Visualizing construction sites with AR! How smartphone surveying LRTK brings innovation to civil engineering surveying

Introducing AR (augmented reality) technology to civil construction sites makes it possible to intuitively share the finished image of a project on site, dramatically improving the speed and accuracy of consensus-building with clients. What was previously explained with drawings or renderings can now be shown by overlaying 3D models on the actual site scenery, allowing all stakeholders to “see” and understand the work. In addition, smartphone surveying that combines a smartphone with a high-precision GNSS terminal makes acquiring and managing position information far easier, enabling efficiency gains and labor savings in surveying tasks themselves. This article explains, with concrete examples, the benefits and use cases AR brings to civil surveying, the effects of integrating high-precision positioning technology RTK, and the innovations enabled by the smartphone surveying solution “LRTK.”

Now, let’s look in detail at the innovations smartphone surveying LRTK brings to civil surveying.

Challenges of traditional civil surveying and on-site operations

On civil surveying sites, it has been common to use total stations and large GPS surveying equipment, requiring multiple personnel. For example, even a single layout (stakeout) task to derive positions from control points has required a two-person team including an experienced operator to set up the surveying instrument and targets, and the equipment is heavy and must be repeatedly set up for each site. Also, for as-built verification after completion, staff typically measured many points with instruments and compiled drawings and tables to finally identify discrepancies from the design. Traditional surveying work is therefore labor- and time-intensive, and there is considerable room for efficiency improvements at the site.

Furthermore, there have been challenges in conveying surveying results and design drawings to clients and local residents. Paper drawings and 2D materials make it difficult to grasp the finished image, and it is not uncommon to hear “even after the explanation, it’s hard to imagine how it will look on site.” When stakeholders have different mental images, misunderstandings such as “this wasn’t what we expected” can arise later, causing rework and time-consuming adjustments. Public projects in particular tend to require lengthy consensus-building processes such as explanatory meetings for local residents, and smoothing this process has been a major concern for site managers.

In recent years, the construction industry has faced chronic labor shortages and an aging technical workforce. To perform high-quality surveying and construction management efficiently with limited personnel, the introduction of new technologies that enable accurate measurement and recording with less effort has been needed. Against this backdrop, digital technology and automation have been advancing into civil surveying. Initiatives to use 3D design data such as BIM/CIM on site to improve construction accuracy and productivity have begun, and productivity improvements through ICT use are being strongly promoted under the Ministry of Land, Infrastructure, Transport and Tourism’s *i-Construction* initiative. Expectations for improved on-site productivity are rising accordingly.

Benefits of “visualization” on site using AR technology

Using AR on site brings many benefits to consensus-building and construction management in civil works. By overlaying a 3D design model onto the actual site scenery via the screen of a smartphone or tablet, anyone—including the client—can intuitively imagine the finished form. Content that is difficult to convey with drawings alone can be presented three-dimensionally with AR, reducing misunderstandings and facilitating smoother decision-making. Recently, AR/MR technologies have been increasingly adopted in the construction and civil engineering sectors for presentations, remote attendance, and consensus-building. Visualizing the site with AR is rapidly becoming not just a novel technology but a revolutionary means of on-site communication.

Here are some concrete effects expected from AR utilization.

• Pre-checking design changes: If a design change is needed during construction, AR can project a 3D model of the proposed change on site so the client and others can share the image of the finished work before starting work. For example, overlaying an additional structure or a change in shape on the live site view allows the client to intuitively grasp “how it will change,” making it easier to obtain understanding and agreement on the change. Visual confirmation beforehand prevents misunderstandings of the “this isn’t what we expected” variety and shortens the time needed for consensus-building.

• Sharing the image of the completed work: Visualizing the completed form at full scale on site before construction begins has a major impact on communication with clients and nearby residents. Even for new bridges or roads, showing how the completed structure will look within the surrounding landscape via AR allows non-experts to concretely grasp the finished appearance. This not only reassures clients but also makes explanations to local residents much easier to understand. When all stakeholders can share the same image of the goal, consensus-building proceeds far more smoothly.

• Remote progress checks: With AR and the cloud, clients do not need to visit the site every time to check progress. If the site team uploads photos and point cloud data with high-precision positioning, or screen captures showing AR overlays, to the cloud, the client can grasp the latest site situation from the office. Images or videos comparing as-built conditions with the design model can be shared, enabling real-time information sharing and consensus-building beyond physical distance.

There are also real-world success stories. For example, in an intersection improvement project, AR-capable headsets were linked with an auto-tracking surveying instrument to achieve an AR overlay error of about 5 mm (0.20 in) over a wide area of approximately 220 m (721.8 ft). Projecting the finished shape of the road surface and gutters at full scale improved the precision of as-built verification and the reliability of explanations. As a result, local residents could intuitively understand the post-construction road shape, and consensus-building proceeded smoothly. Discussions over design changes that used to take time were shortened, contributing to operational efficiency.

Thus, AR-enabled visualization of the site also helps build trust with clients. Field reports note that explaining while viewing the AR screen on a tablet clearly improves client reactions. Meeting frequency has decreased in some cases, and time spent halting work while awaiting approval has been reduced. Using AR models also enables accurate confirmation of baseline layout and structure installation positions even by non-experts, improving construction accuracy. AR combined with high-precision positioning creates an on-site environment “anyone can understand,” and is becoming a new standard for consensus-building.

AR’s application is not limited to consensus-building. It is effective in many areas, including pre-construction reviews through process visualization, heavy machinery placement planning, verification of safety measures with the completed form in mind, and training and education of junior engineers. Major contractors are already using tablets to overlay BIM models on real scenes to check equipment piping above ceilings, and using AR in renovation work to inspect hidden areas, reduce construction mistakes, and strengthen overall site information sharing. This technology is expected to become increasingly widespread.

Additionally, the Ministry of Land, Infrastructure, Transport and Tourism has been actively introducing remote attendance for on-site confirmations in recent years, and smartphone surveying and AR-based site information sharing are being supported by such regulatory trends.

Evolving as-built management with point cloud scanning and 3D model use

In the field of as-built management (verification of the shape and dimensions of completed work), AR and point cloud data can greatly improve efficiency. Tasks that traditionally required staff to carefully measure as-built conditions and compare them with drawings can be verified instantly on site using digital 3D data.

For example, point cloud data of terrain obtained by laser scanners or drone photogrammetry can be compared with the 3D design model and displayed in AR as a heat map showing as-built errors. This makes it possible to intuitively grasp on site how much embankments or pavement heights are higher or lower than the design, reducing rework and accelerating discussions on corrective measures. The need to measure many points on site and then compare them with drawings back at the office is reduced, rationalizing the as-built inspection process. In practice, such visualization has been reported to improve inspection efficiency and accuracy and make explanations to clients easier.

Recently, mobile scanning using smartphones has made acquiring point clouds easier. Combining a LiDAR-equipped smartphone with high-precision GNSS allows walking scans of surrounding structures and terrain, giving accurate coordinates to the point cloud. A pocket-sized smartphone alone can complete 3D surveying of required areas immediately. The obtained point cloud data can be overlaid with the design model on a tablet or shared with headquarters via the cloud, creating a seamless link between the field and the office.

This combination of 3D scanning and AR transforms as-built management into real-time, high-precision visualization. Quality checks become faster, inspection results are easier to share with stakeholders, and reporting and approval processes with the client are streamlined. Moreover, the 3D as-built data collected once can be stored as digital records and used for future maintenance and renovation planning. These efforts also contribute to DX (digital transformation) in the civil engineering field.

Smartphone × high-precision GNSS enables smartphone surveying

The emergence of “smartphone surveying,” which uses high-precision RTK-GNSS technology with smartphones, is revolutionizing surveying work itself. RTK (Real Time Kinematic) uses correction information from a reference station to reduce GPS positioning error to several centimeters. Conventional smartphone built-in GPS has errors of several meters and was difficult to use for civil surveying, but combining it with RTK secures the accuracy required on site.

Smartphone surveying realizes RTK positioning without expensive dedicated equipment by combining a smartphone with a small GNSS terminal. A representative solution is LRTK, where a pocket-sized RTK receiver device attaches to a smartphone and receives correction data from an electronic reference point network (or virtual reference station VRS) over the internet, allowing positioning to fix (stabilize) in tens of seconds and obtain centimeter-level coordinates. The smartphone instantly becomes a high-precision surveying instrument.

With smartphone surveying, layout and survey tasks that traditionally required two people can be done by one person. Without expensive equipment or specialized skills, site supervisors and municipal staff who are not surveying specialists can perform the necessary positioning and recording with a smartphone in hand. Dedicated apps let users measure coordinates with a tap and save and share them to the cloud, making operation intuitive and easy even for non-expert surveyors. Because the cloud automatically organizes data, photos taken are automatically tagged with centimeter-level coordinates (half-inch accuracy) and the camera’s orientation (azimuth). Using this information, photos can be accurately placed on a map in the office to smoothly create reporting materials, directly linking to effective use of surveying results.

Moreover, in areas where mobile communication is difficult—such as mountainous regions or disaster sites—centimeter-level augmentation services from quasi-zenith satellites (“Michibiki”) make centimeter-precision positioning possible without deploying a local reference station. LRTK terminals support this CLAS signal, making them powerful tools for infrastructure inspections and emergency surveying in environments lacking network connectivity.

In this way, smartphone surveying realizes high-precision positioning “anyone, anywhere,” delivering great benefits on sites facing labor shortages and cost constraints. Not only general contractors’ construction managers and surveyors at small and medium civil engineering firms, but also maintenance personnel for railways and highways increasingly use smartphone surveying to easily record and measure local conditions. Labor-saving and digitalization of surveying tasks are expected to contribute to productivity improvements across the construction industry.

How LRTK brings innovation to civil surveying

The LRTK solution that integrates AR and high-precision GNSS delivers dramatic efficiency gains and communication reforms to civil surveying and construction sites. Because it can be operated with only a smartphone and a small terminal, there is no need to procure dedicated surveying equipment for each person, offering advantages in introduction and operating costs. Sites that have introduced LRTK report feedback such as “client reactions are clearly better because we can show AR rather than rely on paper drawings and verbal explanations” and “meeting frequency has decreased and time spent stopping work while awaiting approval has shortened.” In one road construction project, as-built verification tasks that used to be performed separately by the surveyor and construction manager could be done simultaneously with a single tablet equipped with LRTK, and reported work time was cut in half. Because acquired data can be shared immediately via the cloud and approvals obtained on the spot, the number of days required for consensus-building was also greatly reduced.

LRTK is an integrated system in which devices, apps, and cloud services collaborate. Positioning and photo data acquired on site can be uploaded and shared to the cloud instantly, and sending a shareable URL lets clients and other stakeholders view the latest site data and AR images from a web browser without logging in. Timely information sharing supports rapid decision-making regardless of physical distance.

The LRTK terminal is lightweight at approximately 165 g and can perform continuous positioning for more than 6 hours on its internal battery. It is realistic to operate on a “one device per person” basis, with workers carrying it at all times and using it for positioning as needed.

Smartphone surveying with LRTK is a new workstyle that lets each person complete positioning, inspection, and recording with a single device. Combining high-precision position data with AR makes the site understandable to anyone, greatly contributing to building trust with clients and rapid consensus-building. The LRTK series is compatible with the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction initiative and strongly supports DX (digital transformation) in the construction industry.

The future of civil surveying will see visualization using smartphones and AR become the standard. From an era relying on cumbersome manual tasks to a site where data is shared in real time and everyone can understand the situation—smartphone surveying enabled by LRTK has already brought that future to the doorstep. Why not evolve your company’s sites to the next stage with LRTK?