AR Surveying with iPhone + RTK: Layout, Stakeout & As-Built in One Device

In the construction and surveying industries, a wave of DX (digital transformation) is currently sweeping through, and on-site digitization—“on-site DX”—has become a major theme. Amid the introduction of various technologies such as drones, 3D surveying, and AI-based analysis, "RTK AR," which combines high-precision satellite positioning technology RTK with augmented reality (AR), is attracting attention as a technology that will revolutionize surveying and construction management on-site.

By leveraging RTK AR, field operations that previously relied on experience and manual work can be dramatically streamlined, enabling anyone to intuitively handle high-precision information. This article explains RTK AR from a professional perspective, covering the basics, benefits, effects of introduction, real-world use cases, operational cautions, and future outlook, to convey a concrete image of on-site DX to surveying companies, municipal civil engineering departments, and construction contractors.

Basics of RTK AR

RTK (high-precision GNSS positioning): RTK stands for Real-Time Kinematic, a technology that uses GNSS (Global Navigation Satellite Systems) to achieve centimeter-level positioning accuracy (cm-level accuracy, half-inch accuracy) in real time. With ordinary GNSS positioning (standalone positioning), errors in satellite signals typically cause position errors of several meters (several ft), but RTK positioning uses two receivers—a base station (a receiver installed at a point with known coordinates) and a rover (the device being positioned)—and corrects errors by using the difference in satellite observations between the two. As a result, positioning accuracy improves dramatically, enabling horizontal position errors of a few centimeters (a few in) and vertical errors of about a few centimeters (a few in). Traditionally, tasks requiring centimeter accuracy such as road layout marking and positioning of structures required optical surveying instruments like total stations. However, RTK-GNSS has made it possible to perform such high-precision tasks using satellite positioning alone, and it is being adopted in a wide range of fields including surveying, civil engineering construction, agriculture, and autonomous driving.

AR (augmented reality): AR stands for Augmented Reality, a technology that overlays digital information onto real-world imagery. Through cameras on smartphones, tablets, or AR glasses, virtual displays of design drawings, 3D models, measurement data, and more can be placed in the real-world space. For example, displaying a design model in AR on a construction site allows you to confirm the completed appearance at full scale or visualize dimension lines from drawings in the real space for checking. By intuitively closing the gap between the site and the drawings, AR is expected to smooth communication and prevent mistakes before they occur.

What does RTK AR make possible? RTK AR is a solution that combines this high-precision positioning by RTK with AR visualization. If you use a device capable of RTK centimeter-level accuracy, the digital information displayed in AR can be made to align exactly with real-world positions. Ordinary smartphone GPS has meter-level offsets, so AR objects misalign with reality and cannot be used for surveying or construction purposes. But with RTK AR, digital data can be accurately projected to the coordinate positions specified in the design. For example, you can virtually place stakes at design-specified points, overlay the designed completed shape on-site, or guide someone from the current location to a target point with AR arrows (coordinate guidance). With AR visualizations supported by high-precision positioning, on-site “visualization of position” progresses dramatically, and surveying and construction management workflows change significantly.

Benefits of Using RTK AR

Introducing RTK AR brings the following benefits to on-site work:

• Significant efficiency gains in surveying tasks: High-precision GNSS allows rapid positioning, so surveying and layout work that previously required multiple people and considerable time is greatly accelerated. By following AR arrows for coordinate guidance, workers can reach designated survey points simply by moving as directed, greatly reducing the time spent searching for points. With one device per person, each worker can perform surveying and checks, helping to address shortages of surveyors and reduce overtime.

• Improved surveying accuracy and construction quality: RTK’s centimeter-level accuracy (cm-level accuracy, half-inch accuracy) minimizes errors in stakeout positions and as-built measurements. Because design models and current site conditions can be overlaid and checked in AR, construction mistakes can be prevented in advance, contributing to as-built quality control.

• Intuitive information sharing: AR visualization enables drawings and numerical data to be visualized on site, so everyone from site supervisors to workers can share the same image. Completed forms and cautions that are hard to convey with paper drawings can be shown on the spot, smoothing communication among stakeholders and preventing missed or misinterpreted instructions.

• Immediate data utilization and DX promotion: Positioning data and point cloud data can be shared instantly via the cloud, allowing data submission and reporting directly from the site without returning to the office. Real-time progress awareness enables quick decision-making, realizing true on-site DX (digitization). Eliminating paper and manual processes also reduces recording errors and enables centralized data management.

• Improved safety: Reducing surveying work in hazardous areas is another benefit. For example, if base point installation on steep slopes or roadways can be confirmed and guided remotely via AR, the number of times workers enter danger zones can be reduced. Visualizing the locations of underground utilities with AR can also reduce the risk of accidental damage during excavation. Municipal infrastructure management initiatives are also underway to use high-precision measurement data obtained on site and share it immediately via the cloud to support repair planning.

Effects of Introducing RTK AR

When RTK AR is actually introduced on sites, the following specific effects have been reported:

• Dramatic reduction in work time: Required time for surveying and layout is drastically reduced, shortening construction cycles. For example, at one site, foundation layout work that used to take two days was reported to be completed in about half a day using RTK AR. Real-time positioning and confirmation reduce waiting times and allow work to proceed more smoothly.

• Labor-saving and improved personnel efficiency: With RTK AR, surveying tasks that used to be done by a two-person team can be handled by one person. Freed personnel can be reassigned to other tasks, improving overall productivity. Because even non-experts can follow machine guidance, dependence on specific skilled individuals is reduced.

• Quality assurance and error reduction: By constantly comparing the design and the site in AR, deviations can be detected before rework is required. Catastrophic mistakes like “it differed from the drawings after completion” can be prevented, reducing rework and redo due to quality defects. Real-time as-built management also elevates the quality management cycle.

• Overall cost reduction: Time savings, labor reductions, and error prevention lead to overall project cost reduction. Shortened schedules reduce overhead, and eliminating rework reduces waste, enabling a competitive construction system through on-site DX.

On-site Use Cases

RTK AR is being used for various purposes on actual civil engineering and construction sites. Here are some examples:

• High-precision layout and stakeout: In roadworks and foundation works, RTK AR can display virtual stakes at design points in AR for stakeout operations. Workers viewing the site through AR devices see design center lines and outlines of structures overlaid on reality, eliminating positioning mistakes. Traditionally, surveyors marked positions on-site, but with RTK AR anyone can accurately mark layout on the spot. On large-scale earthwork sites, heavy equipment operators can confirm their position and design lines in AR while operating machinery, leading to efficient and accurate construction.

• As-built management and earthwork volume measurement: For as-built checks on dams and earthworks, overlaying the design model onto the constructed terrain in AR makes it easy to identify excesses and shortages in fill and cut. Scanning the site with an RTK AR-capable smartphone can instantly capture 3D point cloud data and allow immediate comparison with design data on site. For example, overlaying the design surface on the completed surface and color-coding “areas that are too high” and “areas that are too low” makes it intuitive to see where additional adjustment is needed. Processes that used to require taking survey data back for CAD comparison can now be completed on site in real time, drastically improving the speed and accuracy of as-built management.

• Use in infrastructure inspection and maintenance management: RTK AR is beginning to play a role in regular inspections of tunnels and bridges. For example, AR arrows can indicate the locations of crack photos taken during previous inspections so that re-photographing from the same angle allows accurate comparison of aging changes. Visualizing the locations of buried pipes and cables with RTK AR lets you identify sewer and gas pipes before road excavation, enabling safe and efficient maintenance work. Municipal infrastructure management is also progressing by immediately sharing high-precision measurement data obtained on site via the cloud to assist in repair planning.

Operational Cautions

Even with convenient RTK AR, there are several points to be careful about to maximize its use on site:

• Securing suitable GNSS positioning conditions: RTK uses satellite signals, so open sky visibility is ideal. Underpasses, urban canyons between buildings, and heavily wooded areas make satellite acquisition difficult and reduce positioning accuracy. Be mindful of radio interference as well. When installing a base station, choose as clear a location as possible, and have the rover (worker) regularly check satellite acquisition status. When positioning is unstable, wait a few minutes for satellite geometry (constellation) to improve, or remeasure at another time as needed.

• Handling coordinate systems and reference points: It is important to ensure the design drawing coordinate system matches the GNSS positioning coordinate system. Public surveying in Japan uses plane rectangular coordinate systems, while GNSS results are obtained in WGS84 or the Japanese Geodetic Datum (JGD). Some RTK systems automatically convert to plane rectangular coordinates, but confirm this in advance. If necessary, apply corrections using known points and perform translations to local coordinates before AR display to prevent discrepancies between the site and design data. Also, if the base station’s position is not strictly tied to a known point, the same offset will affect all positioning results, so take care.

• Equipment handling and power management: When using smartphones or tablets on site, pay attention to waterproofing, dust protection, and drop prevention. Use dedicated cases and straps, and take measures to keep devices dry in rainy conditions. Batteries drain quickly, so carry spare batteries or mobile power banks for long surveying sessions to ensure continuous power. Include GNSS receivers in these checks and make it a habit to verify device operation and charging before starting work each morning.

• Verifying AR display accuracy: Make it a habit to verify that AR composite images are accurate on site. For important survey points, cross-check RTK AR displays against values measured by conventional methods to confirm that errors are within acceptable ranges. Vertical accuracy in particular can vary with the environment, so it can be effective to use leveling surveys for verification when necessary. Also, to prevent AR objects from appearing shifted due to parallax or device tilt, stabilize device holding during observation (for example, by mounting on a pole).

• Training and proficiency: When introducing new technology, education and sufficient trial periods for site staff are essential. Although intuitive to use, users must become familiar with RTK-specific concepts (e.g., confirming FIX solutions and monitoring satellite status) and AR operation. Start with simple tasks and gradually expand the scope of use for a smooth transition. Share know-how within the company and confirm troubleshooting procedures in advance (for example, recovery steps when positioning is lost).

Future Outlook

RTK AR technology will continue to evolve and is expected to become a core element of on-site DX. On the hardware side, more lightweight, high-performance GNSS receivers and wider adoption of AR glasses are expected. Currently, smartphones and tablets are the main platforms, but in the future, helmet-integrated AR devices or goggle-type AR glasses may become common for work. This would free workers’ hands and provide continuous digital information in their field of view, further improving efficiency and safety.

Improvements in infrastructure will also enhance positioning accuracy and convenience. In Japan, centimeter-level augmentation services such as CLAS provided by the Quasi-Zenith Satellite System are being developed, which could enable high-precision positioning without receiving base station information via the Internet. The expansion of 5G connectivity makes real-time sharing of large 3D data and cloud-side advanced point cloud processing and analysis with immediate AR feedback increasingly feasible. Integration with AI could enable automatic as-built judgment from point cloud data acquired on site and display corrective instructions in AR as advanced feedback in the future.

As government and industry efforts such as MLIT-promoted i-Construction and spreading CIM make construction using 3D design data commonplace, RTK AR will be an important tool supporting this trend. In the future, RTK AR is expected to become standard equipment on many sites as a “next-generation site interface” that replaces surveying instruments and paper drawings. For surveying and construction companies, cultivating personnel who can use RTK AR and building workflows will be key competitive factors. With technological progress, a future that now sounds like a dream—where everyone manages sites by overlaying them with virtual spaces in real time—seems likely to be realized before long.

Conclusion

RTK AR is a solution that combines two advanced technologies—surveying and AR—to bring a digital revolution to construction site workflows. By combining high-precision positioning with intuitive visualization, it dramatically improves the productivity and quality of surveying and construction management and strongly promotes on-site DX. RTK AR is becoming an attainable solution not only for large-scale projects but also for small- and medium-scale construction and infrastructure management.

In particular, by using the simple surveying and AR visualization tool for smartphones, LRTK, even sites without specialized surveying equipment can easily achieve centimeter-level positioning and AR-based information sharing. By incorporating RTK AR into your own sites, you can proceed with work at unprecedented speed and accuracy. Consider adopting RTK AR technology and take a step toward next-generation site operations.