Table of contents

• How network RTK works and basics of error correction

• How smartphone RTK (LRTK) changes field accuracy, procedures, and speed

• UX design that enables solo surveying (apps, AR guidance, photo positioning, etc.)

• Compatibility with point cloud scanning, as-built management, CAD and cloud integration

• Real-time office-field collaboration (cloud maps, point sharing, coordinate navigation)

• Time savings, eliminating reliance on specific individuals, safety improvements, applications in disaster response

• Natural introduction and guidance for adopting simplified surveying with LRTK

• FAQ (frequently asked questions)

The fusion of smartphones and RTK (real-time kinematic) technology is bringing major changes to the surveying world. Tasks that traditionally required multiple people can now be carried out by a single person at centimeter-level accuracy using smartphone RTK. By leveraging network-based RTK correction services, positioning can begin on site immediately without installing a dedicated base station, dramatically shortening surveying procedures and required time. This article starts with how network RTK works and its benefits, then explains how smartphone-mounted RTK systems (LRTK) improve accuracy and efficiency on site. It also covers UX design that supports solo surveying, compatibility with point cloud scanning, cloud integration, AR guidance, productivity and safety improvements, and applications in disaster response. Finally, an FAQ addresses common questions about adopting smartphone RTK.

How network RTK works and basics of error correction

First, RTK (real-time kinematic) is a technology that corrects GPS or GNSS positioning errors in real time, drastically improving positional accuracy. Standalone GPS positioning typically produces errors of several meters (several ft) due to satellite signal errors, but the RTK method uses a base station—whose coordinates are accurately known—to compute those error corrections and apply them to a rover’s positioning data. This reduces what would normally be errors of several meters (several ft) down to several centimeters (several in).

Conventional RTK surveying required installing your own base station near the site and transmitting correction data by radio. Preparing by setting up a tripod and antenna before surveying, and relocating and reinstalling the base station when the survey area is large, consumed time and effort. Also, as the distance between base and rover increases, correction effectiveness diminishes and accuracy degrades, so maintaining high accuracy required baseline distances within a few km. High-performance RTK equipment was also very expensive and required expertise, so it was not a technology everyone could use casually.

Network RTK solves these issues. In network RTK, users utilize a network of reference points (continuous operating reference stations) set up by national or private entities, and a “virtual reference station” is established near the user to provide correction information. The user device sends its approximate location to a server via mobile data, and the server integrates and analyzes data from multiple nearby reference stations to generate correction information (correction data) for a virtual base station near the user in real time. This mechanism, also called VRS (Virtual Reference Station), allows positioning under conditions as if “a reference station were right next to you,” enabling centimeter-level positioning without physically placing a base station on site.

The advantages of network RTK go beyond avoiding per-site base station setup. Because correction information is calculated and provided close to the user at all times, accuracy degradation while moving is suppressed, and uniform high accuracy can be maintained over wide-area surveys. When properly operated, accuracy itself is comparable to traditional local RTK (both can achieve centimeter-level errors), and the major difference is the superior operational cost and convenience. Recently, network RTK accessible wherever communication is available is becoming the mainstream for high-precision positioning, and on many survey sites the practice of “try measuring with VRS first” has become commonplace. Optical total stations and standalone GNSS positioning are still used when appropriate, but in many cases network RTK now supports the field in both accuracy and efficiency.

Using network RTK requires subscribing to a correction information distribution service and having a communication environment. In Japan, services using the roughly 1,300 electronic reference points installed by the Geospatial Information Authority of Japan (GNSS continuous observation system) and commercial correction data distribution services from carriers and surveying companies are available. Users connect their smartphones or positioning devices to those services over the internet to receive correction data (typically via the Ntrip protocol). If within communication coverage, accurate coordinates in a global geodetic reference frame can be obtained in real time anywhere in the country, but in mountainous areas where network connections are unstable, maintaining accuracy can be difficult. As a countermeasure, methods to receive correction information directly from satellites have emerged—such as the centimeter-class augmentation service (CLAS) provided by Japan’s quasi-zenith satellite system “Michibiki.” With CLAS-capable devices, high-precision positioning can continue via satellite even outside mobile network coverage, serving as a backup that preserves positional accuracy in disaster-stricken areas where terrestrial communication infrastructure is down. In this way, network RTK combines ground reference station networks and satellite augmentation to provide the foundational technology for stable centimeter-level surveying in a wide variety of environments.

How smartphone RTK (LRTK) changes field accuracy, procedures, and speed

Now that high-precision RTK positioning has become so accessible, smartphone RTK has emerged as a new solution that maximizes those benefits. Traditionally, RTK surveying equipment required investments on the order of millions of yen, with fixed receivers, antennas, and controllers. Recently, however, products consisting of a small RTK-GNSS receiver that attaches to a smartphone and a dedicated app have been developed, ushering in an era where a smartphone itself becomes a centimeter-accuracy surveying device. A representative example is LRTK, released in 2022 by a startup from Tokyo Institute of Technology: a tiny device weighing just in the 100-gram range that attaches to iPhone or Android smartphones and delivers positioning comparable to expensive dedicated equipment.

Using an attachable smartphone RTK system like LRTK transforms field surveying. In terms of accuracy, smartphone built-in GPS typically has errors on the order of 5–10 m (16.4–32.8 ft), while a dedicated antenna plus RTK corrections reduces errors to several centimeters (several in). Horizontal positioning accuracy of ±2–3 cm (±0.8–1.2 in) and vertical accuracy of a few centimeters are attainable, comparable to traditional surveying instruments. This meets stringent accuracy requirements that were difficult with standalone positioning—such as as-built checks requiring within a few centimeters.

Survey procedures and preparation are also simplified. Smartphone RTK eliminates heavy tripods and fixed equipment. Carrying only the smartphone and a pocket-sized receiver to the site and powering them on is enough to start positioning immediately. Previously, time was spent assembling equipment and installing reference points for each survey; that is no longer necessary. For example, LRTK connects wirelessly to the phone via Bluetooth or Wi‑Fi, removing complicated cabling. The convenience of completing surveying and recording with “just a smartphone” has now reached the field.

Speed and efficiency have dramatically improved. Previously, post-processing—returning to the office to plot coordinates on drawings or calculate volumes—introduced delays in utilizing survey results. With smartphone RTK, collected data can be shared to the cloud in real time from the field, allowing immediate verification and follow-up actions. The “measure and immediately confirm/share” workflow has shifted processes that once required specialized teams or days to complete into workflows that can finish in a day or even a few hours. In one road construction case, tasks that took days using a total station and laser scanner—establishing control points, point cloud measurement, and as-built inspection—were completed in a single day with one smartphone equipped with LRTK. Field staff can now measure and verify without waiting for surveyors, leading to major labor savings and speedups across the workflow.

Smartphone RTK systems also lower the financial barrier to entry. Because a pocket-sized device and a smartphone suffice, initial costs are an order of magnitude lower than traditional equipment. Equipping each person with a device becomes realistic, and site foremen or construction managers begin carrying smartphone RTK devices to perform routine measurements and checks. Being able to measure immediately and share results to the cloud helps prevent construction errors and optimize schedules—enabling a rapid PDCA cycle that stems from everyone carrying a high-precision positioning tool.

UX design that enables solo surveying (apps, AR guidance, photo positioning, etc.)

Achieving solo surveying requires not only high accuracy but also usability that a single operator can manage and design features that let one person perform measurements reliably. Smartphone RTK apps feature intuitive UX design so even users with little experience operating specialized equipment can learn the basics quickly. For example, the app can start positioning and save records with a single button press while handling complex settings and calculations automatically. Latitude, longitude, and elevation coordinates are automatically logged per point, along with date/time and measurement state (such as whether a fixed FIX solution was achieved). Taking photos attaches the capture location and orientation to each image, eliminating the hassle of later organizing which photo was taken at which point. There’s no need to transcribe notes into paper field books, greatly reducing the risk of human error. The system prevents missing records or transcription mistakes on site, enabling anyone to collect consistent data.

Challenges like identifying specific measurement points or stake-driving—tasks that traditionally required multiple people—are supported by smartphone RTK’s AR guidance features. Dedicated apps provide coordinate navigation that displays guide arrows and bearings on the phone screen toward preset target coordinates. Workers simply walk following the phone’s directions to reach target points that may not be clearly visible on the ground. Even when reference markers are buried by vegetation or snow, following the indicated direction leads to them efficiently. When approaching the target, users can enable AR overlay via the phone’s camera; a virtual stake or marking is rendered in CG at the target coordinate, appearing as if a physical stake were present. This AR stake display enables single operators to perform layout and stake-driving that previously required two people. There’s no need to rely on intuition and drawings—novices are guided visually to precise points. Field reports have noted that AR eliminated the need for traditional batter boards for layout, enabling new operators to execute accurately without veterans, and that visual guidance significantly improved efficiency—demonstrating the power of AR combined with RTK.

Smartphone RTK also enables tasks that were hard alone, such as photo-based positioning and 3D scanning. For example, taking multiple photos of an object with a smartphone and processing them with photogrammetry software can produce a high-accuracy 3D model of a small structure. RTK-based location tags on each photo ensure correct scale and orientation without installing many ground control points. Devices like iPhones with LiDAR scanners can capture surrounding terrain and structures by walking with the phone, yielding high-accuracy 3D point cloud data. Since the acquired point cloud is already georeferenced in a global coordinate system (absolute coordinates), later alignment (georeferencing) with other survey data is unnecessary. All of these functions can be executed with just a smartphone and one RTK device, allowing a single operator to complete surveying while simultaneously recording photos and obtaining 3D measurements. The versatile smartphone is strongly accelerating digital transformation (DX) on site.

Compatibility with point cloud scanning, as-built management, CAD and cloud integration

Positioning data acquired with smartphone RTK integrates well with CAD software and cloud systems. Previously, points measured on site were re-plotted into CAD back at the office, and point clouds from laser scanners were processed later on a PC for as-built inspection. With smartphone RTK, you can upload data to the cloud on site and readily use it for CAD or point cloud processing.

For example, LRTK systems automatically plot measured coordinates and photo notes from smartphones onto a cloud map. Office staff can access that map via a web browser and view coordinates and photos in real time. Measurement results can be downloaded as CSV or PDF, and common civil surveying formats such as SIMA or DXF are supported, enabling smooth import into existing CAD drawings or BIM models. In as-built management, measured 3D point cloud data can be overlaid directly on the design 3D model for comparison. The combination of smartphone RTK and the cloud makes the workflow from surveying → drawing creation → inspection seamless, greatly reducing the effort of data handoff and format conversion.

By issuing a shared URL on the cloud, stakeholders such as clients and subcontractors can view the latest survey data without logging in. Information that used to be exchanged on paper or USB drives can now be shared instantly over the internet. This achieves real-time site visualization, dramatically shortening the time needed for post-survey data organization and communication. For example, on a large earthwork site, daily surveys uploaded to the cloud let all stakeholders always access the latest terrain model and as-built progress, aiding construction planning and schedule management. Because point cloud data and photos are stored with spatial coordinates, it is always clear where a given point is or from which position a photo was taken, which is invaluable for report generation and later verification.

As-built management is particularly well-suited. Using 3D data obtained by smartphone RTK, on-site as-built inspection can be performed immediately and results presented to the client via the cloud. In one project, point clouds acquired with smartphone RTK were instantly overlaid with the design model in AR for on-site comparison, enabling immediate verification of finished work. This eliminated the traditional time lag between measuring and issuing corrective instructions, allowing corrections to be made the same day and enabling smooth, rework-free quality control. With cloud integration, office and field data are directly linked, synchronizing CAD and field data in real time and dramatically improving the accuracy and speed of construction management.

Real-time office-field collaboration (cloud maps, point sharing, coordinate navigation)

As noted above, smartphone RTK effectively reduces the data distance between the field and office to zero. Points plotted on cloud maps appear on the office PC the instant they are measured on site. This lets field personnel and office engineers share the same information and communicate in real time.

Specifically, coordinates, photos, and notes captured on a field smartphone can be uploaded to the cloud with a single tap, and the office can view the latest data on a web map. During layout work, an office supervisor can instantly check whether measured points match the design and provide feedback to the field by phone or chat if necessary. Conversely, if the office wants to add measurement points or design lines, a coordinate list can be sent via the cloud to the field smartphone, and field workers can find and mark those positions using the coordinate navigation feature—enabling two-way collaboration.

This real-time linkage is especially powerful when managing multiple distant sites or responding to urgent surveying needs. Even if only one person is at the site, headquarters or supervisors can monitor the situation via the cloud and provide instructions, effectively enabling remote-assisted solo surveying. In situations requiring complex decisions, measured data can be shared immediately to consult specialists. Cloud maps also maintain history, so you can see when and where measurements were made or how many times a point was remeasured. Because “the latest truth” is always the cloud data, differences in understanding and communication errors are less likely.

Using coordinate navigation and AR guidance in smartphone RTK, office-designed drawings can be accurately reproduced in the field. For example, if CAD data for the planned excavation area is preloaded into the app, a virtual excavation guideline can be projected on the ground via the phone’s AR display. Machine operators can then follow the line shown on the screen to achieve the design shape and slope. This is another example of office and field (design data) integration. Real-time information sharing and immediate feedback at the site have significantly changed surveying and construction workflows.

Time savings, eliminating reliance on specific individuals, safety improvements, applications in disaster response

The benefits of solo surveying using smartphone RTK boil down to significant productivity gains and stabilized work quality. With fewer people and less time required to obtain sufficient survey data, the burden of staffing and on-site waiting times decrease, substantially shortening total work time. If surveying that used to require two to three people for a full day can be done by one person in less than half a day, labor cost reductions and redeployment of resources to other tasks produce substantial economic effects. Immediate sharing of survey results for construction use shortens overall schedules and reduces rework.

Eliminating reliance on specific individuals is another key advantage. Historically, advanced surveying tasks depended heavily on experienced technicians, and work could stall without a particular expert. Smartphone RTK embeds surveying know-how and calculations in the app, so operations are performed by tapping buttons and following on-screen instructions. Newcomers or non-surveying staff can obtain data with consistent accuracy, reducing situations where work halts “waiting for surveying.” Standardizing and leveling tasks across the site so anyone can perform as-built checks or surveys at a stable quality is extremely valuable in the construction and surveying industries facing severe labor shortages. This democratization of high-precision positioning is also attracting attention as part of work-style reform and DX in the industry.

Safety improvements should not be overlooked. Reducing the number of personnel and time spent on surveying lowers workers’ exposure to hazardous environments. Solo surveying eliminates the need for flaggers at busy roadside locations and reduces risks from prolonged work near operating heavy equipment. AR guidance can allow positioning from a distance without approaching dangerous areas, and functions that enable measurement from safe locations (high places or restricted zones) are available. The small, lightweight equipment is easy to bring into rugged mountain areas or rubble fields after a disaster, lowering physical burden. Robust devices with dustproof and waterproof ratings make it possible to survey in locations where large equipment cannot be set up, enabling quick and safe situational assessment.

Smartphone RTK is also highly effective in disaster response. Immediately after a major disaster, rapid measurement and recording of damage are crucial. One CLAS-capable device like LRTK allows high-precision positioning even in areas where communication infrastructure is cut off, enabling teams to start surveying on site without setting up reference points. In the 2023 Noto Peninsula earthquake, LRTK was used in field surveys under communication outages. Pocket-sized devices recorded conditions in rubble-strewn areas and uploaded high-precision geolocated data via satellite-based corrections to share with relevant agencies. Where damage used to be recorded roughly (e.g., “a crack about △m from point ○○”), smartphone RTK allows recording latitude, longitude, and elevation precisely. This makes planning recovery efforts and monitoring long-term changes much easier.

Thus, solo surveying with smartphone RTK supports both routine construction management and emergency disaster surveying. Japan’s Ministry of Land, Infrastructure, Transport and Tourism promotes i-Construction, where ICT and DX-based labor savings and productivity improvements are key themes; smartphone RTK is a solution central to that vision. By enabling on-site personnel to collect and share data previously handled by surveyors, smartphone RTK can transform work processes. As a new force that inexperienced staff can handle, smartphone RTK addresses structural shortages of skilled personnel. The solo surveying trend is already producing concrete results across fields and is expected to expand further.

Natural introduction and guidance for adopting simplified surveying with LRTK

As outlined above, combining network RTK and smartphone RTK brings significant benefits to surveying and construction sites. With “centimeter-accuracy solo surveying” now a reality, there is no reason not to adopt it on site. Fortunately, smartphone RTK systems like LRTK are very simple to introduce and operate. The basic components are just “a smartphone,” “a small RTK receiver,” and “a connection to a correction information service.” Attach the receiver to the smartphone, launch the app, and the device functions as a surveying instrument. Hold the smartphone at the point to be positioned and tap a button to record high-accuracy coordinates along with date/time and notes, which sync to the cloud. Initial setup is guided and can be completed in minutes—no complex configuration is required.

After introduction, not only surveying departments but also construction managers and site technicians can perform routine position measurements and checks. For example, they can quickly measure a spot height between tasks, or quickly scan current ground elevations with smartphone RTK to estimate earthwork volumes. Work that previously required outsourcing or specialized teams can now be handled in-house, improving on-site capabilities. Cloud sharing also smooths reporting to supervisors and clients. Although high technology can sound daunting, smartphone app operation is quite similar to map apps or camera use that people are already familiar with. Intuitive UI and comprehensive support let even those uncomfortable with machines start with confidence.

Adoption of simple surveying tools like smartphone RTK is progressing across the construction industry as part of DX initiatives. Early adopters report effects like “being able to concentrate workforce on other tasks instead of assigning people to surveying,” “fewer construction errors and easier quality control,” and “all records are digitized, reducing reporting burdens.” Smartphone RTK is not limited to special sites; it is immediately practical for general civil engineering and surveying work. If you face challenges like “not enough personnel to keep up with surveying” or “want to advance site DX but don’t know where to start,” trial introduction of smartphone RTK is a good step. Start with small-scale trials and expand use gradually to experience the benefits. Please try centimeter-accuracy solo surveying at your company or organization’s sites and use it to improve operations and safety.

FAQ（よくある質問）

Q1. What do I need to use smartphone RTK? A1. Basically, you need a smartphone (iOS or Android) and an RTK-capable small GNSS receiver that can attach to the smartphone. In addition, you must connect to a correction information service to achieve centimeter-level positioning. Specifically, register with a network RTK (e.g., VRS) service provided by national or private entities and configure login settings for that service in the smartphone RTK app. A surveying pole (monopod or telescopic staff) is convenient for accurately measuring ground points by mounting the smartphone and receiver on the pole tip. With the required equipment, simply launch the app, receive correction data, and start positioning to perform centimeter-accuracy surveying.

Q2. Is the accuracy of smartphone RTK really centimeter-level? A2. Yes—under appropriate conditions you can achieve horizontal positions within a few centimeters and vertical positions within a few centimeters. Many smartphone-mounted GNSS receivers support dual- or multi-frequency signals and use RTK corrections, so their accuracy rivals that of dedicated surveying GNSS equipment. Field results show single-point real-time positioning with a standard deviation around 1–2 cm, and averaging dozens of measurements can yield sub-1 cm accuracy in some cases. However, achieving this accuracy requires a clear sky view with a sufficient number of satellites. Urban canyons surrounded by tall buildings or dense forests can block satellite signals and increase errors. In such environments, positioning may become unstable or deviate by several tens of centimeters. Selecting suitable environments and, if necessary, increasing measurement duration for averaging can help obtain stable high accuracy.

Q3. Can I use network RTK anywhere? What about places without signal? A3. If network (communication) is available, network RTK positioning is possible in almost all areas nationwide. In mobile coverage areas, your smartphone can connect to correction services and receive virtual reference station data. However, in areas without coverage or with poor signal you cannot obtain correction data, and typical network RTK becomes difficult. A countermeasure is to use receivers that support CLAS augmentation signals from Michibiki (quasi-zenith satellites). With CLAS-compatible smartphone RTK equipment, centimeter-level positioning can continue via satellite-based corrections even outside mobile coverage. Alternatively, some sites may set up a simple local base station to transmit corrections to smartphones (offline RTK). Generally, network RTK covers most locations except some special environments such as mountainous areas, remote islands, or inside tunnels, but satellite augmentation or a local base station can be considered where communication is unavailable.

Q4. Can you really survey alone? Aren’t there tasks that still need two people? A4. The advent of smartphone RTK has made most surveying tasks that previously required two or more people possible for one person. For example, total station surveying used to require one person operating the instrument and another holding the prism, but GNSS surveying needs no instrument setup—one person can carry the rover and record points. Line-of-sight is not required, so no assistant is necessary. For stake-driving and layout, AR coordinate guidance lets a single person place stakes accurately without assistance. Mounting the smartphone on a pole lets you maintain the usual posture to indicate points, so one person can hold the pole, check the screen, and mark positions. There are still situations where having extra personnel is preferable for safety or efficiency, but the surveying tasks themselves can generally be completed solo. Sites that adopted smartphone RTK have reduced surveying crew sizes and redeployed personnel to other construction management tasks. When surveying alone, take extra care with safety checks and work within a reasonable scope.

Q5. What are the running costs for smartphone RTK? A5. The main running cost to consider is the correction information service fee. Some network RTK correction services are provided free by national or municipal bodies, but many charge monthly or usage fees (varying by provider and guaranteed accuracy level). These fees are generally lower than maintenance contracts for traditional surveying equipment, and short-term subscriptions are often available. Communication costs are typically covered by normal mobile service plans when using a smartphone (correction data traffic is minimal and not comparable to heavy video transfer). Device maintenance mainly involves battery charging and consumable replacement—there are no large calibration or installation costs typical of big equipment. Overall, smartphone RTK operational costs are often much lower than those for traditional surveying tools. Investigate correction service plans before introduction and choose a contract that matches your usage frequency. Discounts for bulk device deployment may also be available.

Q6. Is survey data from smartphone RTK acceptable for legal or public surveying use? A6. For typical construction surveying, as-built management, and design/construction uses, data obtained with smartphone RTK can generally be used as-is. National guidelines such as MLIT’s i-Construction and related standards already define GNSS-based surveying and as-built management methods. However, fields that legally require strict accuracy and procedures—such as public surveying or cadastral surveys—still require surveying under the supervision of a licensed surveyor with prescribed accuracy control using control point surveys. Even in those cases, smartphone RTK data can be used as a provisional base to streamline detailed surveys. The treatment depends on whether the final deliverable will be used as an official survey record. For ordinary construction management and private surveys, smartphone RTK accuracy is usually sufficient, but when submitting drawings to public agencies it is prudent to cross-check against known points or perform verification measurements. As smartphone RTK accuracy and reliability are further validated, its use in official surveying contexts is expected to expand.

Q7. Can I survey with smartphone RTK in rain or at night? A7. In general, GNSS surveying works in rain. Many LRTK-like devices are waterproof, and light rain usually does not impede work (but take care not to expose devices directly during heavy rain). GNSS positioning itself is not affected by day or night, so accuracy does not change; in some cases positioning is more stable at night due to reduced ionospheric disturbances. Be mindful of safety when working in darkness and note that AR displays may be harder to see through a dark camera image—using strong lighting or relying on navigation displays rather than camera overlays can help. Also prepare lighting such as headlamps, as smartphone screens and documentation are harder to read at night. Overall, smartphone RTK’s flexibility allows surveying irrespective of time or weather, and it is even used for nighttime shoulder measurements without traffic regulation.

以上、スマホRTKとネットワークRTKがもたらす新しい測量手法について解説しました。センチメートル精度での一人測量という革新は、測量士や施工管理者にとって大きな可能性を秘めています。技術の進歩により「誰でも・どこでも・すぐに・正確に」測れる環境が整いつつある今、ぜひ現場でそのメリットを体感してみてください。従来の常識を覆すスマホRTKで、測量業務の効率化と品質向上を実現し、安全で生産性の高い現場づくりに役立てていただければ幸いです。