A single surveyor can complete reverse-setting stakeout! What is the power of high-precision smartphone surveying?

Surveying technology is now entering a new turning point. The reverse-setting stakeout work (survey layout / marking), which used to require multiple people, is increasingly becoming something a single surveyor can complete thanks to the combination of smartphones and high-precision positioning technology using RTK (real-time kinematic). Behind this shift are technological innovations such as improved satellite positioning accuracy, the evolution of smartphone apps, and the practical application of AR (augmented reality). In this article, we unpack the challenges of reverse-setting work that traditionally burdened surveyors, explain the efficiency and labor-saving effects that smartphone high-precision surveying technologies (such as LRTK) bring to the field, and introduce concrete use cases, comparisons with conventional methods, and future prospects to explore the benefits of on-site implementation.

What is reverse-setting stakeout: position-marking work in surveying

First, let’s clarify what reverse-setting stakeout is. This refers to the survey layout work of accurately indicating on the actual site the positions of structures or reference points defined by coordinates on design drawings. It is generally also called "staking out" or "marking" and is an indispensable process in building and civil engineering work for indicating the placement of foundations and the locations where structures will be erected. Surveyors and technicians measure distances and angles from known points (benchmarks) on site based on the coordinates given on the drawings, and mark on the ground or structures where stakes should be driven. For example, in an open graded site, it is common to install reference frames called chōhari around the perimeter and use their intersection points with tape measures to derive target positions. In contrast, in narrow urban lots or underground works where installing large reference frames is difficult, it is necessary to repeatedly remeasure from nearby structures or temporary references to determine positions. In any case, even millimeter-level errors in stakeout positions can affect subsequent processes, so the work has long required the carefulness and seasoned intuition often described as a craftsman’s skill.

Problems with conventional reverse-setting work

However, conventional stakeout work has been accompanied by the following issues:

• Multiple people are required: For surveying with a total station (TS), a two-person team—one operator for the instrument and one assistant holding a prism at the target point—is the standard. Deploying personnel in limited spaces imposes a significant safety burden, and in sites with labor shortages, simply securing personnel is a challenge.

• Reliance on experience and intuition: In tight sites or environments with poor visibility, it is often necessary to remeasure from reference points multiple times, and ultimately the intuition of veteran technicians can determine accuracy. Work tends to become person-dependent, posing a risk of quality variation depending on the skill of the person in charge.

• Time-consuming and labor-intensive: Each time a TS or level is set up, time is required for instrument installation and setting references. Moving instruments and recalculating for each underground floor and repeated inefficient steps for staking out even a single stake can pile up and impede overall construction progress.

• Risk of human error: Human mistakes such as tape sag, misreading, mis-marking, and transcription errors in notes are unavoidable. If markings are erased or shifted during construction, re-surveying and re-marking are required. In stakeout work that demands precision, such minor mistakes can lead to serious errors.

Smartphone RTK technology and features of high-precision positioning

So what is smartphone-based RTK positioning? RTK (real-time kinematic) is a method of high-precision GNSS positioning that receives GNSS satellite signals simultaneously at both a reference station and a rover, and dramatically reduces positioning errors in real time by correcting the rover’s observations with the reference station’s observation data. While standalone GPS can produce errors on the order of meters, using RTK can determine positions with accuracy within a few centimeters (a few inches), and in some cases within a few millimeters (a few tenths of an inch). RTK positioning used to require dedicated large GNSS receivers and base station equipment. Recently, however, ultra-compact RTK-capable receivers that attach to smartphones and tablets have appeared, enabling centimeter-level positioning (half-inch accuracy) with ease. In Japan, the proliferation of the Geospatial Information Authority’s continuous GNSS reference station network and the quasi-zenith satellite "Michibiki" has made services like CLAS (centimeter-level positioning augmentation service (half-inch accuracy)) more available, so correction information can be obtained from communication lines or satellites and applied on the smartphone for real-time correction. In other words, with just a smartphone you can know your high-precision position in a global coordinate system anywhere, and obtain survey-accuracy coordinates on-site instantly without heavy surveying instruments or long static observations.

Why smartphone + RTK + AR makes solo stakeout possible

In addition to high-precision positioning by smartphone, the use of AR (augmented reality) is a major key that enables a single person to perform stakeout work. An AR navigation function in a dedicated app overlays target points from the design drawings and directions to move onto the camera view, guiding the user to the stakeout position simply by looking at the screen. For example, if you call up stake coordinates registered in the cloud in advance and start "navigation," the smartphone screen will display an arrow pointing toward the target and the distance from your current location in real time. The worker only needs to walk in the direction the arrow points, and the displayed distance decreases as they approach. Near the target, the arrow makes fine directional adjustments, and by following the instructions you can reach the specified coordinate with an error within a few centimeters (a few inches). Because you can reach the correct stake position by simply following on-screen guidance without complex calculations or advanced surveying knowledge, this achieves efficiency on a completely different level from the traditional method where experienced workers would coordinate vocally to find the correct position.

Furthermore, the smartphone’s AR display can visually indicate the target point itself as a marker. For example, even on paved surfaces where you cannot mark directly on the ground, or in areas that are dangerous to enter, you can set a virtual AR stake on the camera image to identify the position. In locations you cannot physically approach—such as on a steep slope—you can later project a virtual stake onto that point by combining photogrammetry features, allowing you to confirm the target position from a safe location. This is a revolutionary function that enables stakeout guidance in situations that were previously impossible.

How the stakeout workflow changes with smartphone RTK introduction

Introducing smartphone RTK dramatically simplifies the stakeout workflow compared to conventional methods. Here is a typical sequence:

• Coordinate data input: Extract stake coordinates from design drawings in advance and load them into the smartphone surveying app. If you enter the coordinates manually or upload a CSV file via the cloud, you can immediately call up the target list on site.

• Movement guided by the screen: Start positioning on site, select the target point, and begin navigation. Move to the target location following the arrow and distance information displayed on the smartphone screen. Because positioning is updated in real time and the current position can be known with centimeter-level accuracy (half-inch accuracy), the need for iterative measurements and fine adjustments is greatly reduced.

• Marking the target point: Once you reach the coordinate, mark the point on the ground with a stake or spray paint. Since the smartphone and RTK receiver are used mounted on the tip of a dedicated pole (such as a monopod), you can place the pole tip on the ground and align it with the on-screen marker; that position is the stakeout point. When the virtual stake shown on the screen and the pole tip coincide, you make a physical mark with paint, drive in a wooden stake or pin, and indicate the target point on site.

• Recording survey results: At the same time as marking, the measured coordinates are automatically recorded in the app. Point names, date and time, time taken for guidance, arrival accuracy, and other data are saved and can be uploaded to the cloud with a single button. Managers in the office can instantly verify results, eliminating the need to take notes on paper at the site.

Use cases of smartphone RTK in reverse-setting stakeout

• Residential land development: In land readjustment and residential development sites, it is necessary to accurately indicate many stakeout points such as lot boundaries, road centerlines, and plumbing positions. With smartphone RTK, one person can move around large development sites and stake out points sequentially. Tasks that used to require a surveying team rotating shifts and half a day to complete can be finished by one person in a short time, directly improving construction speed and reducing personnel.

• Slope work: In slope works such as those along roads or dam embankments, it is necessary to indicate on site the heights and positions at key points to achieve the designed slopes and thicknesses. It is dangerous to set up surveying equipment on steep slopes or have assistants enter them, but with smartphone RTK a single worker can measure coordinates of the crest and toe of the slope from a safe position and project virtual stakes with AR to confirm points. Instructions to heavy equipment operators can be accurately conveyed with screen sharing, easing quality control of slope shaping.

• Bridge piling: For piling that forms the foundations of piers and abutments, each pile center must be located exactly to the millimeter. Even in cases that would normally require multiple remeasurements and confirmations by a surveying team, smartphone RTK dramatically improves point-setting efficiency. For pile center points scattered over a wide area, GNSS positioning can guide without relocating instrument stations, so it performs well in riverside or reclaimed land bridge works. Construction managers can check points themselves, reducing the need for double-checks and simplifying quality control.

• Disaster recovery: After earthquakes or landslides, rapid situation assessment and recovery planning are required. Smartphone RTK is highly mobile and can be used by a single person to survey affected areas where bringing in large equipment is impossible. Even if communications infrastructure is down, high-precision positioning is possible by using augmentation signals from satellites, allowing you to map and record damage on the spot. Measurement data can be synchronized with the cloud later for sharing among multiple people, enabling rapid recovery activities.

Comparison with conventional methods and benefits of labor reduction

• Dramatic improvement in work efficiency: Coordinate navigation by smartphone RTK greatly shortens the time required to set out points. Time spent securing lines of sight or setting up instruments is unnecessary, and a person can be guided from point to point while walking, which speeds up operations. In fact, demonstrations using GNSS + AR stake systems have reported examples where surveying work time was reduced to about 1/6 compared to conventional optical surveying. Tasks that used to take two people half a day can be completed by one person within a few hours, contributing to shorter construction periods and the ability to move schedules forward.

• Improved accuracy and reliability: RTK itself provides centimeter-level accuracy (half-inch accuracy), and AR visual guidance nearly eliminates human misreading and communication errors. Because people are directly guided to the target point indicated on the design coordinates, conventional error factors such as other workers misreading marks on the ground are removed. Also, since guidance history and arrival errors are automatically recorded, it is easy to investigate and verify causes in case of mistakes. Quality control based on digital data becomes possible, greatly improving the credibility of survey results.

• Safety and cost benefits from labor reduction: Above all, enabling surveying and stakeout to be completed by one person achieves significant labor reduction. Reduced personnel directly saves labor costs and is attracting attention as a solution to chronic skilled-worker shortages. More importantly, fewer people need to enter active sites with heavy machinery, lowering the risk of contact accidents. The number of times workers need to descend into dangerous excavation areas is minimized, and where confirmation can be done remotely with AR, work at high places or on unstable scaffolding can be reduced. Reducing personnel is an example where safety and staffing efficiency are directly linked.

Future possibilities and prospects: AI utilization, remote support, and on-site DX

The innovations that smartphone × RTK surveying brings to the field are likely to expand further in the future. One future prospect is the use of AI to further improve positioning accuracy. AI could automatically detect and correct GNSS signal outages or error sources, or use machine learning on past positioning data to suggest optimal correction parameters, enabling stable centimeter-level positioning (half-inch accuracy) even under difficult conditions. AI might also provide smart surveying support functions that derive actionable insights for construction from the large amount of site data acquired.

Next, strengthening remote support and real-time collaboration should not be overlooked. Because smartphone RTK connects to the cloud, surveyors or designers in the office can share real-time positioning information from the field and give immediate advice, enabling remote assistance. In the future, office personnel might display instruction markers on the field worker’s smartphone AR screen from afar, or monitor multiple sites simultaneously in real time. If experts can provide their knowledge without traveling to the site, overall productivity will improve.

Furthermore, as the construction industry advances DX (digital transformation), smartphone RTK surveying strongly supports on-site digitization. Integration with 3D models such as BIM/CIM will enable consistent data utilization from design through construction and maintenance. You can overlay as-built point clouds with design models on the spot for verification, or project completed images in AR to share with stakeholders, improving communication quality. In the future, combining smartphone RTK with smart glasses-type AR devices could enable hands-free surveying and stakeout. In the context of initiatives like the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction and on-site DX, such smartphone high-precision surveying technologies will be positioned as indispensable solutions.

Conclusion

Smartphone high-precision surveying technology that can enable a task that once required multiple people to be completed by a single person demonstrates great potential for improving productivity and driving DX on construction sites. This article has shown how these technologies overcome conventional limitations of manpower, time, and accuracy, enabling safer and smarter surveying and stakeout work. These new technologies are not particularly difficult; indeed, with smartphone devices like LRTK, anyone can easily bring advanced surveying to the site. Reducing the burden on surveyors, alleviating worker shortages, and addressing skills succession are among the immeasurable benefits of introducing these technologies on site. Take this opportunity to harness the power of high-precision smartphone surveying and experience a new standard for stakeout work.