Visualize the site with high-precision AR stake layout! Layout marking and positioning completed with just a smartphone

Challenges of Piling and Layout Work on Construction Sites

At civil engineering and construction sites, it is essential to set out positions based on design drawings and to carry out tasks such as driving piles and marking out. Pile driving is a critical process in which piles (kui) that support a structure’s foundation are accurately installed in the ground, and marking out (setting out) is the task of marking on-site the positions of building columns and the locations for installing structures. Both are extremely important processes that determine construction accuracy and safety, but conventional methods have many challenges in terms of efficiency and precision.

First, there is the difficulty of positioning in stake driving and layout marking. Points where stakes should be driven and layout lines are indicated as numerical coordinates on the drawings, but pinpointing those locations on an actual site required high surveying skills and effort. Typically, a multi-person team including a surveyor uses a total station (optical surveying instrument with a tripod) and tape measures to measure distances and angles from reference points and mark the ground with stake markers or chalk. Even determining a single stake location requires multiple steps, and on a large site where tens of stakes must be installed, the layout work alone can often take more than a full day. Moreover, manual surveying cannot avoid the risk of human error, and if misreadings or marking mistakes cause stake positions to be off, it can lead to rework or construction errors in later stages.

Next, the issue of work efficiency and safety cannot be overlooked. There are cases where surveying work does not proceed as planned due to weather or terrain, and cases where workers must mark stake positions in areas where heavy machinery is operating, which entails time losses and hazards. In particular, checking stake-driving positions on steep slopes or muddy ground requires workers to enter areas with unstable footing, exposing them to a high risk of serious accidents. With conventional methods there are also places where physical stake markers cannot be installed, and in such cases they have been forced to use approximate positions, resulting in compromises in construction accuracy.

In other words, traditional pile driving and layout marking work was labor- and time-intensive, with challenges in accuracy control and safety assurance. However, in recent years, new technologies have emerged to solve these on-site problems. This is a method of positioning and guidance that leverages high-precision GNSS (RTK) and AR (augmented reality).

How RTK and AR Are Changing Pile Positioning

Advances in positioning and digital technologies have recently brought major innovations to the layout and guidance work for pile driving. The key to this is the fusion of RTK and AR. First, RTK (real-time kinematic) high-precision GNSS positioning is a technology that dramatically reduces satellite positioning errors by using correction information from a base station. While a typical smartphone GPS produces errors of several meters (several ft), RTK can reduce errors to several centimeters (several in) through corrections. Therefore, when determining positions for pile driving or layout marking on site, it becomes possible to know your current position with accuracy comparable to conventional total stations. In Japan, services to improve satellite positioning accuracy (for example, the CLAS signal from the Quasi-Zenith Satellite System Michibiki) have been put in place, creating an environment where RTK positioning can be used relatively easily even without a dedicated base station.

One form, AR (augmented reality), is a technology that overlays digital information onto a smartphone or tablet camera feed. Familiar examples include smartphone games that make characters appear on the camera view and map apps that display arrows on the real scene to provide route guidance. Applied to construction sites, this AR can directly visualize instructions on drawings such as “drive a pile here” on the real-world imagery. For example, if you load the pile-position data specified in the design drawings into a smartphone app, you can display a virtual pile or marker (the so-called AR pile) at that location through the camera feed. When a worker views the site through the smartphone screen, a mark indicating “this is the pile tip” appears to float on the ground in front of them. This allows even non-experts to immediately identify the exact point, eliminating the need to mentally match drawings with the site as was traditionally necessary.

By combining RTK-based centimeter-level positioning (cm level accuracy (half-inch accuracy)) with AR display, the guidance for stake-setting operations has evolved into a next-generation style that can rightly be called “construction-site car navigation”. Because the smartphone shows a highly accurate current position, it provides real-time navigation to the target point on the design coordinates. For example, when you select a pre-registered stake position, the screen displays guidance with arrows and numbers such as "Target: 5 cm (2.0 in) east" and "10 cm (3.9 in) north", and by taking just a few steps as instructed you can arrive at the exact location. Tasks that used to require two or more people stretching a tape measure for position layout can now be completed by a single person with only a smartphone. When you reach the target point, a virtual stake on the camera view lines up perfectly with the real ground, allowing you to intuitively confirm "this is the stake location." It feels as if the navigation destination marker of a car GPS appears as a real-world landmark, enabling even inexperienced workers to identify the prescribed position without hesitation. Reports from sites that have actually adopted this method indicate that the time required for stake layout has been dramatically reduced compared with conventional methods, and that re-driving stakes or corrections in later processes have almost disappeared. Thanks to the power of RTK × AR, stake positioning is becoming dramatically more efficient and higher in precision.

How LRTK Works and Its Main Features

Now, let's take a look at LRTK, a concrete solution that is attracting attention for realizing pile-driving guidance using RTK×AR.

*An example image of using LRTK for point cloud measurement with a compact RTK receiver attached to a smartphone. The smartphone itself functions as a high-precision surveying instrument.* LRTK is an all-in-one on-site DX tool composed of an ultra-compact RTK-GNSS receiver that can be attached to a smartphone, a dedicated app, and cloud services. By simply attaching a receiver of about 165g to your smartphone, it becomes a compact surveying instrument that fits in your pocket and can acquire real-time, centimeter-level (cm-level) positioning. Furthermore, because it manages design data (coordinates) in the cloud, sends them to the on-site smartphone app, and provides AR display end-to-end, it is characterized by enabling the previously fragmented processes of surveying, recording, and issuing instructions to be completed with a single smartphone.

The main features of LRTK are summarized as follows:

• High-precision positioning: RTK-GNSS allows stake driving and layout marking positions to be determined to centimeter-level accuracy (cm level accuracy; half-inch accuracy). Precise measurement of stake-center positions that was difficult with conventional GPS can now be done easily with a smartphone, minimizing deviations from pre-set design coordinates.

• AR stake visualization: You can place a virtual stake (AR marker) at a specified coordinate on the app and view it through the screen. For example, if you select the point designated as “Pile position A” on the drawings, a vivid virtual stake will appear in the camera view at that location. Even at night or on vacant lots with few landmarks, AR prevents missing the points where stakes should be driven.

• Coordinate navigation function: By calling up stake position data pre-registered in the cloud and selecting the target point, the app displays the remaining distance and direction in real time to guide you. When moving toward a distant point, a large arrow on the screen indicates the direction to go, and as you approach it switches to a precise distance display such as “○ cm remaining” (○ in), finally overlaying a marker on the screen when you reach the target. It’s a convenient feature that guides you pinpoint to the designated position without hesitation.

• Handling physical constraints: By utilizing AR display, positioning is possible even where physical installation of stakes is not feasible. For example, if you cannot drive nails into hard concrete or the site is a dangerous steep slope where people cannot approach, you can place a virtual stake at that location from a safe distance to confirm the position. Cases where marking was previously abandoned are no problem with digital display.

• Easy portability: High-precision positioning equipment may seem bulky, but with LRTK you only need a smartphone and a small receiver, making it extremely portable. It won’t be a burden when walking around the site; you can quickly take it out and perform positioning and AR display whenever needed. The convenience of not having to carry heavy tripods or cables is a major practical advantage on site.

• Cloud integration: Position data, photos, and point-cloud scan data acquired on site can be uploaded to the cloud and shared immediately. Stake-driving point coordinates can be centrally managed in the cloud, smoothing pre-job data preparation and post-construction record organization. Photo-attached data of stake positions recorded on site are shared with the office right away, aiding as-built checks in subsequent processes and the preparation of reporting materials.

Now, let's briefly go through the process of conducting pile-driving guidance using LRTK:

• Preparation of design data: Register the coordinates of the pile locations planned for installation in the construction project to the LRTK Cloud. Simply upload your existing drawings or coordinate lists (CSV, etc.), and the survey data for on-site use will be ready.

• Device and positioning setup: On site, attach an RTK receiver (LRTK device) to a smartphone and launch the app. The receiver acquires signals from satellites and correction information and initializes to a state capable of positioning with centimeter-level accuracy (half-inch accuracy). Preparation takes only a few tens of seconds, and surveying can start immediately.

• Guidance to the pile position: When you select the target pile number or point in the app, the aforementioned navigation function activates. By following the on-screen arrows and distance readout, you can reach the target position without getting lost. For example, you might be instructed "5 m (16.4 ft) to the northeast", and as you approach you will receive finer guidance such as "20 cm (7.9 in) remaining" → "5 cm (2.0 in) remaining". Finally, the app displays "You have arrived at the destination!" to confirm you are standing at the precise position.

• Position confirmation and marking: Once you reach the indicated point, compare the live camera view on the smartphone screen with the AR pile marker to confirm the location. If the virtual pile aligns perfectly with the ground, that proves you are standing at the exact design location. Mark the point with spray or chalk, or signal the heavy equipment operator to drive the pile with the pile-driving machine. Because the AR pile serves as a real-world reference, you won’t miss the intended point even on large sites.

• Saving and sharing construction records: After pile driving is complete, take a photo at that location with your smartphone camera and record it with one tap. The photo is automatically linked to the measured coordinates and saved to the cloud, so the office can later check in bulk within how many centimeters (inches) each pile was installed relative to the design position. Keeping digital construction records also makes reporting to clients and quality assurance easier.

As described above, by using LRTK, even people without surveying expertise can accurately determine stake positions simply by following the guidance on their smartphone screen. It can truly be called an innovative tool that makes "stake positioning anyone can do" a reality.

Main benefits of implementation

When LRTK is actually introduced on-site, various benefits can be obtained in terms of accuracy, efficiency, and safety. The main effects are summarized as follows:

• Improved accuracy: Guidance with centimeter-level accuracy (cm level accuracy, half-inch accuracy) virtually eliminates pile misplacement. It enables construction exactly according to the design drawings and prevents rework or construction errors caused by pile-center deviations. This is particularly effective for projects that require strict positional accuracy, such as high-rise buildings and bridges.

• Dramatic improvement in work efficiency: The time required for surveying and staking out positions is greatly reduced. For example, replacing conventional optical surveying for pile positioning with AR guidance has been verified to cut work time to one-sixth of the previous time. Because each person can move by following the navigation, tasks that formerly required multiple people can be accelerated with a minimal crew.

• Labor reduction and skill leveling: The number of surveyors and support staff can be reduced, leading to lower labor costs. It can be operated without highly skilled personnel, making it easy to introduce even at sites facing labor shortages. Also, since the equipment is smartphone-based, initial investment costs can be kept down, and provisioning one device per person becomes realistic.

• Improved safety: There is no need to force personnel to stake out pile positions in hazardous locations. AR allows position confirmation from safe zones, reducing the risk of accidents at heights, on slopes, and around heavy machinery. Worker burden is reduced, enabling them to undertake construction with greater peace of mind.

• Quality control and recording accuracy: Because digital positioning data and photographic records are retained, post-construction quality inspections and reporting become easier. A history remains of which pile was driven at which coordinates, which is useful for subsequent position checks or additional work. Objective data can also be presented as explanatory materials to clients or supervisory authorities, increasing credibility.

• Versatility and promotion of DX: LRTK can be used for a wide range of applications beyond pile driving, such as layout marking (staking out), as-built measurement, locating buried objects, and overlaying 3D design models on site; therefore, once introduced it serves as a multipurpose DX tool for the construction site. It becomes an “all-purpose surveying tool” active in various scenarios—for example, performing point-cloud scans of the ground between piling operations or overlaying drawing data to display a completed-image in AR. It will accelerate the site’s digital transformation and comprehensively enhance productivity and the quality of information sharing.

AR Uses Beyond Pile Driving: Point Cloud Measurement and Design Data Projection

LRTK can be applied broadly to the digitalization of construction sites beyond staking out pile locations. Representative examples are point cloud measurement and projection of design data using AR.

First, in point cloud scanning to measure as-built conditions after construction, you can use a smartphone’s camera and sensors to scan the surrounding terrain and structures and acquire three-dimensional point cloud data. By combining RTK positioning via LRTK, the acquired point clouds are assigned high-precision survey coordinates from the outset, automatically aligning with the design model on the drawings. Therefore, it is possible to overlay and compare with the design data immediately after scanning on site. For example, if you acquire a point cloud of the road surface after paving and compare it with the design elevations, a heat map will show on the spot which locations are how many cm (how many in) higher or lower than the design, allowing you to immediately judge whether rework is necessary. In an actual railway construction project, operations were carried out in which the height and position of replaced rails were measured with a smartphone and checked against the planned alignment the same day, adjusting without overlooking even deviations of a few centimeters (a few inches). A process that used to take several days—survey crews setting out control points, laser scanners measuring point clouds, and matching with CAD data in the office—was completed on site the same day thanks to the introduction of LRTK.

Additionally, LRTK also supports AR display of design models and drawing data. If you import architectural and civil engineering 3D models, or 2D drawing data such as DWG, into the system along with coordinate information, they can be overlaid directly onto the on‑site scenery. For example, you can project a 3D model of the completed building onto the site in AR to share the expected finished appearance with stakeholders, or read foundation grid lines from drawing data and display them on the ground in AR to omit layout marking work. Conventional AR apps required placing markers or manual alignment, but thanks to coordinate synchronization via RTK, LRTK can fix models in place according to the drawings without the hassle of alignment.

*An image of point-cloud data of underground pipes obtained during buried-pipe construction being displayed in AR on the road surface to visualize their position and depth.* Furthermore, in buried-pipe construction and similar work, we have also realized advanced functionality such as scanning underground pipes during construction, saving the data to the cloud, and then presenting that point-cloud model in AR as a "see-through" display after backfilling. This introduces a new approach to recording and sharing underground buried objects and to preventing damage to buried items during excavation. A workflow that completes everything from scanning to modeling and AR visualization with a single smartphone greatly simplifies tasks that previously required specialized equipment and promotes on-site data utilization.

Summary

An LRTK pile-driving solution that leverages high-precision GNSS and AR realizes a smart transformation of job sites that overturns conventional practices. Positioning work, which used to be labor- and time-intensive and could not tolerate mistakes, can now be carried out accurately, quickly, and safely with just a smartphone, and the construction process is beginning to change dramatically. The intuitive AR guidance that can be used without surveying expertise is truly the first step toward "surveying that anyone can do".

By actually implementing LRTK, you will be able to handle not only pile driving and layout marking but also a variety of surveying and measurement tasks on your own. If you are looking to advance on-site DX, before relying on expensive dedicated equipment, why not consider this simple, smartphone-based surveying? With compact equipment and easy-to-use applications, LRTK can dramatically improve on-site productivity and quality control, making it a powerful tool that anticipates the construction style that will become the norm in the future. As a new step toward smart construction, be sure to experience its effects on your site.