Low-Cost, Cloud-Shared iPhone RTK Devices Expand Agriculture and Drone Surveying

Table of Contents

• The revolution that high-precision positioning brings to agriculture and drone surveying

• What is RTK? The importance of centimeter-level positioning

• Easy high-precision positioning enabled by iPhone RTK devices

• One surveying instrument per person becomes reality at low cost

• Linking field and office in real time via cloud sharing

• Use cases and benefits in agriculture

• Use cases and benefits in drone surveying

• New possibilities opened up by smartphone surveying

• Realizing simple smartphone surveying with LRTK

• Frequently Asked Questions (FAQ)

How High-Precision Positioning Is Revolutionizing Agriculture and Drone Surveying

In recent years, high-precision positioning technology has been attracting significant attention in agriculture and drone surveying. Tasks that have relied on experience and manual labor—such as crop management, field preparation, and drone-based topographic surveying—are being dramatically streamlined and enhanced by satellite positioning. However, conventional high-precision positioning required expensive dedicated equipment and specialized knowledge, presenting a high barrier for small-scale farmers and small businesses. Against this backdrop, the emergence of an iPhone RTK device that can be used in combination with a smartphone has opened the door for anyone to utilize centimeter-level positioning at low cost. This new technology, which also supports cloud sharing, is poised to revolutionize a wide range of areas, from agricultural sites to drone surveying.

What is RTK? The importance of centimeter-level positioning (inch-level positioning)

First, let’s briefly outline what RTK (Real Time Kinematic) is. RTK is a technique that operates a base station (a GNSS receiver installed at a known location) and a rover (the device whose position you want to determine) simultaneously, and improves positioning accuracy in real time by sending the satellite positioning error information detected by the base station to the rover as corrections. With this method, GPS positioning, which typically has errors of several meters (several ft), can be reduced at once to errors within a few centimeters (a few in). When centimeter-level positioning (inch-level positioning) becomes possible, you obtain information suitable not only for simple location awareness but also for precise surveying work. For example, RTK is an indispensable foundational technology in scenes that require accurate positional information, such as measuring farmland area, determining elevation differences, and improving the accuracy of drone photogrammetry.

Traditionally, achieving this RTK positioning required preparing specialized, high-performance GNSS receivers for both a base station and a rover and conducting measurements while communicating via radio or the Internet. The equipment—tripods, poles, large batteries, control terminals, and so on—was bulky, and simply bringing it to the site was hard labor. Furthermore, an "initialization wait" (time until FIX) of a few minutes occurred before obtaining high-precision information from the satellites, so one had to patiently wait for positioning to stabilize. In addition, this equipment was very expensive, entailing significant costs for acquisition and maintenance, and was therefore out of reach for small-scale businesses and individuals.

Easy high-precision positioning made possible by iPhone RTK devices

The recently introduced iPhone RTK devices are a groundbreaking solution that addresses these traditional challenges all at once. Put simply, by using a small GNSS receiver that can be attached to the back of a smartphone (particularly higher-end iPhones), the smartphone itself can be turned into centimeter-level surveying equipment (cm level accuracy (half-inch accuracy)). GPS in a smartphone alone, which can have errors of several meters (several ft), can achieve accuracy of several centimeters (several in) when combined with an external RTK-capable receiver. For example, by mounting a GNSS antenna on an iPhone via a dedicated case or attachment and connecting it via Bluetooth, etc., the smartphone can continuously measure its position with high accuracy.

The advantage of this iPhone RTK unit is its ease of use. The receiver weighs only a few hundred grams, is thin, and small enough to fit in a pocket. Because it has a built-in battery and requires no complicated wiring, you can quickly attach it to your smartphone on-site and start measuring immediately. Launch the dedicated app and, by configuring it to receive correction data from a base station over the network (connecting to a distribution service called Ntrip) or by selecting the reception mode for the Japan-specific Quasi-Zenith Satellite System "Michibiki" that provides the centimeter-level augmentation service (CLAS), high-precision positioning can begin within a few tens of seconds. Even in mountainous areas or fields where radio signals don’t reach, a CLAS-compatible unit can obtain correction signals directly from satellites, so maintaining stable centimeter-level accuracy even outside communication coverage is a major strength.

Furthermore, taking advantage of a smartphone's large touchscreen and high processing power, operation is intuitive. You can record survey points simply by pressing a button while checking your current location on the map, and latitude, longitude, and elevation are automatically recorded for measured points. Entering point names or adding notes is easy within the app, and it also has a photo-capture function with location data. In other words, from positioning to recording and photography, everything can be completed with just a single smartphone, eliminating the need to transcribe into paper field notebooks. Because it can be used with the feel of a smartphone app by people without specialized training, high-precision positioning is becoming an accessible tool even for those who previously had no connection to surveying.

Low cost makes one surveying instrument per person a reality

One reason smartphone surveying with iPhone RTK terminals is attracting attention is its low cost and ease of adoption. Traditionally, surveying equipment with centimeter accuracy (cm level accuracy (half-inch accuracy)) required investments on the order of several million yen, and at job sites it was common to operate by sharing a single expensive piece of equipment among a team. Because equipment was limited, waiting in line and personnel adjustments occurred, and there were many situations where work could not proceed efficiently. That is beginning to change with the advent of smartphone RTK. Devices such as the LRTK mentioned later are priced lower compared to traditional units, to the point that they are sometimes described as "astonishingly affordable." If each person can own their own high-precision positioning terminal, there will be no need to compete over equipment for every survey, and an environment where you can measure whenever you like will be established.

The benefits this "one device per person" surveying instrument can deliver are immeasurable. On sites facing labor shortages and an aging workforce, where a limited number of personnel must manage large areas, if everyone can carry a surveying device small enough to fit in a pocket it directly enables labor and manpower savings. In fact, there are reports that tasks that used to be done by two people working as a pair for half a day can now be completed by one person in about two hours, leading to significant reductions in work time and labor costs. It also eliminates the need to coordinate multiple people's schedules and creates the ability to go to the site and take measurements immediately when needed, contributing to shortening the overall project schedule and enabling faster decision-making.

Also, smartphone-based systems have refined UIs (user interfaces), and the fact that anyone can operate them without hesitation further promotes their adoption. Because they allow measurements with stable accuracy even by those who are not experienced surveyors, they are expected to help alleviate issues such as a shortage of know-how caused by the retirement of veteran surveyors. In other words, cost reduction and simple operation broaden the user base, making surveying no longer something only specialized experts do.

Real-time Coordination Between Field and Office via Cloud Sharing

Another innovative feature of the iPhone RTK device is data integration through cloud sharing. Positioning data and photos captured with a smartphone can be uploaded to the cloud and shared on the spot. Point coordinates, notes, photos, and other information measured by field workers are accumulated in the cloud in real time, allowing staff in the office and other team members to access that information immediately. This means information that previously had to be taken back to the office, compiled into reports, and could not be communicated until the next day is now shared instantly, eliminating the time lag.

There are various advantages to cloud integration. First, because data is centrally managed, the risk of data becoming dispersed or lost due to paper notes or USB drives is reduced. Since all survey points and photos are organized and stored in the cloud, necessary information can be accessed from anywhere. In addition, cloud data can be exported as CSV or image files and can be immediately used for importing into other analysis software or for report preparation. For example, at a soil investigation site, sharing the soil data and photos for each location via the cloud allows all stakeholders to grasp the results and issue the next instructions immediately after the survey is completed. The barrier between the field and the office disappears, leading to faster decision-making and earlier detection of mistakes.

Furthermore, because the data stored in the cloud is linked to precise location information, situations where "it is unclear which location a photo is of" can be prevented. Photos automatically record the coordinates and orientation of the location at the time of capture and are managed together with the survey point list. As a result, site information can be shared along with spatial context, enabling teams in different locations to have the same understanding as if they were looking at the same site. This kind of data-sharing system not only streamlines operations but also improves the quality of on-site work itself.

Examples of Applications and Benefits in Agriculture

High-precision positioning technology using smartphone RTK provides many benefits in agricultural settings. For example, in field improvement (reorganizing plots of fields and rice paddies and leveling ground), tasks include measuring ground elevation and recording the positions of waterways and field ridges. Traditionally, ground elevation surveys were carried out by teams of two using levels and total stations, repeatedly repositioning equipment and taking a long time; with an RTK-capable smartphone, these surveys can be completed quickly by a single person. As a result, even vast agricultural land can be surveyed efficiently, helping to alleviate labor shortages.

Also, in as-built management (post-construction verification) of agricultural irrigation and drainage channels, it is necessary to measure heights and slopes accurately, but with smartphone RTK, the construction personnel themselves can measure on site immediately and share the data to the cloud. This reduces the time lag caused by waiting for survey results to adjust the work, leading to improvement in the speed of construction management. The government is also promoting the use of ICT and smart agriculture in the agricultural civil engineering sector, and the adoption of digital technologies will become increasingly important. Affordable and easily portable smartphone RTK is the ideal tool to serve that role.

The introduction of smartphone RTK also advances visualization in agriculture. By using a smartphone’s camera and LiDAR to capture three-dimensional data (point cloud) of fields and adding RTK-derived position coordinates to it, it becomes possible to generate a terrain model of farmland on-site. For example, visualizing field slopes and low-lying areas prone to puddling as a 3D model can help with planning drainage measures and improvement works. Also, using AR (augmented reality) technology, you can confirm the placement of planned irrigation and drainage channels on-site through your smartphone screen. Because you can share on-site the completed image that was hard to grasp from drawings alone, building consensus among stakeholders will also be smoother. In this way, smartphone RTK contributes to the improved maintenance and planning of agricultural infrastructure and has become a technology that plays a part in smart agriculture.

Use Cases and Benefits of Drone Surveying

Drone-based surveying (photogrammetry and laser surveying) has rapidly spread in the construction and civil engineering sectors in recent years, and is also expanding into agriculture and environmental fields. Drone surveying analyzes many images taken from the air to create high-precision topographic maps and 3D models, but securing positioning accuracy is a challenge. Since the GPS on typical consumer drones can have errors of several meters (several ft), maps generated as-is will also be offset. For high-precision surveying, it has been necessary to either use RTK-capable drones or to install ground control points (Ground Control Point) on the ground to provide accurate coordinates. The former has the problem that industrial RTK-equipped drones are expensive and their adoption is limited, and the latter is not easy because it requires surveying knowledge and effort.

This is where smartphone RTK comes into its own. By measuring the coordinates of multiple ground points with your handheld iPhone RTK device to centimeter-level accuracy (half-inch accuracy) and using them as control points in drone photogrammetry, you can generate high-precision 3D maps even with standard drones that lack RTK. For example, when photographing an entire farmland with a drone to map crop growth, if you record the coordinates of the field’s four corners and reference points with smartphone RTK, you can correct positional offsets of each location on the map. As a result, the produced orthophotos and terrain models will align with real-world coordinate systems (latitude/longitude or planar coordinates), allowing area calculations and slope analyses to be performed with high reliability.

Furthermore, when combined with services that upload photos captured on-site to the cloud for automatic processing, it becomes possible to handle everything from drone capture to point cloud model generation in a one-stop workflow. Because the photo analysis is completed in the cloud even without a high-performance PC, you can obtain results quickly even while on the move. As the foundation supporting these workflows, smartphone RTK plays the role of ensuring accuracy.

The combination of drone surveying and smartphone RTK is highly effective even for surveys of rugged mountain forests and wide-area farmland. Drones can safely collect data from areas people cannot enter, and when that data is supplemented with reliably accurate positioning information, downstream data utilization (for example, calculating earthwork volumes or reflecting results in crop planning) becomes smoother. Also, by cross-checking drone survey results with field survey points obtained using smartphone RTK, you can perform data reliability checks on the spot. Because deliverables can be shared in real time between the field and the office, you can also respond flexibly, for example by immediately directing additional photography or measurements as needed. This sequence of processes dramatically shortens surveying work that used to take several days and helps accelerate on-site DX (digital transformation).

New possibilities unlocked by smartphone surveying

Smartphone surveying, which combines smartphones with high-precision GNSS, not only reduces manpower and time but also brings unprecedented new possibilities to the field. One such possibility is visualization through 3D measurement and AR. The latest iPhones are equipped with LiDAR scanners and high-performance cameras, and when fused with RTK high-precision positioning information, anyone can 3D-scan their surroundings on the spot and assign accurate coordinates to the resulting point cloud data. Previously, there was a problem in which a smartphone’s positional errors accumulated during scanning and distorted the model, but because RTK support allows assigning geodetic coordinates (latitude, longitude, height) to all acquired point clouds, data acquired at different locations or at different times can be easily integrated and compared. For example, analyses such as regularly measuring subsidence of farmland to track changes over time, or overlaying pre- and post-construction terrain in 3D models to calculate earthwork volumes, can be performed on-site.

The use of AR (augmented reality) is also an attractive feature of smartphone surveying. If you overlay lines from the design drawings or models of the planned structures onto the real scenery shown on the smartphone screen, you can intuitively grasp the finished image while on site. For example, when laying a new irrigation channel, showing the virtual position of the channel on the ground with AR allows you to check how it will interface with the surroundings and the landscape before construction. This virtually replaces the traditional work of marking the ground with stakes or chalk. Positioning can be done safely even in areas with poor footing or on paved surfaces, contributing to improved safety for workers. The visual information provided by AR is also useful for explanations to clients and local residents, helping to smooth the process of achieving consensus.

By leveraging digital technologies centered on smartphone RTK in this way, the site becomes more "visible" than ever. Information that could not be fully conveyed by drawings and numbers alone can now be shared in forms that anyone can intuitively understand through 3D models and AR. If you link photos and comments to the acquired data, you can recreate past conditions in detail at your desk without having to revisit the site later. Because aspects that used to rely on veterans' intuition and experience can be supplemented with data, this also contributes to knowledge transfer and error prevention. The new form of sites opened up by smartphone surveying can truly be described as the image of next-generation smart agriculture and smart construction.

Realizing Simple Smartphone Surveying with LRTK

Finally, as a concrete solution that makes it easy to achieve high-precision positioning with smartphone RTK, we introduce LRTK. LRTK (Eruāru Tīkē) is a series of compact RTK-GNSS receivers developed by a venture company originating from Tokyo Institute of Technology. It can be attached to an iPhone via a dedicated smartphone case, and at about 150 g it is lightweight yet enables centimeter-level positioning. It operates on an internal battery and connects to the smartphone via Bluetooth, allowing cable-free handling. LRTK supports CLAS, the Japanese GPS augmentation signal mentioned above, enabling high-precision satellite-based positioning even in locations without mobile coverage. In fact, there are examples of iPhones equipped with LRTK proving useful in farm field surveys in mountainous areas and at disaster sites where communications infrastructure had been severed.

By attaching the LRTK to your iPhone and launching the dedicated app, anyone can immediately start simple smartphone surveying. At the location you want to measure, you can record the position simply by holding up the smartphone and tapping the button in the app. Measurement data is uploaded to the cloud on the spot and can be shared instantly with colleagues in the office. Measured points are automatically plotted on a map, so other team members can understand the situation even without being on site. If you take photos, the shooting position and orientation are saved as metadata, so when you review them later it's immediately clear what was photographed and from which direction. There is no longer any need to mark up paper drawings by hand or paste photos into a logbook and write explanations.

This is how LRTK-enabled smartphone surveying represents a new surveying style where "anyone can take it out of their pocket and measure anytime." There is no need to transport and assemble heavy equipment as with traditional methods, so you can start measuring the moment the need arises. If one device per person becomes commonplace, you can respond immediately to measurement needs that occur on site, dramatically improving productivity and accuracy. It can be operated without special skills, so it provides reassurance even at sites where surveying specialists are in short supply. An era has arrived in which affordable, high-performance smartphone RTK devices like LRTK bring the benefits of high-precision positioning to every field, including agriculture and drone surveying. Experience this simple surveying at your site and realize next-generation smart workflows.

Frequently Asked Questions (FAQ)

Q: What is RTK? A: RTK stands for "Real-Time Kinematic" and is a technique that uses error correction information from a reference station to dramatically improve GPS positioning accuracy. It can raise position measurements that normally have errors of several meters to centimeter-level accuracy in real time.

Q: What is an iPhone RTK device? A: An iPhone RTK device is a small, high-precision GNSS receiver that attaches to a smartphone such as an iPhone. By pairing with a smartphone, you can use the phone as a centimeter-level (cm-level) positioning device. Simply attach the dedicated device and use a compatible app to easily perform high-precision surveying that previously required specialized equipment.

Q: Can a smartphone alone really achieve centimeter-level accuracy? A: Yes — under good conditions, a combination of a smartphone and an RTK receiver can achieve horizontal positioning accuracy of approximately ±1–2 cm (±0.4–0.8 in) and vertical accuracy of approximately ±3 cm (±1.2 in). This is accuracy comparable to professional surveying equipment. However, accuracy is affected by the surrounding line of sight (satellite signal reception conditions) and atmospheric conditions, so it is important to use it in the best possible environment at all times.

Q: What preparations and services are required to use smartphone RTK? A: Basically, you need an RTK-capable GNSS receiver (a device that attaches to the smartphone) and a smartphone app. Attach the device to the smartphone and configure the app to receive correction data. There are two ways to obtain correction data: receiving reference-station data over the Internet (using Ntrip services), or directly receiving the CLAS signal from the Quasi-Zenith Satellite System "Michibiki". The latter allows corrections even in areas without cellular coverage, such as mountainous regions. In Japan, CLAS is available in many areas.

Q: What are the benefits of supporting cloud sharing? A: A cloud-sharing-enabled smartphone RTK system lets you save data measured on-site to the cloud immediately and share it with the entire team. This eliminates waiting for reports from the field to the office, allowing you to grasp the situation in real time and issue instructions. Because the data is consolidated in the cloud, the risk of loss is reduced and you don’t have to spend time searching for data later. Photos and notes are also saved with location information attached, preventing omissions or mix-ups of information.

Q: What exactly can RTK be used for in agriculture? A: In agriculture, RTK can be used for surveying elevation differences across fields, measuring the area of plots, and mapping the layout of irrigation channels and field ridges. For example, it can be applied to measure paddy heights in detail to improve drainage or to create high‑precision maps of fields for autonomous tractor navigation. With smartphone RTK, farm workers can survey fields themselves and immediately share the data, making the development of field improvement plans and the input of data into smart agriculture systems smoother.

Q: Why is RTK necessary for drone surveying? A: When creating maps or models from aerial photos taken by drones, it is important that each photo has accurate position information. Ordinary GPS has large errors, so using it as-is causes misalignment in the generated models. Using RTK can reduce errors to a few centimeters (a few in), dramatically improving the accuracy of drone surveying. There is also a method of using RTK-equipped drones, but because they are expensive, measuring ground points with smartphone RTK and using them as control points to correct photos from a standard drone is attracting attention as a low-cost solution.

Q: Can smartphone RTK be used in remote mountain areas outside of cellular coverage? A: Yes — if you use a receiver that supports CLAS (Centimeter-Level Augmentation Service), you can receive correction information directly from satellites even in places where cellular signals don’t reach, enabling high-precision positioning. For example, in agricultural surveys in mountainous areas or surveying in forests, a smartphone RTK device can maintain centimeter-level accuracy as long as it can receive signals from the satellites. Conversely, devices that do not support CLAS require corrections via the internet, so their accuracy may deteriorate outside of cellular coverage.

Q: If you use smartphone RTK, will conventional surveying instruments become unnecessary? A: Smartphone RTK can now handle many surveying needs, but there remain situations where conventional instruments are advantageous. For example, highly precise construction measurements that require millimeter-level accuracy, and measurements using total stations equipped with specific sensors. However, for general positioning, terrain surveying, and as-built management, smartphone RTK increasingly provides sufficient coverage, and its role as a primary tool on site is steadily expanding.

Q: What is LRTK? A: LRTK is the name of a compact GNSS receiver device and its service designed to make smartphone RTK easy to achieve. By attaching it to an iPhone, you can turn your smartphone into a surveying instrument with centimeter-level accuracy. It also includes a dedicated app and cloud services, allowing data collected in the field to be shared to the cloud instantly. With LRTK, you can handle everyday surveying tasks without owning specialized surveying equipment.