Introduction to LiDAR for the Construction Industry – Easy Surveying for ICT Beginners with LRTK

As construction sites undergo digital transformation, one technology that has garnered attention in recent years is LiDAR. LiDAR, a high-precision laser ranging sensor, is bringing major changes to surveying and construction management in civil engineering and construction. In particular, by leveraging LiDAR built into smartphones, 3D measurements that once required specialized equipment can now be done easily.

This article explains the basics of LiDAR sensors and the meaning of point cloud data in simple terms for beginners, and presents concrete use cases at construction sites. It also clearly explains the role of GNSS (RTK/VRS) in linking LiDAR-derived point cloud data to accurate positional information, and the necessity of handling data in public coordinate systems. Finally, through the latest solution LRTK that combines smartphones and LiDAR, we explore the potential for simple, high-precision surveying that ICT beginners can adopt immediately.

What is a LiDAR sensor? Easy explanation of its principle and features

LiDAR (Light Detection and Ranging) is a sensor technology that emits laser light at a target and measures distance based on the time it takes for the reflected light to return. By measuring the round-trip time of light (Time of Flight) at extremely short time intervals, LiDAR can determine accurate distances to surrounding objects. Whereas radar uses radio waves, LiDAR uses laser light with much shorter wavelengths, enabling detection of fine irregularities down to the millimeter scale (mm scale) and allowing acquisition of highly detailed data.

With this mechanism, a LiDAR sensor can rapidly measure the positions of surrounding environments and objects as a collection of points.

A key feature of LiDAR is its ability to acquire distance data at high speed and high density. The sensor emits hundreds of thousands to millions of laser pulses per second, and by collecting the return signals it gathers countless distance points, enabling measurement of wide-ranging shapes in a short time. For example, buildings and terrain that once took workers hours to measure manually can be captured by machines that automatically acquire large numbers of points at once, producing current 3D data in minutes to tens of minutes. Because LiDAR measures remotely and non-contact, it is also advantageous for surveying hazardous areas without entering them. For these reasons, LiDAR is being used across many fields such as surrounding detection for autonomous vehicles, terrain surveying by drones, and 3D scanning of buildings.

What is point cloud data? Recording a site as a collection of 3D "points"

Point cloud data obtained by LiDAR or photogrammetry is three-dimensional data represented as a collection of numerous points that compose space. Each point includes X, Y, and Z coordinate values indicating position, and depending on the acquisition method can also include color (RGB values) or return intensity. For example, when a building or terrain is converted to a point cloud, every point on its surface is digitally reproduced.

If you scan a slope with LiDAR, the roughness of rocks and soil on the slope, and structures installed there, are expressed in detail by millions of points, yielding three-dimensional data that looks like a realistic 3D model.

A major characteristic of point cloud data is that it can digitally copy the site “as is” in its entirety. Unlike traditional paper drawings or photos that record only planar information, point clouds include depth information and preserve the site three-dimensionally. Once point cloud data is acquired, you can later observe from arbitrary viewpoints or easily measure distances or elevation differences between any two points. Because almost no measurements are missed, there is little worry about “forgetting to measure that spot.” It is also possible to extract necessary shapes from the massive set of points and create CAD drawings or 3D models, which can be used for design and construction planning. In other words, point cloud data is a high-precision digital record of physical space and a key technology for building a digital twin of the site.

Expanding LiDAR use with smartphones – start 3D scanning easily

Advanced 3D measurement used to be thought to require specialized equipment and expertise, but recently it has become possible to use LiDAR easily with smartphones. Some latest smartphones and tablets are equipped with compact LiDAR sensors, and by using dedicated apps to scan the surroundings, anyone can easily obtain point cloud data. For example, apps have appeared that let you walk around a room while holding a smartphone and quickly measure wall and floor dimensions or areas on the spot. If you try scanning the ground at a site with a smartphone, a 3D model of the surrounding terrain and structures will appear on the screen in minutes, and first-time users are often surprised that such measurements can be made with such a small device.

The advantages of smartphone-mounted LiDAR are its ease of use and mobility. A single pocketable smartphone can perform the work end-to-end; heavy tripods and complicated setup are unnecessary, so you can start measuring whenever you need. Results can be checked on the spot, allowing you to verify in real time that you’ve recorded all required areas. Smartphone LiDAR sensors have a limited effective range of a few meters (a few ft), but they provide sufficiently practical accuracy for small-scale measurements and rough surveys—on the order of several centimeters (on the order of several in). As sensor performance improves, outdoor daytime scanning has also become more stable than before. By combining dedicated attachments or external GNSS receivers, smartphone 3D surveying can be elevated to a professional level (described later). In this way, smartphone use is making 3D scanning an accessible technology that site managers and municipal staff, including ICT beginners, can try immediately.

LiDAR use cases at construction sites

LiDAR technology can be applied in many ways on construction and civil engineering sites. Here are some representative use cases.

• Law slope surveying (measurement of slope shapes): Scanning steep slopes or embankment/cut surfaces with LiDAR allows acquisition of detailed terrain data from a safe position in a short time. Traditionally, workers climbed slopes to measure angles and elevation differences, or used a total station from a distance to measure a few points and estimate cross-sections, but LiDAR point clouds can record an entire slope without omission, enabling accurate later calculation of slope angles, surface area, and soil volumes. Because it can survey remotely even on slopes at risk of collapse, LiDAR contributes to worker safety, and makes it easy to quantitatively compare terrain changes before and after construction.

• As-built management (verification of completed work): As-built management verifies whether completed structures and engineered terrain match the design. Scanning completed structures with LiDAR digitally records the as-built condition down to every detail. By overlaying the acquired point cloud with the design 3D model or reference cross-section data, you can check in plan and 3D whether fill heights are as planned or whether concrete structures have any deformation or chipping. Since point clouds allow whole-object comparison, they prevent omission of checks compared with traditional methods that compare representative point measurements to drawings, thereby enhancing the reliability of quality control. As-built 3D data also becomes a long-term asset useful for future repairs and inspections.

• Disaster recording (3D documentation of damage): In disasters such as landslides, floods, and earthquakes, LiDAR is powerful for rapid documentation of site conditions. Point cloud data of collapsed slopes, displaced soil volumes, or the state of collapsed structures helps with disaster response planning and later investigations. Drone-mounted LiDAR or photogrammetry can quickly document large affected areas, while smartphone LiDAR can capture detailed scans of damaged spots on the ground. Because data can be acquired without people spending long periods in dangerous areas, it also improves safety in initial response. Acquired disaster point clouds serve as valuable material for municipal staff and disaster management personnel to accurately grasp damage and plan recovery works.

• AR-supported construction: Point cloud data captured by LiDAR can be combined with AR (augmented reality) technology to support construction. For example, when viewing the site through a tablet screen, overlaying the scanned 3D data with the design model lets you project the finished 3D model or design lines precisely into real space. This enables intuitive confirmation of “where materials should be placed” and “whether there are discrepancies between design and actual conditions” as construction guidance. Because smartphone or tablet LiDAR understands surrounding terrain and structures and serves as a positioning reference, AR overlays remain accurately aligned rather than drifting. Site supervisors can share completion images via AR on-screen instead of paper drawings and give specific instructions to workers. Visualizing the location of buried objects or the as-built condition of completed structures on site also helps reduce rework due to misunderstandings.

• Realization of one-person surveying: LiDAR contributes to labor-saving in surveying. Traditionally, site surveying was typically done in teams of two, with one operator handling the surveying instrument and another holding the staff at the measurement point. However, with LiDAR scanners or smartphone 3D scans, a single person can walk with the device and acquire surrounding point cloud data, completing measurements without multiple personnel. For example, when measuring a structure’s dimensions with a tablet-mounted LiDAR, a single operator can perform necessary measurements that formerly required an assistant to hold a tape or target. In an industry facing severe labor shortages, LiDAR technology that enables one-person surveying becomes a valuable asset. Efficiently conducting inspection tasks with fewer people directly improves overall site productivity. Moreover, enabling single-person operation allows better redeployment of limited skilled staff, contributing to work-style reform and improved personnel utilization.

The relationship between point cloud data and GNSS (RTK/VRS) – measuring in public coordinates

LiDAR point cloud measurement can capture object shapes in detail, but positional (positioning) information is indispensable to correctly identify “where” the data refers to. Simply put, LiDAR excels at acquiring relative distances, but by itself does not provide absolute coordinates that indicate where the terrain lies on a map. For example, when scanning the ground with a smartphone LiDAR, the point cloud is expressed in a local coordinate system relative to the smartphone. As is, it will not match the coordinate system used in design drawings or public maps, so georeferencing is required for use in construction management or as-built verification.

This is where pairing with GNSS positioning is useful. GNSS (global navigation satellite systems) such as GPS determine positions on Earth from satellite signals, but standalone GNSS typically has errors on the order of meters. To achieve the accuracy required for construction surveying, correction techniques such as RTK or VRS are necessary to reduce errors to the centimeter level. RTK (real-time kinematic) positioning compares GNSS data at the measurement point with known coordinates at a reference station in real time to correct position errors. By continuously correcting the rover’s position, RTK can provide high-precision positioning on the order of ±1–2 cm in plan and about ±3 cm in height. VRS (virtual reference station) uses data from multiple reference stations in a region to create a virtual reference point near the user, delivering stable RTK correction information over a wide area. With these technologies, surveying instruments and smartphones can obtain high-precision coordinate values in real time.

By combining RTK-positioning information with point clouds obtained by LiDAR, each point in the point cloud can be assigned an accurate global coordinate (latitude, longitude, elevation). In other words, scanned point clouds can be mapped onto the coordinate systems used in public surveying. In the construction industry, data must be handled in public coordinate systems specified by governments or municipalities (in Japan, for example, plane rectangular coordinate systems based on the World Geodetic System). If point clouds do not align with these official coordinates, conversion or adjustment to control points will be necessary when overlaying with design drawings or other survey results, potentially introducing positional errors. Therefore, it is ideal to perform georeferencing to public coordinates at the point cloud acquisition stage.

This is where the value of LRTK comes into play. LRTK integrates smartphone LiDAR measurement with high-precision GNSS (RTK) to enable immediate assignment of accurate coordinates to acquired point clouds. For example, if you attach an LRTK device to a smartphone and perform surveying, the point clouds and measured points obtained on the spot are recorded from the outset as values based on public coordinate systems (such as plane rectangular coordinates). This removes the need to convert or adjust data later to match control points, allowing immediate use of measurements for comparisons with design data or creation of as-built reports. Combining high-precision GNSS positioning with LiDAR’s high-density measurement produces 3D data with high reliability in both shape and position—this is a major strength of LRTK.

Conclusion: Easy, high-precision smartphone surveying with LRTK

This article has explained the basics of LiDAR technology useful on construction sites and its use cases. Point cloud data from LiDAR sensors captures site conditions in full detail and dramatically improves the accuracy and efficiency of surveying and construction management. Three-dimensional surveying that once required specialized instruments and experienced personnel has become widely accessible with smartphones. Using solutions like LRTK, a single smartphone can achieve professional-level surveying accuracy, and the acquired data can be immediately used for site management and design verification.

Smartphone LiDAR surveying with high-precision positioning combines user-friendly operation that even ICT novices can handle with accuracy that meets public surveying standards. For example, by attaching a small dedicated device to a smartphone and launching an app, your position is corrected to high precision in real time without complicated settings, and scanned point clouds are saved with correct coordinates. There is no need to carry heavy equipment or deploy multiple people; a single person can point a smartphone and capture the site’s “now” in its entirety. Site supervisors and survey personnel, even those unfamiliar with digital technology, can adopt this with a short learning period and quickly see benefits.

Digital transformation in construction, such as the Ministry of Land, Infrastructure, Transport and Tourism’s promotion of i-Construction, is accelerating. Smartphone surveying that combines LiDAR and GNSS is expected to play a central role in this trend. LRTK is an innovative tool born from this movement, supporting “smart construction” that directly improves productivity and safety on site. Use LRTK’s combination of accuracy and ease to experience a new era of site management where anyone can easily perform surveying anytime. Even those lacking confidence in digital technologies can take the first step toward ICT-enabled construction with LRTK starting tomorrow.