Are Expensive Survey Instruments No Longer Necessary? Low-Cost, High-Precision Surveying Enabled by LRTK

Challenges at Survey Sites: Labor Shortages, High Costs, and Heavy Equipment

On construction and surveying sites, it has long been standard to use expensive, large surveying equipment. Recently, however, severe labor shortages at sites and increasing demands for cost reduction and efficiency have emerged. Traditional surveying requires skilled surveyors and costly equipment, and voices saying "we don't have enough people or equipment" have become more common. For example, surveying with a total station involves carrying a heavy set of equipment, and simply transporting it to the site is laborious. Moreover, achieving high-precision surveying typically assumes teamwork, requiring at least two people. These kinds of personnel and weight burdens have been a major challenge for small sites or sites with limited manpower.

In addition, the cost barrier cannot be ignored. High-precision GNSS receivers and 3D laser scanners often require substantial investment, making them difficult to acquire for budget-constrained municipalities, small and medium-sized enterprises, and sole proprietors. Such dedicated instruments also require periodic calibration and maintenance, which entails sending equipment back to the manufacturer for inspection and generates operational costs and downtime. On sites, situations such as "we bought expensive equipment but have few people who can operate it" and "maintenance costs are a burden" have been observed, and these have been becoming a bottleneck for surveying operations.

Limitations of Traditional Surveying Equipment

Beyond the aforementioned manpower and cost issues, traditional surveying equipment has technical and operational limitations. Typical total station surveying can achieve millimeter-level accuracy, but because each point is measured manually, surveying large areas takes significant time and effort. It also requires skilled operation, with careful work from instrument setup to sighting. Efficient total station work also requires an assistant to hold and guide the prism, so it has been conventional wisdom that one person cannot complete the task alone.

On the other hand, GNSS surveying using GPS exists, but ordinary standalone GPS positioning has errors on the order of 5–10 meters, making it unsuitable for civil engineering surveying. High-precision RTK-GNSS surveying requires a base station and dedicated receivers, which are expensive and require specialist knowledge. Furthermore, signal conditions can affect use, posing challenges in mountainous areas or areas without communication coverage.

Methods for recording three-dimensional site conditions such as drone photogrammetry and terrestrial laser scanners have also appeared, but these too have many constraints. Drones can capture wide areas quickly, but flight requires certification and compliance with aviation laws, and there are weather and airspace restrictions. Processing photos into 3D data takes time, and achieving sufficient accuracy requires ground control point installation and other effort. Terrestrial laser scanners can acquire dense point clouds with millimeter precision, but the equipment is large and extremely expensive, and setup and scan data processing require specialized work. As a result, there remains a barrier of "equipment too expensive to introduce" and "must rely on specialized experts," making it difficult for many sites to benefit from the latest technologies.

Thus, conventional surveying methods had limits in cost, manpower, and ease of use, creating a dilemma where it was not possible to survey needed locations quickly and data utilization took time. The new approach that addresses these challenges is called smartphone surveying.

What Is LRTK, a New Surveying Method Completed with a Smartphone?

Smartphone surveying, as the name implies, uses a smartphone as the surveying instrument. By combining a dedicated small sensor with an app, a smartphone becomes a high-precision surveying terminal. One solution attracting attention is called LRTK. LRTK is an ultra-compact RTK-GNSS receiver used attached to a smartphone, and it can be described as an innovative surveying system that fuses smartphones with satellite positioning technology.

LRTK devices are pocket-sized—about 165 g in weight and approximately 1 cm thick—small enough to carry stacked on a smartphone. Despite their compact size, they support the real-time kinematic (RTK) method, applying correction information to satellite positioning data to enable centimeter-level high-precision positioning. The acquired position points are tagged with latitude, longitude, and height, allowing immediate retrieval of coordinates in a global geodetic system on site. By attaching an LRTK to a smartphone and using a dedicated app, surveying work that previously required bulky equipment and specialized skills can be completed with a single smartphone.

Notably, the operation and workflow are exceptionally simple. Because LRTK operates integrated with a smartphone, it offers the mobility to take measurements whenever needed. Tapping a button in the app completes recording of a survey point, and results are displayed on the screen in real time. If higher stability is required, the smartphone can be mounted on a dedicated pole (monopod) for tasks like establishing control points, but the basic operation is intuitive and straightforward. This makes it easy for site staff without formal surveying education to handle, creating an environment where anyone can measure immediately when necessary.

Features of LRTK

Centimeter-Level High-Precision Positioning

The foremost feature of LRTK is its positioning accuracy. Using the RTK method, it reduces errors that were meters with conventional GPS down to a few centimeters or less. Single-point observations typically fall within about 1–2 cm of error, and averaging multiple observations can achieve sub-centimeter precision. This enables precise measurements with a smartphone, suitable for tasks such as staking out locations on maps and drawings, installing structures, and as-built management.

In Japan, LRTK also supports the centimer-level augmentation service (CLAS) provided by the satellite positioning system "Michibiki." This allows acquisition of high-precision correction information directly from satellites even in mountainous areas or disaster sites that are outside mobile communication coverage, enabling continued positioning. Scenes that previously required base stations or long-range radios can now secure stable centimeter accuracy anywhere with LRTK. Its technological capability has even been introduced on official Cabinet Office websites, and actual adoption by municipalities and others has begun.

Lightweight, Compact, Enabling Single-Person Surveying

With just an LRTK device and a smartphone, there is no longer a need to carry heavy surveying gear. You can head to the site with pocket-sized equipment and survey necessary points one after another by yourself—such solo operations are now a reality. Tasks that once required two people can be completed by one person with LRTK. This mobility is a major advantage for sites with limited personnel or when urgent measurements are needed.

Although compact and lightweight, the device can be firmly mounted to a pole when stable measurement is required. Using a dedicated smartphone mounting case, the smartphone and LRTK can be integrated and attached to the tip of a pole to perform stable observations similar to conventional GNSS surveying instruments. Even so, the total equipment remains very light and easy to carry, so transporting and setting up in rugged areas such as forests or disaster sites is not burdensome. One person can go anywhere and survey immediately when needed—LRTK dramatically improves site footwork.

3D Point Cloud Scanning with a Smartphone

LRTK is not limited to point measurements; it is also adept at recording the surrounding environment as three-dimensional data. By leveraging a smartphone's built-in LiDAR sensor and cameras, it can scan nearby terrain and structures as surfaces and has point cloud acquisition functionality. While a smartphone alone can perform simple floor and wall scans, integrating with LRTK attaches accurate coordinates (latitude, longitude, height) to all acquired point clouds. This allows point clouds to be integrated directly into GIS or CAD alongside other survey data or used for volume calculations.

For example, you can quickly scan the shape of a slope or embankment with a smartphone and calculate soil volume on the spot. Tasks that traditionally required many grid-point measurements with a total station or lengthy laser scanning can be completed in minutes by waving a smartphone. Even large slopes can typically be scanned in about a minute, and the resulting point clouds are saved with XYZ coordinates. The ease of use, requiring only brief instruction for anyone to operate, makes point cloud scanning more accessible.

Intuitive On-Site Visualization with AR

LRTK also harnesses augmented reality (AR) to offer new ways to use surveying and design. Through a smartphone screen, you can overlay design drawings or 3D models onto the real landscape. High-precision positioning enables AR overlays with displacement within a few centimeters, producing accurate projections.

Using this AR feature, for example, you can display a BIM/CIM design model at true scale on site, sharing the finished image immediately. This makes it easier to convey the completed appearance to clients and stakeholders, smoothing consensus building and reducing post-construction “it wasn't supposed to be like this” issues. AR is also powerful for stake staking and foundation layout. Based on coordinate positions from drawings, the smartphone displays guiding markers and arrows, allowing workers to place stakes or structures at the specified locations. Processes that used to require time-consuming ink-lines and point confirmations can now let anyone visually confirm accurate positions via AR.

AR is also useful for as-built inspections during construction. Overlaying the design model with current point cloud data and displaying deviations as a color-coded heat map makes it easy to identify excesses, shortages, or deformed areas at a glance. Such visual checks contribute to preventing rework and improving quality control efficiency.

Cloud Sync for Data Sharing and Utilization

Survey data collected with LRTK can be synchronized to the cloud directly from the field smartphone. Coordinate lists, point clouds, photos, and other data are automatically saved in the cloud, eliminating the need for manual USB transfers after returning to the office. On the cloud, uploaded survey results can be viewed immediately on 2D maps or in a 3D viewer. Office personnel can check point cloud data or verify numbers remotely while the field staff are collecting data.

Data stored in the cloud can be easily shared among stakeholders. By issuing shared links, clients or other departments unable to visit the site can access the latest survey status online and provide comments or instructions. Centralized management and instant sharing of survey data help bridge the information gap between site and office and greatly accelerate decision-making. Additionally, cloud storage enables comparing current data with past data to analyze changes or directly measuring dimensions on point clouds—streamlining post-acquisition data utilization.

Coordinate Navigation Makes Stake Placement Easy

The LRTK app includes a coordinate navigation function that guides you to a target coordinate. If you know the coordinates of a design center point or boundary stake, you can input those values into the app, and the smartphone will display the direction and distance to the target in real time. Like a car navigation system, it will indicate guidance such as "2.5 m east to the target," allowing even first-time users to reach the survey point without getting lost. Combining this navigation with AR display makes stake placement much easier.

Traditionally, stake placement and layout required experienced technicians to determine positions on site by careful comparison with drawings and painstaking checks for errors. With LRTK, you can be freed from such analog tasks, and anyone can accurately set stake locations. As a result, site staff can perform control point setups without relying on survey specialists, reducing waiting times and compressing schedules.

Photogrammetry Enables Measurement of Inaccessible Locations

LRTK is also powerful for measuring locations that are hard to access using its photogrammetry function. When you photograph a target with the smartphone camera, the shooting position and orientation are automatically recorded in the photo. By using multiple photos or AR markers, the system can calculate distances and heights to objects in the images, allowing indirect measurement of points at a distance.

For example, you can estimate the height of a structure on the opposite bank of a river or the location of a collapse on an inaccessible slope just by taking photos from the other side—allowing you to grasp approximate dimensions and coordinates without physically going there. Locations that were previously impossible to survey or places unsafe to approach can now be measured safely and easily with LRTK’s photogrammetry.

Because photos are automatically tagged with positioning information, organizing later is simple. Related to this, LRTK offers a fixed-point observation support mechanism. It guides the smartphone to capture the same composition at predetermined points, enabling you to record long-term changes as if from a fixed camera. When taking photos for periodic inspections, you can accumulate data without positional or angular variance, making change detection reliable and straightforward.

Supports Multiple Coordinate Systems for Operational Integration

A critical point when handling survey data is coordinate system unification. The LRTK app can convert acquired survey point data into arbitrary coordinate systems, such as Japan's Plane Rectangular Coordinate System, and save them. If you perform localization (known-point calibration) beforehand, you can view data in a site-specific local coordinate system. This facilitates alignment with other survey outputs and comparison with design drawings.

For example, public surveying requires converting geodetic latitude/longitude to the Plane Rectangular Coordinate System, but with LRTK, data can be automatically transformed into the specified system at the time of measurement. Reducing tedious post-processing and calculations to provide immediately usable survey results for practical work is a significant advantage. In addition, survey data can be exported in CSV or DXF formats for integration with CAD software or GIS systems. Point clouds and drawings can also be overlaid in the cloud, making LRTK a genuine all-in-one surveying tool directly connected to operations.

Use Cases: Smartphone Surveying Expands Across Many Fields

Because of its versatility, smartphone surveying with LRTK is being adopted not only in civil engineering and construction but in a variety of fields. Here are some representative examples.

Municipal Use: Rapid Surveying in Disasters

In recent years, municipalities have begun using LRTK to quickly grasp damage after natural disasters. In one local government, staff recorded the conditions of a landslide caused by heavy rain using smartphone surveying and shared the data with the municipal office via the cloud. Situations that previously required enlisting specialist surveying companies to obtain accurate terrain data can now be addressed with a smartphone and LRTK on hand, greatly speeding initial response.

For example, Fukui City quickly introduced a simple surveying system using smartphones and utilized it for disaster recovery. Reports indicate that 3D data and photos of damage taken by staff in the field were shared immediately, allowing the headquarters to promptly formulate recovery plans. With low-cost equipment like LRTK, it becomes realistic for municipalities to maintain several sets, making it an effective initial investigation tool during emergencies.

Construction Site Use: Improved Efficiency and Quality Control

On construction sites, LRTK serves as a productivity and quality assurance tool. When site supervisors and construction managers conduct smartphone surveying themselves, the adage "measure when you need to measure" becomes real. For instance, excavation depth for foundations or the height of embankments can be checked and recorded on the spot without waiting for a dedicated survey team. This eliminates the need to request surveying from other departments and adjust schedules, contributing to shorter construction times and prevention of rework.

Smartphone surveying is also effective for as-built management. Measuring required locations with a smartphone during construction enables discovery of deviations from drawings before completion, preventing post-completion corrections. AR lets you overlay the design model on site for high-precision, real-time as-built checks. Moreover, comparing scanned point clouds of the current site with design data and displaying a heat map makes it possible to instantly visualize excesses or shortages in embankment or excavation volumes. These capabilities enhance efficiency and sophistication in quality control.

On-site safety benefits are notable too. Because surveying dangerous slopes or high places with LRTK takes less time, the risk of remaining on site for extended periods is reduced. Eliminating the need to carry heavy equipment across scaffolding also reduces workers’ physical burden, yielding benefits for safety management.

Infrastructure Inspection: More Efficient Ongoing Maintenance

Smartphone surveying is also used in infrastructure inspection tasks such as roads, bridges, and forest management. If maintenance personnel carry LRTK, they can easily obtain accurate, position-tagged data during routine inspections. For example, for pavement crack surveys, simply photographing areas of concern with a smartphone attaches coordinates and timestamps to the photo. When organizing photos later, it is immediately clear which location each record corresponds to, significantly reducing the effort of report preparation.

By photographing the same locations periodically, you can accumulate chronological records like an electronic medical chart. The fixed-point observation feature ensures consistent composition and angle, so progression of cracks or signs of slope failure will not be overlooked. Because data can be shared via the cloud, headquarters or specialized departments can access information in real time to promptly consider countermeasures. LRTK adoption is digitizing and streamlining infrastructure inspection tasks that were once performed with notebooks and cameras.

Benefits of Introduction: Low Cost, High Efficiency, and Easy to Use

As described above, LRTK-based smartphone surveying brings many advantages to sites. Let’s summarize the benefits of introduction once more.

First and foremost is the low barrier to initial adoption. Because LRTK leverages existing smartphones, its cost is overwhelmingly lower than purchasing a complete set of dedicated instruments. You can start high-precision surveying simply by attaching a pocket-sized device to a smartphone. This makes it easier for municipalities and small and medium-sized companies with limited capital to introduce the technology, and widespread adoption as "one surveying device per person" is expected.

Ease of use is another key point. Operated via a smartphone app, the UI is easy to understand, and staff without surveying expertise can master it with short training. Features like automatic recording and cloud integration prevent human errors such as transcription mistakes or forgetting to transfer data via USB. Being able to perform measurements without relying on veteran know-how helps eliminate dependency on specific individuals.

Furthermore, LRTK is a multifunctional package, so its versatility is very high. Tasks that previously required separate instruments and teams—surveying, 3D scanning, photo documentation, stake placement—can all be covered with a single smartphone. On-site data are integrated in real time, enabling overall optimization of construction management rather than suboptimal local solutions. As smartphone and cloud performance improve, further functionality can be added via software updates. Introducing LRTK means acquiring a digital technological foundation that will continue to evolve.

Overall, LRTK is a cost-effective solution. For sites suffering from labor shortages, single-person operation yields significant cost reductions, and faster data utilization boosts productivity. Reducing mistakes and rework improves quality and lowers costs by preventing unnecessary remedial work. Safety also improves, making LRTK an ideal system that balances efficiency and worker protection.

Closing: The Future Opened by Smartphone Surveying

Surveying is now in a major period of transformation driven by the familiar tool of the smartphone. Even without relying on expensive, heavy dedicated equipment, the advent of LRTK has made it possible for anyone to handle high-precision surveying data. Tasks that were once left entirely to surveying specialists can now be performed on site, improving both the speed and quality of decision-making.

It may be premature to say definitively that "expensive surveying instruments are no longer necessary," but at least the spread of smartphone surveying has dramatically expanded on-site options. In cases that want to reduce costs while still using conventional instruments, or where speed is prioritized, simple surveying with LRTK can be highly effective. Going forward, the new style of smartphone surveying will continue to evolve and will strongly support DX (digital transformation) in construction sites.

If you are involved in surveying, consider trying smartphone surveying at least once. The low-cost, high-precision world enabled by LRTK will surely bring new efficiency and value to your site.