Smartphone-Only RTK Surveying Realizes Centimeter-Level Accuracy (cm level accuracy (half-inch accuracy)) × AR-Enabled Field Revolution

Table of Contents

• What is RTK surveying?

• The importance of centimeter-level accuracy (cm level accuracy (half-inch accuracy))

• Traditional surveying methods and on-site challenges

• Enabling RTK surveying with smartphones

• Benefits AR technology brings to the field

• Use cases for smartphone RTK surveying and AR

• The field revolution brought by smartphone RTK surveying

• Conclusion

• FAQ

What is RTK surveying?

RTK surveying is a method that uses Real Time Kinematic positioning technology to perform high-precision surveys. By applying error correction information transmitted from a base station in real time to the position information obtained from satellite positioning systems (GNSS such as GPS and GLONASS), positioning errors that are normally on the order of meters can be reduced to the centimeter level. In short, RTK surveying is the technique of combining GNSS satellite signals with correction information to determine the “precise coordinates at the site” in real time. This enables highly accurate surveys with minimal deviation on map coordinates and is widely used for tasks such as civil engineering surveying and staking out positions on construction sites.

RTK surveying typically uses two GNSS receivers: a rover (mobile unit) and a base (reference station). The base station is installed at a known, precise coordinate, where it computes the error in the received satellite signals. That correction data is then sent to the rover via radio or the Internet. The rover (carried by the surveyor) applies the received correction information to its own positioning data to compute high-precision positions immediately. Recently, network RTK surveying, which uses public electronic reference point networks or commercial correction services, has become widespread; with an Internet connection, RTK surveying can be performed with only a single rover. This reduces the need to set up a personal base station on site and makes high-precision positioning increasingly accessible.

The importance of centimeter-level accuracy (cm level accuracy (half-inch accuracy))

Conventional GPS positioning errors are said to be on the order of several meters. By contrast, centimeter-level accuracy (approximately ±1–2 cm (±0.4–0.8 in) horizontal error) achievable with RTK surveying makes a decisive difference in tasks that require precise positioning. For example, when driving reference stakes or staking out the positions of structures on a construction site, errors of several meters are completely unusable, and even deviations of several tens of centimeters are a major problem. With accuracy driven down to the centimeter level (cm level accuracy (half-inch accuracy)), surveying tasks that require millimeter-level precision—such as determining building foundations, road centerlines, or boundary markers—can be handled. High accuracy is directly linked to ensuring construction quality and safety, and it reduces costs by lowering the need for re-surveys and rework.

Moreover, centimeter-level accuracy enables new technological applications. For example, machine control for heavy equipment—which automatically shapes the ground according to preprogrammed design surfaces—requires high-precision positioning via RTK for accuracy control. In aerial photogrammetry using drones, RTK methods to increase the precision of geotags are drawing attention to create precise terrain models. Thus, centimeter-level positioning is not only about “knowing the current location accurately” but serves as a foundational technology that supports the latest construction ICT and DX (digital transformation).

Traditional surveying methods and on-site challenges

Traditional advanced surveying methods have included total stations and electronic distance meters, as well as standalone positioning without RTK or static GNSS surveying (a method that removes errors through long-duration observations). These conventional methods have several challenges.

First, surveying with a total station often requires multiple personnel. A typical scene is a surveyor looking through the instrument while another person stands at the survey point holding a prism; with current labor shortages, tasks that cannot be completed by a single person are a heavy burden. Instrument operation requires specialized knowledge and experience, and the aging of skilled personnel and lack of successors are on-site challenges. To produce survey drawings, on-site records and subsequent office calculations and drafting are necessary, which lack real-time capability and can delay decision-making.

On the other hand, while RTK surveying itself is highly accurate, it traditionally required expensive dedicated GNSS receivers, radios, and data-processing terminals. High equipment costs made adoption difficult except for specialized contractors or large-scale projects, meaning RTK was “high-precision but not easy to use.” Setting up and managing a private base station was also time-consuming, and in mountainous areas where base station radio signals cannot reach, positioning can become unstable. Data sharing could not be done instantly, so sharing coordinates measured on site with others or checking them against drawings immediately on site was not easy under conventional systems.

Thus, conventional surveying methods left much room for efficiency improvements in terms of personnel, time, and cost, hindering rapid on-site decision-making and productivity improvements. This motivated a new approach that leverages smartphones to solve these issues.

Enabling RTK surveying with smartphones

Recent technological advances have made it possible to use smartphones as platforms for high-precision surveying. High-performance GNSS chips for smartphones and compact external RTK-GNSS receivers have appeared, and by combining them with smartphones, “smartphone-only” RTK surveying has become feasible. Specifically, a compact, lightweight RTK-capable GNSS receiver small enough to fit in a pocket (around 100 g) can be attached to a smartphone, and a dedicated app on the smartphone receives and processes correction information from base stations. This enables high-precision positioning that previously required large stationary equipment and dedicated controllers to be performed with a palm-sized smartphone.

Because smartphones have communication capabilities (4G/5G), they can connect to correction information services over the Internet and receive data in real time. The smartphone’s high processing power also allows RTK calculations and coordinate transformations to be performed smoothly within the app. Positioning results are displayed immediately on the smartphone screen, and plotting on maps or embedding location information into photos is automated. The entire workflow—confirming results on site, uploading to the cloud, and sharing as needed—can be completed entirely on the smartphone.

The benefits of smartphone-only RTK surveying are immense. First, intuitive app operation makes surveying accessible even to non-specialist operators, allowing each field worker to “measure whenever they need to”. The small equipment footprint and smartphone-only setup are highly portable, enabling immediate surveying from a pocket whenever required. Tasks that formerly required waiting for a surveying team or pausing heavy equipment until survey results were available can now be addressed instantly with just a smartphone, greatly reducing downtime. In addition, equipment acquisition costs are drastically reduced. High-precision GNSS equipment used to cost millions of yen, but smartphone-compatible receivers are inexpensive, and existing smartphones can be used, lowering initial investment barriers. Deploying one device per person and having it carried at all times becomes realistic, and the technology is expected to spread as a general-purpose tool anyone on site can use.

Benefits AR technology brings to the field

Another major strength of using smartphones as surveying instruments is their built-in AR (augmented reality) capabilities. AR functions that overlay design drawings and survey data onto the real-world imagery seen through the smartphone camera provide intuitive on-site support that was previously unavailable. For example, projecting 3D design models or drawing lines from plans onto the actual ground or structures makes it possible to instantly confirm any “discrepancy between design and site.”

Traditionally, marking locations from drawings on site required taking coordinates with surveying instruments and marking with stakes or chalk. With AR, you can simply follow the on-screen guides to stand at the correct spot or mark it. For example, staking and positioning of equipment can be performed accurately by a single person using AR guidance, dramatically improving work efficiency. AR-displayed arrows and target markers can tell you in real time “move ○ cm north,” enabling pinpoint positioning without the repeated measurements or communications that used to be necessary.

AR visualization is also powerful for sharing the finished-image. Showing stakeholders and local residents a projected view of the completed design over the actual site smooths consensus building and helps explain construction plans intuitively. Furthermore, combining a smartphone’s AR features with high-precision positioning enables the “visualization” of normally invisible objects. If the positions of buried utilities such as pipes and cables are recorded in advance, you can simply point the smartphone at the location later to display them in AR, helping prevent accidental damage during excavation and improving safety. In this way, AR aligned with centimeter-level accuracy (cm level accuracy (half-inch accuracy)) strongly supports on-site decisions and tasks, delivering efficiency and safety improvements that were previously unattainable.

Use cases for smartphone RTK surveying and AR

The combination of smartphone-only RTK surveying and AR technology has produced various practical on-site use cases. Below are some representative scenarios.

• Locating underground utilities: Used to record and confirm positions of buried facilities such as sewer and gas pipes. After exposing buried pipes during exploratory excavation, record their positions with high-precision smartphone surveying and save the coordinates. Even after backfilling, projecting the buried locations in the smartphone AR view lets you know exact locations without re-excavation, reducing the risk of damaging pipes in future works.

• Checking finished grades of slopes and developed land: Used to verify whether slopes or site elevations created by development work match the design. Using a smartphone to capture terrain point clouds (LiDAR scan or photogrammetry) and automatically calculate deviations from the design model on the obtained 3D data, and overlaying design lines with AR on site, reveals where fill is lacking or cut is excessive at a glance. This streamlines finished-shape management and inspection and reduces rework.

• Finished-shape management for roads and structures: Used to confirm whether completed structures in roadwork or bridge construction conform to designed positions and shapes. Measure coordinates of important structure points (edges, centerlines, etc.) with smartphone high-precision positioning, compare that data with design data, and project the completed model onto the actual structure with AR to visually grasp even slight deviations. This enhances quality control and enables early detection and correction of construction defects.

• Streamlining staking and layout tasks: Use smartphones and AR for staking and layout tasks that indicate structure positions on site for building and civil engineering projects. If reference point coordinates and design drawings are preloaded into the smartphone, the worker can move according to on-screen instructions to place stakes or marks at exact positions. Tasks that used to be performed by surveying teams can now be rapidly completed by a single field worker, resulting in significant labor savings.

• Consensus building via AR display of design models: In the planning stage of construction projects, display designed structures or exterior elements in AR on the actual site to share the finished-image with stakeholders. For example, projecting exterior designs for a residence onto the lot helps clients experience the completed appearance. Spatial concepts that were hard to convey with paper drawings can be confirmed in real space, smoothing communication with clients and local residents and shortening time to consensus.

The field revolution brought by smartphone RTK surveying

As shown above, the introduction of smartphone-only RTK surveying and AR technology is dramatically changing conventional on-site practices. The environment in which “anyone can perform accurate surveying when needed” greatly increases on-site productivity and flexibility. Work interruptions due to waiting for surveys are reduced, and with real-time data enabling immediate decisions and construction, timelines shorten and costs are lowered.

Additionally, immediate data sharing and accumulation strengthen coordination between the field and the office. Survey data uploaded to the cloud can be reviewed by office engineers immediately and reflected in design changes. Remote managers can monitor progress in real time, speeding decision-making and improving overall team efficiency.

Smartphone RTK surveying is also a democratizing technology for the field. Surveying, once limited to specialists, becomes part of everyday work for all field staff through intuitive smartphone operation, eliminating situations where “work stops because there’s no one who can measure.” Even inexperienced personnel can follow digital tool guidance to perform accurate work, which is beneficial for skill transfer and human resource development. By visualizing and digitizing parts of the work that depended on veterans’ intuition and tricks, work quality can be standardized and improved.

Furthermore, these technological advances align with nationwide initiatives to promote DX in construction and i-Construction. Smartphone- and app-based methods have low barriers to introduction and can be deployed to many sites in a relatively short time. This “field revolution,” which could fundamentally renew workflows, is likely to become the standard in the future.

Conclusion

Smartphone-only RTK surveying has made centimeter-level accuracy (cm level accuracy (half-inch accuracy)) more accessible, and combining it with AR technology is beginning to dramatically evolve on-site work. With high-precision location information and intuitive visual support, surveying and construction efficiency and quality improve significantly, positioning this approach as a key tool for on-site DX that overturns conventional wisdom. As adoption increases, construction and surveying sites will move toward an era where everyone can handle accurate, real-time data.

One example of a solution that makes these latest technologies easy to adopt is LRTK. By using LRTK, anyone can start centimeter-level surveying easily with a smartphone and a compact RTK receiver. It provides an all-in-one set of features introduced in this article—cloud sharing of positioning data and intuitive AR-guided layout—making it possible to deploy on site without specialized knowledge. If you are considering realizing a field revolution with smartphone-only RTK surveying, consider leveraging such modern tools.

FAQ

Q. What do I need to perform RTK surveying? A. RTK surveying requires an RTK-capable high-precision GNSS receiver (rover) and correction information from a reference station. Traditionally, preparing your own base station was common, but nowadays many use services that provide correction information via the Internet (electronic reference point networks or commercial VRS services). For smartphone-only RTK surveying, you need a small RTK-GNSS receiver that can connect to a smartphone, a dedicated app, and a communication line to begin surveying.

Q. Can a smartphone alone really achieve centimeter-level accuracy? A. Yes, it is possible. A smartphone’s native GPS has errors on the order of meters, but by combining an external RTK-capable receiver with correction information, positioning accuracy comparable to traditional dedicated surveying equipment—about 1–2 cm (0.4–0.8 in)—can be achieved. There are increasing cases where smartphone-plus-compact-receiver combinations have been used for control point surveying and finished-shape management with results comparable to conventional equipment. However, note that high-precision positioning still requires conditions common to traditional equipment, such as a clear sky view and stable communications.

Q. What is the difference between RTK surveying and normal GPS positioning? A. The biggest difference is positioning accuracy. Standalone GPS (GNSS) positioning typically has errors of around 5–10 m (16.4–32.8 ft) due to satellite signal errors, whereas RTK surveying uses correction data to reduce that error to a few centimeters. Also, normal GPS simply provides the current location, but RTK surveying, through relative positioning to known points, yields accurate coordinates in the survey reference frame, allowing survey results to be used directly in drawings and construction management. In short, RTK surveying is “fast and accurate,” while normal GPS positioning is “convenient but limited in accuracy.”

Q. How does AR technology help on site? A. AR technology overlays information from drawings and 3D models onto live site imagery. For example, you can view a projected completed image of a planned structure or display the positions of underground utilities as if you were seeing through the ground. This lets you intuitively understand “what is where” and “how construction will proceed” on site, making it far easier to reconcile survey data with reality and to verify layout tasks. As a result, it helps prevent mistakes and facilitates smoother communication, contributing to safer and more efficient site operations.

Q. Can I use smartphone surveying without specialized knowledge? A. Yes—once you learn the basic operations. Smartphone surveying apps are designed with easy-to-understand user interfaces, allowing you to record coordinates by simply pressing a button at the desired point. The app automatically handles complex settings and calculations that traditional surveying instruments require, so non-specialist operators can perform tasks at a certain level of accuracy. However, having basic knowledge of surveying principles and data handling will make it easier to make full use of the system, so learning on the job and gradually deepening your understanding is recommended.