LRTK Phone How Accurate Is It? The Capabilities of Smartphone cm-Level Positioning

Table of Contents

• What is LRTK Phone?

• How smartphones achieve cm-level positioning (RTK technology)

• Verifying the accuracy of LRTK Phone

• Use cases unlocked by centimeter-level positioning

• What is simple surveying with LRTK

• Conclusion

• FAQ

When it comes to smartphone GPS positioning, errors of several meters have been the norm. However, in recent years, smartphones have become capable of surprisingly high-precision positioning. A representative example is Refixia’s "LRTK Phone". With LRTK Phone, the typical GPS error of about 5-10 m (16.4-32.8 ft) can be reduced to as little as about 1 cm (0.4 in). How accurate is LRTK Phone in practice? This article explains in detail the mechanism and performance of centimeter-level positioning achievable with a smartphone, and the use cases that follow. At the end, we also introduce simple surveying using LRTK.

What is LRTK Phone?

LRTK Phone is a GNSS receiver device that can be attached to a smartphone to achieve centimeter-level high-precision positioning. It was developed by Refixia Inc., a startup spun out of Tokyo Institute of Technology, with the concept of “turning a smartphone into a pocket-sized, all-purpose surveying instrument.” In practice, simply attaching LRTK Phone to an iPhone or Android smartphone (or tablet) enables high-precision position measurement and surveying tasks that previously required professional surveying equipment to be done with just a smartphone.

The LRTK Phone unit is small and lightweight, weighing about 125 g and about 13 mm (0.51 in) thick—pocket-sized. It houses a high-performance RTK-GNSS receiver, an antenna, and a battery, and is used integrated with a smartphone. It can be attached and detached in one touch using a dedicated smartphone case, making it easy to fit when needed. Because it has a built-in battery, there is no need to worry about power even when used on-site for long periods (almost an entire day). It connects to the smartphone via Bluetooth or similar, and positioning is performed through a dedicated app. Since this single device handles positioning, data recording, and sharing, it truly functions as a “universal surveying instrument.”

How smartphones achieve cm-level positioning (RTK technology)

Why can a smartphone achieve ultra-high accuracy at the centimeter level? The key is the positioning technology called RTK (Real Time Kinematic). RTK is a method that uses signals from multiple GNSS satellites and derives the relative position to a base station with high precision. Ordinary GPS positioning yields errors of several meters due to satellite signal errors (ionospheric delays, satellite clock errors, etc.). RTK, however, compares the known location of a nearby reference point (base station) with the observation data of the rover (the smartphone) in real time, canceling atmospheric errors and enabling relative positioning on the order of centimeters.

LRTK Phone contains a GNSS receiver compatible with high-precision RTK positioning. A notable feature is that it is triple-frequency compatible. Whereas conventional GNSS receivers were often single-frequency (L1 only), LRTK Phone can receive multiple bands such as L1, L2, and L5. Multi-frequency support improves the correction of ionospheric errors and leads to faster and more stable convergence to a fixed solution. As a result, smartphone-based centimeter-level positioning with higher reliability than before becomes possible.

RTK positioning normally requires base station correction information, but LRTK Phone can use not only internet-based reference station networks but also the centimeter-level augmentation service (CLAS) broadcast by Japan’s quasi-zenith satellite “Michibiki.” By receiving CLAS, high-precision positioning is possible even in environments without internet connectivity, such as mountainous areas or at sea where cellular signals do not reach. In fact, the ability to perform RTK positioning even outside of communication coverage thanks to Michibiki’s augmentation signals proves powerful in disaster sites. For example, during the 2023 Noto Peninsula earthquake damage survey, where communication infrastructure was disrupted, LRTK Phone was used effectively to perform accurate positioning and recording with only compact equipment.

Thus, by combining advanced GNSS positioning technology and communication technologies, LRTK Phone enables acquisition of precise location information that was previously impossible with a smartphone alone.

Verifying the accuracy of LRTK Phone

So how accurate is it in practice? LRTK Phone is nominally “centimeter-level” in accuracy, but let’s look at specific numbers. According to manufacturer tests, when repeatedly measuring the position of a fixed point, the single-measurement error (standard deviation) was about 12 mm (0.47 in). That is an error of about 1.2 cm (0.5 in), already orders of magnitude more precise than conventional GPS. Furthermore, by averaging multiple observations using the LRTK app, an error of about 8 mm (0.31 in) (0.8 cm (0.3 in)) was achieved. Eight millimeters is under 1 cm—truly in the “sub-centimeter” realm. Under favorable conditions, horizontal positioning has been confirmed to achieve accuracy below 1 cm (0.4 in).

These figures are comparable to professional surveying instruments. General high-precision GNSS receivers and surveying equipment also report errors of a few centimeters for RTK positioning on flat terrain, so LRTK Phone’s performance is comparable. Of course, actual accuracy depends on environmental conditions. The best results are obtained in open areas without obstructions; in urban canyons or forests, where satellite signals are reflected or attenuated, positioning can become unstable or errors increase. Still, this is a level of precision enhancement unattainable by a smartphone’s standalone GPS. Refixia’s CEO has emphasized this, noting that “while ordinary GPS has errors of about 5-10 m (16.4-32.8 ft), LRTK can measure accurately to about 1 cm (0.4 in),” underscoring LRTK Phone’s high positioning accuracy.

LRTK Phone also performs well in the vertical (elevation) direction. RTK positioning generally has slightly larger errors vertically than horizontally, but it still stays within a few centimeters. For example, the tests above measured horizontal positions under 1 cm (0.4 in) and vertical positions within a few centimeters (a few inches). This level is sufficient for checks such as finished surface elevation confirmation at construction sites.

Overall, LRTK Phone’s accuracy lives up to its “centimeter-level” name. It represents a clear step up from conventional smartphone GPS and is proven robust enough for serious positioning and surveying applications.

Use cases unlocked by centimeter-level positioning

When centimeter-level accuracy becomes available on a smartphone, the scope of on-site tasks and services expands greatly. Below are the main use cases and benefits enabled by LRTK Phone.

• Improving efficiency of surveying and layout tasks: On construction and civil engineering sites, surveyors frequently use high-precision instruments for establishing control points (layout) and as-built checks. With LRTK Phone, site supervisors or workers can perform simple surveying tasks themselves and obtain or verify coordinates instantly. For example, building placement checks or guiding the installation location of structures (coordinate navigation) can be done accurately by viewing coordinate information on the smartphone screen in real time.

• Use in infrastructure inspection and surveys: For road and bridge inspections, or post-disaster damage surveys, it is important to tag photos with accurate location coordinates. With LRTK Phone, photos taken on a smartphone can be automatically linked and saved with cm-precision location information and shooting orientation (cm level accuracy (half-inch accuracy)). For example, recording the location of concrete cracks or surveying the extent of a landslide becomes easier: photos and geographic coordinates are shared to the cloud immediately, allowing precise situational understanding on a map later. In situations requiring rapid data collection, such as disaster sites, this one-stop positioning-and-recording workflow is highly useful.

• AR visualization and design verification: High-precision positioning from LRTK Phone can be combined with smartphone AR (augmented reality). For example, if you have location data for underground pipes or cables, you can display 3D models or markers at precise locations in AR on-site through the smartphone. During subsequent excavation, workers can view the positions of buried utilities through the phone to avoid damaging pipes. You can also project design lines or structural models onto the site to check whether placements match the plan. Historically, AR displays suffered from positional drift, but LRTK-level accuracy enables an AR experience that does not drift while walking, supporting consistent visualization. This helps stakeholders share a completed-image on-site and speeds up consensus building.

• 3D measurement and point cloud acquisition: Combining LRTK Phone with a smartphone camera makes 3D point cloud surveying easy. By moving the phone to scan the camera view within a dedicated app, surrounding terrain and structures can be captured as point cloud data. On iPhones, even models without LiDAR can generate point clouds via photogrammetry techniques. The resulting point clouds are already tagged with absolute coordinates (world coordinates), so they can be overlaid onto maps or CAD drawings in post-processing. From on-site measured terrain data, you can perform earthwork volume calculations or automatically generate as-built drawings in a short time. For instance, you can measure the fill volume of a large development site on-site and immediately check differences from the plan.

With centimeter-level positioning available on everyday smartphones, the workflow of “measure and check on the spot” becomes widespread on sites. Tasks that previously required specialists and expensive equipment can be performed quickly in-house, reducing schedules, improving quality, and cutting costs.

What is simple surveying with LRTK

One productivity-enhancing initiative enabled by LRTK Phone is “simple surveying.” Simple surveying refers to enabling on-site personnel to perform some measurement tasks that used to require professional surveyors. With LRTK, even untrained users can achieve centimeter-level positioning with minimal operation. For example, routine dimensional checks, as-built verification, and site boundary confirmation can be performed immediately as simple surveying tasks.

Specifically, attach an LRTK Phone-equipped smartphone to a pole or monopod, point it at the survey point, and press the app button to record the coordinates (latitude, longitude, height) of that location. Recorded points are automatically synced to the cloud and shared in real time with office staff. This allows quick numeric verification of on-site questions and prompt sharing for decision-making.

Traditional surveying equipment often requires operator training and is expensive. LRTK Phone stands out in that it is usable without training and has low introduction costs. Subscription-based plans are available, lowering initial expenses and reducing adoption barriers for sites. Simple surveying with LRTK can be seen as a new on-site style anticipating a “one-device-per-person” era. LRTK Phone is gaining attention in the construction industry as an essential on-site tool, and many companies have begun trial deployments. There are also cases of delivering 3D as-built results to the Ministry of Land, Infrastructure, Transport and Tourism, showing usage in public projects.

Integrating high-precision positioning into daily operations dramatically speeds up the on-site PDCA cycle. If simple surveying with LRTK Phone spreads, more flexible and efficient construction management and maintenance practices will become possible.

Conclusion

We have reviewed the capabilities and use cases of cm-level positioning achievable with smartphones. With LRTK Phone, centimeter-level high-precision positioning that was previously difficult is now possible in the palm of your hand, contributing to efficiency across construction, civil engineering, inspection, and surveying. Its measured accuracy can fall below 1 cm (0.4 in), matching professional equipment. Features such as operation outside communication coverage, AR visualization, and point cloud measurement combine to make it a genuine “universal surveying instrument” that is transforming fieldwork.

As high-precision positioning becomes accessible, the barrier to “measuring” has been greatly lowered. The era where anyone on-site can take quick measurements without hiring a specialist is coming. Simple surveying with LRTK supports this new work style. A world in which precise location information is available on a smartphone is imminent, and its future applications are expected to expand further.

FAQ

Q. What kind of product is LRTK Phone?

A. It is a small, high-precision GNSS receiver attached to a smartphone. It dramatically improves smartphone GPS accuracy to enable centimeter-level positioning. It is a pocket-sized device that mounts to a dedicated case and contains the antenna, GNSS module, and battery, with positioning data obtained and managed via a dedicated app.

Q. How accurate is LRTK Phone?

A. Horizontal errors are typically about 1–2 cm (0.4-0.8 in), and under good conditions can be below 1 cm (0.4 in) (on the order of several millimeters). Tests recorded about 12 mm (0.47 in) for single measurements and about 8 mm (0.31 in) when averaging. Vertical errors are within a few centimeters (a few inches), making it comparable to professional surveying equipment.

Q. How can such high accuracy be achieved on a smartphone?

A. Because it uses RTK (Real Time Kinematic) positioning. By using correction information from base stations to cancel satellite positioning errors, centimeter-level accuracy is achieved. LRTK Phone supports multi-frequency GNSS signals and can also use Japan’s “Michibiki” augmentation signals (CLAS), enabling high-precision positioning even outside cellular coverage.

Q. What preparation or environment is required to use it?

A. Basically, you need a compatible smartphone (iPhone or Android), the LRTK Phone unit, and the dedicated app. Initial setup is simple: install the app and connect the device to start positioning. For high-precision positioning, an outdoor environment where GNSS satellite signals can be received is preferred (it cannot be used indoors or underground). Internet connectivity helps stabilize and speed up positioning, but in areas without connectivity, receiving Michibiki’s correction data can maintain accuracy.

Q. What are the advantages and disadvantages compared to traditional surveying equipment?

A. The main advantages are portability, ease of use, and lower cost. LRTK Phone is pocket-sized and ready to use when needed. No professional training is required, and operation is intuitive. It is also cheaper than typical surveying GNSS equipment, and subscription plans can reduce initial investments. Disadvantages include increased smartphone battery consumption during prolonged use and that it cannot be used entirely indoors. However, for outdoor positioning it offers accuracy comparable to traditional equipment and sufficient operating time (the device itself has a long-lasting battery), making it suitable for most field tasks.

Q. In what situations is LRTK Phone useful?

A. It is useful in a wide range of situations requiring high-precision location information, such as construction and civil engineering surveying, infrastructure inspection, and disaster situation surveys. Examples include setting control points and as-built checks on construction sites, routine inspection rounds for bridges and roads, and photo records at disaster sites. It is also being used in advanced applications like AR visualization of drawings and buried utilities on-site. In short, LRTK Phone helps in any situation where knowing an accurate position is beneficial.

Q. Will centimeter-level positioning become standard on smartphones in the future?

A. Built-in smartphone GPS chips are improving year by year, but achieving centimeter-level positioning solely with an internal chip is still difficult at present. External devices like LRTK Phone and augmentation services remain key. Demand for high-precision positioning is growing, and the future will likely see smartphones combined with peripheral devices routinely providing centimeter-level accuracy. LRTK Phone is a forerunner of that trend. In the long term, smartphones themselves may include multi-frequency GNSS and correction reception as standard, but for now solutions like LRTK are the most practical way to achieve cm-level positioning.