Civil Engineering Construction Supervisors Can Finally Perform High-Precision Surveying Alone: Achieved by Simple LRTK Operation

In recent years, digital technology has been increasingly introduced at construction sites, and the work of civil engineering construction supervisors is undergoing major changes. One notable development is a new solution that enables high-precision surveying to be performed by a single person. A system called LRTK has emerged, allowing labor-saving surveying that previously required multiple people to be performed using a smartphone and a compact GNSS terminal, generating high expectations for improved site efficiency.

This article整理s the challenges of surveying work, the background of labor shortages, the basics of high-precision positioning technology and the issues of conventional equipment, and then describes in detail the mechanism and benefits of one-person surveying using LRTK. With simple operation that even young engineers and site managers can master, let’s explore the potential of LRTK to support various on-site scenes such as as-built measurement and batterboard installation.

Surveying challenges faced by civil engineering construction supervisors on site

For civil engineering construction supervisors, surveying at the construction site is one of the indispensable tasks. Accurate surveying is essential for quality control, whether it’s layout marking based on design drawings or as-built measurement to confirm finished work. However, surveying tasks have always involved the challenge of requiring substantial personnel and time. Traditionally, equipment such as total stations and leveling instruments were used, and it was common for teams of two to three people to work together. For example, one person operates the survey instrument mounted on a tripod while another person stands at a distant point holding a staff to receive instructions. On large sites or when there are many survey points, it is not uncommon for surveying to occupy an entire day from morning to evening.

Manual surveying also carries the risk of human error. Misreading or recording mistakes can lead to discrepancies with the design later, causing rework and resulting in unnecessary costs and schedule delays. Because time and personnel are limited, it is difficult to measure every part of the site in detail, and often only the main points are measured. As a result, problems hidden in unmeasured areas may be overlooked, which is a continual source of concern for site managers.

Background driving the need to streamline surveying and enable single-person operation (labor shortage and multi-skilled workers)

Recently, the construction industry has faced serious labor shortages and an aging workforce, making labor-saving of surveying tasks strongly demanded. With fewer veteran surveyors, site personnel must handle many tasks with limited staff. As a result, “multi-skilled workers” who take on multiple roles instead of relying on a single specialty are becoming more common. Civil engineering construction supervisors themselves increasingly take on surveying duties, but conventional surveying methods require specialized knowledge and experience, making them difficult to adopt.

Additionally, digital transformation (DX) initiatives at construction sites, such as the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction, are accelerating efforts to improve productivity using ICT technologies. One-person surveying is an innovative approach born out of this broader industry trend.

Basics of high-precision surveying (RTK-GNSS) and operational burdens of conventional equipment

GNSS (Global Navigation Satellite System), which uses artificial satellites to measure position, is widely known as a positioning technology. Systems such as the U.S. GPS, Russia’s GLONASS, Europe’s Galileo, and Japan’s quasi-zenith satellite “Michibiki” are in place and are commonly used in smartphone map apps and car navigation. However, standalone positioning with a typical GNSS receiver yields an accuracy on the order of several meters, and smartphone-integrated GPS can produce errors of 5–10 m (16.4–32.8 ft). This level of accuracy is insufficient for construction surveying tasks such as layout marking and boundary confirmation, where centimeter-level precision is required.

To address this problem, real-time kinematic (RTK) positioning was developed as a high-precision positioning technology. RTK exchanges positioning data between a base station installed at a control point and a mobile rover, subtracting common error factors to correct position accuracy in real time down to the centimeter level. Traditionally, obtaining accurate coordinates for control points required long static observations, but RTK made immediate centimeter-level surveying possible and gradually spread into civil surveying from the 1990s onward. Today, network RTK services using the Geospatial Information Authority of Japan’s electronic reference point network and the free high-precision augmentation information (CLAS) distributed by Japan’s Michibiki are available, creating an environment where high-precision positioning can be performed without preparing a dedicated base station.

Nevertheless, conventional RTK surveying equipment was often large, expensive, and required specialized knowledge to operate. Preparation of base station receivers and radio equipment, contracts for correction information services over network connections, and other setup tasks raised the barrier to adoption. The traditional style—experienced operators carrying several kg of equipment to the site and operating it with multiple people—meant that high precision obtained by RTK did not directly translate to labor reduction. Against this backdrop, voices from the field called for “RTK equipment that is easier to use and operable by fewer people.”

Mechanism of one-person surveying using smartphone-linked LRTK (accuracy, operability, lightweight)

To meet these needs, an innovative surveying system combining a smartphone and a compact GNSS receiver—LRTK—has emerged. LRTK is an ultra-compact RTK-GNSS terminal designed to attach to an iPhone; it weighs only about 100-some grams and is about 1 cm (0.4 in) thick, roughly smartphone-sized. By fixing it to the back of an iPhone and connecting via Bluetooth or Lightning, your handheld smartphone instantly becomes a high-precision GNSS surveying instrument. Equipment that previously required a tripod and weighed several kg is now pocket-sized, eliminating the need to carry tripods or staffs. A single smartphone now makes it realistic to complete surveying and staking tasks alone on site.

The LRTK device is designed to perform RTK positioning throughout Japan and supports correction information via the Geospatial Information Authority’s electronic reference point network (Ntrip) and the Michibiki CLAS high-precision augmentation service. Even in mountainous areas or disaster sites without cellular coverage, receiving CLAS directly from satellites can correct errors to within several centimeters (several in) in real time. Despite its simple design powered by the smartphone, it contains a battery that allows several hours of continuous surveying, achieving ease of use anyone can handle. With no difficult settings or adjustments required, bringing an iPhone and LRTK to the site lets you start centimeter-level accuracy (cm level accuracy (half-inch accuracy)) surveying on the spot.

Practical situations where young engineers and site managers can use it (as-built measurement, batterboard installation, site verification, etc.)

With its easy operation, LRTK can be immediately utilized by young technicians and site managers. Specifically, one-person surveying proves effective in the following practical scenarios:

• As-built measurement and quality control: For as-built management, which verifies the shape of structures and ground after construction, LRTK can record many point elevations and positions in a short time. Using point-cloud scanning features, you can obtain 3D as-built data simply by walking around a wide area, allowing you to detect subtle unevenness that previously went unnoticed. Post-construction quality inspections become more efficient and measurement omissions are reduced.

• Batterboard installation and staking: One-person surveying is also useful for setting batterboards (surveying boards and guideline strings) during foundation work and land development. If you input the control point coordinates from the design into the LRTK app in advance, you can follow on-screen guidance at the site and accurately position stakes by moving to the target location. With AR functions, virtual arrows and stake markers are overlaid on the camera view, so you can mark the designated points without hesitation even in unfamiliar locations.

• Existing-condition surveying and inspection confirmation: LRTK is useful for verifying existing terrain and structures before and after work. One person can survey and record ground elevations and the positions of surrounding structures before work begins, or quickly obtain the coordinate data needed to check work progress during intermediate inspections. Measured points can be saved to the cloud with timestamps and notes, making it easy to review site conditions later or share them with clients.

Accuracy validation and field feedback (presented as case examples)

Sites that have introduced LRTK report dramatic efficiency gains. In one civil engineering project, as-built measurement that previously required two people and a full day was completed by one person within a few hours after switching to LRTK. Surveying work time was reduced by about 70%, and personnel requirements were greatly diminished. Furthermore, because LRTK can acquire high-density point-cloud data in real time, it succeeded in thoroughly measuring entire sites to improve accuracy and quality (LRTK positioning errors have been reported to be within about 1 cm (0.4 in) horizontally, and on the order of several centimeters (several in) vertically, confirming accuracy comparable to dedicated conventional surveying instruments). Point-cloud measurement enabled verification of details that had been overlooked before, leading to early detection of construction errors and preventing rework.

As a case of local government utilization, one city rapidly introduced the LRTK system to disaster recovery sites in 2023. Because staff could start smartphone surveying immediately at damaged locations, the burden of dispatching survey teams back and forth between the field and the municipal office was reduced, enabling more detailed damage records to be made in a shorter period than before. As a result, lead time from recovery planning to construction start was shortened, contributing significantly to early recovery and cost reduction. The relatively low cost of the equipment also encouraged introduction; by performing surveying in-house rather than outsourcing it as before, the city achieved cost reductions and internalized the technology.

Thus, one-person surveying using LRTK contributes not only to improvements in work efficiency and labor costs but also to increased data accuracy and on-site safety. Because sufficient survey data can be collected in a short time, workers’ time on site is reduced, lowering the risk of heatstroke in extreme heat and accidents during high-altitude work. The simplicity and ease of mastering the equipment and methods make it accessible to less experienced technicians, and digital measurement reduces human error, making quality assurance easier. As a result, overall site productivity and reliability improve, producing benefits for all stakeholders from clients to contractors.

Finally, an introduction to simple surveying, coordinate guidance, and cloud linkage with LRTK (natural walkthrough)

Finally, let’s confirm how easy it is to perform one-person surveying with LRTK.

• Preparation: Upon arrival at the site, attach the LRTK device to your iPhone and power it on. Launch the dedicated app and start GNSS reception; within a few tens of seconds you can obtain RTK centimeter-class positioning (cm level accuracy (half-inch accuracy)) (initialization may take a little longer the first time in a new location).

• Measurement: Move to the point you want to measure and record the coordinates of that location instantly with a single button press in the app. No assistant is required, and you can freely increase measurement points on your own. For wide-area surveys, you can scan point-cloud data continuously simply by walking with the smartphone in hand, and automatically generate a 3D terrain model.

• Coordinate guidance: LRTK is also powerful when you need to drive stakes to positions specified in design drawings. By specifying the target coordinates in the app’s coordinate navigation feature, the screen shows the direction and distance to move in real time. By following guidance like “5 cm (2.0 in) east” or “10 cm (3.9 in) north,” staking work that once required multiple people can be done accurately by one person. When AR display is enabled, virtual arrows and stake markers appear in the camera view, allowing you to place targets correctly even on unfamiliar sites.

• Sharing: After surveying is complete, you can upload data to the cloud with one tap from the app. You can share results with stakeholders before returning to the office, enabling real-time feedback on missed measurements or requests for additional surveys. Uploaded data can be viewed as maps or 3D point clouds on the LRTK web cloud, and reports automatically generated from measurement photos and notes can be downloaded.

In this way, LRTK makes site surveying that used to require several people astonishingly simple. One-person surveying using GNSS and a smartphone dramatically improves surveying efficiency, and immediate data sharing enhances construction management accuracy. The high-precision GNSS terminal LRTK is becoming the new standard on site. If you are a young engineer who has been uneasy about surveying tasks, consider introducing LRTK and experience its ease and effectiveness on site.