3D Surveying DX Revolution: Achieving High Accuracy and Labor Savings at Low Cost with LRTK

In recent years, digital transformation (DX) using 3D surveying has been rapidly advancing in surveying and construction sites. By enabling the acquisition and utilization of three-dimensional site information that conventional planar surveying methods could not obtain, as 3D data, productivity, accuracy, and safety are undergoing revolutionary changes. Among these, the new technology combining smartphones and GNSS, "LRTK," is a groundbreaking solution that makes 3D surveying—which previously required specialized equipment and significant manpower—easy for anyone to perform with high accuracy and low cost. This article explains in detail the basics of 3D surveying, how it differs from conventional methods, its relationship to DX in the construction industry, and how using LRTK can realize high accuracy, cost reduction, and labor savings. We also introduce concrete reasons why LRTK is effective and touch on a simple surveying method using LRTK at the end of the article.

What is 3D surveying? How it differs from conventional surveying methods

"3D surveying" is a surveying method that measures the position and shape of terrain and structures in three dimensions—width, depth, and height—and acquires them as digital 3D data. Various means such as laser scanners, photogrammetry, drone aerial photography, and more recently smartphone LiDAR sensors are used to capture surrounding point cloud data (a collection of countless 3D coordinate points). This allows the actual shape of the site to be recorded in its entirety as a "digital twin," reproducing details that cannot be captured by plan views or cross-sections alone.

In contrast, conventional surveying typically used total stations, levels, GPS receivers, and so on to manually measure the coordinates of individual points at key locations on the terrain and then produce drawings from those points. For example, even when surveying a site covering several tens of meters square, surveyors would spend hours measuring the positions and elevations of several dozen points and then create contour lines and cross-sections based on that data. Such methods limit the number of measurable points, and complete understanding of site conditions often required judgment based on experience. On the other hand, 3D surveying can measure on the order of millions of points, treating objects as surfaces and measuring large areas in detail at once. As a result, the ability to efficiently create precise terrain and structure models without omissions is a major difference.

Data handling is also markedly different. Conventional surveying outputs were mainly two-dimensional information such as paper drawings, PDFs, or CAD drawings, whereas the outputs of 3D surveying are point clouds and 3D models that can be viewed and analyzed on a computer from arbitrary viewpoints. For example, you can freely measure the distance between any two points on the point cloud obtained at the site or extract cross-sections later, so once the data are acquired, there is no need for additional re-measurement or site revisits. In this way, 3D surveying differentiates itself from traditional methods in both measurement density and the scope of data utilization.

The necessity of 3D surveying for construction DX

The wave of DX (business transformation through digitization) is also sweeping the construction industry, and at its center is the utilization of 3D data. Since 2016, the Ministry of Land, Infrastructure, Transport and Tourism has promoted improved construction efficiency using ICT technologies under the "i-Construction" initiative. As part of this, the introduction of drone-based 3D surveying, machine guidance (automatic control of construction machinery), and BIM/CIM (design and construction methods using 3D models) has progressed, and beginning in fiscal 2023, the principle application of 3D models in public works (making BIM/CIM mandatory) has started. This has accelerated the trend of sharing 3D data between contractors and clients, and the use of 3D survey data on-site is now being demanded.

Moreover, the construction industry faces severe labor shortages and the need to respond to work style reform-related laws (the so-called "2024 problem"). With the aging of veteran survey technicians and fewer young entrants, and with overtime limits applying to the construction industry from 2024, work must be carried out efficiently with limited personnel. In this context, 3D surveying demonstrates its power by enabling labor savings. There are reports that surveying work that used to take several days can be completed in a few hours to half a day using drones or laser scanners, and some sites have seen surveying periods shortened to one quarter of traditional durations. This not only shortens time but directly contributes to correcting long working hours and reducing labor burdens. As a key to DX promotion, 3D surveying—which can digitize the entire site—is an important element supporting a productivity revolution.

Data obtained from 3D surveying and utilization benefits

Point cloud data, a representative deliverable of 3D surveying, can be described as a precise copy of the physical space. It is digital data that represents the shapes of terrain, buildings, and structures with countless points, allowing detailed understanding of site conditions without physically visiting the site. By utilizing point clouds and the 3D models created from them, various benefits that were not achievable with conventional methods arise.

• Detailed current condition understanding: Subtle irregularities and shapes that cannot be discerned from paper drawings or planar photos can be accurately recorded in point clouds. For example, even if drawings of aging infrastructure facilities are missing, point cloud surveying can create and preserve a 3D model of the current condition. This makes it easy to thoroughly document the site and later check specific areas in detail as needed.

• Design and construction optimization: Overlaying acquired point cloud data with design data (CAD or BIM models) enables intuitive recognition of discrepancies between plans and the field. You can simulate on the terrain 3D model before construction to optimize heavy equipment access routes and earthwork plans. After construction, comparing the point cloud of the completed work with design data allows checking of as-built deviations, helping prevent rework and ensuring quality.

• Construction management and safety improvement: 3D scanning is powerful for measuring dangerous places where people cannot enter. For instance, deep excavations or slopes prone to collapse can be safely measured from a distance with laser scanning. Volume calculations from point clouds streamline management of embankment and excavation quantities. In fact, when laser scanners were used to check pile inclination and positional deviation during bridge foundation excavation, reports showed reduced work time and greatly improved safety compared to manual measurement.

• Maintenance and inspection: 3D surveying is also used for post-completion infrastructure inspections. For roads and bridges, scanning surface shapes with laser scanners during periodic inspections and comparing them with past point clouds can detect minute cracks and deformations. Because displacement amounts can be quantified from point cloud differences, anomaly detection that previously relied on craftsmen’s experience can now be conducted objectively using data. Research into AI-based automatic extraction of degraded areas is also progressing, promising further labor savings and sophistication of inspection work.

• Accumulation of construction records: If pre- and post-construction sites are recorded as point clouds, information that photos and drawings cannot fully capture can be referenced in the future. For example, drone scans of collapsed terrain at disaster recovery sites can be used to compare topography before and after landslides. 3D construction records are useful for future project planning and post-incident verification, and they enable preservation of veteran technicians’ insights as digital data.

By utilizing the data obtained from 3D surveying, speedy and accurate decision-making becomes possible, dramatically improving on-site productivity, safety, and quality.

What is LRTK? A 3D surveying revolution realized with a smartphone

However, enjoying the benefits of 3D surveying previously required expensive equipment and specialized knowledge. Introducing large-scale laser scanners or dedicated surveying drones required investments of millions of yen, making it difficult for small- and medium-sized sites to adopt them. Enter LRTK—a state-of-the-art positioning and measurement technology provided by Lefixea. LRTK is a pocket-sized small device attached to a smartphone or tablet that integrates RTK-GNSS receiver functionality (real-time kinematic) and 3D scanning into an all-purpose surveying tool.

Specifically, by attaching the dedicated ultra-compact GNSS receiver "LRTK Phone" to an iPhone or iPad and launching the LRTK app, you can simply hold the device at the site to instantly turn the surrounding environment into 3D point cloud data. Because it combines photogrammetry technology using the smartphone camera (and in some cases the LiDAR sensor) with centimeter-class GNSS positioning, the point clouds obtained include high-accuracy position information (world coordinates). Distances, areas, and volumes can be measured immediately on the point cloud generated on site; for example, you can scan an embankment or soil pile in minutes and instantly calculate accurate soil volumes. Tasks that previously required subcontracting to specialists or moving soil with heavy machinery to survey can now be completed by your own staff simply walking while holding a smartphone.

LRTK is truly a revolutionary solution that allows a single person to scan a site. The device itself is lightweight and fits in the palm of your hand, making it easy to carry to the field.

Furthermore, the LRTK series includes multiple devices for different use cases. For example, when you want to measure a wider area at high density, using the dedicated 3D laser scanner "LRTK LiDAR" makes long-distance laser measurements, which were traditionally expensive, affordable and fast.

There are also wearable devices that allow workers to scan their surroundings just by walking, and helmet-integrated GNSS receivers, among other devices that facilitate positioning and point cloud acquisition both outdoors and indoors.

By combining these tools according to site scale and purpose, 3D data can be utilized in every situation. The fact that high-accuracy point cloud measurement, which previously required specialists, can now be incorporated into everyday operations through easy technologies like LRTK is proof that the DX of 3D surveying is becoming a reality.

High accuracy, low cost, and labor savings realized by LRTK

Here are the concrete effects obtained by introducing LRTK, organized from the perspectives of high accuracy, low cost, and labor savings.

• High-accuracy positioning: LRTK is equipped with an RTK-capable GNSS receiver and improves position information, which with ordinary GPS has errors of several meters, to about 1-2 cm (0.4-0.8 in). This ensures that acquired point clouds and survey points are positioned with accuracy comparable to public surveying control points and can be used directly for design checks and as-built management. In addition, LRTK devices support the Japan Quasi-Zenith Satellite System "Michibiki"'s centimeter-class augmentation information (CLAS) (cm level accuracy (half-inch accuracy)), enabling high-precision positioning even at sites in mountainous areas without internet access. Advanced attitude correction functions also compensate for antenna tilt errors to maintain stable positioning accuracy.

• Reduced introduction and operational costs: As mentioned, with LRTK you can start 3D surveying without expensive large-scale equipment or costly surveying instruments. All you need is the device and a compatible smartphone, significantly reducing initial investment. The 3D laser scanners that previously cost hundreds of thousands of yen are no longer necessary, and high-accuracy 3D surveying can be achieved simply by combining LRTK with a general-purpose drone. Bringing work in-house that was previously outsourced to external surveying companies also reduces outsourcing costs. Equipped with cloud services for data sharing, it minimizes transport and communication costs for transferring data between the field and the office.

• Labor savings and single-person operation: LRTK is lightweight and compact, enabling survey work to be completed by one person without forming a multi-person surveying team. For example, in topographic surveys of large sites, there is no need for personnel to carry prisms while taking measurements; one responsible person can complete the task by walking around. Post-processing of acquired point clouds is also automated, and uploading to the cloud allows quick model generation and analysis, eliminating in-office drawing work and manual calculations. In short, LRTK can greatly reduce the manpower and time required for surveying—an enormous benefit for sites struggling with staff shortages.

• Dramatic increase in work speed: Because high-density data can be acquired in a short time, on-site work speed improves dramatically. Field surveys that used to take a full day can sometimes be completed in tens of minutes with LRTK and a smartphone. Being able to check results on the spot enables real-time decision-making, which also contributes to speed improvements. For example, scanning site conditions in the morning and immediately calculating volumes allows you to plan earthwork in the afternoon based on that data, enabling a rapid PDCA cycle. The resulting overall shortening of construction schedules and rapid decision-making contribute to strengthening competitiveness.

As shown above, introducing LRTK improves surveying accuracy, cost, and efficiency. In addition, its benefits in terms of data shareability and ease of use make it well suited to the DX era. Survey data uploaded to the cloud can be shared instantly among stakeholders, enabling remote support and real-time understanding of site conditions. The smartphone-based operation is intuitive and easy to learn, allowing even untrained personnel to handle it. These comprehensive advantages illustrate why LRTK is effective.

Comparison with other 3D surveying methods and how to choose

Various 3D surveying methods other than LRTK are currently in use. Each has different strengths, so using or combining them according to site conditions yields the greatest effect.

• Drone (UAV) photogrammetry: This method generates 3D models from aerial photos taken by small unmanned aerial vehicles. Because it can capture wide areas quickly from the air, it is suitable for topographic surveys of development sites and grasping conditions at disaster sites. Recently, high-precision drones equipped with RTK-GNSS have appeared, allowing positioning information to be directly attached to point clouds obtained from aerial photos. However, drones have difficulty capturing the back sides of structures or indoor spaces and are affected by radio environments and flight restrictions.

• Terrestrial laser scanners (TLS): Using tripod-mounted laser scanners, 360-degree laser beams are emitted from the ground to acquire point clouds. This method excels at densely measuring details of complex structures such as bridge piers and plant piping. However, the equipment is large and difficult to transport, and covering wide sites requires measurements at multiple locations and data integration, which can be time-consuming.

• Mobile mapping / wearable surveying: Mobile mapping, which mounts sensors on vehicles and measures while driving, and backpack- or helmet-mounted surveying equipment that scans while a person walks, are effective when you want continuous measurement outdoors or indoors. They are used for applications such as pedestrian flow simulation and tunnel measurement.

• Conventional GNSS surveying / total stations: For single control point surveys or pinpoint measurements for installed stakes, conventional surveying instruments are still used. Particularly for stake setting based on design drawings (layout) or boundary confirmation, where single-point high-precision positioning is required, GNSS receivers or total stations are useful. Since LRTK also has GNSS receiver functionality, it can be used as an extension of conventional single-point surveying.

These methods are not mutually exclusive, and combining them can compensate for each other's weaknesses. For example, in tunnel construction in mountainous areas, the interior can be scanned precisely with TLS while the exterior terrain is captured by drone photogrammetry, and the two point clouds can be merged to build a seamless integrated model. Also, high-accuracy positioning data acquired with LRTK can be used to geotag drone photos, allowing point clouds generated from non-RTK drone imagery to be given surveying control point-level accuracy afterward. In this way, LRTK adds value when combined with other measurement methods and can serve as a hub for fully and accurately digitizing the entire site.

Conclusion: Start the 3D surveying DX revolution with LRTK

The introduction of 3D surveying and data utilization is a central theme of the DX revolution in the construction and surveying fields. Converting the entire site into digital data and feeding insights back into design and construction management allows projects to be executed with unprecedented efficiency and accuracy. Facing labor shortages and work style reforms, it is necessary to adopt new technologies with flexible thinking that is not bound by traditional methods.

Fortunately, now that easy-to-use and powerful 3D surveying tools like LRTK have emerged, an era has arrived in which anyone can acquire high-accuracy 3D data whenever needed. As a first step, we recommend conducting a trial simple survey using LRTK on your own site. For example, by attaching an LRTK device to a smartphone, establishing RTK positioning, and then using a commercially available drone to photograph the site from above, you can combine those images with LRTK positioning information to generate point cloud data. This approach lets you experience the benefits of 3D surveying without purchasing expensive equipment. Comparing the acquired point cloud models with traditional drawing results will quickly reveal differences in data volume and accuracy and help you appreciate the potential of site DX.

The DX revolution in 3D surveying has the potential not only to improve work efficiency but to change industry norms and working styles themselves. Take this opportunity to introduce the latest technology, LRTK, on your sites to achieve high accuracy, low cost, and labor savings, and ride the wave of 3D utilization that will become the future standard. As LRTK-based 3D surveying becomes commonplace, the nature of surveying will change dramatically, creating new opportunities for value generation. In the sites of the future, LRTK may well hold the key.

For more detailed feature introductions and case studies of LRTK, please check the LRTK official site: https://www.lefixea.com/lrtk