LiDAR×AR Navigation Evolving Site Management – LRTK Opening the Way to Next-Generation Smart Construction

In the fields of construction site management and surveying, the combination of LiDAR sensors and AR navigation has recently attracted attention as a cutting-edge technology. LiDAR (light detection and ranging) is a sensor that measures distances to the surroundings with laser light and can convert an entire site into 3D data. This allows work that previously relied on craftsmen's intuition and experience to be digitally "visualized," enabling intuitive and precise site management. This article explains in detail the potential of using 3D point cloud data captured by LiDAR sensors, the accuracy improvements of AR navigation realized by integrating high-precision GNSS (Global Navigation Satellite Systems), and real use cases (layout of structures, visualization of buried utilities, as-built verification, safety guidance, disaster response). For construction managers, survey personnel, ICT implementation staff, and municipal employees, we present the vision of next-generation smart construction using a smartphone and an LRTK device.

The Potential of LiDAR Sensors and 3D Point Cloud Data

LiDAR (Light Detection and Ranging) is a technology that measures distances to objects by the time of flight of laser light, and in recent years compact LiDAR sensors have begun to be incorporated into smartphones and tablets. For example, on the latest smartphones, by simply waving and walking within approximately a 5 m (16.4 ft) range you can instantly acquire 3D point cloud data consisting of millions of points that make up the surroundings. It is an innovative feature that enables the entire site to be captured as a digital three-dimensional record, almost like taking a video.

A point cloud is a collection of three-dimensional data that records the surfaces of objects and terrain with countless points. It is, so to speak, a "digital copy of real space," and its characteristic is that it can record a site including heights and depths that cannot be conveyed by two-dimensional drawings or photographs. Point clouds are already being widely used in construction and civil engineering sites, and for example they offer the following advantages:

• Intuitive 3D visualization: Displaying the point cloud gives a lifelike three-dimensional view, allowing even non-experts to intuitively grasp the spatial image. It is powerful for explanations to clients and newcomers.

• High-precision measurement: On a point cloud you can freely measure the distance between any two points, areas, and volumes. It is more accurate than manual measurement with tape measures or staffs and reduces human error.

• Information richness and reusability: Because the acquired point cloud contains data of every corner of the site, if "additional measurement is needed later" you can check and analyze it from the data. Secondary uses such as extracting cross-sections or feeding back into design models are also easy.

Thus, point cloud data strongly complements traditional materials as a digital record of the site and becomes a valuable information resource useful for construction planning, progress management, and maintenance. Recently, with the improvement of computer and cloud performance making large-volume data easier to handle, and with tailwinds such as the Ministry of Land, Infrastructure, Transport and Tourism’s promotion of *i-Construction*, point cloud utilization is expected to be a key to site DX (digital transformation).

Accurate AR Navigation Realized by High-Precision GNSS Integration

Augmented reality (AR) technology, which overlays digital information on the real environment through a smartphone camera, holds great potential for construction sites as well. However, to introduce AR into the field at a practical level, alignment accuracy to "display virtual objects at the correct real-world positions" is indispensable. Conventional smartphone internal GPS and compass-based positioning have errors of several meters, so even if you display a model of an underground buried pipe, it will be offset from the actual position and far from the precision required for field work. Moreover, older common AR systems required placing markers (registration marks) on each site or performing manual calibration each time. Doing this across a wide construction area was unrealistic.

This is where the combination of "smartphone + LiDAR + RTK-GNSS" enables markerless high-precision AR. The latest smartphones are equipped with excellent AR platforms (e.g., Apple ARKit) and use the camera and IMU (inertial measurement unit) to track device motion. Additionally, LiDAR sensors built into higher-end models acquire the surrounding spatial shape as point clouds in real time and measure distances to the ground and structures with high accuracy, allowing virtual objects to be stably overlaid on the real world and enabling realistic occlusion where virtual objects are hidden behind real objects. In other words, a smartphone can instantly build a 3D map of its surroundings, greatly strengthening the foundation for AR displays.

The remaining challenge is accurately knowing "where the smartphone is now." High-precision positioning technology, RTK-GNSS (real-time kinematic satellite positioning), demonstrates its power here. Standalone GPS can have errors of several meters, but using the RTK method with correction information from a base station improves position accuracy to a few centimeters (a few inches). While this technology has long been used in surveying, recent miniaturization of receivers has produced RTK-capable GNSS receivers that can be attached to smartphones. By combining such a device with a smartphone, the device’s position can be measured on the Earth coordinate system to centimeter-level, making it possible to reduce the discrepancy between AR-displayed design models and reality to nearly zero.

By integrating the 3D point cloud data of the surroundings acquired by LiDAR with the global-coordinate self-position obtained by RTK-GNSS, it becomes possible to finally bring AR navigation to the field at a practical level of accuracy. For example, if you load 3D models of structures or buried utilities prepared in advance into the smartphone, simply pointing the device on-site will display those models exactly aligned with their real-world positions. Because ground shapes are being grasped in real time by LiDAR, virtual models are always placed with accurate position and orientation, and the display will not shift as the user moves around. This breakthrough of "overlaying design information in space without alignment work" has made AR navigation robust enough for practical site management.

Furthermore, RTK-GNSS positioning is performed in an absolute coordinate system. This allows point cloud data and design models acquired on site to be handled in a unified coordinate frame, enabling consistent AR displays even when combining multiple datasets. In the past, expanding the scan range could cause distortion or scale errors in point clouds due to self-position estimation errors, but combining high-precision GNSS allows point clouds to be stitched together over wide areas without positional shifts. As a result, a single smartphone can function like a high-performance surveying instrument, enabling 3D measurement and AR visualization with accuracy comparable to specialized equipment.

Specific Use Cases for AR Navigation

Next, let’s look at specific use cases of AR navigation on site. An AR system that combines LiDAR and GNSS can dramatically streamline many construction management and surveying tasks that were previously difficult. From precise layout of structures to transparent views of underground infrastructure, on-site as-built verification, safety measures, and even disaster response, a variety of practical applications are becoming a reality.

Precise Layout of Structures

The layout (staking) work required when constructing buildings and civil engineering structures traditionally required skilled surveyors to mark the site with stakes or markings based on coordinates on drawings. Teams of two would set up a total station, and craftsmen would use the stakes as references to install structures, which involved considerable effort. Using AR navigation dramatically simplifies this layout work.

If reference points and edge position data of structures from the design drawings are imported into the AR system in advance, you can see a “virtual stake here” through the phone screen on site. For example, markers or arrows indicating pile-driving positions or column placements can be displayed on the ground in AR, and users simply follow those guides to reach the intended points. In places where you cannot physically drive a stake (such as on a concrete floor or a steep slope at height), you can place a virtual stake in AR to indicate the position, making layout possible in locations that were previously difficult.

With this AR layout, one person alone can perform precise point staking. By walking with a pole equipped with a GNSS receiver attached to the smartphone, there is no longer a need for a second person to hold a prism. Since the screen provides guidance, even workers with limited surveying experience can accurately mark points without getting lost. This reduces personnel (labor-saving) and enables highly reproducible work that does not rely on a veteran’s intuition, thereby contributing to consistent quality.

AR Visualization of Buried Utilities (Making Underground Infrastructure Visible)

Buried utilities such as water and sewage pipes, gas pipes, and power and communication cables are normally invisible, creating a risk of accidental damage during construction. Damage incidents to buried pipes are reported nationwide almost every year, and many are caused by not accurately knowing what is buried where. The conventional method relied on paper drawings and ground markings with experienced workers using intuition and experience, but in urban areas with complex intersections underground this approach has limits.

AR navigation makes it possible to “make the invisible visible.” By combining LiDAR-acquired 3D terrain data with pre-measured and recorded location information of underground utilities, you can display underground piping through the smartphone as if it were transparent. For example, if there are previously buried water or sewage pipes in a road construction area, loading the point cloud model or 3D drawings of those pipes into the device allows you to intuitively grasp the routing and depth of the pipes on site simply by pointing the phone at the road surface. Like X-ray imaging, the pipes appearing on the screen let workers instantly understand "what is buried directly below and where."

Of course, accurate registration is essential for safely performing such underground AR visualization. Combining centimeter-class positioning (half-inch accuracy) from GNSS with terrain scanning by LiDAR makes the virtual pipe models align exactly with the actual buried positions. Even across wide road areas, marker placement or manual adjustments are unnecessary, and the display remains accurate as you move. This technology dramatically improves the accuracy of buried-utility location identification, greatly reducing near-miss incidents and accidental damage during excavation. In future works, there will be no need to squint at paper drawings when digging; AR can accurately identify buried utilities and significantly enhance safety.

Moreover, once acquired, point cloud data of underground infrastructure can be shared and stored in the cloud, so handover of information is smooth. For example, if the pipe point cloud was scanned by LiDAR before backfilling, a different person can later display that data in AR on site to confirm locations. This allows objective data-based decisions regardless of personnel changes, eliminating reliance on individual experience and intuition. Incorporating AR visualization into routine maintenance will also make infrastructure inspection and replacement planning for aging pipes more efficient.

AR for As-Built Verification and Quality Inspection

AR combined with point cloud data is also powerful for as-built verification and quality inspection to confirm whether constructed elements match the design. Traditionally, measurements were taken with tape measures and staffs or selective sampling inspections were performed, but checks were inevitably partial and could miss issues. Instead, immediately after completion you can scan the entire structure with a smartphone LiDAR and save it as high-precision point cloud data. This point cloud (a digital copy of the completed form) can be overlaid with the design’s 3D model in AR on site to instantly show whether the as-built matches the drawings.

Consider the case of point cloud measurement of the floor after concrete placement and AR comparison with a BIM/CIM model. When the virtual model and the actual floor point cloud are overlaid on the smartphone screen, any bulges or voids will appear as protrusions or depressions relative to the model. By visualizing deviation amounts as a color heat map, areas above tolerance are shown in red and low areas in blue, making the degree of displacement intuitively clear. Recently, attempts have emerged to display such heat maps in AR on tablets or smartphones to verify construction accuracy on site.

The advantage of AR-based as-built verification is that you can check the entire site immediately. If a localized deviation is found, you can correct it before the concrete hardens or promptly arrange additional work. As-built data is saved in the cloud, allowing supervisors and clients to share it in real time. This enables all stakeholders to verify quality based on the same information, smoothing explanations and reporting. The final point cloud serves as a complete record of the finished work, useful for future repairs and inspections. AR＋point clouds for visualized quality inspection offers significant on-site value in reducing rework and improving quality.

AR Navigation Applied to Safety Management and Guidance

Safety management is paramount on construction sites, and AR navigation offers a new approach to safety guidance for workers. Sites always have points requiring attention, such as restricted areas, crane swing ranges, and overhead or underfoot hazards. Previously, warnings were given with traffic cones, safety signs, and pre-work meetings, but it is not easy for newcomers or those entering large sites to grasp everything.

With AR, safety information can be overlaid directly onto the scene, making hazards intuitively visible to anyone. For example, pointing a smartphone or tablet may display a red virtual fence on the ground for a restricted area, or warning icons may appear above head-height danger zones. Workers can immediately understand where safety risks exist relative to their position and increase their awareness. AR navigation can also guide safe routes. Even first-time visitors can follow arrows on the screen to move along designated routes that avoid hazards, preventing straying and accidents due to inattention.

AR is also useful for emergency evacuation guidance. Displaying evacuation routes as guiding lines on the floor in AR or projecting large AR signs at assembly points helps people act calmly even during panic. Furthermore, by displaying IoT sensor information in workers’ fields of view (for example, approaching heavy equipment or abnormal environmental values), it is conceivable that safety managers can share real-time warnings even when not physically present. These AR safety measures visualize on-site hazards and help prevent human errors, ultimately leading to fewer occupational accidents and improved safety awareness.

Use in Disaster Response

LiDAR×AR navigation technology is also highly useful in disaster zones such as earthquake or heavy rain damage areas. Immediately after a disaster, rapidly grasping the situation and planning rescue and recovery activities is essential. However, in collapsed buildings or landslide sites it is difficult to accurately record and share the situation, and previously one had to wait for specialized survey teams to perform 3D measurements or for drone aerial photography results. The combination of a smartphone with LiDAR＋GNSS devices enables agile on-site measurement in such initial response phases.

A single worker can walk through a disaster site with a smartphone-mounted RTK-GNSS receiver and scan while positioning, quickly obtaining a detailed point cloud model that reflects the surroundings. Positioning errors are on the order of a few centimeters (a few inches), so the data can be matched with maps or existing design information with high precision. For example, overlaying a point cloud of a collapsed building with the original design drawings in AR can provide clues as to which rooms or equipment might be buried under debris. At landslide sites, comparing pre-disaster terrain models with current point clouds can reveal buried roads and topographic changes, helping identify locations at risk of secondary disasters.

A strength of smartphone LiDAR combined with high-precision GNSS is that it is not dependent on communications infrastructure. Although RTK corrections usually require base station data via the internet, using the Japanese Quasi-Zenith Satellite System "Michibiki" centimeter-class augmentation service (CLAS) allows you to obtain correction data directly from satellites and maintain positioning even outside of mobile communication coverage. In recent local earthquakes, on-site scanning using smartphones＋LRTK has been conducted in communication-blackout affected areas, contributing to rapid sharing of damage information. Being able to record the current situation in 3D with maintained accuracy anytime, anywhere is a major benefit for disaster response.

In addition, disasters typically involve multiple organizations and units operating jointly, and point cloud data and AR visualization provide a shared situational awareness platform. Uploading point cloud models of the disaster area to the cloud allows stakeholders to share and view them in AR on their respective devices, enabling remote personnel to understand the three-dimensional situation. On site, dangerous areas and locations of people requiring rescue can be indicated with AR markers so everyone references the same spatial information, reducing miscommunications in the command chain. The field capabilities provided by smartphones, LiDAR, and GNSS will greatly increase the speed and accuracy of disaster response and contribute to reducing damage.

Labor Saving and Efficiency Gains Brought by Smart Construction

As described above, introducing AR navigation on site is expected to greatly improve efficiency and safety across various aspects of construction management and surveying. Smart construction is a next-generation construction style that uses ICT and digital tools to save labor and time while ensuring quality and safety. LiDAR×AR navigation is a representative solution of smart construction, and its effects can be summarized as follows.

First, the effects of labor and effort reduction are remarkable. Surveying tasks and staking that used to require two people can be completed by one person, and machine guidance and safety monitoring can be assisted by AR displays, improving responsiveness even on sites with labor shortages. At the same time, standardization of work independent of skill level is realized. Intuition that used to rely on veterans can now be confirmed accurately by anyone with AR, which is beneficial for skills transfer and human resource development. Even inexperienced workers can perform tasks without errors with digital assistance, raising and equalizing work quality.

Improvements in efficiency and speed are also notable. From point cloud measurement to design matching, as-built checks, and report generation, processes that previously required separate steps and personnel can be executed seamlessly with a single smartphone. Data obtained on site is immediately shared to the cloud, simplifying drawing creation and report preparation after returning to the office and enabling real-time collaboration between site and office. In addition, safety improvements provide indirect efficiency gains: fewer accidents and rework lead to shorter schedules and reduced costs.

Moreover, AR-visualized information can be used to explain plans to clients and local residents. Showing a completed 3D model overlaid at the site facilitates consensus building, and visualizing as-built results increases satisfaction during inspection attendances. Thus, smart construction not only improves on-site work efficiency but also produces ripple effects such as smoother communication and increased trust. Transitioning to smart construction using digital technologies is an unavoidable trend for the construction industry facing chronic labor shortages and work-style reforms, and introducing LiDAR×AR navigation is a strong first step.

Conclusion: Smart Construction Anyone Can Start with a Smartphone＋LRTK

Once, 3D surveying and AR utilization required expensive dedicated equipment and specialist skills, but now an era has arrived where anyone can easily handle them through the combination of a smartphone and a compact GNSS receiver. In particular, using a smartphone-mounted RTK-GNSS receiver (such as LRTK) together with a LiDAR-equipped smartphone enables real-time acquisition of centimeter-precision positioning and 3D scans on site. It is also easy to display acquired point cloud data and design models in AR on the spot, so advanced surveying and construction management tasks that used to be entrusted to specialists can now be completed with “one smartphone.” The convenience of attaching a palm-sized device to a smartphone and launching a dedicated app to start high-precision positioning within tens of seconds is also attractive.

With such lowered barriers, the era in which each person carries their own high-precision surveying and AR tool is becoming realistic. In practice, systems using LRTK have intuitive Japanese UIs that allow operation without specialist knowledge, enabling site staff to measure and check whenever needed. As these supporting technologies for smart construction become widespread, site productivity, quality, and safety will improve to unprecedented levels. The evolution of site management through LiDAR×AR navigation is no longer the domain of a few advanced companies. From the moment you pick up a smartphone and an LRTK, anyone can realize next-generation smart construction on site. As digital power is about to transform construction sites, let’s ride this wave and create new value.