The Future of 3D Surveying Pioneered by LRTK: Accelerating Construction DX with High Precision and Labor Savings

Recently, digital transformation (DX) in the construction industry has been progressing rapidly, and "3D surveying" is attracting attention as a core technology. Traditional surveying required skilled technicians and a lot of time, but the emergence of new 3D surveying technologies is expected to improve productivity on site. In this article, we review the basics of 3D surveying and the challenges of conventional methods, and introduce how the latest solution LRTK, which combines smartphones with RTK (real-time kinematic) technology, is changing industry norms, achieving both labor savings and high precision, and accelerating construction DX. Please read to the end and use this information when considering the introduction of 3D surveying.

What is 3D surveying?

3D surveying is a surveying method that measures the shape and position of an object from three directions—vertical, horizontal, and height (X, Y, Z axes)—to obtain three-dimensional data. A major feature is that it can capture terrain undulations and structural shapes in detail, which conventional planar surveying could not. The 3D measurement results are represented as a collection of many points (point cloud data) or 3D models, digitally reproducing the site as it is. Many methods allow non-contact, remote measurement, making them suitable for surveying steep terrain or large structures that are difficult for people to access. This technology enables consistent high-precision data-based process management from pre-construction terrain understanding to post-construction as-built management.

The importance of 3D surveying demanded by construction DX

The construction industry faces serious labor shortages and stagnant productivity, and DX (digital transformation) is being promoted as a trump card to solve these issues. The Ministry of Land, Infrastructure, Transport and Tourism's [i-Construction](https://www.mlit.go.jp/tec/i-construction/index.html) initiative set a goal to improve construction site productivity by 20% by 2025 through full utilization of ICT. Furthermore, the recently formulated "i-Construction 2.0" aims to reduce the number of construction site workers by 30% by fiscal 2040 (labor-saving), promoting further automation and DX.

3D surveying plays a particularly important role in this trend. 3D data acquired on site can be linked with BIM/CIM models at the design stage for construction planning and with maintenance management after completion. Issues that may be overlooked in flat drawings or paper reports can be intuitively understood with 3D data, facilitating smoother communication between clients and contractors. In addition, in 2022 the Ministry of Land, Infrastructure, Transport and Tourism revised the guidelines (draft) for as-built management using 3D surveying technology, and the introduction of 3D surveying on sites has started to become an industry standard.

Moreover, the ability to digitally record and share the site in real time enables remote progress management and quality checks, significantly transforming business processes. Against this backdrop, "how to efficiently conduct high-precision 3D surveying" is becoming the key to promoting DX.

Conventional surveying methods and challenges of 3D conversion

Conventional surveying on construction sites typically used dedicated equipment such as total stations and levels (surveying spirit levels), with multiple people measuring coordinates and heights point by point. Total stations can measure point positions with millimeter-level accuracy, but require setting up the instrument at each measurement point and sighting/reading point by point, which involves enormous effort and time to measure large areas or complex structures. Naturally, there is no data between measured points, so to understand the overall shape of the site one would need to interpolate between points or measure a very large number of points. Surveying work also typically required two-person teams (operator and staff holding the prism), increasing labor costs.

In recent years, technologies that can more efficiently acquire 3D data of the entire site, such as drone (UAV) photogrammetry and 3D laser scanners for point cloud surveying, have emerged. Drone photogrammetry creates 3D models of terrain and structures by analyzing many photos taken from the air, greatly reducing labor compared to traditional methods. However, ensuring accuracy requires placing ground control points, and it is also affected by weather conditions and flight regulations. Laser scanners can automatically acquire high-density point clouds with high accuracy, but the equipment is large and expensive, and because scans are taken from fixed points with tripods, combining data from multiple locations for large sites involves additional work. Furthermore, acquiring different devices for different purposes—RTK-GNSS positioning devices, photogrammetry cameras, etc.—meant that initial investment, operator training, and data integration work became significant burdens.

Thus, conventional technologies have pros and cons, and challenges remain in "easily acquiring high-precision 3D data." There was a demand for a simpler, all-in-one surveying solution.

Smartphone + RTK: an evolving 3D surveying solution

Amid this, a new 3D surveying solution combining smartphones and compact RTK positioning devices has appeared in recent years. By attaching a palm-sized RTK-GNSS receiver to the latest smartphones equipped with high-performance GPS, cameras, and LiDAR sensors, centimeter-class positioning and 3D scanning can be achieved surprisingly easily. The receiver is an all-in-one design with antenna and battery built in, and weighs just over 100 grams, making it very lightweight. It attaches to the device like a smartphone case and connects wirelessly via Bluetooth, etc., so there is no need for complicated wiring or large-scale setup. RTK surveying, which used to require stationary base stations and heavy tripods, can now be completed on-site within the range of a single hand with a smartphone plus a small device.

In the solution called LRTK, a dedicated app is launched on the smartphone screen to obtain high-precision position data from the GNSS receiver in real time. It supports correction information distributed from base stations and network RTK using Japan’s GNSS reference network (continuously operating reference stations and virtual reference station (VRS) methods), and the time from powering on the device to achieving a "FIX" position solution is only a few seconds, enabling very fast operation. Even if satellites are temporarily lost in mountainous areas or near tunnels, high-precision positioning is quickly restored, allowing surveying to continue without stress even on mobile sites.

Another noteworthy point is that the smartphone + RTK device combination becomes an all-in-one surveying instrument that performs multiple roles with a single unit. By using the LRTK system, the following versatile functions can be instantly realized on site:

• 3D point cloud scanning: With a LiDAR-equipped smartphone, simply walking around the surroundings allows you to laser-scan terrain and structures in a short time and obtain high-density point cloud data. Each point is tagged with absolute coordinates (global positioning coordinates) from RTK, so the resulting point cloud can immediately be used as a 3D model aligned with real-world coordinates. It digitalizes the current state with accuracy comparable to that of large laser scanners and can be used directly for earthwork volume calculations and as-built management.

• Positioning & single-point measurement: By pointing the device at the point you want to measure and pressing a button, you can record the point’s coordinates including latitude, longitude, and elevation. Measured points are automatically saved with a number and timestamp, and conversion to plane rectangular coordinate systems or geoid height calculation is performed instantly. There is no need to record in a field notebook with paper and pencil or convert coordinates later, and managing a string of points recorded on the fly does not become cumbersome.

• Photogrammetric measurement (high-precision geotagged photos): High-precision coordinates and camera orientation (azimuth) information can be automatically appended to site photos taken with the smartphone. For example, in inspections of buried utilities where photos are taken inside a manhole, the exact location and direction from which the photo was taken can be accurately plotted on a map. When organizing photos later, there is no need to guess shooting locations, streamlining report preparation.

• Stakeout and placement guidance: The system includes a navigation (guidance) function for guiding you to pre-set reference points or coordinates on design drawings while viewing the smartphone screen. Arrows and distances are displayed on the screen to guide you to the target position, enabling pile driving or placement at specified coordinates even by non-experts. In AR mode, markers of the target position are overlaid on the real camera view, making it intuitive to stake out positions as if a marker were actually visible there. Traditionally, surveying required multiple people—an operator handling the instrument and an assistant moving the stake—but with LRTK one person can quickly and accurately stake out positions.

• AR visualization: Leveraging LRTK’s high-precision position information, you can perform advanced on-site AR display of design models and the positions of underground utilities. Previously, GPS error caused misalignment between virtual models and reality, but with centimeter-accuracy RTK (cm level accuracy (half-inch accuracy)), design lines and as-built models can be overlaid on the actual site with precise alignment. This enables contractors and clients to share completed images or verify underground pipes before excavation, functioning as a communication tool unique to the DX era.

Thus, the era has arrived in which surveying, measurement, stakeout, and verification can all be performed with one device through the integration of smartphones and LRTK devices. Moreover, initial costs are lower than for dedicated instruments, the devices are easy to carry, and they are user-friendly, accelerating their adoption on sites. Because point clouds, photos, and positioning data obtained within the same system are already aligned in a unified coordinate system, there is no need to reconcile results measured with different instruments afterward. Information acquired on site can be reflected in CAD drawings or BIM models immediately, significantly speeding up data utilization.

Effects on the field: balancing improved accuracy and labor savings

The benefits of smartphone + RTK 3D surveying solutions are immense. First, there is the labor savings in surveying work. There is no need to transport and set up large equipment, and one person can efficiently measure a wide site. Topographical surveys that used to take survey teams several days can, in some cases, be completed in a short time using LRTK. There are reports that topographic surveys for road construction sites that previously required several days were completed in less than half a day with 3D scanning using LRTK, demonstrating significant on-site efficiency improvements. Not only does this reduce manpower, but completing surveying in a short time can shorten the overall construction schedule.

Next, there is improved data accuracy and reliability. Centimeter-class positioning from RTK (centimeter-level (cm level accuracy (half-inch accuracy))) is comparable to total station surveys and fixed laser scanning. In the past, photogrammetry sometimes required post-processing checks for errors of tens of centimeters, but point clouds and coordinates acquired with LRTK are immediately mapped to a high-precision absolute coordinate system. This reduces the risk of rework and makes measured values directly trustworthy for as-built management.

Also, the improvement in safety and work efficiency is notable. Surveying dangerous areas such as cliffs or disaster sites carried significant risks, but measurements using small devices and smartphones allow quick recording of conditions without spending long periods in hazardous locations. For example, even at large landslide sites, you can perform 3D scans from a safe distance to immediately understand the collapse extent and the volume of debris. Combining with drones or telescoping poles allows acquisition of high-precision position data from afar as needed. Shorter work times reduce the duration of workers’ exposure to hazards.

Furthermore, the range of data utilization expands. 3D point cloud data and positioning information can be uploaded to the cloud and shared immediately, enabling timely coordination between the field and the office. Engineers at remote locations can instantly check on-site 3D data and issue instructions. By deriving volumes, detecting displacements, or comparing progress from accumulated point clouds, construction management precision is dramatically increased. Under DX promotion, data-driven decision-making is emphasized, and frequent acquisition of high-precision 3D data contributes to realizing a rapid PDCA cycle led by site teams.

In addition, the reduction in introduction costs is a significant advantage. Survey equipment that can utilize commercially available smartphones, like LRTK, is overwhelmingly less expensive than dedicated 3D laser scanners or high-precision GNSS equipment. High-precision surveying that used to require investments of several million yen can now be started with a fraction of that budget using a smartphone plus a small device, making it easier to introduce even for small and medium-scale sites. With the cost barrier lowered, the idea of "one device per person" as a portable surveying tool that each site worker carries to measure and record as needed is now realistic. In this way, LRTK is transforming high-precision surveying, which was once entrusted to a limited number of specialists, into an everyday tool that anyone on site can use.

Conclusion: the future opened by LRTK

The evolution and spread of 3D surveying technology are strongly supporting the DX of the construction industry right now. LRTK solutions at the forefront are combining the twin values of high precision and labor savings, revolutionizing on-site surveying styles. It is groundbreaking that surveying work once entrusted to specialists is becoming something anyone can do with a smartphone in hand. This is expected to help maintain and improve surveying quality on site even as the workforce shrinks through generational change. The use of such advanced technologies can also improve the image of the construction industry, encouraging young people to enter the field and facilitating the efficient transfer of skilled techniques.

Finally, companies and engineers who want to easily introduce high-precision 3D surveying should consider LRTK-based simple surveying solutions. Because they can utilize existing smartphones, initial adoption hurdles are low, and they can be put to immediate use on site as part of your DX promotion. Advanced construction sites are already beginning to adopt these smartphone surveying technologies. Don’t fall behind this trend—embrace evolving technologies and experience the new era of 3D surveying opened by LRTK on your sites.