Are expensive surveying instruments no longer necessary? Low-cost, high-precision surveying made possible by LRTK

Challenges at survey sites: labor shortages, high costs, and weight burden

Until now, construction and surveying sites have typically relied on expensive, large surveying instruments. However, in recent years severe labor shortages at sites have increased demands for cost reduction and efficiency. Traditional surveying requires skilled surveyors and costly equipment, and voices saying "we lack both people and equipment" have become more common. For example, surveying with a total station involves heavy equipment, and merely carrying the gear to the site requires significant effort. In addition, performing high-precision surveys usually assumes work by a team, so securing two or more personnel is necessary. These kinds of personnel and weight burdens have been major challenges for small sites and sites with limited staff.

Moreover, the cost barrier cannot be ignored. High-precision GNSS receivers and 3D laser scanners often require large upfront investments, making them difficult to acquire for budget-constrained local governments, small and medium-sized enterprises, or sole proprietors. These specialized devices also require periodic calibration and maintenance, which entails sending the equipment to the manufacturer for inspection and causes operational costs and downtime. On site, there are situations like “we bought expensive equipment but have few people who can use it” and “maintenance costs are a burden,” and these are becoming bottlenecks in surveying operations.

Limitations of traditional surveying equipment

Traditional surveying instruments have not only the manpower and cost issues described above but also technical and operational limitations. A typical total station survey can achieve millimeter-level high accuracy, but because measurements are taken point by point manually, surveying large areas requires time and effort. Skilled operation is required, and careful work is needed from instrument setup to sighting. Efficient total station measurement also requires an assistant to hold and guide the prism, so it has been the norm that one person cannot complete the job alone.

On the other hand, GNSS surveys using GPS are available, but typical standalone GPS positioning has errors of about 5–10 m, making it unsuitable for civil engineering surveying. High-precision RTK-GNSS surveying requires base stations and dedicated receivers, which are expensive and require expertise. Furthermore, radio conditions affect performance, posing challenges for use in mountainous areas or out-of-coverage areas.

Methods for recording 3D conditions such as photogrammetry from drone imagery and terrestrial laser scanners have also emerged, but these too have many constraints. Drones can capture wide areas quickly, but flights require certification and compliance with aviation laws, and they are limited by weather and airspace restrictions. Processing photos into 3D data takes time, and obtaining sufficient accuracy often requires placing ground control points. Terrestrial laser scanners can acquire dense point clouds with millimeter accuracy, but the devices are large and extremely expensive, and setup and scan data processing demand specialized work. As a result, the barriers “equipment is too expensive to introduce” and “we must rely on specialized experts” exist, making it difficult for many sites to benefit from the latest technologies.

Thus, conventional surveying methods face limits in cost, manpower, and ease of use, resulting in dilemmas such as being unable to survey required locations quickly and lengthy data utilization processes. Emerging to address these issues is a new approach called smartphone surveying.

What is the new smartphone-based surveying “LRTK”?

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

The LRTK device is pocket-sized, weighing about 165 g, with a thickness of about 1 cm (0.4 in), so it can be carried on top of a smartphone. Despite its small size, it supports the real-time kinematic (RTK) method, allowing centimeter-level high-precision positioning (cm level accuracy (half-inch accuracy)) by applying correction information to satellite positioning data. Acquired points are tagged with latitude, longitude, and height, providing immediate geodetic coordinate values on site. By attaching this LRTK to a smartphone and using a dedicated app, surveying tasks that previously required heavy equipment and specialized skills can be completed with a single smartphone.

Notably, its operability and workflow simplicity stand out. Because LRTK operates integrated with a smartphone, it offers the mobility to measure immediately when needed. Tapping a button in the app completes recording a survey point, and results are displayed on the screen in real time. When higher stability is required, the smartphone (with the LRTK attached) can be mounted on a dedicated pole, enabling tasks like establishing control points, but basic operation is intuitive and simple. This makes it easy for site staff without specialized surveying training to use, creating an environment where anyone can measure immediately when needed.

Features of LRTK

Centimeter-level high-precision positioning

The greatest feature of LRTK is its positioning accuracy. Using the RTK method, it reduces errors that were several meters with conventional GPS down to below several centimeters. Single-point observations have errors of about 1–2 cm (0.4–0.8 in), and averaging multiple observations can achieve accuracy under 1 cm (below 0.4 in). This enables precise measurements on maps and drawings as well as precise tasks such as installing structures and managing as-built conditions—precise surveying using a smartphone.

In Japan, LRTK also supports the centimeter-class augmentation service (CLAS) provided by the Quasi-Zenith Satellite System “Michibiki.” This allows LRTK to obtain high-precision correction information directly from satellites and continue positioning even in mountainous or disaster areas where mobile communication is unavailable. Scenes that used to require base stations or long-range radio can now, with LRTK, secure stable cm precision (cm level accuracy (half-inch accuracy)) anywhere. Its technological capability has even been introduced on official Cabinet Office websites, and adoption by local governments has already begun.

Lightweight, compact, and operable by one person

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

Although compact and lightweight, when firm fixation is desired it can be attached to a pole. Using a dedicated smartphone mounting case, the smartphone and LRTK can be mounted together at the pole tip, allowing stable observations similar to conventional GNSS surveying instruments. Even so, the full setup remains very light, making transport easy and reducing the burden of carrying and installing equipment in rough terrain such as forests or immediately after disasters. One person can go anywhere and survey immediately when needed—LRTK dramatically improves field agility.

3D point cloud scanning with a smartphone

LRTK is not limited to point measurements; it also excels at recording the surrounding environment as 3D data. By leveraging the smartphone’s built-in LiDAR sensor and cameras, it can scan nearby terrain and structures as surfaces and acquire point clouds. While a smartphone alone can perform simple floor or wall scans, when integrated with LRTK all acquired point cloud points are assigned accurate coordinates (latitude, longitude, height). This allows the point clouds to be directly integrated with other surveying data in GIS or CAD or used for volume calculations.

For example, you can quickly scan a slope or embankment with a smartphone and calculate soil volume on the spot. Tasks that previously required measuring numerous grid points with a total station or lengthy scans with a laser scanner can now be completed in minutes by waving a smartphone. A wide slope can be scanned in about a minute, and the acquired point cloud is saved with XYZ coordinates. The ease of use—anyone can handle it after a short operation briefing—will make point cloud scanning more accessible.

Intuitive onsite visualization with AR

LRTK also harnesses augmented reality (AR) technology to provide new ways to utilize surveying and design. Through the smartphone screen, positions on design drawings or 3D models can be overlaid onto the real landscape. Because of the high-precision positioning, AR overlays can achieve projections with errors within a few centimeters, enabling stable alignment.

Using this AR feature, for example, a BIM/CIM model can be displayed life-size on site so stakeholders can share the expected finished appearance immediately. This makes consensus-building smoother and reduces “it wasn’t supposed to look like this” after construction. AR is also powerful for stakeout and foundation positioning. Based on coordinate values on the drawings, the smartphone can display markers or arrows as guides on the screen so workers can place stakes or structures exactly where indicated. Processes that once required careful marking and checking of survey points can now allow anyone to visually confirm accurate positions via AR.

AR can also be used for as-built inspections during construction. By overlaying the design model with the current point cloud and displaying deviations as a color-coded heat map, excesses, deficits, or deformations can be identified at a glance. Such visual checks help prevent rework and improve quality-control efficiency.

Cloud sync for data sharing and utilization

Survey data collected with LRTK can be synchronized to the cloud directly from the smartphone. Coordinate lists, point clouds, and photos are automatically saved in the cloud, eliminating the need to return to the office and transfer data via USB. Uploaded survey results can be viewed immediately in 2D maps or 3D viewers in the cloud. Office personnel can check point cloud data measured by field staff or verify numerical values remotely.

Data stored in the cloud can also be easily shared among stakeholders. By issuing a share link, clients or other departments that cannot visit the site can view the latest survey status online and provide comments or instructions. Centralized management and instant sharing of survey data bridge the information gap between the field and the office and dramatically speed up decision-making. Additionally, cloud-based comparison with past data, direct dimension measurement on point clouds, and other post-acquisition data uses improve overall efficiency.

Coordinate navigation makes stakeout easy

The dedicated LRTK app includes a coordinate navigation feature that guides you to a target coordinate point. For example, if you know the coordinates of a center point or boundary stake from a design, entering those numbers into the app makes the smartphone display the direction and distance to the target in real time. Like a car navigation system, it can indicate “east 2.5 m (8.2 ft) to the target,” guiding even first-time users to the survey point without getting lost. Combining this navigation with AR display makes stakeout operations significantly easier.

Traditionally, stakeout and layout required experienced engineers to painstakingly derive positions from drawings on site and thoroughly check for errors. With LRTK, those analog tasks are eliminated, allowing anyone to accurately stake out positions. As a result, site staff can perform control-setting without relying on survey specialists, shortening wait times and compressing schedules.

Photogrammetry for measuring inaccessible locations

LRTK is effective for measurements in locations that are difficult to access. One such capability is photogrammetry. When you photograph an object with the smartphone camera, the photo automatically records shooting position and orientation information. Using multiple photos or AR markers, the system can calculate distances and heights to subjects in the images and indirectly measure points at a distance.

For example, you can estimate the height of a structure across a river or the location of a collapse on a slope you cannot enter simply by photographing from the opposite bank—allowing you to grasp approximate dimensions and coordinates without reaching the site. Photogrammetry extends surveying capabilities to places that were previously unmeasurable or unsafe to approach, enabling safe, easy measurements.

Photos are automatically tagged with positioning information, making it easy to organize which location each photo corresponds to later. Relatedly, LRTK provides a fixed-point observation support function. It guides the smartphone so you can take photos with the same framing at designated points each time, allowing you to record temporal changes as if using a fixed camera. When comparing photos of the same location during periodic inspections, data without positional or angular variation is accumulated, making change detection reliable and straightforward.

Supports multiple coordinate systems for workflow integration

A key point when handling survey data is coordinate system unification. The LRTK app can convert acquired survey data to arbitrary coordinate systems such as Japan’s plane rectangular coordinate system and save them. If you perform localization using known points in advance, you can also view data in a site-specific local coordinate system. This facilitates consistency with other survey results and comparisons with coordinates in design drawings.

For example, public surveying requires transforming geodetic coordinates to the plane rectangular coordinate system, and LRTK can automatically perform the specified coordinate conversion on site. Reducing tedious post-processing and calculations to deliver survey results ready for practical use immediately is a major advantage. In addition, survey data can be exported in CSV or DXF formats and integrated with other CAD software or GIS systems. Point clouds and drawings can also be overlaid in the cloud, making LRTK a true all-in-one surveying tool directly tied to operations.

Use cases: smartphone surveying advancing across many fields

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

Local government use: rapid surveying during disasters

Recently, local governments have started using LRTK to quickly grasp damage after natural disasters. In one municipality, staff recorded landslide damage from heavy rain using smartphone surveying and shared the data with the municipal office via the cloud immediately. Situations that previously required contracting a specialized surveying company to obtain accurate terrain data can now be addressed with a smartphone and an LRTK on hand, greatly speeding up initial response.

For example, Fukui City early adopted a simple surveying system using smartphones and used it in disaster recovery. Reportedly, 3D data and photos of damage measured by staff on site were shared instantly, enabling the headquarters to quickly formulate recovery plans. Because low-cost equipment like LRTK can realistically be stocked in multiple sets per municipality, it is effective as an initial investigation tool in emergencies.

Construction site use: improved efficiency and quality control

On construction sites, LRTK is proving valuable for productivity and quality control. Field supervisors and construction managers can perform smartphone surveying themselves, making “measure when you need to measure” possible. For example, excavation depth or embankment height can be checked and recorded on the spot without waiting for a dedicated surveying team. Eliminating the need to request measurements from other departments and coordinate schedules shortens construction periods and prevents rework.

LRTK is also effective for as-built management. Measuring necessary dimensions with a smartphone during construction enables you to detect and correct deviations from the plans before completion. Overlapping the design model with the site using AR allows real-time high-accuracy as-built checks. Comparing scanned as-built point clouds with design data and displaying heat maps makes it easy to see excess or deficiency in embankment and excavation volumes at a glance. These features improve both the efficiency and sophistication of quality control.

LRTK also contributes to safety on construction sites. Surveys on dangerous slopes or at heights can be completed quickly, reducing the time workers spend in risky locations. Not having to carry heavy equipment while moving on scaffolding also reduces physical strain on workers, contributing to safety management benefits.

Infrastructure inspection use: efficient continuous maintenance

Smartphone surveying is also applied to infrastructure inspections such as roads, bridges, and forest management. If maintenance personnel carry LRTK, they can easily obtain accurate, georeferenced data during routine inspections. For example, in a road crack survey, simply photographing a problematic spot with a smartphone attaches coordinates and timestamps to the photo. When organizing photos later, it is immediately clear which location each record corresponds to, greatly reducing report preparation work.

If the same location is photographed regularly, temporal changes can be accumulated like an electronic medical record. The aforementioned fixed-point observation function preserves the same framing and angle each time, so progression of cracks or signs of slope collapse are not missed. Data can be shared in the cloud, allowing headquarters or specialist departments to receive real-time updates and consider necessary countermeasures promptly. LRTK adoption has thus digitized and streamlined infrastructure inspections that were once done with notebooks and standalone cameras.

Benefits of introduction: low cost, high efficiency, and easy for anyone to use

As described above, smartphone surveying with LRTK brings many benefits to sites. Here we summarize the advantages of introduction.

First and foremost is the low initial barrier to entry. Because LRTK leverages existing smartphones, the cost is far lower than purchasing a full set of dedicated equipment. Attaching a pocket-sized device to a smartphone enables you to start high-precision surveying immediately. This makes it practical for municipalities and small businesses that cannot invest heavily, and widespread adoption as a “one surveying device per person” is expected.

Ease of use is another key point. The smartphone app’s UI is easy to understand, and staff without surveying expertise can master it with short training. Features like automatic recording and cloud integration reduce human errors such as transcription mistakes from handwritten notes or forgetting to transfer data via USB. Because site measurements can be performed without relying on veteran know-how, LRTK also helps resolve person-dependency.

Moreover, LRTK bundles many functions into a single package, giving it high versatility. Surveying, 3D scanning, photo documentation, stakeout—previously performed by different equipment and teams—can all be covered by a single smartphone. Field data are integrated in real time, enabling overall optimization of construction management rather than local optimizations. As smartphone and cloud performance improve in the future, further functionality can be added via software updates. Introducing LRTK means acquiring a digital technology platform that will continue to evolve.

Overall, LRTK is a cost-effective solution. On sites suffering from labor shortages, the ability to work solo greatly reduces costs, and faster data utilization increases productivity. Improving quality by reducing mistakes and rework ultimately lowers costs. Safety is also enhanced, making LRTK an ideal system that balances efficiency and safety for workers.

Conclusion: the future opened by smartphone surveying

The surveying world is now undergoing a major transformation driven by the familiar tool of the smartphone. Thanks to the arrival of LRTK, an era has come in which anyone can handle high-precision survey data without relying solely on expensive, heavy dedicated devices. Tasks once left entirely to surveying specialists can now be performed by site personnel, improving the speed and quality of decision-making.

It may be premature to declare that “expensive surveying instruments are entirely unnecessary,” but at the very least smartphone surveying has vastly expanded site options. In cases where cost savings are desired while still using conventional equipment, or where speed is prioritized, LRTK-based simple surveying can be a powerful solution. Going forward, smartphone surveying will continue to evolve and strongly support DX (digital transformation) in construction sites.

If you are involved in surveying, why not try smartphone surveying once? The low-cost, high-precision world enabled by LRTK is sure to bring new efficiency and value to your site.