is useful not only for stake setting during construction but also for inspection and maintenance of completed structures. For example, if the positions of buried pipes previously measured and registered are displayed in AR on site, the risk of damaging pipes during subsequent excavation is reduced. Visualizing boundary lines or design alignments on the ground via AR helps clients and contractors share the intended finished appearance. LRTK Phone’s AR guidance realizes site “visualization” and enables anyone to perform accurate positional tasks without getting lost.

3D measurement and as-built management by point-cloud scanning

Next is the smartphone point-cloud scanning feature. With LRTK Phone and a compatible smartphone, you can perform three-dimensional site surveying without a dedicated 3D laser scanner. Using the phone’s camera and LiDAR sensor, you can scan surrounding structures and terrain, recording them as a dense collection of points (point-cloud data).

Typical smartphone 3D scanning often lacks absolute coordinate information on the acquired point clouds, causing distortions when combining multiple scans. However, because LRTK Phone always knows its own position with cm level accuracy (half-inch accuracy) while scanning, it can assign accurate global coordinates to all acquired points. Even when walking to scan a wide area, you obtain high-precision 3D data without positional drift or distortion. The ability for anyone to perform point-cloud measurement with absolute coordinates using only a smartphone greatly lowers the barrier for on-site 3D measurement.

The scanning procedure is also simple. Start point-cloud scan mode in the app and move the smartphone around as if surveying the area you want to record. In about five minutes of scanning while walking, you can generate point clouds for a road or a wide slope. Objects that were previously difficult to measure—such as slopes or the underside of bridges—can be captured by pointing the phone from the ground. LRTK Phone can acquire point clouds for targets approximately 60 m (196.9 ft) away, reliably capturing distant structures. Also, if GNSS reception is lost at multiple positions during acquisition, the device’s IMU and the phone’s AR technology estimate position and continue recording a continuous point cloud (an indoor positioning mode is also provided, useful under bridges, etc.).

The resulting point-cloud data can be used for various measurements and analyses on LRTK Cloud. Upload the on-site point cloud to the cloud to view the 3D data in a PC browser without installing dedicated software. You can measure arbitrary distances between two points on the point cloud or calculate area and volume with a single click.

This point-cloud measurement capability dramatically improves as-built management in civil engineering. For example, after earthwork for embankments or cuts, scan the terrain and compare the result with the design 3D model to instantly compute required fill or cut volumes. On LRTK Cloud, the design model and current point cloud can be automatically aligned and displayed as a color-coded heatmap. Green and blue areas indicate conformity with the design, while red indicates surplus or deficit at a glance. Because outputs can be generated in data formats compliant with the Ministry of Land, Infrastructure, Transport and Tourism’s as-built management guidelines, point clouds acquired with LRTK Phone can be used as deliverables for inspections.

Previously, as-built volume calculations and shape verification required survey teams to measure many points on site or bring heavy laser-scanning equipment. With LRTK Phone, field workers themselves can acquire 3D point clouds quickly and complete necessary calculations on site. In large projects, combining drone surveying can make point-cloud generation even more efficient, but for small to medium sites, LRTK Phone alone enables “walk-and-measure, immediate output.” This convenience increases the frequency of as-built checks and quantity estimation, improving quality control accuracy.

Precise site records with photogrammetric positioning

LRTK Phone also includes a useful photogrammetric positioning function for site documentation and reporting. This records the exact coordinates and camera orientation (heading) of the photo’s capture point along with photos taken by the smartphone. Ordinary smartphone photos can save geotags, but their accuracy is on the order of meters and insufficient for construction management. With LRTK Phone, you can save capture locations at cm level accuracy (half-inch accuracy), making photos more reliable site records.

Usage is simple. In the LRTK app’s “positioned photo” mode, take a picture with the camera and the photo file will be automatically linked with the corresponding coordinate data (latitude, longitude, height) and shooting direction. For example, when inspecting a bridge and photographing a crack in a girder, it can be hard later to determine exactly which part of the bridge the photo shows. If you used the positioned photo function, the photo’s location and direction are recorded, allowing the photo to be overlaid on point-cloud data or drawings in the cloud. You can then share “which location the crack was found at” together with spatial information.

An advanced application called target photogrammetry is also available. Using a LiDAR-equipped smartphone, you can measure the coordinates of a target located a short distance away from the camera. For example, you can positionally measure a sign placed in an inaccessible area or a point on a high structure from a safe distance. Internally, this is an extension of positioned photos that estimates target location by combining measurements from multiple directions and AR technology. Target photogrammetry is an advanced function available on the latest smartphones (such as Pro models with high-performance LiDAR sensors) and further expands on-site measurement capabilities.

Combining positioned photos and point-cloud data significantly enhances the quality of site records. For example, if you capture a 3D record of an entire bridge with point-cloud scanning and manage high-precision geo-referenced photos of key points in the cloud, you can link structural shape and detailed conditions. Having photos paired with coordinates reduces the effort to create photo logs and ensures that you can identify “the same spot as before” during future inspections.

Benefits of introducing LRTK Phone

As you have seen, LRTK Phone brings a variety of revolutions to on-site positioning work. Here are the main benefits of introduction, organized by user perspective.

• For beginners and non-specialist staff: It is easy to use with intuitive smartphone-based operation, so specialized surveying knowledge is not required. Training costs are low, and LRTK beginners can become proficient quickly. Field workers who were not accustomed to operating surveying instruments can conduct required measurements themselves, expanding their capabilities.

• For field workers: The small pocketable device can be carried at all times, enabling immediate measurement whenever needed. There is no need to take heavy equipment out of storage and set it up. Because light measurements such as stake position checks and self-inspections of as-built can be completed by on-site staff, waiting times and setup complexity are reduced. AR guidance to visualize buried utilities also contributes to improved safety.

• For surveyors and technicians: As a multifunction surveying instrument with high-precision RTK-GNSS and various sensors, it meets professionals’ demands for accuracy and reliability. From single-point surveys to point-cloud measurement and positioned photos, and continuous positioning for longitudinal and cross-sectional acquisition, one person can handle many tasks, contributing to labor savings and increased efficiency for surveying teams. Tasks that were previously outsourced can be insourced, and as-built checks that were rarely performed can be conducted more frequently, improving workflow.

• For managers and executives: Using LRTK Phone accelerates site digitalization and DX. Because data flow from site to the cloud is immediate, progress and construction quality can be checked remotely, accelerating decision-making. Equipping every employee with surveying functionality improves productivity, reducing labor and outsourcing costs. Moreover, it represents the adoption of cutting-edge technology aligned with the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction and ICT construction initiatives, enhancing competitiveness and demonstrating quality improvements.

In summary, LRTK Phone is a revolutionary tool that combines “ease of use” and “high precision.” With simple LRTK surveying, site measurement tasks are no longer the sole domain of specialists—site staff can become data collectors, creating new workflows. Use this technology that overturns conventional wisdom to streamline and sophisticate surveying and measurement work on your sites.

FAQ

Q: How does LRTK Phone achieve high-precision positioning?

A: LRTK Phone combines a high-precision GNSS receiver with a smartphone to perform RTK (real-time kinematic) positioning. By applying network correction information (or the Michibiki CLAS signal) to signals from multiple satellites, it improves positioning accuracy to about 1–2 cm. It provides surveying-level precision far beyond a smartphone’s native positioning.

Q: Can beginners use it? Is special training required?

A: Yes. Basic operations are very simple, so beginners can use it immediately. Positioning is done by pressing buttons in the smartphone app, and AR displays are intuitive. While surveying expertise is not necessary, some basic knowledge (for example, what coordinates are) helps make better use of the data. The manufacturer provides manuals and support, and on-site training is brief.

Q: Are there requirements for smartphone models or conditions?

A: The device is used with iOS smart devices (smartphones and tablets) running the dedicated app. High-end recent models have better camera and sensor performance to fully utilize LRTK Phone features. Models equipped with LiDAR enable advanced features such as point-cloud scanning and target photogrammetry. The recommended models are the latest Pro series smartphones. Check official information for the full list of supported devices.

Q: Is the positioning accuracy really centimeter-level? What kind of errors occur?

A: Under proper satellite reception and with RTK corrections yielding a Fix solution, horizontal positioning of approximately ±1–2 cm (±0.4–0.8 in) and vertical accuracy of about ±2–4 cm (±0.8–1.6 in) can be expected. This is far more precise than typical handheld GNSS devices or standalone smartphone GPS. Average positioning in a static state or in open areas with many satellites can yield even better accuracy. However, occasional larger errors can occur due to surrounding obstructions or atmospheric conditions, so for critical surveying outcomes, we recommend confirming by taking multiple measurements.

Q: Can it be used in remote mountain areas or sites with no infrastructure where there is no network coverage?

A: Yes. LRTK Phone can be used even in out-of-coverage areas. Coverage-capable models can receive correction information without the internet via private high-precision GNSS correction services or Japan’s Michibiki CLAS. Therefore, centimeter-level positioning is maintained in mountain areas or disaster sites without cellular coverage. However, in environments where satellite signals cannot reach at all (such as underground or in tunnels), positioning is difficult. In such cases, use the LRTK app’s indoor positioning mode to track positions relative to a reference point in an area with signal reception.

Q: How long does the battery last? Can it be used for long periods on site?

A: The LRTK Phone unit is powered by an internal battery and is designed to operate continuously for about half a day to a full day in typical surveying use (varies by usage and environment). If the battery runs low, you can continue using it while charging with a mobile battery. The device is also designed with durability in mind, resisting some rain and dust for outdoor use. However, as with any electronic device, avoid extreme conditions such as prolonged heavy rain; using a waterproof case or cover for additional protection is recommended.

Q: How can measurement data be used? Can it interoperate with other software?

A: Measurement data can be used immediately as maps or point clouds within the LRTK app and LRTK Cloud. Point data can be exported in CSV or SIMA formats, and point clouds can be exported in LAS format, allowing import into common CAD and point-cloud processing software. Conversely, design drawings and 3D models can be uploaded to LRTK Cloud for comparison with on-site point clouds, enabling two-way use. Even without special viewers or high-performance PCs, stakeholders can review data via the cloud, which is another advantage.