Whoever Masters Stakeout Controls the Site! New Surveying Methods for the DX Era

Basics of stakeout and its importance on site

A stakeout is the work of accurately indicating the positions (survey points) of structures on site based on design drawings and survey data—positioning (stakeout). In construction and civil engineering, positioning is so important that people say, “Whoever masters stakeout controls the site.” For example, points indicated by initial stakeout—such as building foundations or bridge pile centers—become the reference for the entire subsequent construction.

If the stakes from the stakeout are even slightly off, it can lead to distortion of the entire structure or construction defects. Therefore, meticulous surveying and calculation that do not overlook even errors of a few millimeters (a few 0.1 in) are required on site. Stakeout is also the starting point for as-built management. As-built management, which verifies after construction whether a structure’s position and shape match the design, is conducted based on the reference points and coordinates established by the stakeout. By accurately positioning at the initial stage, as-built verification during later measurements and inspections can be carried out quickly and reliably, enabling early corrections and quality assurance.

Problems with conventional stakeout methods (dependence on survey crews, manpower, mistakes, inefficiency)

When performing stakeout surveying using traditional methods, the following issues have been pointed out on site.

• Dependence on survey crews: Stakeout work has long relied on specialized survey crews, making it difficult to perform flexibly alongside other on-site tasks.

• Manpower and time burden: High-precision positioning has required at least two people—a surveyor and an assistant—and much time was consumed by setting up total stations, securing lines of sight, and installing reference stakes (batter boards).

• Risk of human error: Manual surveying always carries the risk of human error—tape sag, misreading, transcription mistakes in calculations—so careful double checks are indispensable.

• Inefficient repetitive work: Markings can be erased during construction or shifted by the passage of heavy equipment, necessitating frequent rework by the survey crew. Re-doing stake points leads to schedule losses and puts particular pressure on stakeout operations.

Stakeout in the DX era: what changes with smartphone + RTK + cloud

To solve these traditional problems, a new stakeout method attracting attention in the DX era is the combination of smartphone + RTK + cloud. Recently, technologies (e.g., LRTK) have emerged that realize RTK-GNSS surveying—which used to be fixed and expensive—on a single smartphone, opening an era in which high-precision positioning can be handled by anyone.

RTK (Real Time Kinematic) is a method that achieves positioning accuracy within a few centimeters (in some cases within a few millimeters (a few 0.1 in)) by receiving GNSS satellite signals simultaneously at a base station and a rover and applying real-time error corrections. By using a small GNSS receiver attached to a smartphone and an internet connection to incorporate correction information from a base station and centimeter-class augmentation services (CLAS) from Japan’s quasi-zenith satellite “Michibiki,” high-precision positioning has become possible without expensive dedicated equipment.

By combining this with a navigation feature that displays guidance on the smartphone camera image using AR (augmented reality), users can be guided to pile-driving positions simply by following on-screen instructions without needing to think about complex calculations or surveying procedures. And with cloud integration, design data (pile center coordinates and structural model coordinates, etc.) can be shared in advance, and survey results obtained on site can be immediately reviewed with the office or client. Stakeout work is no longer something that relies solely on a craftsman’s intuition and experience; it is evolving into a process that can be shared across the whole team based on digital data.

Labor reduction and elimination of reliance on individuals through smartphone RTK stakeout

One major benefit of stakeout using smartphone + RTK is labor reduction. Pile staking, which previously required two or more people to operate survey equipment and align prisms, can now be completed by a single person with a smartphone. Without having to arrange a survey crew, site agents or heavy equipment operators themselves can perform position setting immediately when needed, improving personnel efficiency. There are cases in which pile center setting that used to take two people half a day was completed by one person within a few hours using smartphone RTK.

At the same time, eliminating reliance on specific individuals is another important point. Since the app performs angle and distance calculations and provides guidance automatically, accurate positioning is possible without relying on the intuition and experience of skilled surveyors. The craftsmen-only skills of veterans are standardized by digital tools, allowing young staff and those outside surveying specialties to handle the work. Moreover, because survey data and operation histories are automatically recorded in the cloud, information such as “which point was measured when and to what accuracy” becomes visible and shareable, reducing the degree of task personalization.

Linking AR navigation and point clouds to as-built management

A unique smartphone feature is intuitive position guidance via AR navigation. Arrows and distances to the target point are displayed in real time on the phone screen, and the user simply walks in the direction the arrow indicates to approach the target. As the distance approaches zero, the arrow’s direction is refined, and by moving the smartphone according to the final on-screen guidance, the user can arrive at the specified coordinates with an error of only a few centimeters (a few 0.4 in). This system—where anyone can stand at the correct location by simply “following the screen”—differs fundamentally from traditional stakeout guidance that relied on experienced personnel.

AR displays can also visualize the target point itself. For example, in locations where direct ground marking is impossible, a virtual stake (AR stake) can be placed on the smartphone screen to indicate the position. This enables identification of target positions from a safe distance even on floors covered with concrete or in restricted hazardous areas. Combined with photogrammetry, one can obtain coordinates of points photographed remotely and later project AR stakes on site to identify positions. This is a revolutionary technology that enables stakeout in situations that were previously difficult.

This smartphone AR feature is closely linked with as-built management. By matching three-dimensional design data (BIM/CIM, etc.) uploaded to the cloud in advance with point cloud survey data acquired on site, the design model can be overlaid on the actual structure and displayed in AR. With GNSS-based self-position tracking, the virtual model seen through the smartphone remains fixed and aligned with reality. Such high-precision AR overlay makes it easy to intuitively show “how closely the design model matches the actual structure” during as-built inspections, or to project the completed image onto the real scene during construction planning to share with stakeholders.

Real-time sharing, remote attendance, and automated reports enabled by the cloud

Cloud utilization dramatically improves information sharing and procedures related to stakeout. The main points are as follows.

• Real-time sharing: Survey and construction data are saved and synchronized in the cloud instantly, so points positioned on site and as-built measurement results can be shared in real time with remote offices and stakeholders. This eliminates the time lag of “measuring on site, then checking the drawings and reporting,” enabling rapid decision-making based on the latest information.

• Support for remote attendance: Because site status can be understood via the cloud, construction management and inspections can be conducted without physically visiting the site. For example, as-built measurement data can be shared online for the client or inspector to review from the office, or remote witness inspections can be conducted by overlaying AR information on smartphone camera images. Such digital remote attendance is also being highlighted as part of the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction initiative.

• Automated reports: Digitally acquired survey data can be automatically reflected in as-built management drawings and surveying deliverables. In LRTK, coordinates for each survey point and guidance histories are all recorded, eliminating the need to manually recompute or transcribe numbers for inspections. Data obtained on site can be output directly as deliverables for electronic submission or repurposed for quality control reports, streamlining these tasks.

Field implementation examples and achieved benefits (work time, accuracy, safety, inspections)

Actual implementations of smartphone RTK stakeout on sites have reported the following significant benefits.

• Reduced work time: Time required for stakeout surveying has been dramatically shortened compared to traditional methods. Because cumbersome equipment setup and line marking are unnecessary and a person can walk and set points sequentially, the work is faster. In one comparison, using a GNSS + AR pile staking system reduced point-setting work to about 1/6 of the time required for optical surveying.

• Improved surveying accuracy: High-precision GNSS positioning combined with AR guidance enables stakeout and as-built measurement with better accuracy than before. Human reading and transmission errors are reduced because operators are always guided to digitally precise target points. For example, at one site, a pile-driving operator simply followed on-screen instructions to install piles at the design coordinates. This achieved accuracy comparable to double-checks by multiple survey crews, without requiring dedicated seasoned personnel.

• Improved safety: Labor reduction reduces the number of personnel who need to enter hazardous areas for surveying, improving safety. Tasks such as layout marking previously done at excavation bottoms or high places can be performed from safe locations using smartphone AR. Surveyors no longer need to be near operating heavy equipment, lowering the risk of contact accidents. Indeed, there are cases in confined sites where the operator, checking the smartphone screen, completed pile alignment without anyone entering the area around the equipment.

• More efficient inspections: The cycle of as-built inspection and feedback has also been accelerated. Because survey results are shared to the cloud immediately, all stakeholders can see differences from design values on the spot and decide on rework early. In one underground project, coordinates of major structures on each floor were measured with LRTK after completion, and differences from design values were color-coded in the app and shared with the client instantly. Any deviating areas were immediately corrected, and all column and wall positions were ultimately delivered within allowable tolerances. Real-time as-built confirmation and information sharing reduced rework associated with inspections, enabling smooth completion inspections and handovers.

Conclusion: Guiding adoption of smart surveying with LRTK

As stakeout methods become more widespread, the surveying and pile-driving technologies that support them are entering a new phase. As represented by the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction initiative, site DX through digital technology is an industry-wide challenge. LRTK, which combines smartphone RTK and AR navigation, is precisely a solution aligned with this trend and can be considered a key technology that brings digital transformation (DX) to stakeout sites. With concerns about the aging and shortage of experienced surveyors, intuitive AR surveying that anyone can use has the potential to establish a new norm in future construction management.

What LRTK enables is not only high-precision pile guidance. An era has arrived in which routine site surveying, as-built management, and locating buried objects—tasks that previously required dedicated equipment and advanced expertise—can be handled simply with a single smartphone. For example, tasks such as boundary surveys or earthwork volume measurements can be measured by the site supervisor in a short time and shared to the cloud immediately with LRTK. The advantage of performing sufficient surveying without arranging a dedicated survey team is immeasurable. LRTK breaks the traditional notion that surveying is difficult and time-consuming, creating an environment where anyone can easily achieve high-precision positioning.

Those responsible for sites in the DX era can achieve safer and more efficient construction management by introducing smart surveying with LRTK. Make the smartphone AR technology that has become the new norm in stakeout a part of your next project and experience its power firsthand.