LiDAR sensors are changing layout marking on construction sites: Improving positioning accuracy and efficiency with AR

Layout marking (positioning) work, which accurately indicates the positions of buildings and structures on construction sites, is a critical process that affects construction quality and efficiency. However, traditional layout marking methods have faced various challenges related to equipment, manpower, and environmental conditions. In recent years, the combination of smartphone LiDAR sensors and high-precision GNSS (RTK positioning) with AR technology has enabled the digitalization of layout marking, dramatically improving efficiency and accuracy. This article explains the issues with conventional layout marking work, the technical background of AR layout marking using smartphone-integrated LiDAR sensors × RTK, concrete on-site use cases, and the benefits of adoption. Construction managers and those considering ICT construction or i-Construction implementation should find this a useful hint for on-site DX.

Conventional layout marking work and challenges

Layout marking refers to the process of indicating reference lines and points on-site based on design drawings. In building construction, this includes positioning foundations and columns; in civil engineering, it includes marking the centerline of roads and positions for structure installation. It is an essential process that supports construction accuracy. However, performing layout marking by traditional methods has presented the following challenges:

• Equipment setup effort: It is necessary to install dedicated surveying instruments such as total stations and levels, set up tripods, level them, and align references, which requires time and effort for preparation.

• Work requiring multiple people: Because operating surveying instruments and placing/marking targets are performed simultaneously, normally two or more personnel are required. One person looks through the instrument while another holds a staff rod or prism, so manpower must be allocated.

• Risk of position shifts and measurement errors: When measuring manually with tapes or strings, small reading mistakes or position shifts can occur. Mistakes in transferring dimensions from reference points can lead to problems such as “positions don’t match” in later processes, causing rework, schedule delays, and quality degradation.

• Outdoor visibility: When projecting lines or points using laser line tools, the laser can be hard to see outdoors in daylight due to sunlight. On bright sites, reference lines can be difficult to confirm, and using auxiliary devices such as receivers may increase work complexity.

• Labor shortages and skills transfer issues: There is a shortage of skilled surveyors capable of advanced layout marking, making it difficult to maintain traditional methods. Surveying and layout marking that relied on manpower have limits for improving productivity and workstyle reform.

Thus, conventional layout marking requires significant time and personnel to maintain accuracy, and efficiency can drop depending on environmental conditions. A new approach using digital technologies to solve these challenges is therefore attracting attention.

AR layout marking evolved with smartphone LiDAR sensors × RTK

By combining recently introduced smartphone-integrated LiDAR sensors with high-precision RTK-GNSS, layout marking work is evolving significantly. A LiDAR sensor scans the surrounding environment by measuring reflections of infrared laser light and can acquire high-precision three-dimensional data (point clouds). Some iPhone and iPad models are equipped with LiDAR, which helps instantaneously capture distances and shapes and enables spatial recognition for AR (augmented reality).

On the other hand, RTK positioning (Real Time Kinematic) is a positioning technology that corrects satellite positioning (GPS, etc.) errors in real time and can determine positions with errors down to several centimeters. By connecting a dedicated compact GNSS receiver to a smartphone or receiving correction information from a base station, a smartphone can obtain self-position coordinates with surveying-equipment-level accuracy. In Japan, combining augmentation signals from the “Michibiki (QZSS)” satellites that provide sub-meter-level/sub-centimeter-level augmentation signals and network RTK services via the Internet enables stable, high-precision positioning even outdoors.

AR layout marking applies this smartphone AR technology to layout marking work. Specifically, it overlays virtual markings (lines or stakes) corresponding to positions on construction drawings or design data onto the real-world view displayed on a smartphone or tablet screen. For example, information such as “erect a column at this foundation position” or “this point on the road is the design centerline” can be displayed as 3D guides on the camera view at the site.

A key feature is that the smartphone’s LiDAR sensor captures the shapes of surrounding floors, ground, and walls while RTK-corrected self-position information is combined to project digital design coordinates onto the real world with almost no error. In conventional smartphone AR, position tracking relied only on device accelerometers and image recognition, so virtual objects could drift when the user moved. However, introducing RTK for high-precision positioning reduces AR drift even on large outdoor sites and reduces the initial alignment effort. Moreover, in environments with few visual landmarks, such as bare lots, the GNSS-based coordinates allow pinpoint placement of virtual models, enabling precise positioning that was previously difficult.

In other words, with smartphone + LiDAR + RTK AR technology, a palm-sized device is beginning to function as a “portable surveying instrument.” Let’s look at how this LiDAR × RTK × AR combination addresses the previously mentioned layout marking challenges.

Problem solving and benefits via digital technology

• Instant surveying and simple setup: Take out the smartphone and launch a dedicated app to start positioning and AR display immediately. There is no need to transport and set up heavy equipment or spend a long time installing tripods, so preparation time for small layout marking tasks can be greatly reduced.

• One-person positioning possible: With a smartphone in hand, following on-screen instructions allows a single person to mark required positions, enabling layout marking that previously required pairs to be done solo. Even without a skilled assistant, anyone can perform accurate marking by following AR guidance.

• High-precision, non-drifting display: RTK-based centimeter-level positioning accuracy (cm level accuracy (half-inch accuracy)) ensures that lines and points displayed by AR match the correct design coordinates. This prevents manual dimensional transfer errors and reduces construction mistakes due to incorrect marking. Demonstration experiments have confirmed that smartphone + RTK can achieve an average error of less than 1 cm (0.4 in), enabling positioning accuracy comparable to traditional optical surveying instruments.

• Improved outdoor visibility: AR guidance can be displayed on-screen with clear shapes such as arrows and virtual stakes, making it easier to retain targets even in bright daytime conditions. Laser lines that were hard to see can be clearly displayed on the smartphone screen, allowing work to proceed while confirming accuracy even under the sun.

• Labor savings and safety: Even workers without surveying expertise can operate the system intuitively, reducing reliance on veterans for layout marking. Completing tasks solo reduces the burden of personnel coordination and allows work during times with fewer people on site. Shortened work times reduce labor load and, by cutting time spent at heights or under vehicle traffic, contribute to improved safety.

• Data integration and DX promotion: Layout marking results and point cloud data acquired on-site can be stored and shared in the cloud as digital information. There is no need to record on paper drawings by hand, and by linking with BIM/CIM models and construction management software, a consistent digital workflow from surveying to construction management can be realized. Thus, digitizing layout marking contributes to more efficient quality inspection and completion management in subsequent processes.

As described, using smartphone AR with LiDAR sensors and RTK brings multifaceted benefits to layout marking. Now let’s look at how it is actually used on construction sites in specific scenes such as building and civil engineering.

AR layout marking use cases on building sites

In the building sector, AR technology can be used in many situations, from positioning foundations, columns, and walls to layout marking for piping routes and finishing positions in interior work. For example, when marking column base positions on the foundation top after concrete placement, the traditional method required measuring with a tape measure from the drawing and marking with chalk. Replacing this with smartphone AR layout marking means simply marking to match the virtual column positions displayed on the screen. As a result, temporary batter boards (string lines used as references) and measurement tasks can be omitted, allowing multiple column positions to be set accurately in a short time.

In interior work, piping and duct routes inside ceilings and walls, and the attachment positions for finish materials can be confirmed in advance by AR display. Even without drawing guideline lines on wall studs, holding up a tablet lets workers see at a glance where piping routes run, reducing mistakes caused by misalignment between trades. Construction managers can verify in real time whether work is proceeding in the design-specified positions, and if a discrepancy occurs, issue correction instructions immediately on-site. Thus, AR layout marking on building sites is expected to improve construction accuracy and prevent rework, leading to shortened schedules and improved quality.

Furthermore, AR is effective for validating overall building layouts. For example, visualizing partition wall layouts on an office floor on the floor surface via AR allows stakeholders to share a pre-completion image of the space. This reduces the risk of having to redo work afterward because the completed layout doesn’t match expectations and prevents communication losses. AR layout marking thus contributes as a communication tool on-site, not just for marking points.

AR layout marking use cases in civil engineering

In civil and infrastructure projects, smartphone AR layout marking also contributes to productivity improvements. In road work, curves and lane-marking positions based on design drawings can be displayed directly on the road surface via AR, allowing operators to work while confirming on-screen. Even in cases where wooden stakes were traditionally driven for each survey point to indicate extents, only a few key marks may be needed, significantly reducing intermediate stake driving and batter board setup. Because site staff can perform excavation or paving following the AR-displayed lines without a surveyor always present, a new style where each worker handles surveying with a personal smartphone becomes possible.

On large earthworks sites, examples exist in which the final design is AR-displayed over terrain models obtained from drone aerial photography or terrestrial laser scanning. Machine operators can check tablet displays from the cab while excavating or filling, reducing the need for intermediate checks and additional layout marking. For instance, in solar panel installation projects, accurately setting out initial site grading and pile-driving positions has allowed omission of intermediate layout marking while maintaining accuracy. This reflects that AR layout marking has greatly reduced construction mistakes and increased trust to the extent that correcting work in later processes became unnecessary.

Civil engineering also sees major safety benefits. Reducing the time that personnel spend in the roadway for surveying at road construction sites lowers the risk of traffic accidents. If AR displays the locations for sign installations remotely, there is no need to approach risky areas like overgrown or nighttime sites for measurement. The ability to confirm positions non-contact in hazardous locations contributes to the prevention of occupational accidents. Thus, AR layout marking in civil works is effective for both large-scale construction efficiency and safety improvement.

Application to installation of temporary structures

Construction sites frequently install and dismantle temporary structures. Accurate positioning is essential even for temporary scaffolding, temporary fencing, shoring, temporary bridges, and work platforms. AR layout marking is also highly effective for planning the installation of such temporary structures.

For example, when erecting scaffolding around a building, it is necessary to accurately mark the positions of scaffold support poles on the ground or walls. Traditionally, this involved marking at fixed intervals based on building dimensions, but with AR, scaffold material placement can be virtually displayed on the building model and AR can indicate the positions where supports should be erected. Simply marking according to the AR instructions prevents misalignment of scaffold materials and allows efficient installation. High attachment points can be confirmed from the ground via tablet, reducing climbs and improving safety during preparation.

When installing temporary fencing, displaying fence positions along property boundaries by AR eliminates the need to string lines or rely on visual estimation. Even for long stretches, it becomes easier to check positions midway, and accurate arrangement can be maintained for curved or angled layouts. For shoring or temporary bridges, virtual columns and beams can be displayed at design support locations and assembled while checking for interference with existing structures or terrain. If the temporary plan has issues, they can be discovered and the design revised on the spot before construction, preventing major construction mistakes.

By applying AR layout marking to temporary structure installation, setup work can be expedited and assembly accuracy improved. This leads to shorter schedules and reduced workload for site staff, and ensures safe, reliable construction even for temporary works.

Conclusion: Bring layout marking DX to your site now with smartphones

AR layout marking using smartphone LiDAR sensors and RTK positioning is transforming positioning work that once relied on the intuition and experience of veterans through digital technology. By adopting smartphone high-precision positioning solutions referred to as LRTK, a handheld smartphone can act as a surveying instrument, smoothly realizing DX (digital transformation) for layout marking. Because you can start with relatively inexpensive devices and apps rather than acquiring costly specialized equipment, the adoption barrier is low even for small and medium construction sites.

Once applied on-site, you will realize positioning completed with speeds and accuracy that were unimaginable when carrying surveying gear, and information sharing among stakeholders will proceed more smoothly. The layout marking DX delivers “time savings,” “labor savings,” “improved safety,” and “stable quality”—not just two but four benefits at once—and is a technology worth implementing now.

As the industry seeks workstyle reform and productivity improvements, why not quickly introduce this smartphone AR layout marking revolution to your sites? The future of on-site work truly begins with the smartphone in your hand.