Realizing On-site Visualization with High-Precision Positioning × AR! Smart Construction with LRTK

Table of Contents

• What high-precision positioning is (such as RTK) and why it is necessary

• The impact of site visualization brought by the fusion of AR and high-precision positioning

• Use cases at actual construction sites (layout marking, as-built verification, pile center guidance, structure placement checks, point cloud overlay)

• Workflow for high-precision AR positioning that anyone can perform alone with LRTK

• Benefits from four perspectives: accuracy, labor saving, communicability, and safety

• Next-generation smart construction style realized with LRTK + smartphone + AR

• Tips for smooth on-site introduction and phased expansion of use

• Recommendation for simple surveying with LRTK

In recent years, digitization (DX) of construction sites has progressed rapidly, and a new construction management method that combines high-precision positioning and AR (augmented reality) is attracting attention. By using smartphones or tablets together with specialized positioning devices, drawings and 3D models can be overlaid directly onto the site for intuitive verification. This article explains the impact of on-site "visualization" enabled by the fusion of high-precision positioning technologies and AR, including concrete use cases and tips for implementation. It also explores the next-generation smart construction approach through the notable tool “LRTK”, which enables centimeter-class surveying by a single person.

What high-precision positioning is (such as RTK) and why it is necessary

First, "high-precision positioning" literally refers to technologies that obtain position information far more precise than usual. The GPS built into typical smartphones can have position errors on the order of several meters. Employed to address this is high-precision positioning technology such as RTK positioning (Real Time Kinematic). RTK is a method that corrects GNSS satellite positioning errors in real time between a fixed reference station and a rover, enabling positioning with an accuracy of a few centimeters (a few in) in both horizontal and vertical dimensions. In Japan, centimeter-level augmentation services such as the quasi-zenith satellite system Michibiki’s CLAS have been developed, and even in mountainous areas outside communication coverage, offline correction information can be used to achieve stable high-precision positioning.

Why is such high precision necessary in construction and civil engineering project management? One reason is the need to confirm and control the positions of structures and reference points with the design-specified accuracy. For example, if the elevation of a finished road deviates by several centimeters (a few in) from the design, it can become a serious issue; if the installation position of bridge components is off by several tens of centimeters (several tens of in), it could be a construction error. Traditionally, such precise measurements required dedicated surveying instruments like total stations (TS) and levels, and experienced surveyors typically worked in pairs on site. However, with the spread of GNSS technologies capable of high-precision positioning (RTK-GNSS), it has become possible to obtain equivalent accuracy using more convenient methods. In particular, the combination of smartphone + high-precision GNSS receiver has emerged, making it increasingly possible for anyone to readily acquire centimeter-level positioning information (cm level accuracy (half-inch accuracy)). High-precision positioning is not only improving surveying efficiency but, as discussed below, is a key technology that—when merged with AR—can greatly change on-site operations.

The impact of site visualization brought by the fusion of AR and high-precision positioning

When high-precision positioning and AR technologies are combined, on-site "visualization" advances dramatically. AR (Augmented Reality) is a technology that overlays digital information onto real-world scenes viewed through a camera. Applied at construction sites, this makes it possible to overlay drawings and 3D models onto the actual scene. For example, if a smartphone or tablet displays a life-sized 3D model from the design phase as AR over the live camera view of the site, you can intuitively verify on the spot whether the finished result matches the design.

Traditionally, when inspecting as-built conditions after construction, survey equipment was used to measure elevations and dimensions point by point, and results were compared with drawings back at the office. This analog method often involved a large time lag from measurement to judgment, and it could take days to discover a problem on site and implement corrective measures. Inspections also required skilled technicians, with two-person teams being the norm, making the process inefficient amid worsening labor shortages. With "digital as-built inspection" using high-precision positioning + AR, however, measurement and judgment can be completed on the spot with a single smartphone. Because design data can be accurately overlaid onto the real environment, simply holding up the device lets you visually grasp any deviations in the finished work, reducing re-measurement and rework. Modern smartphones also feature high-performance cameras and LiDAR sensors; when combined with high-precision positioning devices and dedicated AR apps, AR technology—which was once at an experimental level—has now become practically usable in everyday construction management.

Moreover, the government is supporting this trend as part of on-site DX. Since 2016 the Ministry of Land, Infrastructure, Transport and Tourism has promoted the i-Construction initiative, advancing ICT surveying and BIM/CIM adoption. In fiscal 2024, a policy was indicated allowing trial substitution of conventional standards when contractors propose efficiency improvements using 3D models or AR for as-built management, and AR-based as-built management methods are increasingly being formally introduced on sites. Against this backdrop, the fusion of AR and high-precision positioning for site visualization is gaining strong expectations as a powerful solution that enhances both quality and efficiency.

Use cases at actual construction sites (layout marking, as-built verification, pile center guidance, structure placement checks, point cloud overlay)

When high-precision AR positioning is realized, it can support many aspects of construction management. Below are representative use cases and their descriptions.

• Layout marking (point/line marking): Layout marking, the process of marking the ground or structures based on design drawings during foundation and structural work, can be streamlined with AR. If an AR app that supports high-precision positioning overlays design lines and points onto the ground, workers can simply mark along the lines shown on the screen for accurate layout. This greatly simplifies the cumbersome traditional layout work using tape measures and mason’s lines.

• As-built verification (as-built inspection): AR is powerful for as-built inspections that confirm whether constructed elements match the design in shape and dimensions. For instance, after concrete placement, displaying the finished 3D model as AR over the actual element lets you instantly compare shapes and elevations. Using a LiDAR-equipped smartphone to scan the construction area and automatically comparing the collected point cloud data with the design model enables advanced inspections—such as color-coded difference displays—to be performed on site. Discovering defects immediately and taking corrective action on the spot reduces later rework.

• Pile center guidance (solo piling work): Accurate positioning for foundation piles or boundary stakes typically requires a surveying technician and an assistant, but high-precision AR positioning enables one person to guide pile locations. By walking the site with a tablet, virtual pile center markers are displayed on the actual ground, so when you reach the target location it is immediately apparent on the screen. This reduces manpower while ensuring piles are driven at accurate positions.

• Structure placement checks: AR visualization is useful when installing or placing structures and equipment on site. For large machinery or prefab components, overlaying the design model in AR beforehand lets you check interference with surroundings and placement positions. By simulating in actual size whether a component will collide with other structures or whether it can be installed in the correct orientation, installation errors and rework can be prevented.

• Construction visualization by point cloud overlay: Overlaying current conditions and planned data is also valuable during active works. For example, in embankment or excavation works, scanning the interim terrain with a smartphone to obtain a point cloud and overlaying it in AR with the design final-shape model lets you visually grasp progress and surplus/deficit. Comparing point cloud data and color-coding differences identifies areas that have not reached the required elevation or have been over-excavated, allowing decisions for additional fill or correction the same day. By supporting on-site use of point clouds through AR, progress and quality can be visualized in real time.

Workflow for high-precision AR positioning that anyone can perform alone with LRTK

To realize the high-precision AR positioning described above on site, a workflow using dedicated devices and apps is used. A representative method uses the compact high-precision GNSS terminal LRTK. With LRTK, surveying and construction management tasks that previously required multiple skilled technicians can be performed by anyone alone. Below is an outline of the basic flow.

• Prepare the device and app: Attach the LRTK unit to a smartphone or tablet and launch the compatible surveying/AR app. The LRTK unit links to the smartphone to receive GNSS correction information and applies real-time corrections to the device’s position. Connect to Michibiki (CLAS) or network-based reference station data and initialize RTK positioning (Fix solution) on the device.

• Coordinate alignment and data loading: Next, set the positioning system to the site’s coordinate system. If known points (control points) exist, measure over them with the smartphone and use the acquired coordinates to correct the model position within the app. Load design drawings or 3D model data into the app and align them with the site coordinate system. This aligns digital data with the real world so AR overlays can be matched without error.

• Positioning and construction management with AR: Once set up, simply walk the site while holding up the smartphone or tablet. Because your current position is always known to within a few centimeters (a few in) thanks to high-precision positioning, the design drawings and models will appear perfectly overlaid on the real scene in the AR view. For pile location guidance or layout marking, follow the target markers displayed on screen to mark or install piles at the designated positions. For as-built verification, overlay the model on the constructed portion to check finish quality, and scan as needed on site.

• Record and share results: Taking screenshots of the AR view provides photographic records that clearly show differences from the design. Point cloud data and surveyed coordinates can be automatically saved and shared via the cloud. There is no need to transfer data via USB after returning to the office; you can proceed with verification while sharing data with the team in real time on the cloud. The ability to complete the entire workflow alone and immediately share results with stakeholders is a major advantage.

With this flow, LRTK and a smartphone alone let you conduct site surveying and as-built management quickly and accurately. Next, we summarize the concrete benefits from four perspectives.

Benefits from four perspectives: accuracy, labor saving, communicability, and safety

Introducing high-precision positioning × AR on site yields major benefits in the following four areas.

• Improved accuracy: Positioning information obtained by RTK GNSS eliminates traditional manual measurement errors and recording mistakes, ensuring accuracy within a few centimeters (within a few in) at all times. Human errors decrease and quality inspections of finishes attain high reliability. Point clouds and surveyed coordinates obtained with high-precision positioning are based on public coordinate systems, allowing strict comparisons with design drawings and existing survey results. As a result, quality control accuracy and reliability improve dramatically.

• Labor saving and efficiency: Because large areas can be visualized on site at once, repeated point-by-point measurement and recording work can be greatly reduced. Intuitive on-screen confirmation via a smartphone replaces time-consuming back-office comparisons with drawings. Being able to complete measurement through evaluation by a single person simplifies personnel allocation and scheduling, leading to reduced work time. The need to transport and set up heavy equipment is eliminated, reducing physical burden.

• Improved information transfer: AR enables visually easy-to-understand information sharing on site, facilitating smoother communication among stakeholders. For example, during inspections with supervisors or clients, showing the overlaid finished image on a tablet helps reach on-the-spot agreement. Uploading measurement data to the cloud allows remote supervisors or colleagues to check site conditions in real time. Situations that were hard to convey with text or numbers alone can be intuitively communicated via AR imagery, reducing time required for reporting and discussion.

• Enhanced safety: Completing surveying and inspection with fewer people and in less time contributes to safety. Reducing on-site work time lowers the risk of traffic accidents or collisions with heavy equipment. Visualizing the locations of underground utilities in advance with AR can help prevent accidental damage to pipes or cables. Reducing dangerous tasks such as multi-person heavy equipment placement or high-altitude work also raises overall site safety management levels. Thus, DX technologies not only reduce manpower but also strengthen safety measures.

Next-generation smart construction style realized with LRTK + smartphone + AR

As described above, combining high-precision GNSS positioning and AR makes dramatic improvements in efficiency and sophistication of construction management possible. Using a device like LRTK together with a smartphone enables a single unit to function as an all-purpose tool from surveying to as-built inspection. Replacing workflows that once required multiple instruments and personnel—such as total stations and 3D scanners—with the familiar combination of smartphone + LRTK + AR app is revolutionary. This is not merely a replacement of equipment but a transformation of the way on-site work is conducted—a new smart construction style.

Smart construction is a next-generation approach that optimizes construction production processes using ICT and IoT. In line with the government-promoted i-Construction movement, various smart technologies such as BIM/CIM and drone surveying are being introduced on sites. Among these, high-precision positioning × AR is a representative initiative to digitize the site as is. The sight of each site staff member holding a smartphone and performing real-time data measurement and sharing may well become the next-generation norm. Shifting traditional site management—which relied on veteran intuition and experience—to data-driven management that anyone can perform addresses problems such as labor shortages and skills transfer.

Furthermore, connecting site and office via smartphone and the cloud to visualize the site remotely is another major benefit. Point clouds and photos captured on site are immediately synced to the cloud, allowing head office or branch offices to check progress and issue instructions. This can dramatically raise productivity and quality, while promoting paperless operations and automated recordkeeping for streamlined administration. The smart construction style realized by LRTK + smartphone + AR is already being adopted by some advanced companies and is expected to become increasingly mainstream.

Tips for smooth on-site introduction and phased expansion of use

To embed new technology on site, planned introduction and promoting understanding among stakeholders are essential. Here are some points to help smoothly integrate high-precision AR positioning into routine site work and gradually expand its use.

• Verify effectiveness with small-scale trials: Don’t try to apply it to all sites and all processes at once; start with pilot introduction on a portion of sites or specific processes. For example, implement AR-based as-built verification on one section and compare in data how much efficiency improved or errors decreased versus traditional methods. Starting small and accumulating success stories provides evidence for both field workers and management/clients, making full-scale adoption easier.

• Start with IT-savvy members to gain traction: Initially, have younger staff or IT personnel who are comfortable with digital devices start using the system. By demonstrating AR positioning’s convenience on site, their experience will pique others’ interest. Showing on-site operation and letting people experience that "you can survey easily by following on-screen guidance" helps dispel veteran skepticism. The operations are not difficult and can be learned through short training or on-the-job training.

• Incorporate into existing workflows: Don’t let it remain a one-off demo; embed it into standard site procedures. Specify concrete usage steps in construction plans and checklists, such as "Confirm with AR at XX stage" or "Perform point cloud scanning once per week." Also decide in advance how to record and report AR-measured/verified results. For example, save AR screenshots to the cloud and attach them to electronic as-built submission documents. Making it a scheduled activity that everyone uses helps the tool become a routine part of site work.

• Share success stories and scale horizontally: After achieving results, actively share case studies internally and externally. Specific outcomes—such as "Using AR positioning reduced work time by 30%" or "Inspection passed with zero quality issues"—attract interest from other departments and subcontractors. Standardize on-site know-how into manuals and checklists and roll them out internally for easy application to other projects. As success experiences spread, an organization-wide culture of using high-precision AR positioning will take root, amplifying DX promotion effects.

Recommendation for simple surveying with LRTK

Finally, as a concrete solution supporting the practice of high-precision positioning × AR, we introduce LRTK. LRTK is a palm-sized high-precision GNSS receiver device that attaches to a smartphone and transforms it into a centimeter-class surveying instrument. While internal smartphone GPS typically has errors of several meters, using LRTK achieves dramatically higher precision—on the order of a few centimeters (a few in). This enables one person to complete control point surveying and as-built inspections that previously required specialized equipment and skilled operators. Even in mountain sites with unstable communications, stable positioning is possible using correction information from Michibiki (CLAS) or offline reference station data. In other words, even without a veteran surveyor on site, you can perform control point setup and post-construction inspection using only a smartphone.

LRTK also seamlessly integrates with AR functions. By projecting drawings and 3D models into the real world without displacement based on the highly accurate GNSS-derived current position, troublesome alignment tasks are eliminated. For example, simply moving around the site with a tablet will accurately display virtual pile positions on the actual ground so target points are easily identifiable even from a distance. Additionally, point clouds captured by a smartphone can be instantly compared with design models in the cloud, and advanced analyses—such as generating colored heat maps to check whether construction matches plans—can be executed with one touch.

LRTK includes a cloud platform, so measured and scanned data on site are synchronized to the cloud in real time and shared with the team. Remote offices can immediately view on-site 3D point clouds and photo-tagged measurement points and discuss site conditions as if in an online meeting.

Moreover, the LRTK series offers various tools that strongly support on-site DX, such as a "coordinate navigation" function that guides pile-driving positions for one person, an automatic embankment volume calculation from smartphone LiDAR point clouds, and the ability to attach high-precision position and orientation information to photos for management. It is designed so surveying, as-built recording, and inspection—tasks that once required multiple devices and personnel—can be completed with a single iPhone. Results obtained with LRTK can be output in formats compliant with the Ministry of Land, Infrastructure, Transport and Tourism’s electronic delivery guidelines, and many construction companies have already begun adopting LRTK to achieve both labor savings and quality improvement.

By leveraging LRTK, "surveying and construction management that anyone can do alone" becomes a reality. Why not experience next-generation smart construction based on high-precision positioning × AR on your site? For those interested, detailed product information and case studies are available on the [official site](https://www.lrtk.lefixea.com/). Embrace digital technology and elevate your projects to the next stage.