RTK Inspection Use Cases: On-Site Scenes Where High-Precision Technology Shines and Its Effects

Table of Contents

• Introduction

• Challenges of Conventional Inspection Work

• What High-Precision RTK Technology Is

• On-Site Scenes Where RTK Excels (Use Cases) - Application to Infrastructure Inspection - High-Altitude Inspection (Using Drones) - Precision Management at Construction Sites

• Effects Brought by High Precision

• Simple Surveying with LRTK

• FAQ

Introduction

In Japan, infrastructure structures such as highways, bridges, and tunnels that were developed during the period of rapid economic growth have reached the stage of deterioration after several decades since construction. Regular infrastructure inspections and maintenance are indispensable to safely extend the service life of social capital.

However, on-site inspection work has long relied on the experience and manual labor of veteran technicians, with analog methods such as recording on paper drawings and simple surveying being mainstream. With limited personnel and budgets, how to carry out inspections efficiently and accurately is a major challenge.

Recently, the trend of “on-site DX (digital transformation)” using digital technologies to address these issues has attracted attention. Among these, the method of combining high-precision satellite positioning technology called RTK (Real Time Kinematic) with mobile devices is changing the conventional wisdom of inspection work. RTK is originally a specialized surveying technology capable of centimeter-level positioning, but it has become possible to use it on smartphones and tablets even without dedicated equipment. This new high-precision technology is dramatically evolving how measurements, records, and information sharing are done on site.

This article explains in detail how inspection work is transformed and how on-site productivity and safety are improved by using RTK, including comparisons with conventional methods. It also introduces several concrete on-site scenes where high-precision technology is actually effective and the benefits achieved. At the end of the article, we touch on simple surveying using the easy-to-introduce solution LRTK and propose ways to deploy it on site.

Challenges of Conventional Inspection Work

In conventional infrastructure inspections, methods and procedures have been followed with little change for many years. Inspectors first visually confirm structures on site and take photos of deteriorated areas with a digital camera. They then handwrite the shooting position, direction, and location of damage on paper drawings or ledgers. When measuring crack lengths, a tape measure is applied and measured, and descriptions of the damage location must rely on experience-based expressions such as “around ◯ m (◯ ft) from the south side of the ◯◯ Bridge.” Information collected on site is recompiled into Excel or Word back at the office and organized as a report. This entire process is very time-consuming, and the accuracy and expression of records inevitably vary depending on the person in charge.

In addition to the complexity of record-keeping, insufficient positional accuracy has been a major issue. With simple handheld GPS or manual position records, it is difficult to accurately reproduce the damaged location on a structure. Even when trying to re-inspect years later, you can only estimate “probably around here” based on past records, and it is almost impossible to retake photos from exactly the same position and angle as before. As a result, quantitative comparison of deterioration over time becomes impossible, and there is a risk of overlooking the progress of degradation.

Furthermore, inspections of locations that are difficult for people to approach—such as high parts of bridges, tunnel inner walls, and steep slopes—are also problematic. Detailed observation and dimensional measurement often cannot be performed without arranging high-reach vehicles or installing temporary scaffolding, increasing the burden on site in terms of both safety and cost. With labor shortages and the aging of skilled technicians becoming more serious, continuing such inefficient analog work raises concerns that inspection demand, which will only increase in the future, cannot be met.

Thus, conventional inspection work was plagued by problems such as time-consuming record-keeping, low measurement accuracy, lack of reproducibility, and insufficient manpower and time. The trump card expected to solve these problems and revolutionize inspection methods is the high-precision positioning technology described next: RTK.

What High-Precision RTK Technology Is

RTK (Real-Time Kinematic) is a type of positioning method that uses GNSS (Global Navigation Satellite Systems) and can identify positions within an error range of several centimeters by correcting positioning errors in real time. Normal GPS positioning incurs errors on the order of several meters (several ft) due to signal propagation delay and atmospheric effects. However, RTK performs relative positioning with a known reference point called a base station and uses correction data that cancels out satellite signal error factors, dramatically improving positioning accuracy.

In the past, using RTK on-site required expensive dual GNSS receivers (base station + rover) and dedicated radio communication equipment. Today, however, network RTK that distributes correction information via the Internet has become widespread, and an environment is being established in which high-precision positioning can be easily used without specialized equipment. In Japan, real-time correction data is provided from an electronic reference point network maintained by the Geospatial Information Authority, and the launch of the centimeter-level positioning augmentation service (CLAS) by the quasi-zenith satellite “Michibiki” has built a foundation for stable RTK positioning nationwide.

In short, with the advent of RTK, as long as appropriate correction data can be obtained, smartphones and tablets can now perform high-precision positioning comparable to equipment used by professional surveyors. For example, using a small RTK-compatible antenna attached to a tablet makes it possible to immediately determine your position on site to centimeter precision and attach accurate latitude, longitude, and height data in a global coordinate system to measured points. The development of RTK positioning technology has begun to bring new possibilities to various field operations, especially infrastructure inspection.

On-Site Scenes Where RTK Excels (Use Cases)

Here we introduce concrete use cases focused on inspection and surveying to show how high-precision RTK positioning is actually useful on site.

Application to Infrastructure Inspection

In routine inspections of aging roads, bridges, tunnels, and other structures, using RTK dramatically improves recording accuracy and work efficiency. Traditionally, the location of damage was hand-drawn on paper drawings, but with RTK-capable positioning devices you can acquire accurate coordinates on the spot and record them digitally. For example, if you find a minute crack during a bridge inspection and measure and save its latitude, longitude, and height with RTK, you can easily locate exactly the same spot in the next inspection. It also becomes possible to retake photos from the same angle and distance as the previous shooting, making comparisons of changes over time far more accurate.

Solutions that combine RTK with tablets allow simultaneous photo capture and positioning records, and that data can be shared on the cloud immediately. Because information recorded on site is instantly shared with the company database and stakeholders, not only is the work of report creation reduced, but inspection data can be managed in a consistent accuracy and format across different personnel.

Comparing with past data also becomes easy, enabling even less experienced technicians to accurately grasp the state of deterioration. In other words, digital records based on high-precision positional information dramatically improve the reproducibility and reliability of inspection work.

High-Altitude Inspection (Using Drones)

RTK technology is also active in inspections of high or hazardous locations that are difficult for people to approach, such as high parts of bridges, dam faces, and power transmission towers. While high-altitude inspections used to be carried out with high-reach vehicles or scaffolding, drone inspections have become common in recent years. If a drone is equipped with a high-precision RTK-capable GNSS receiver, the photos and point cloud data captured can be tagged with accurate positional coordinates. This enables recording the spatial coordinates of damage found under girders or at the tops of towers, so detailed locations and scales of deterioration can be understood from the office.

Using RTK-equipped drones greatly reduces the need to set many ground survey control points or to spend time on post-processing alignment. When creating a 3D model (digital twin) from drone imagery, having RTK-derived high-precision absolute coordinates improves the dimensional accuracy of the model, allowing quantitative analysis of crack widths and displacements. Most importantly, because workers do not need to climb dangerous heights, safety is improved and inspection costs and days are reduced. The combination of RTK and drones is expected to be a new solution for infrastructure maintenance and management.

Precision Management at Construction Sites

In civil engineering and construction sites, high-precision RTK positioning is applied to construction management and quality checks. “As-built control,” which checks whether structures and prepared land conform to design shapes and dimensions, is an important process, and RTK enables this work to be performed efficiently. For example, when surveying the height or slope of embankments in roadworks, surveyors traditionally measured points with a total station. With an RTK-capable tablet, site staff can walk over the embankment and measure heights in real time, confirming differences from design values on the spot. Immediate corrections can be made as needed, preventing rework and ensuring uniform quality.

Furthermore, RTK-linked apps can leverage AR (augmented reality) to overlay the designed finished shape on live site imagery. Through the tablet screen, you can visualize buried pipe routes or the finished appearance of structures on the ground, helping to prevent construction errors and share understanding among stakeholders. It is precisely because of RTK’s precise positional alignment that such advanced digital technologies can be applied to real construction. The flexibility of a single mobile device to cover surveying, inspection, and construction management is a major strength that can simultaneously improve site productivity and quality.

Effects Brought by High Precision

Introducing inspection and surveying methods utilizing RTK brings various effects to the field. First is a dramatic improvement in work efficiency. Digitizing surveying and record-keeping reduces the duplicated work that used to be done at both the site and the office. Because measurement results on site can be immediately digitized and shared, the time required to prepare reports is shortened. Also, a single worker can safely measure large areas, enabling efficient inspections with fewer personnel.

Second is an improvement in data accuracy and reproducibility. Recording positions to the centimeter level (half-inch level) allows exact comparisons at re-inspection after years. Being able to grasp deterioration quantitatively based on data enables more accurate prioritization of repairs and life expectancy predictions. Since recorded data are stored in the cloud and managed in standardized formats, situations can be evaluated consistently even when personnel change. Complementing or replacing parts that relied on veteran “intuition and experience” with data is a major advantage for technological succession.

Third is improvements in safety and cost. Replacing work in dangerous locations with drones or remote measurement directly reduces worker risk. Fewer days required for inspections and surveys also shortens the time high-reach vehicles or traffic control are needed, resulting in cost savings. Early detection of defects and appropriate repairs can prevent large-scale accidents and emergency repairs, thus reducing the overall maintenance cost of social infrastructure. In this way, introducing high-precision technology is the key to simultaneously raising on-site productivity, quality, and safety to a higher level.

Simple Surveying with LRTK

That said, some may feel that introducing high-precision RTK surveying on site seems difficult. Enter the easy-to-start solution, the LRTK (LRTK) series. LRTK is an integrated system of a compact GNSS receiver and a mobile app developed by a startup originating from Tokyo Institute of Technology; simply attaching it to a tablet or smartphone instantly converts your device into a high-precision surveying instrument.

With LRTK, you can immediately experience on site the benefits of high-precision positioning discussed so far. In addition to single-point positioning, you can continuously record trajectories while walking, acquire surrounding point cloud data using a LiDAR-equipped model, and visualize design positions on site with AR—an all-in-one set of functions useful on site. Measurement data can be uploaded to the cloud with one tap, allowing remote offices to monitor site conditions in real time.

Moreover, LRTK series GNSS receivers support multi-band (L1/L2/L5), so even in mountainous areas where mobile communication does not reach or in environments where the Internet is cut off during disasters, they can directly receive high-precision augmentation signals (CLAS) broadcast from Japan’s quasi-zenith satellite “Michibiki” and continue positioning. This characteristic is a major advantage in infrastructure inspections and emergency disaster response sites where stable positioning regardless of communication environment is required.

LRTK is already being introduced at construction and civil engineering sites in Japan, and due to its ease and practicality it is quietly spreading as a “one-person-one-tool” site surveying solution. Its simple design—attach the device to a tablet in a dedicated case and switch it on—lets you start surveying as soon as you arrive at the site, enabling quick precision measurements whenever needed. No expensive surveying equipment or special qualifications and technical training are required, so site staff themselves can promote DX in infrastructure inspection, which is revolutionary.

LRTK makes it easy for anyone to realize the revolution in infrastructure inspection brought by high-precision technology. If you feel inefficiencies or challenges in your current work, why not try introducing this new method? The tablet in your hands becomes a high-precision positioning device, and the conventions on site will change—experience that transformation for yourself.

FAQ

Q: What is RTK positioning? A: RTK (Real-Time Kinematic) positioning is a technology that corrects satellite positioning errors in real time to identify positions with centimeter-level accuracy. Whereas conventional GPS has errors on the order of several meters (several ft), RTK uses correction information from a base station to achieve dramatically higher accuracy. It is becoming usable even without specialized equipment and is useful for obtaining accurate positional data on site for infrastructure inspections and other field work.

Q: What do I need to start using it? A: Basically, you need a mobile device (e.g., tablet or smartphone), an RTK-capable GNSS receiver, and a means to receive correction information (either a communication environment or augmentation satellite signals). Specifically, prepare a small RTK-GNSS antenna that can be attached to a tablet and a dedicated app to control and display it. To obtain RTK correction data, connect to an internet-based service (e.g., VRS via Ntrip) or, if supported, receive satellite augmentation signals (such as Michibiki’s CLAS). Once set up, you can start high-precision positioning on site simply by turning on the device.

Q: What level of positioning accuracy can I get? A: Under good conditions with sufficient satellite visibility, horizontal positioning errors of a few centimeters (a few inches) and vertical accuracy on the order of a few centimeters to several tens of centimeters (a few inches to several inches) can be expected. This is far more precise than standalone GPS (errors of several meters). For example, even the location of a tiny crack on a bridge can be recorded within a few centimeters (a few inches) of error with RTK. However, positioning accuracy is affected by satellite visibility and local radio environments, so accuracy may degrade in areas like high-rise building districts or inside tunnels. In such cases, techniques such as performing averaged measurements at suitable locations can help.

Q: Can I position in areas without network coverage? A: Yes. Even when network-based correction data is unavailable, RTK positioning can be continued by several methods. One method is to use the centimeter-level augmentation service (CLAS) provided by Japan’s quasi-zenith satellite system “Michibiki.” CLAS-capable receivers can directly receive correction information from satellites and maintain high-precision positioning even in regions where mobile signals do not reach. Another option is to set up a temporary movable base station on site and transfer correction data via radio. Systems like LRTK that include CLAS reception functionality can continue surveying even when the Internet is interrupted, such as during disasters.

Q: Are specialized knowledge or qualifications required to operate it? A: No; basic operations are designed to be intuitive. Dedicated apps are user-friendly for beginners, and handling typically involves simple steps like pressing a button to start positioning and pressing a record button at the point to measure. Tasks that used to require a surveyor’s qualification or advanced equipment skills can now be operated by site staff after short training with RTK-capable simple surveying systems. However, having a basic understanding of positioning principles and coordinate systems is helpful for confident data utilization and troubleshooting.

Q: In what specific situations is it useful? A: It can be used widely, from routine infrastructure inspections to as-built control during construction and damage surveys immediately after disasters. For example, in roadworks you can measure as-built conditions (embankment height and slope) on site for quality control. In bridge inspections, detected deterioration can be recorded as high-precision 3D data and shared on the cloud to aid repair planning. AR functions also allow overlaying designed structures or pile-driving positions on the site view to share the finished image with all stakeholders. This flexibility to cover surveying, inspection, and construction management with a single device is a major strength of RTK utilization.

Q: How much does implementation cost? A: Traditionally, professional RTK surveying equipment cost several million yen or more. Compared to that, the cost of introducing RTK positioning using a tablet plus a small antenna is reduced by orders of magnitude. Actual costs vary depending on the receiver device and service usage, but since you only need a high-precision antenna and an app, you can start at a relatively low cost compared to purchasing dedicated surveying equipment. The ability to utilize existing tablets is also a cost advantage.