Table of Contents

• How iPhone and RTK Are Changing Surveying Sites

• Challenges of Traditional Surveying

• What Is iPhone RTK Surveying?

• How an iPhone Achieves Centimeter Accuracy

• Benefits of Smartphone RTK Surveying

• Use Cases Expanded by Smartphone Surveying

• Easy High-Precision Surveying with LRTK

• Frequently Asked Questions

How iPhone and RTK Are Changing Surveying Sites

For many years, surveying meant that expensive total stations or large GNSS receivers—specialized surveying equipment—were indispensable. Setting up tripods and mounting instruments, working in teams of two to pursue millimeter-level precision—this was the norm. However, this conventional wisdom has begun to change dramatically in recent years. By combining everyday smartphones with the latest GNSS technology, we are entering an era where specialized equipment is not necessary to achieve centimeter-level positioning accuracy. In particular, iPhone models equipped with high-performance cameras and LiDAR sensors have appeared, and “smartphone surveying” that leverages these features is attracting attention. If you can scan a site’s 3D shape and attach high-precision position information with just the iPhone in your hand, it’s easy to imagine a revolution in surveying workflows.

Challenges of Traditional Surveying

First, let’s look back at the issues inherent in conventional surveying methods. The biggest problems are labor and manpower. For example, surveying with a total station requires at least two people: one to operate the instrument and another to carry the target and move between points. Setting up a tripod, leveling the instrument, and repeating aiming, reading, and recording for each point takes tremendous effort and time. When many points must be measured, it is not uncommon for the work to take an entire day, posing a heavy burden on sites already struggling with staff shortages. In addition, operating advanced equipment requires skilled personnel, creating dependence on individual expertise; inexperienced workers often find it difficult. Measurement or recording errors can propagate into mistakes in later drawing creation or construction.

Another frequently cited issue is the lack of real-time capability. Traditionally, field data were taken back to the office and checked against design drawings or CAD data before confirming that as-built shapes or installed positions were correct. Because results could not be judged on site, finding discrepancies required returning to the field for re-measurement, wasting valuable time. Surveying in dangerous locations—such as cliff tops, steep slopes, or under bridge piers—was also a serious problem. In places with poor footing or restricted access, it is difficult to ensure safety, and in some cases sufficient accuracy had to be abandoned.

Cost and inefficient data utilization are also significant concerns. High-precision GNSS receivers, 3D scanners, and total stations are all very expensive, making it difficult for small and medium-sized businesses to equip each site with enough units. Rental or sharing arrangements are often necessary, and scheduling delays can affect project timelines. Transferring coordinate data obtained on site into CAD drawings often involves manual transcription or coordinate conversion, which becomes a breeding ground for human error and inefficiency. In these ways, traditional surveying styles contained many inefficiencies and challenges.

What Is iPhone RTK Surveying?

A new approach that can address these issues is iPhone RTK surveying, which combines smartphones with high-precision GNSS technology. “RTK” stands for *Real Time Kinematic*, a method that achieves dramatically higher accuracy by exchanging GNSS positioning error information in real time between a rover (mobile unit) and a base station. With RTK, positional errors of about 5–10 meters in standalone GPS positioning can be reduced to a few centimeters. RTK provides sufficient accuracy for public surveying that requires millimeter precision, layout of batter boards, inspections of as-built shapes of structures, and similar tasks. Traditionally, RTK surveying required expensive GNSS receiver sets and radio equipment, but miniaturization and cost reductions have made it possible to perform RTK surveying using compact GNSS receivers and apps that attach to smartphones. For iPhone specifically, dedicated devices and apps that make RTK technology easy to use have emerged, bringing centimeter-accuracy positioning—once the exclusive domain of specialists—within reach of many users.

How an iPhone Achieves Centimeter Accuracy

So how can a smartphone, whose GPS may have errors of several meters, perform centimeter-level surveying? The key is the use of RTK correction information. Specifically, a small RTK-capable GNSS receiver attached to the iPhone receives error correction data via a network connection or satellite. In Japan, a network RTK service (commonly provided via Ntrip) based on the Geospatial Information Authority of Japan’s Continuously Operating Reference Stations (GEONET) is available; by connecting from a smartphone app to a correction information distribution service, you can typically obtain a high-precision “fixed solution” within tens of seconds to about a minute. Once a fixed solution (a solution where errors have converged) is obtained, centimeter-level position information continues to be updated in real time even while moving. Tap a button at the point you want to measure, and you can instantly record a highly accurate coordinate.

Moreover, Japan’s own advantage includes the centimeter-level augmentation service (CLAS) provided by the Quasi-Zenith Satellite “Michibiki”. Some recently released RTK-capable devices can receive this CLAS signal directly. Combining a CLAS-capable device with an iPhone makes it possible to perform real-time high-precision positioning using augmentation signals from Michibiki even in mountainous areas where mobile communications are unavailable. In other words, even without deploying your own base station, you can correct positioning errors to within a few centimeters in environments without network connectivity. With the combination of an iPhone, a small receiver, and correction information, it is now possible to stably achieve horizontal accuracy of about 2–3 cm and vertical accuracy of about 3–4 cm across Japan. This centimeter-level location information obtainable with a smartphone is a key enabler for accelerating on-site digitalization (DX).

Actual usage is simple. Attach an RTK-capable small GNSS receiver to an iPhone or iPad, launch a dedicated positioning app, and connect to a correction information service—preparation is complete. No complicated setup is required, and you can start positioning as soon as you want to measure. The device pairs with the iPhone via Bluetooth or Wi‑Fi, and positioning data are displayed in real time within the app. Because the position accuracy stabilizes shortly after measurement begins, you simply move around the site and press the record button at the points you need. Your current position and measured points are plotted on a map on the smartphone screen, allowing intuitive operation for surveying tasks.

Benefits of Smartphone RTK Surveying

The new surveying style that leverages smartphones and RTK offers many advantages not found in traditional methods. Here are the main points summarized.

• Reduced labor and time savings: There is no need to transport and set up large equipment; one person can survey a site while moving around, greatly reducing preparation and setup time. Without the need to set tripods, surveying can start immediately upon arrival, allowing far more points to be measured within limited work hours.

• Improved mobility: Handheld smartphone surveying offers the mobility to measure as soon as you think of it. Traditional methods required time whenever equipment was repositioned, but smartphone RTK lets you freely walk around the site and acquire points one after another. It is fast for measuring points scattered over a wide area or for continuous surveying across varying elevations.

• Safety and flexibility: Small, portable smartphone surveying equipment makes it easier to survey poor-footing areas, heights, and confined spaces. There is less need to carry heavy instruments into hazardous locations, reducing worker burden and improving safety. You can easily measure from above a slope without using an aerial work platform, or measure in narrow indoor spaces where tripods are hard to set up—providing flexible operation.

• Cost efficiency: Smartphone RTK systems are significantly lower cost than total stations or professional GNSS sets. You often only need to add a small receiver to an existing iPhone, avoiding the need to purchase multiple expensive precision instruments. This makes it easier for small and medium-sized projects or infrequent surveying tasks to adopt cutting-edge technology.

• Real-time data utilization: Positioning data obtained with smartphone RTK can be synchronized to the cloud on-site or used in formats that are easy to compare with design drawings. Measured point coordinates are automatically converted and recorded in the Japanese geodetic system or the site coordinate system, eliminating the need for post-office coordinate conversion or manual entry. Field data can be reflected immediately on drawings on a tablet or PC to confirm as-built conditions in real time and decide whether additional measurements are needed.

Use Cases Expanded by Smartphone Surveying

Centimeter-level accuracy enabled by iPhone RTK surveying can be applied to a wide range of field tasks. Here are some representative examples.

As-built management and quality checks: For as-built management in civil engineering—checking whether embankments or excavated ground meet design heights and slopes—the combination of smartphone RTK and point cloud data is powerful. If you scan the ground surface with an iPhone’s camera or LiDAR while assigning precise coordinates from RTK to each point, you can easily obtain high-precision 3D point cloud data. Overlaying this on the design model allows color-coded visualization of where the surface is a certain number of centimeters above or below the design, making it easy to see construction deviations at a glance. This enables immediate decisions about additional excavation or fill.

Layout and batter board placement: Smartphone RTK is also useful for setting out positions and heights for structures in building and civil engineering (so-called batter board layout). If you preload design reference point coordinates or boundary line data into the app, the design positions are displayed on the smartphone on-site. Using AR (augmented reality), the real scene seen through the phone can be marked with “here is where to place a stake,” enabling intuitive and accurate layout. There is no need for an assistant with a prism or a tape measure—one person can set stakes at the planned positions, greatly improving efficiency.

Survey map creation and data sharing: Coordinate lists measured with smartphone RTK can be used directly in survey maps or CAD drawings. Export measured point data from the dedicated app in DXF or LandXML formats, open in drawing software, and site survey maps can be created immediately. There is no need to draft drawings from paper field notebooks; you handle data as error-free digital data from the start. Project members can also easily share data via cloud services, enabling smooth information flow between field and office.

Other applications: iPhone RTK surveying also improves drone surveying accuracy (using smartphone RTK for GCP placement in photogrammetry), enables rapid damage assessment at disaster sites, supports high-precision navigation for autonomous agricultural machinery, and is expected to be applied across many fields. The advantage of “accurate measurement anywhere with a smartphone” will expand possibilities for various field operations.

Easy High-Precision Surveying with LRTK

As described above, combining iPhone and RTK technology now makes centimeter-level surveying possible for anyone. Still, some may feel it is difficult to build a system from scratch. That’s where LRTK, a solution developed by Reflexia Inc., a startup originating from Tokyo Institute of Technology, comes in. LRTK is a system consisting of an ultra-compact RTK-GNSS receiver for smartphones (iPhone/iPad) and a dedicated app that turns an iPhone into a surveying instrument. The compact device—about 1 cm thick and weighing roughly 165 g—attaches to an iPhone and connects wirelessly, and you’re ready. With the LRTK app, a tap of a button records your current position with ±2–3 cm accuracy.

What makes LRTK outstanding is that it combines ease of use for those without specialized knowledge with performance comparable to traditional professional surveying instruments. The device is multi-frequency and uses multiple satellite systems needed for high-precision positioning, including GPS, GLONASS, and Galileo. It also supports Japan’s Michibiki satellites, allowing reception of CLAS signals from satellites in mountainous areas without cellular reception to continue receiving corrections. This means no base stations, tripods, or other large equipment are required—just a smartphone and an LRTK device enable stable centimeter-class positioning anywhere.

Field usability is also considered. The LRTK device can be mounted on a slim monopod pole and held vertical with the tip on the ground for more precise point measurement or stake-driving tasks. Even then, it is far lighter and more agile than traditional mounted equipment, and you can flexibly choose whether to use the pole or measure handheld depending on the situation. Measured data are automatically backed up to the cloud and can be checked from a PC, enabling smooth information sharing between field and office.

Using LRTK makes it possible for anyone to perform high-precision surveying that previously required specialists or extensive preparation. If you have an iPhone, you can measure the moment you think of it—this new era of surveying is becoming a reality. If your company is considering DX promotion or workflow efficiency improvements, why not try smartphone RTK surveying at least once?

Frequently Asked Questions

Q: Can a smartphone really achieve centimeter-level accuracy by itself? A: Yes—when combined with a dedicated RTK-capable receiver and correction information. Standalone smartphone GPS has meter-level errors, but applying corrections from a base station via RTK can reduce errors to a few centimeters. For example, attaching a device like LRTK to an iPhone and receiving correction data from continuously operating GNSS reference stations over a network can achieve accuracy comparable to traditional large surveying instruments. Various validations have confirmed horizontal accuracy of about 2–3 cm and vertical accuracy of about 3–5 cm.

Q: Do you need to provide your own base station to use RTK? A: In principle, you do not need to set up your own base station. In Japan, a network RTK service (VRS method) leveraging the Geospatial Information Authority’s continuously operating reference station network is established, and commercial RTK-capable apps can receive correction information. Also, by using the Quasi-Zenith Satellite Michibiki’s CLAS, you can receive corrections directly from satellites in areas where base station communications do not reach. Therefore, smartphone RTK surveying can typically rely on existing correction services, eliminating the need to deploy dedicated base station equipment on site.

Q: Which iPhone models can be used for RTK surveying? A: Essentially, any iPhone/iPad that can pair with an external device via Bluetooth or Wi‑Fi is capable of RTK surveying. Newer iPhones offer higher performance, and iPhone Pro series models with LiDAR make it easier to combine 3D scanning with point cloud surveying. However, RTK device and app support depend on OS versions and supported models, so check the official information of the solution you plan to use (for example, LRTK) for compatible devices.

Q: Are there communication or subscription fees for smartphone RTK surveying? A: If you obtain correction information over a network, some services may require a contract or subscription fee. There are free correction services run by government or local authorities in some cases, but many opt for paid commercial services for real-time performance and convenience. Receiving Michibiki’s CLAS signals is free of charge. Mobile data usage for correction information is lightweight, so typical mobile data plans do not incur significant costs.

Q: Can someone without surveying experience use it? A: Smartphone RTK surveying systems are designed for intuitive operation. In most dedicated apps you can simply tap “Start Measurement” or “Record” to capture coordinates, and the screen displays your current position and measured points, making it easy to use. With basic GPS knowledge and an understanding of the surveying purpose, you can generally operate the system without a professional license. However, note that official public surveying or legal boundary determination may require licensed surveyors and adherence to regulations. It is recommended to start with simple field surveys or as-built checks and gradually build experience.