RTK Inspections You Can Do Alone: High-Precision Field Measurements Completed with Just a Smartphone

Table of Contents

• What is RTK? Basics of high-precision positioning technology

• Challenges in traditional field inspections

• Single-person positioning enabled by network RTK

• Your smartphone becomes a surveying instrument: the revolution of solo RTK inspections

• Main benefits brought by smartphone RTK

• Use cases for RTK inspections: what kinds of sites benefit?

• The future and prospects of high-precision positioning

• Summary: possibilities opened by simple surveying (use of LRTK)

• FAQ

What is RTK? Basics of high-precision positioning technology

First, let’s explain what “RTK” is. RTK stands for Real-Time Kinematic, and is one of the high-precision positioning techniques using GNSS (Global Navigation Satellite Systems). Normally, positioning accuracy obtained from smartphones or general GPS devices has errors on the order of several meters (several ft). These arise from factors such as atmospheric effects and satellite orbit errors. However, by using RTK, these errors can be corrected in real time, making it possible to measure positions with centimeter-level accuracy (half-inch accuracy).

The mechanism of RTK lies in “relative positioning” using two receivers called a reference station and a rover. One receiver is a reference station whose position is known accurately, and the other is a rover that measures while moving. By comparing signals received from the same satellites by both receivers, error factors are eliminated and high-precision positions are calculated. Because this processing is done in real time, the rover can keep positioning errors down to a few centimeters (a few in) even while moving.

Furthermore, with the increasingly widespread network RTK, high-precision positioning is possible without setting up your own reference station. This system obtains correction information over the internet from a network of multiple reference stations maintained by government or private entities (such as Continuously Operating Reference Stations or private VRS services), enabling stable high-precision positioning over wide areas. Users carry a receiver that acts as the rover (for example, a high-precision GNSS antenna connected to a smartphone) and access regional reference station data via cellular communication. This allows centimeter-level positioning to be performed alone, without having to set up a reference station yourself or assign two or more personnel for surveying.

In Japan, data from the Geospatial Information Authority’s network of Continuously Operating Reference Stations and private network RTK services are well developed, enabling centimeter-class positioning (half-inch accuracy) across wide areas from urban to mountainous regions. Also, by utilizing QZSS’s CLAS, Japan’s unique satellite augmentation system, correction information can be received directly from satellites even at sites without cellular coverage, maintaining high-precision positioning and enabling RTK use in a wider range of situations.

Challenges in traditional field inspections

Although RTK provides high-precision location information, full-scale surveying and inspection work traditionally required specialist technicians or multi-person teams. Traditional infrastructure inspections and surveying relied heavily on manual labor and analog methods, which presented the following issues.

• Large manpower and time burden: Detailed on-site inspections and surveys required multiple workers, and traffic control was sometimes necessary for measurements. Inspecting a single site could require significant personnel and time, increasing costs.

• Complicated data management: Recording and managing field measurements on paper drawings or ledgers makes it time-consuming to find or share data later. It is also difficult to utilize past inspection histories for degradation trend analysis or to quickly share information when problems occur.

• Limits to accuracy and reproducibility: Traditional methods using tape measures or visual estimation made it hard to record locations such as deterioration points or boundary points as accurate coordinates. As a result, reliance on veteran experience and intuition was common, introducing subjectivity into measurement results. Accurate judgment is difficult without skilled personnel, posing challenges for skill transfer.

As shown, it has been difficult to achieve both “accuracy assurance” and “efficiency” with conventional approaches. However, digital inspection methods using RTK have emerged to address this. Especially in recent years, RTK-compatible devices and services have advanced, creating an environment where even one person can perform high-precision positioning and data collection. Next, let’s look at the key topics of network RTK and smartphone utilization.

Single-person positioning enabled by network RTK

As mentioned above, the advent of network RTK eliminated the need to operate your own base station for positioning. This has brought major changes to field work. For example, traditionally surveying teams split roles between a base station (reference point) and a rover, typically working in pairs. But with network RTK, as long as you carry a rover receiver you can receive correction information anywhere, allowing you to complete surveying while moving as a single person.

The specific procedure involves bringing an RTK-capable GNSS receiver (rover) to the site and connecting to a correction data distribution service via a communication protocol called Ntrip on a smartphone. You then receive correction information in real time, and the coordinates measured by the receiver are instantaneously refined to high precision. By checking this on the smartphone screen, you can measure and record required points. The operator can move while operating the device with one hand and use the other hand for safety, enabling lightweight work.

Enabling single-person RTK surveying yields effects such as the following at sites. First, since minimal personnel are required, schedule coordination becomes easier and inspections can be carried out quickly. One person can respond to sudden inspection needs, improving responsiveness. Also, with minimal equipment required, maneuverability increases, allowing high-precision positioning even in remote mountains or confined areas. This is useful not only for infrastructure maintenance but also for disaster situation assessment.

Your smartphone becomes a surveying instrument: the revolution of solo RTK inspections

To maximize the advantages of network RTK, you need a portable receiver and an information terminal. Recently, smartphone RTK has attracted attention as a solution that combines both. This involves attaching a small RTK-capable GNSS antenna (receiver) to a smartphone and using a dedicated app for positioning and inspection. In other words, it’s a technology that “turns your smartphone into a high-precision surveying instrument,” allowing tasks that once required specialized surveying instruments or heavy equipment to be completed with a single pocketable smartphone.

A representative example of smartphone RTK is the LRTK series, which combines an RTK receiver for smartphones and cloud services. Attach the receiver to your smartphone, launch the app, and with a push of a button you can record the latitude, longitude, and height of your current location with centimeter-level accuracy (half-inch accuracy). No complicated operations are required; you can attach date/time and notes to measured points and save them. Measurement data is displayed on the smartphone as a map on the spot, and organized for easy review later.

Moreover, by integrating with the smartphone’s camera and sensors, the site conditions can be digitized as-is. For example, if you scan the surroundings with the smartphone camera while performing RTK positioning, you can generate high-precision 3D point cloud data on the spot. Each acquired point is tagged with accurate coordinates in real time, making it easy to analyze point clouds later to calculate distances or areas, or to import them into CAD drawings for use.

Thus, smartphone RTK enables people without surveying expertise to intuitively handle high-precision positioning. Tasks that previously relied on specialists can now be performed by on-site workers themselves, helping to alleviate labor shortages. Also, since measurement to recording is completed digitally, there is no need to transcribe measured data and the risk of mistakes is eliminated, greatly simplifying the field recording process.

Main benefits brought by smartphone RTK

The combination of smartphone and RTK for “solo inspections” offers various benefits. Here are the main points.

• Centimeter-level high precision: Using RTK reduces conventional meter-level errors down to below a few centimeters (a few in). Small displacements of bridges or roads and installation position deviations of equipment can be accurately identified, dramatically improving inspection reliability.

• Improved efficiency and time savings: Because one person can perform mobile surveying and inspection, preparation, teardown, and travel time are reduced, allowing many points to be measured in a short time. Tasks that previously took half a day can sometimes be completed in tens of minutes, improving overall site efficiency.

• Reduced personnel costs: Fewer personnel are required, reducing labor and travel expenses. If each person has their own high-precision positioning tool, there is no need to wait for shared equipment within the team, reducing wasted standby time.

• Improved safety: Measurements in hazardous locations can be taken from a safe distance. For slopes at risk of landslides or inside deteriorated tunnels, coordinates can be obtained from a distance, helping secure worker safety. Shorter work times also minimize time spent in dangerous areas.

• Immediate data sharing and accumulation: Positioning data can be uploaded directly from the smartphone to the cloud and shared with stakeholders. The need to return to the office to prepare reports is reduced, enabling real-time transmission of site information. Accumulated data can be managed chronologically and applied to comparative analysis with past data and preventive maintenance.

• Digital integration and scalability: Data obtained with smartphone RTK is saved in formats that are easy to link with GIS, CAD software, and other site management systems. Downstream use becomes smoother, and compatibility with 3D design data via BIM/CIM, or visualization on site using AR technology, is high.

As above, solo RTK inspections bring not only improved work efficiency but also major benefits in safety and data utilization. This smartphone-based high-precision positioning is an important piece in advancing digital transformation (DX) at worksites.

Use cases for RTK inspections: what kinds of sites benefit?

So, specifically, where is one-person RTK inspection useful? Here are several use cases.

• Regular inspections of infrastructure: RTK is effective for accurately recording locations of abnormalities in infrastructure such as roads, sewerage, and bridges. For example, when discovering a manhole or a road collapse, a single person can measure the site coordinates and record them immediately on a digital map, facilitating later repair planning and interdepartmental information sharing.

• Construction quality control: On construction sites, verification that structures were built according to design is essential. With smartphone RTK, a single person can measure key points of a constructed structure and check discrepancies from design values on the spot. Compared to surveying with a total station, preparation is simpler and it’s easy to take quick measurements during construction management.

• Post-disaster field surveys: Solo surveying is powerful for quickly grasping damage after earthquakes or heavy rains. Measuring collapsed terrain or the extent of collapsed buildings with smartphone RTK allows wide areas to be digitized quickly. Without deploying multiple personnel, efficient collection of key on-site data supports initial response and recovery planning.

• Agriculture and forestry: For wide agricultural fields, confirming parcel boundaries or irrigation channels, and surveying within forests where manual measurement is difficult, smartphone RTK is effective. Tasks like accurately measuring parcel areas or recording survey points in forests can be done by one person. In open-sky areas where GNSS reception is available, even non-experts can perform simple map creation.

• Other everyday tasks: Examples include position setting when installing equipment in factories or plants, preliminary land surveys, and recording locations of buried infrastructure—any situation where you want to “accurately record what is here.” The portability of a single smartphone makes it possible to measure whenever needed, raising the quality of routine inspection tasks.

In this way, one-person RTK inspections are proving powerful across a wide range of field operations. Fine measurements that were previously abandoned due to time or manpower constraints can now be undertaken easily.

The future and prospects of high-precision positioning

One-person RTK inspections are changing field work styles significantly. As GNSS positioning technology and smartphone performance continue to improve, the potential will expand further.

For example, although current usage is mainly in open outdoor spaces, in the future fusion of satellite positioning with other sensors (inertial sensors, camera imagery, etc.) may make it possible to use high-precision positioning even in places that were previously difficult (under overpasses, indoors, etc.). Also, combined with AR (augmented reality) technology, inspection support that displays desired information directly on the smartphone screen is anticipated. In some cases, pointing your smartphone at a site already brings up the routes of underground pipes or past inspection records as overlays.

National policies such as i-Construction and DX promotion encourage ICT use at worksites, so simple surveying that can be done alone is likely to become more widespread. In construction and infrastructure sectors facing aging workforces and technician shortages, smartphone RTK that anyone can handle could become a valuable asset.

Summary: possibilities opened by simple surveying (use of LRTK)

The “RTK inspections you can do alone” realized by the fusion of RTK technology and smartphones is a new field solution that combines accuracy, efficiency, and safety. High-precision positioning work that once required specialists can now be performed easily by anyone on site. Individuals can carry a high-precision surveying tool in their pocket, quickly measure and record positions as needed—this way of working is becoming reality.

Driving this trend is the smartphone high-precision GNSS solution LRTK. With LRTK, even those without special training can start simple surveying with just their smartphone. Heavy surveying equipment and complicated procedures are unnecessary. If you are considering “trying RTK positioning with your own smartphone” or “digitizing site inspections,” why not experience simple surveying with LRTK? High-precision positioning will surely help improve your operations.

FAQ

Q: What kind of technology is RTK? A: RTK (Real-Time Kinematic) is a technique that applies error information from a reference station to satellite positioning data such as GPS to correct positions in real time. Standard GPS positioning can have errors of several meters (several ft), but RTK can pinpoint positions with errors down to a few centimeters (a few in).

Q: Why does using RTK allow inspections to be done by one person? A: By using network RTK, you can obtain correction information without setting up your own reference station, so high-precision positioning is possible with just one receiver (rover). Carrying that receiver and moving between locations lets one person complete surveying and inspection tasks alone.

Q: Can a smartphone really achieve centimeter-level positioning? A: Yes. By attaching a dedicated RTK-capable receiver to a smartphone and using a compatible app, the smartphone can function as a high-precision GNSS positioning terminal. There are reported cases where combinations of smartphones and small receivers have achieved horizontal and vertical accuracy of a few centimeters (a few in).

Q: Can it be used without special surveying knowledge? A: Smartphone RTK solutions are designed so positioning and recording can be done with intuitive app operations. Simple actions like pressing a button to start positioning and pressing a save button at the desired point are central. They are designed so even beginners can quickly become proficient.

Q: What is LRTK? A: LRTK is a series name for high-precision positioning solutions that utilize smartphones. It combines a small GNSS receiver, a smartphone app, and cloud services so that centimeter-level positioning, recording, and sharing can be done with a single smartphone. For more details, please see the official LRTK website or product information pages.