Table of Contents

• Introduction

• Current State and Challenges of Infrastructure Inspections

• What Is RTK Surveying?

• Background to the Emergence of iPad RTK Surveying

• Benefits Brought by iPad RTK Surveying

• Easy RTK Surveying with LRTK

• FAQ

Introduction

In Japan, many infrastructure structures such as expressways, bridges, and tunnels were constructed intensively during the period of high economic growth. Decades have passed since then, and aged structures have now rapidly increased. Regular infrastructure inspections and maintenance are indispensable to ensure the safe long-term use of public assets. However, on-site inspection work has traditionally relied heavily on the experience of veteran engineers and manual labor, with analog methods based on paper records and simple surveying being mainstream. The challenge is how to carry out inspections accurately and efficiently within limited personnel and budgets.

To address these challenges, “on-site DX (digital transformation)” using digital technologies has attracted attention in recent years. In particular, an innovative method called iPad RTK surveying is poised to significantly change conventional wisdom about infrastructure inspections. RTK is a high-precision satellite positioning (GNSS/GPS) technology, and when combined with mobile devices like iPads, centimeter-level positioning that formerly required specialized equipment can now be performed easily by anyone. This is driving a major evolution in how measurements, records, and sharing are done on site.

This article explains in detail how iPad RTK surveying can transform infrastructure inspection operations and improve on-site productivity. We compare traditional challenges with the benefits of the latest technology, introduce actual use cases and concrete effects, and at the end touch on the easy-to-deploy high-precision positioning solution LRTK and propose ways to introduce it to the field.

Current State and Challenges of Infrastructure Inspections

Methods for inspecting social infrastructure have changed little for many years. Typically, inspectors visit sites and visually check the condition of structures. They take photos of damaged areas with a digital camera and handwrite the photo locations and directions on paper drawings. When measuring the length of a crack they use a tape measure, and when describing a location they often rely on experience with expressions like “at the point X m from the south side of pier Y.” Information collected on site is later reorganized into Excel or Word documents back at the office and compiled into reports. This series of tasks is very time-consuming, and variation in the precision and description of records among individuals is unavoidable.

Another issue with the conventional method is that the positional accuracy is insufficient. Simple handheld GPS or manual measurements can make it difficult to reproduce the exact damaged spot on a structure later. Even if you attempt to re-inspect the same spot years later, you may have to rely on past records and guess “probably around here,” making it difficult to take photos at exactly the same position and angle as before. As a result, comparisons over time become uncertain and there is a risk of overlooking issues.

Furthermore, inspecting high locations on bridges or deep slopes that are hard to reach is also challenging. Detailed observation and measurement often require arranging an aerial work platform or erecting temporary scaffolding, which increases cost and safety burden. With labor shortages and an aging workforce of skilled technicians, there is concern that without streamlining these analog methods, inspection demand will increasingly outpace capacity.

Thus, current infrastructure inspections face problems such as being labor-intensive to record, having low surveying accuracy, lacking reproducibility, and insufficient manpower and time. The trump card expected to solve these issues and revolutionize inspection work is the iPad RTK surveying described next.

What Is RTK Surveying?

RTK (Real Time Kinematic) surveying is a type of positioning method using GNSS (Global Navigation Satellite Systems) that can determine positions within an error range of a few centimeters (a few inches) by correcting positioning errors in real time. Normally, position information from smartphones or handheld GPS devices can have errors of several meters due to signal delays and atmospheric effects. RTK, however, performs relative positioning with a known-accurate base station and uses correction data that cancels out satellite signal errors, dramatically improving positioning accuracy.

In the past, realizing RTK surveying required expensive paired GNSS receivers (base and rover) and radio communication equipment. Today, network RTK services that distribute correction information over the internet have become widespread, making RTK more accessible. In Japan, infrastructures enabling RTK positioning anywhere nationwide have been established, such as correction data provided from the Geospatial Information Authority’s electronic reference point network and the quasi-zenith satellite “Michibiki” centimeter-class augmentation service (CLAS) (centimeter-level accuracy (half-inch accuracy)).

In short, RTK technology makes it possible to achieve surveyor-level high-precision positioning on smartphones or tablets by receiving appropriate correction information without specialized surveying instruments. By combining an iPad with an ultra-compact RTK-capable antenna, you can immediately determine your on-site position to the centimeter and attach accurate latitude, longitude, and elevation in a global coordinate system to measured points. The advent of RTK positioning is opening new possibilities for infrastructure inspection sites.

Background to the Emergence of iPad RTK Surveying

Why has iPad-based RTK surveying gained attention now? The background includes both technological and social advances.

First, the technological progress. Recent iPad Pro models and high-performance smartphones are equipped with LiDAR (light detection and ranging) sensors and high-quality cameras, enabling 3D scanning of surrounding structures on mobile devices. As a result, point cloud measurement that once required expensive laser scanners is becoming possible on handheld devices. However, standalone smartphone GPS accuracy was a barrier to serious surveying-grade use due to large spatial errors. The key enabler has been the miniaturization and cost reduction of RTK technology. Ultra-compact RTK-GNSS receivers that can be attached externally to smartphones and tablets have been developed; when connected via Bluetooth or dedicated cases, mobile devices can achieve real-time centimeter-level positioning.

Next, the social needs. In the field of infrastructure maintenance, chronic labor shortages and an aging workforce of technicians have become serious. Moreover, with the enforcement of workstyle reform-related laws in 2024, stricter limits on overtime for field workers have increased the demand for productivity improvements. In response, the Ministry of Land, Infrastructure, Transport and Tourism has been actively promoting digitalization of construction and inspection sites. For example, in 2022 the guideline for as-built management was revised to formally include the use of smartphone and tablet-based 3D measurement and recording. This marked a major shift from management methods that relied on paper drawings and photos, and has become a tailwind accelerating on-site DX.

It is also notable that startups at home and abroad have sequentially released RTK surveying devices for smartphones. For example, products have been developed that allow anyone to transform an iPad into a high-precision GNSS surveying instrument simply by attaching a dedicated small antenna and operating a dedicated app. Weighing only just over 100 g, they fit in a pocket, making it conceivable for each worker to carry one for on-site surveying. With the advent of such new technologies, iPad RTK surveying has entered a practical stage and is beginning to be widely introduced to infrastructure inspection sites.

Benefits Brought by iPad RTK Surveying

Introducing iPad RTK surveying brings various advantages to infrastructure inspection sites. The main benefits are summarized below.

• Labor savings and enabling single-person operations: Without assembling a professional surveying team, a single on-site staff member can perform high-precision position measurement and recording. With an iPad, a small receiver, and an app, you can eliminate the hassle of transporting and setting up heavy tripods and surveying instruments, greatly reducing preparation time. Intuitive user interfaces make the system easy to handle even for staff without surveying experience, improving inspection productivity.

• Centimeter-level high-precision data acquisition: Position information obtained via RTK has an error on the order of a few centimeters (a few inches) and is extremely high in accuracy. This allows precise measurement and recording of subtle changes such as crack locations on bridges or road settlement, increasing the reliability of inspection results. Small misalignments that were previously overlooked can be detected, enabling a more accurate assessment of infrastructure health.

• Digital records and immediate sharing: Measurement data and photos captured on an iPad are automatically saved digitally on site. When linked to the cloud, information recorded on site can be shared with headquarters and stakeholders at the press of a button. There is no need to transcribe field notebooks or paste photos into reports later, realizing major operational efficiency gains. Centralized data management also makes past inspection histories easy to search and reference, effectively serving as an “electronic medical record” for infrastructure.

• Easy re-inspection and accurate comparisons: Accurate coordinates assigned to each inspection point allow future inspections to locate the exact same spot without ambiguity. In practice, you can navigate to previous measurement points displayed on the iPad map and, by aligning the camera following AR (augmented reality) guidance, anyone can reproduce the exact same composition of photos as before. This makes time-series comparisons simple and precise, allowing quantitative assessment of whether deterioration has progressed compared to the previous inspection. There is no need to pull out past reports and guess locations anymore.

• Improved safety: iPad cameras and LiDAR are powerful tools for assessing conditions in hazardous or hard-to-access areas. By measuring dimensions and deformations from a distance, you can avoid approaching high places or steep slopes. For example, cracks on the underside of a bridge girder can be non-contact measured and photographed from below using an iPad. This reduces worker risk and enables inspections to be carried out with safety as the priority.

• Low-cost introduction: A high-precision surveying system can be built with just an iPad, a compatible app, and a small RTK receiver. Initial investment is much lower than conventional expensive GNSS surveying instruments or 3D scanners, lowering the barrier to on-site introduction. Because equipment can be deployed in larger numbers at an affordable cost, the era of “one device per person” is becoming realistic. As a result, overall team IT literacy improves and DX is promoted.

As described above, iPad RTK surveying provides advantages across accuracy, efficiency, safety, and cost, surpassing traditional methods and becoming the new norm for infrastructure inspections.

Easy RTK Surveying with LRTK

One concrete solution for realizing iPad RTK surveying is the LRTK series. LRTK is an integrated system of a small GNSS receiver and a mobile app developed by a startup originating from the Tokyo Institute of Technology. Simply attaching LRTK to an iPad or iPhone quickly transforms your device into a versatile surveying instrument. Although pocket-sized—weighing about 125 g and with a thickness of only about 13 mm (0.51 in)—it houses a high-performance RTK-GNSS module and a battery, and achieves centimeter-level positioning (half-inch accuracy) via a dedicated app.

Using LRTK, you can immediately enjoy the high-precision positioning and inspection benefits discussed in this article. It supports not only single-point positioning but also continuous positioning for track recording, point cloud scanning, AR-based visualization of stakeout positions, and comparison displays with past data—an all-in-one set of features useful on site. Measurement data can be uploaded to a dedicated cloud with one tap, allowing real-time remote confirmation of site conditions from the office.

Additionally, because the LRTK device is a triple-frequency GNSS receiver, it can directly receive the quasi-zenith satellite “Michibiki” centimeter-class augmentation service (CLAS) (centimeter-level accuracy (half-inch accuracy)) even in mountainous areas without mobile reception or when the internet is down immediately after a disaster. This characteristic provides stable positioning independent of terrestrial communication environments, a major advantage for infrastructure inspections and disaster response where reliable positioning is essential.

LRTK has already been adopted in domestic construction and civil engineering sites, and its ease of use and practicality have quietly sparked a trend toward “one device per person” for on-site surveying. Designed to be ready to use simply by mounting in a dedicated case on an iPad and turning on the power, surveying can begin as soon as you arrive on site, enabling precise measurements whenever needed. It is revolutionary that field staff themselves can drive DX in infrastructure inspection without expensive equipment or special technical training.

With LRTK, anyone can easily start iPad RTK surveying and help bring a revolution to infrastructure inspection. If your site struggles with inefficient conventional workflows, consider adopting this new method. Experience how your iPad transforms into a high-precision surveying instrument and changes on-site norms.

FAQ

Q: What is iPad RTK surveying? A: It is a method that combines a high-precision GNSS receiver (RTK-capable antenna) with a tablet such as an iPad to perform real-time centimeter-level positioning. The hallmark is that precise position measurements that previously required specialized surveying equipment can now be achieved with a simple mobile device. In infrastructure inspections, it enables obtaining accurate coordinates simultaneously with photography and recording of inspection points, dramatically improving efficiency and accuracy.

Q: What is required to start using it? A: Basically, you need a tablet device (e.g., iPad), an RTK-capable GNSS receiver, and a communication environment or satellite reception environment to receive correction information. Specifically, prepare a small RTK-GNSS antenna that can be attached to the iPad (Bluetooth connection or dedicated case type) and a dedicated app to control and display it. To obtain RTK correction data, connect to services that distribute corrections over the internet (such as VRS via NTRIP) or, if supported, receive satellite augmentation signals like Michibiki’s CLAS. Once set up, you only need to turn on the device on site and start positioning.

Q: What level of positioning accuracy can be obtained? A: Under favorable conditions, horizontal positions can be accurate to within a few centimeters and vertical accuracy is typically on the order of several centimeters to several tens of centimeters (several inches to several tens of inches). This is orders of magnitude more precise than standalone GPS (meter-level errors). For example, even very small crack locations on a bridge can be recorded within an error range of a few centimeters. However, accuracy depends on satellite visibility and the radio environment, so it can degrade in narrow urban canyons or inside tunnels. In such cases, techniques like averaging measurements at a suitable location can help.

Q: Can surveying be performed at sites outside mobile coverage? A: Yes. Even where network-based corrections are unavailable, RTK surveying can continue in several ways. One method is to use the quasi-zenith satellite system “Michibiki” centimeter-class augmentation service (CLAS). CLAS-capable receivers can directly receive correction information from satellites and maintain high-precision positioning even in mountainous areas without mobile coverage. Another option is to set up a portable reference station (base station) on site and transmit corrections by radio. Systems like LRTK that include CLAS reception capability allow surveying even when the internet is cut off, such as after a disaster.

Q: Are specialized skills or qualifications required to operate it? A: No, basic operation is designed to be intuitive. Dedicated app interfaces are easy for beginners to understand, with simple steps like pressing a “start positioning” button and a “record” button at the point to be measured. While surveying traditionally required certified surveyors or advanced equipment skills, iPad RTK surveying can be used by on-site staff after a short training session. That said, understanding positioning principles and coordinate systems helps for data utilization and troubleshooting.

Q: In what situations is it particularly useful? A: It is useful not only for routine infrastructure inspections but also for as-built management during construction and damage surveys immediately after disasters. For example, you can instantly measure as-built conditions (like embankment height and slope) with an iPad for quality control in roadworks, or record 3D deterioration data of bridges and share it via the cloud for repair planning. AR features allow projecting design drawings or stakeout positions on site so all stakeholders can share the completed image. The flexibility to cover surveying, inspection, and construction management with one device is a strength of iPad RTK surveying.

Q: How much does introduction cost? A: Historically, professional RTK equipment for business use often cost several million yen. Compared to that, the introduction cost for iPad RTK surveying is much lower. Actual costs vary depending on the receiver device and service contracts chosen, but since you generally only need a dedicated antenna and app, costs are relatively modest. If you already own an iPad, initial investment can be reduced further. Operating costs are typically limited to monthly communication or service fees, and efficiency gains from digital information sharing can reduce overall costs compared to paper-based field records. Implementation can be tailored to your company’s budget.