Save labor and time with just one smartphone! Centimeter-level accuracy — one-person surveying enabled by the iPhone RTK device

Table of Contents

• What is one-person surveying?

• What is centimeter-level positioning with RTK?

• Labor- and time-saving effects of smartphone surveying

• What is an iPhone RTK device?

• Features of iPhone RTK devices

• Use cases for iPhone RTK devices

• Recommendations for simple surveying using LRTK

• FAQ

What is single-person surveying?

Surveying has traditionally been carried out by teams of two or more. In conventional surveying methods, a technician operating optical instruments such as a total station pairs with an assistant who holds a staff (leveling rod) or a prism. Because large, heavy equipment must be set up and measurement points recorded while mutually confirming positions and targets, the work inevitably requires manpower and time. Moreover, in hazardous locations such as mountainous areas or disaster sites, having multiple people enter increases the risk of accidents. Thus, traditional surveying has relied heavily on manual labor, and there has always been demand for reducing personnel and improving safety.

Against this backdrop, the concept drawing attention is "one-person surveying". As the name suggests, this refers to surveying work carried out by a single person, and it has become increasingly feasible due to recent technological innovations. In particular, the spread of surveying methods that utilize GNSS (Global Navigation Satellite System) has opened the door to one-person surveying. GNSS surveying, which can measure your position anywhere using GPS satellites as long as the sky is open, removes the need to carry heavy equipment and secure line of sight, and in principle allows a single operator to perform positioning. In other words, the era in which satellite positioning technology makes "one-man (single-person) surveying" possible has arrived.

However, conventional GNSS surveying also had limitations. Typical commercial GPS receivers can have errors on the order of several meters and thus fall far short of the centimeter-level accuracy required for measuring boundary points or stake-driving work. Therefore, higher-precision positioning technology is indispensable for practical use. The condition for surveying alone is “being able to achieve high-precision positioning without an assistant,” and the technology that makes this possible is RTK (Real-Time Kinematic).

Centimeter-level Positioning with RTK

RTK is an abbreviation for *Real Time Kinematic*, a correction technique that dramatically improves the accuracy of satellite positioning such as GPS. Standalone GPS positioning can result in errors of several meters due to satellite signal errors, but the RTK method uses satellite data observed simultaneously by a base station (reference station) and a mobile station (rover) to correct errors in real time. Specifically, the base station generates correction information from the difference between its known accurate position and the received satellite signals, and transmits this to the mobile station (the surveyor's side). The mobile station applies the received correction information to its observations to achieve centimeter-level positioning.

With the advent of this RTK method, high-precision positioning suitable for surveying has become possible even with GPS. Traditionally, dedicated, expensive RTK-capable GNSS receivers and communication equipment had to be prepared, and correction data obtained via radio communication with a base station or over cellular networks. However, recent advances in satellite positioning technology and cost reductions have made RTK positioning increasingly accessible with small, low-cost devices. Furthermore, in Japan the Quasi-Zenith Satellite System "Michibiki" provides a centimeter-level augmentation signal (CLAS), enabling high-precision positioning even in areas where it is difficult to install base stations, such as mountainous regions. Thanks to these developments, centimeter-level RTK positioning is beginning to spread not only among specialized institutions but also into general surveying work.

Labor Reduction and Time-Saving Effects of Smartphone Surveying

Even though RTK laid the groundwork for high-precision one-person surveying, using it in the field still required specialized knowledge for tasks such as handling equipment and processing positioning data. In addition, conventional RTK-GNSS receivers often cost several million yen for the unit alone, making them difficult for small and medium-sized operators to adopt casually. In recent years, a new approach has emerged: surveying that utilizes smartphones.

If a single smartphone can be used as surveying equipment, the barriers drop dramatically both in terms of usability and cost. Because anyone can check and record position information on a smartphone screen they're already familiar with, no special training like that required for dedicated instruments is necessary. In systems that combine a dedicated receiver and a smartphone, complex processes such as receiving signals from satellites and correction processing are automated in the background, so users complete surveying simply by following on-screen prompts to move and record points. It is also worth noting that you can make use of your existing smartphone without the need for the high initial investment required by conventional high-precision surveying equipment. Since implementation only requires a small receiver and an app, even small and medium-sized businesses can easily adopt the latest technology. This makes the labor reduction (personnel reduction) and time savings (reduced work time) in surveying operations suddenly much more realistic.

In actual cases where smartphone surveying was introduced, there have been reports of site measurements that previously required two to three people and more than half a day being completed by a single person in well under an hour. For example, at one civil engineering site, confirming the as-built shape (final form) of an entire development used to involve placing survey points and conducting leveling surveys, which took more than half a day to finish. When they switched to a method of walking the site while scanning with an iPhone fitted with a high-precision GNSS receiver, they were able to acquire terrain data (point clouds) for the whole site in just a few minutes and instantly visualize elevation differences relative to the design surface. Because they could perform additional measurements or adjustments on the spot and re-scan to confirm in short cycles, this also led to a significant reduction in rework. In this way, smartphone surveying has the potential to deliver dramatic labor savings and efficiency improvements, and it is attracting considerable attention from industry stakeholders.

What is an iPhone RTK device?

So what is the concrete method for achieving single-person surveying using a smartphone? The key is a device called the "iPhone RTK device". Simply put, it is an ultra-compact RTK-GNSS receiver that attaches to an iPhone or iPad and turns the smartphone into a high-precision surveying instrument. By attaching this device to a smartphone, the phone can perform centimeter-level positioning comparable to conventional dedicated GNSS equipment.

Developed by a Japanese startup, LRTK Phone is a prime example of an iPhone RTK device. It consists of a compact receiver of about 165 g that attaches to an iPhone and a dedicated app, realizing a smartphone-integrated surveying system. The high-precision positioning data received by the LRTK device is sent to the app in real time, where it is displayed and saved on the screen as coordinate positions. Users can obtain precise location information, including latitude, longitude, and altitude, with the same ease as operating their everyday smartphone.

iPhone RTK Terminal Features

The main features of the iPhone RTK terminal (LRTK) are summarized as follows.

• Ultra-compact, lightweight design: Weighing approximately 165 g and about 1 cm thick, it’s a compact size that can virtually integrate with a smartphone. Its pocketable, lightweight design lets you carry it on site and take it out for use whenever needed.

• Built-in battery for long operation: The device has a built-in battery that enables continuous measurements for about 6 hours. Charging is via USB Type-C, and it also supports power supply from mobile battery packs, so it can be used outdoors where external power is hard to obtain.

• One-touch attachment/detachment: With a dedicated smartphone case or magnetic attachment, the device can be attached to and detached from an iPhone or iPad with one touch. Easily attach it only when needed and remove it immediately when not in use, preserving the phone’s original portability.

• Centimeter-level positioning accuracy: It includes a high-performance multi-band GNSS antenna and, with real-time RTK corrections, enables high-precision horizontal positioning of about ±1–2 cm. Vertical (elevation) accuracy is also around ±3 cm for obtaining 3D coordinates. This achieves surveying-level accuracy that cannot be obtained with a smartphone’s built-in GPS.

• Supports Michibiki CLAS and network RTK: Because it can receive CLAS, the high-precision positioning augmentation service provided by Japan’s quasi-zenith satellite “Michibiki,” centimeter-level positioning is possible even in mountainous areas where cellular signals are out of range. It also supports network RTK (Ntrip) over the internet, enabling real-time correction-applied positioning anywhere in Japan.

• Supports single-person operation: By mounting the smartphone with the device on a dedicated pole or monopod, you can fix it in place like traditional surveying instruments and perform high-precision point measurements and stake-out (layout) work. Height offset corrections can be easily set in the app, and by simply supporting it with one hand while watching a bubble level, you can accurately measure ground points. Even without an assistant, a single person can carry out full-fledged surveying work.

• Versatile surveying app features: Using the dedicated iOS app, you can access a variety of functions that go beyond simple position measurement: acquisition and recording of current coordinates, averaging values through continuous measurement over several seconds and recording track logs, 3D point-cloud scan surveying using the iPhone’s camera and LiDAR, navigation (guidance) to pre-set target coordinates, and AR functions that load blueprints or 3D models and overlay them on live site imagery — complete everything from surveying to visualization of survey results with a single smartphone.

Use Cases for iPhone RTK Devices

How can iPhone RTK devices with these kinds of features be utilized in real-world fieldwork? Below are some anticipated scenarios and the effects they can deliver.

1. As-built management at civil engineering and construction sites: As-built management—the process of confirming that post-construction terrain and structures have been completed according to design—has traditionally been a time-consuming and labor-intensive task. Using an iPhone RTK device, a single operator can walk the site while performing 3D scans and acquire extensive terrain data in a short time. Because the acquired point cloud data is georeferenced from the start (latitude/longitude and elevation), you can check differences with the design data on-site using a color-coded heatmap display without taking the data back to the office for coordinate transformation. For example, areas where the ground is higher than the design elevation appear red and lower areas appear blue, making it immediately obvious on a smartphone screen. If necessary, you can immediately perform additional measurements or construction adjustments and rescan to verify, enabling a rapid PDCA cycle. As a result, you can greatly reduce the manpower and days required for as-built inspections while ensuring quality.

2. Situation assessment at disaster sites: At disaster sites such as landslides and floods, surveying is essential for assessing and recording damage. However, it is difficult to send large numbers of people into hazardous areas. With smartphone surveying, a single, lightweight worker can inspect the site and take measurements from safe positions. Centimeter‑level positioning using an iPhone RTK device can record the terrain of affected areas with high accuracy, supporting subsequent recovery planning. In fact, Fukui City in Fukui Prefecture was an early adopter of an on‑site surveying system that uses iPhones and RTK positioning for disaster response, successfully mapping damage more quickly and at lower cost than traditional methods. Its ability to efficiently cover wide areas with limited personnel has been highly valued.

3. Public Surveying and Infrastructure Inspection: Local governments and other organizations are exploring the use of smartphone-based surveying for a variety of applications. For maintenance and management of infrastructure such as roads and bridges, geotagged photo records and 3D modeling are useful. Using iPhone RTK devices, it is easy to tag captured photos with precise coordinates and orientation, and to share point-cloud data in the cloud. Because personnel without specialized surveying equipment can perform measurements with a smartphone, the burden of training and human resource development is reduced. In promoting the DX (digital transformation) of surveying operations, the smartphone—a platform anyone can use—will become a powerful tool.

In addition, it can be applied to a wide range of situations depending on your ideas, such as verifying land boundaries, performing field measurements in agriculture, and even measuring indoor positions (relative positions can be measured with AR technology even when outside GPS coverage). The important point is that high-precision positioning and measurement can be performed easily by a single person. Tasks that have been abandoned until now because of manpower or cost issues may become feasible with the combination of a smartphone and an iPhone RTK device.

Promoting Simple Surveying with LRTK

As we have seen so far, smartphone surveying that combines an iPhone with an RTK device represents an innovative approach that overturns conventional expectations. With only a small device that one person can carry and a smartphone app, you can perform everything from surveying large sites to 3D recording and even comparison with design data in a short time. In addition to reducing labor and saving time, the secondary benefits—such as the immediate use of survey data and improved safety—are also very significant.

As a solution that makes this kind of simple surveying easy to carry out, LRTK is a very compelling option. Developed as a surveying system that can be completed with a single smartphone, LRTK Phone pursues user-friendliness that anyone can handle while offering accuracy and functionality comparable to professional surveying equipment. If your company is seeking labor savings and efficiency improvements in its surveying operations, why not consider adopting smartphone-based surveying like this? One-person surveying using the latest technology should dramatically boost on-site productivity.

FAQ

Q: Can you really perform surveying with only a smartphone? A: Yes—by combining a dedicated RTK receiver device with an app, a smartphone can function as a high-precision surveying instrument. By attaching a compact RTK receiver to an iPhone, centimeter-level positioning based on satellite signals becomes possible. Bring the smartphone to the point you want to measure and simply tap the screen to record latitude, longitude, and elevation.

Q: Why can't ordinary smartphone GPS provide high accuracy? A: The GPS built into typical smartphones has positioning errors of several meters due to satellite signal errors and influences such as the ionosphere. This is fine for displaying your current location in map apps or using it as a car navigation system, but it is insufficient for surveying. By using an RTK device, correction information is used to cancel out these errors, making it possible to obtain dramatically higher-precision positions.

Q: Is network connectivity required for RTK surveying? A: If you receive correction information (differential data) over a network, a smartphone data connection (4G/5G) is required. However, within Japan, even in locations without cellular coverage you can achieve high-precision positioning by directly receiving the QZSS (Michibiki) CLAS signal. LRTK terminals support CLAS, so centimeter-level positioning is possible in mountainous areas without the need for a base station.

Q: Can it be used on smartphones other than iPhone? A: At present, it is a solution for iOS/iPadOS devices such as iPhone and iPad. It has been developed leveraging Apple’s high-performance sensors and stable hardware environment, and the dedicated app is also available from the App Store. Support for Android devices is something to look forward to in future developments.

Q: Can it be used without surveying knowledge or qualifications? A: Basic operations are completed within the smartphone app, making it significantly easier than handling specialized surveying equipment. Tap the screen at the point you want to measure to record coordinates, and calculations and corrections are performed automatically. However, qualifications such as a licensed surveyor are required to perform legal surveying tasks, such as surveying official control points or determining boundaries. Smartphone surveying should be used primarily as an aid for simple on-site measurements and preparing materials; if you plan to submit results as formal survey deliverables, it is advisable to have them verified by a professional.

Q: Can you really do pile driving and set out design positions all by yourself? A: Yes, it is possible. A combination of an iPhone RTK device and an app includes a guidance (navigation) function that displays arrows and distances on the smartphone screen toward the set target coordinates. By following this and moving while holding the smartphone, you can reach the target point. On site, attaching the smartphone to a pole allows one person to perform pile driving that used to require two people. It can also use AR technology to display lines and points from the design drawings onto the real-world view, visually assisting accurate positioning.