A New Era of Smartphone Surveying: LRTK Enables Centimeter Precision with a Single Phone

Smartphone-based surveying, so-called “smartphone surveying,” is now attracting considerable attention in surveying, construction, and civil engineering fields. If site as-built management and terrain measurement can be completed with a single smartphone, it would be a great help to industries suffering from a shortage of skilled personnel. However, conventionally, smartphone positioning has had errors on the order of meters and could not be used where high accuracy is required. Added to that, the aging of skilled surveyors and labor shortages have become serious, and with the 2024 work-style reform laws restricting overtime, the need for simple yet high-accuracy surveying methods has grown. Against this backdrop, a solution called LRTK, which achieves centimeter-level positioning with a single smartphone by using a small device attached to the phone and the latest satellite augmentation technology, has appeared. This article systematically explains the current state and challenges of smartphone surveying, the RTK technology that is key to high accuracy, the background and features of LRTK, its practical accuracy and usability, effects of introduction, points of caution, and future prospects. At the end of the article we also introduce an actual case in which LRTK was used for simple surveying, so please read on with the question “Could this work at my site?” in mind.

Current State and Challenges of Smartphone Surveying

In recent years, improvements in smartphone performance have led to the use of phones for field surveying. In particular, the latest iPhones and iPads are equipped with LiDAR (light-based laser ranging sensors), enabling rapid capture of surrounding terrain and structures into point cloud data (3D scanning) simply by pointing the device. Using photogrammetry apps, you can also create 3D models of a site with a smartphone. Such “smartphone surveying” is powerful for understanding complex terrain and making quick records, enabling measurement of complex rock formations and confined spaces that were previously difficult to measure. It also has great potential as an easy way to record dangerous areas where people cannot enter or temporary conditions before buried utilities are backfilled.

However, a major challenge for current smartphone surveying has been accuracy. Standalone positioning with a smartphone’s built-in GPS typically has errors of about 5-10 m (16.4-32.8 ft) due to satellite signal errors and atmospheric effects. For map app navigation, an accuracy of a few meters is acceptable, but it is nowhere near sufficient for surveying that requires centimeter-level precision, such as setting out buildings or as-built confirmation in civil engineering. As a result, the field has continued to rely on total stations and conventional heavy GNSS equipment, with smartphones serving only as auxiliary positioning tools. Satellite positioning also performs best in open-sky environments; in forests or urban canyons, signal blockage and multipath (reflections) worsen errors. In practice, using a handheld GPS under trees can result in errors of more than 5 m (more than 16.4 ft), so the reality is that “high-precision measurement anywhere with just a smartphone” has been difficult where signal conditions are poor.

Furthermore, conventional high-precision surveying instruments require specialized knowledge to operate and the devices themselves are heavy—often several kilograms—so operation often requires two or more people. Equipment costs are also high, creating a high barrier to adoption for small contractors and local governments. With the decline of experienced surveyors, maintaining these traditional methods has limits, and a new approach that combines labor saving with high accuracy has been sought.

Explanation of RTK Positioning Technology

The technology that has provided a leap in the “accuracy” challenge of smartphone surveying is RTK positioning. RTK (Real-Time Kinematic) is a method in which positioning data are shared in real time between a reference station (base) and a rover (mobile) to cancel common error sources. Simply put, by applying correction information from a reference point to GNSS (GPS, GLONASS, Galileo, etc.) observation data, the errors that were several meters in standalone positioning can be reduced to several centimeters. Since RTK became practical from the 1990s onward, reference points that previously required static observation over half a day could be obtained in seconds to minutes, and RTK has been widely used in civil engineering surveying and machine control.

Typical RTK accuracy is said to be about 1–2 cm horizontally and 3–4 cm vertically, and the major advantage is that this accuracy can be obtained in real time. However, conventional RTK operations require dedicated radio equipment or a communication environment to obtain base station data via the Internet, and usage has been limited to within a radius of roughly a dozen kilometers from the base station. Commercial correction services may also require subscription contracts, so RTK has not been universally convenient.

A next-generation method called PPP-RTK, which realizes RTK-level corrections without a local base station, has emerged. In Japan, the quasi-zenith satellite “Michibiki” provides the CLAS (Centimeter-Level Augmentation Service) that implements PPP-RTK. CLAS distributes nationwide correction information generated from the Geospatial Information Authority of Japan’s electronic reference station network directly from satellites on the L6 band. If a receiver is CLAS-compatible, it can achieve real-time centimeter-level positioning from the satellite augmentation signal alone without an Internet connection. It is, in effect, a “satellite-based wide-area RTK,” and a key feature is that it can be used free of charge within Japan. Unlike network RTK (VRS) which requires constant communication via mobile networks or paid services, CLAS allows centimeter accuracy to be maintained even in communication blackouts such as mountainous areas or at sea, as long as the sky is visible. Note that CLAS is based on domestic reference station data, so the service is Japan-only and not available abroad. Nevertheless, the development of high-accuracy satellite positioning technologies like this has made an era of “anyone, anywhere with centimeter accuracy” increasingly realistic.

Background and Features of LRTK

So what technology is the key to turning a smartphone into a full-fledged surveying instrument? One answer is LRTK (pronounced “el-ar-tee-kay”). LRTK is a solution that combines a “ultra-compact RTK positioning device for smartphones” with a dedicated app and cloud service, strongly supporting smartphone surveying. It was developed to supplement the centimeter precision that a standalone smartphone could not provide, leveraging advances in RTK and CLAS described above and improvements in smartphone GNSS support. Recent smartphones support multi-frequency and multi-constellation GNSS reception, making an environment capable of handling high-precision positioning data. On that foundation, LRTK was developed from the idea of “integrating portable RTK equipment with a smartphone so anyone can use it.”

The dedicated LRTK receiver, called the LRTK Phone, is a small device designed to attach to a smartphone. Its specific features include the following:

• Compact, lightweight design: The device body weighs about 165 g and is as light as a smartphone, with a thickness of only about 1 cm (0.4 in). It can be attached to the back of a phone like a sticker, making it easy to carry as a pocketable surveying instrument. GNSS receivers that once required tripods can now be attached to a smartphone and used to position while holding it in one hand. There is no longer a need to carry heavy equipment and run around a site with multiple people, dramatically improving mobility.

• Centimeter-level high-precision positioning: With a high-sensitivity GNSS antenna built in and RTK processing, the device can obtain position coordinates with approximately ±1–2 cm horizontally and ±3 cm vertically. That accuracy rivals national first-order surveying instruments, and comparison tests with high-precision GNSS equipment have even shown errors within 5 mm (0.20 in). Considering that a smartphone’s built-in GPS could only achieve 5–10 m errors, LRTK has effectively given smartphones surveying-grade accuracy. Because height is measured accurately as well as latitude and longitude, the device is suitable for terrain surveys and as-built management.

• Long battery life & easy connection: The device runs on an internal battery for about 6 hours of continuous operation and can be charged via USB Type-C. With a spare mobile battery, it can withstand long survey sessions. Connection to the smartphone is seamless via Bluetooth or Lightning, and high-precision positioning starts as soon as the dedicated app is launched. No complex initial setup or dedicated controller is required—if you have a smartphone, you can start using it immediately.

• Positioning possible even outside communication coverage: LRTK supports the CLAS satellite augmentation signals provided by Japan’s Michibiki, so it can receive correction information directly from satellites and achieve centimeter-level positioning even in environments where mobile phone signals do not reach, such as mountainous areas or disaster sites. While Ntrip-based network RTK via the Internet has been common, LRTK can maintain high-precision positioning via satellite even when communication infrastructure is down (※where communication is available, LRTK also supports network RTK using the Geospatial Information Authority’s electronic reference station network, allowing you to choose the appropriate mode).

• Sensor integration for temporary satellite outages: Even when satellite signals are temporarily unavailable, LRTK supplements positioning by integrating with the smartphone’s sensors and camera. Under bridges or in dense woods where RTK may be interrupted, LRTK can continue positioning for short periods using iPhone/iPad AR (augmented reality) technology and inertial sensors for dead reckoning. Some drift accumulates during movement, but the ability to continuously acquire data in areas that were previously impossible to measure is a major advantage.

• Smartphone-native versatile functions: The LRTK app includes many features that leverage smartphone capabilities beyond high-precision positioning. For example, by using an iPhone’s LiDAR scanner and camera, you can scan a site and obtain high-precision 3D point cloud data with one touch. The resulting point cloud is tagged with global positioning coordinates (latitude, longitude, height), so there is no need for post-processing alignment like with conventional laser scanners. You can also overlay 3D design models on site video with AR display to verify construction against plans without misalignment. The app includes a “survey photo” function that tags captured photos with latitude, longitude, and orientation at the time of positioning, useful for equipment inspection records and change-over-time comparisons. Other functions include coordinate navigation that guides you to specified coordinates with an arrow (useful for staking out points) and tools to measure length, area, and volume on obtained point clouds—an all-in-one design that enables a single smartphone to meet various surveying needs. The value of completing tasks that previously required separate devices and software using only LRTK and a smartphone is considerable.

• Cloud integration for data sharing: Positioning points and point cloud data acquired in the field with LRTK can be synchronized to the cloud with one tap. On the dedicated LRTK cloud service, you can view coordinate points, tracks, photos, and point cloud models on a map or 3D view, perform coordinate transformations, measure distances and areas, and create cross-sections from point clouds in a browser. By sharing a URL with stakeholders, they can review results without dedicated software. Because web-based processing enables simple analysis without expensive point-cloud processing software, data linkage between field and office becomes dramatically smoother.

As described above, LRTK has many features that greatly expand the possibilities of smartphone surveying. It is truly a next-generation device that realizes a “pocket-sized, portable surveying instrument.”

Actual Accuracy and Usability

The accuracy LRTK achieves has been confirmed in field measurements to be comparable to professional surveying instruments. Horizontal positions are roughly ±1–2 cm (±0.4–0.8 in), and vertical accuracy is about ±3 cm (±1.2 in), which is comparable to conventional optical surveying and high-end GNSS equipment. Experiments have reported differences of less than 5 mm (0.20 in) compared with first-class instruments, demonstrating surveying precision that is surprising for a smartphone. However, obtaining this accuracy requires that the solution called a “Fix solution” be established by receiving augmentation signals from satellites. If the LRTK app status displays “Fix,” centimeter-level accuracy is achieved; if it has not reached Fix (a “Float” state), errors are somewhat larger, though still far better than standalone positioning. Typically, in open-sky outdoor conditions, positioning converges to Fix in about 30 seconds to 1 minute from startup.

In terms of usability, LRTK is designed to be operable without specialized knowledge. The actual surveying procedure is very simple and typically follows this flow:

• Prepare the device and app: Attach the LRTK unit to the back of the smartphone and turn the unit on. On an iPhone, launch the dedicated LRTK app and connect to the unit via Bluetooth. Once ready, move to an outdoor location with as few obstructions as possible.

• Start high-precision positioning: Tap “Start Positioning” in the app; the unit will automatically begin acquiring GNSS satellites. During the first several tens of seconds, errors may be on the order of meters, but as CLAS augmentation signals from Michibiki are received and internal processing proceeds, accuracy will improve. In an open place, the solution generally switches to “Fix” within about 30 seconds to 1 minute, enabling centimeter-level positioning.

• Measure and record points: Move to the point you want to measure and, if necessary, attach the unit to an included monopod (pole) to stabilize it. Press the “Measure” button in the app to acquire coordinates for that point. You can also perform continuous measurements for several seconds and take an average to obtain a more stable value. Once sufficient accuracy is achieved, tap “Save” to store the point on the phone (you can add point names or notes).

• Share and utilize data: Use the saved positioning data as needed. With one tap from the phone, sync to the LRTK cloud and immediately view all survey points in the office PC browser or download CSV files. In the cloud you can measure distances and enclosed areas between multiple points, which aids in creating survey drawings and quantity calculations. Because field data can be shared and analyzed instantly, information sharing and report preparation with stakeholders is smooth.

Thus, the LRTK surveying workflow is extremely simple. High-level surveying skills and complicated equipment operations are no longer necessary. The app is intuitive enough for users unfamiliar with surveying to operate, and the process is essentially “Measure → Save → Share” with button presses. Centimeter-accurate positioning data can be obtained in minutes, allowing additional measurements to be performed between site tasks or rapid responses to sudden measurement requests. LRTK, which has made high-precision positioning so accessible, can truly be described as “transforming a smartphone into a high-performance surveying instrument.”

Effects of Introducing LRTK in Work

Introducing smartphone surveying with LRTK can yield various benefits and effects in field operations. The main benefits are summarized below.

• Labor reduction and improved efficiency: Surveying tasks that previously required two people can be completed by one person with LRTK. For example, as-built surveying typically required one person to hold a pole and another to record, but with LRTK one person can both measure and record points. On one site, using LRTK for stakeout cut required time to less than half of the previous time. This allows surveying tasks to proceed even amid labor shortages and directly improves productivity.

• Cost reduction and lower adoption barriers: Because LRTK only requires a smartphone and a small device, initial investment can be drastically reduced. By leveraging existing smartphones and a relatively low-cost LRTK unit compared to conventional large surveying instruments, small contractors and municipalities that had to outsource high-precision surveys can now adopt the technology affordably in-house. Completing surveying internally with fewer staff also reduces outsourcing costs.

• Improved data accuracy and quality: With LRTK enabling anyone to obtain high-precision field data, information that was previously only partially captured can now be collected comprehensively. For example, scanning a wide area with a phone to create point clouds before and after construction for surface comparison becomes easy. Point cloud data allow visualization of subtle terrain changes and minor as-built differences, improving quality control. Decisions that previously relied on experience or intuition can now be based on data, advancing construction management.

• Real-time information sharing: Using the LRTK cloud for data sharing allows on-site measurements to be shared in real time with headquarters and stakeholders. Upload survey results to the cloud immediately so remote members can view and analyze them in a browser, smoothing communication between field and office. Faster report preparation accelerates decision-making, and this immediate sharing can be critical in disaster response or emergency construction.

• Improved safety: Because smartphone surveying uses lightweight equipment and can measure from a distance, it contributes to worker safety. Sites that were previously dangerous to enter—such as landslide zones or inside tunnels—can be assessed using the phone’s camera and LiDAR for remote 3D measurement. Compared to conventional methods that required personnel to enter hazardous areas, LRTK offers a safer way to collect data.

• Skill transfer and DX support: The intuitive nature of smartphone surveying helps transfer skills to junior engineers and promotes DX (digital transformation). Even without mastering complex surveying theory, younger staff familiar with smartphone operation can be productive quickly, enabling faster onboarding. With national initiatives like i-Construction encouraging the use of 3D survey data, LRTK makes it relatively easy to meet such requirements. As a result, field digitalization and smartification accelerate, contributing to industry-wide work-style reforms and productivity improvements.

In these ways, adopting LRTK can simultaneously achieve labor savings, lower costs, and higher accuracy in field surveying, positively affecting workflows and deliverables. Smartphone surveying is becoming the new norm on sites, and attention is growing as media outlets highlight these advanced technologies.

Points of Caution (Considerations for Introduction)

While LRTK is highly useful, there are several points to keep in mind when introducing and operating it.

• Be mindful of the positioning environment: GNSS positioning performs best with a clear view of the sky. In urban areas surrounded by tall buildings or in forests where satellite visibility is limited, achieving Fix may take longer or accuracy may temporarily drop. Start positioning in as open a location as possible to capture sufficient satellites before measuring to obtain stable results. For sites being measured for the first time, checking satellite reception conditions in advance is advisable.

• Confirm the “Fix solution”: As mentioned earlier, centimeter-level accuracy requires the app to show a Fix state. Check the status display during measurement and record only after Fix is established. If Fix is not achieved, errors may be large, so for critical measurements wait for accuracy to converge or improve reception (move location or wait). Also, satellite outages during measurement can revert the solution to Float, so always be aware of the current positioning mode while working.

• Handle the device and battery carefully: The LRTK unit contains a precision GNSS antenna, so avoid covering the antenna with your hand when attaching it to the phone. Blocking the antenna with your hand during positioning can reduce reception sensitivity. The battery lasts about 6 hours, but for long continuous surveys prepare a mobile battery for charging if needed. In cold climates battery performance can decline, so take measures to avoid excessive cooling.

• CLAS usage and service area: LRTK’s major feature—CLAS augmentation—is available only within Japan. In overseas regions where CLAS is unavailable, you will need to contract with a local RTK correction service accessible via the Internet (LRTK also supports Ntrip network RTK). Even within Japan, Michibiki is not always directly overhead, so there may be times and locations (e.g., mountain shadows, high latitudes) when satellite augmentation is temporarily unavailable. Michibiki satellite numbers are planned to increase, and reception of augmentation signals is expected to improve over time.

• Use in combination with conventional methods: LRTK has the potential to replace many surveying tasks, but in some cases it is advisable to combine it with conventional methods. For example, for millimeter-level deformation monitoring or strict verification of reference heights in very small areas, RTK may not meet the required tolerance; in such cases, additional measurements using total stations or levels can provide verification on the safe side. For legal boundary surveys requiring licensed surveyors, it is appropriate to use LRTK data as supplementary and have qualified personnel finalize official documents. It is important to make appropriate choices by combining new technology with traditional methods according to the purpose.

Future Outlook: The Future Brought by Smartphone Surveying

The innovation of “centimeter-level smartphone positioning” enabled by LRTK is expected to bring significant changes to the civil engineering and construction industries. Several future prospects can be identified.

First, further improvements in high-precision GNSS environments are expected. Japan’s Michibiki system currently operates with four satellites but plans exist to strengthen the constellation to seven satellites including spares. In 2025 an update is scheduled to multi-stream CLAS augmentation signals, greatly increasing the number of satellites that can be corrected at once. This will enable more stable reception of corrections from multiple satellites even in urban areas where satellite visibility is limited, improving both accuracy and availability. Globally, satellite augmentation technologies are evolving as services like Europe’s Galileo launch high-precision offerings. As smartphones begin to support these new augmentation signals, it may become possible to perform smartphone surveying nearly anywhere on Earth.

Next, continuous improvements and proliferation of smartphones will advance the field. Android devices already offer models supporting L1/L5 dual-frequency positioning, and iPhone features such as the “precise location” option are improving positioning accuracy. In the future, standard GNSS capabilities in smartphones may become good enough to provide high accuracy without external devices in some cases. However, dedicated antennas and specialized designs still favor external devices, so the smartphone + auxiliary device configuration is likely to remain mainstream for some time. Regardless, the impact of turning ubiquitous smartphones into surveying tools is enormous and will likely spawn new applications and services.

Also, integration with AR and AI will accelerate. High-precision AR overlays enabled by LRTK—aligning design models with on-site video—will be refined further, perhaps enabling AR glasses to display construction instructions and inspection checks simply by looking at a site. AI could analyze point cloud data automatically for as-built judgment or detect terrain changes in real time and issue alerts. Large amounts of field data collected by smartphone surveying can be combined with digital twin and simulation technologies to optimize construction planning and enhance maintenance management.

Industry-wise, smartphone surveying is expected to become standard on sites. Some progressive construction firms and local governments have already adopted technologies like LRTK and report gains in efficiency and accuracy. Educational institutions may begin incorporating smartphone-based surveying methods into next-generation surveying curricula. At the policy level, smartphone surveying aligns with initiatives like BIM/CIM and i-Construction, and regulatory frameworks that encourage adoption may follow—for example, standards recognizing smartphone measurements for simple as-built management could be developed.

Overall, from 2025 onward the combination of smartphone + GNSS + cloud is likely to become one of the mainstream approaches in civil surveying, serving as a catalyst for labor savings and efficiency in field DX. With the lowering barrier to high-precision positioning, how and by whom the technology is applied will reshape site practices. We encourage engineers to consider adopting LRTK and experience the convenience and innovation smartphone surveying offers. As a member who helps lead the new surveying style, why not ride the wave of this new era?

Case Study: A Situation Where LRTK Simple Surveying Proved Useful

Finally, we introduce one actual use case in which LRTK was deployed on site and produced tangible benefits. For example, in Fukui City, Fukui Prefecture, LRTK Phone was trialed at the recovery sites after the 2022 heavy rain disaster, accelerating surveying of damaged areas. Staff attached LRTK to iPhones and quickly obtained terrain data from the disaster area without dispatching surveyors, allowing necessary measurements to be completed on the spot. As a result, they were able to instantly calculate the volume of collapsed slopes from point cloud data and measure dimensions of damaged roads on site, greatly assisting early recovery planning. The trial results were reported in a news article (https://news.yahoo.co.jp/articles/363a7f5dd8ee7b325503aa13d28fce0c600d67f9), noting that even when communications infrastructure was degraded, the satellite augmentation signal enabled accurate positioning and immediate sharing of site conditions with rear support teams. Being able to perform disaster surveying in-house—rather than relying entirely on specialized agencies—yielded significant cost reductions and faster initial response.

Thus, LRTK-based smartphone surveying is beginning to demonstrate real-world effectiveness. The ability to easily leverage centimeter precision is valuable not only for disaster response but also for routine surveying and construction management. Indeed, the new era of smartphone surveying has begun. Why not consider achieving efficiency and sophistication at your site with simple surveys using LRTK?