Low-cost, cloud-shared【iPhone RTK devices】expand agriculture and drone surveying

Table of Contents

• How high-precision positioning is revolutionizing agriculture and drone surveying

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

• Easy high-precision positioning realized with iPhone RTK devices

• Low-cost, one surveying instrument per person becomes a reality

• Real-time coordination between field and office through cloud sharing

• Use cases and benefits in the agricultural sector

• Use cases and benefits in drone surveying

• New possibilities opened up by smartphone surveying

• Realizing simple smartphone surveying with LRTK

• Frequently Asked Questions (FAQ)

The Revolution **High-Precision Positioning** Brings to Agriculture and Drone Surveying

In recent years, high-precision positioning technology has been attracting significant attention in the fields of agriculture and drone-based surveying. Tasks that previously relied on experience and manual labor—such as crop management, field preparation, and drone-based terrain surveying—are being dramatically made more efficient and advanced by satellite positioning. However, conventional high-precision positioning required expensive dedicated equipment and specialized knowledge, posing a high barrier for small-scale farmers and small businesses. Against this backdrop, the emergence of iPhone RTK devices that can be used in combination with smartphones has opened the way 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

First, let's briefly cover what RTK (Real Time Kinematic) is. RTK is a technique that operates a reference station (a GNSS receiver installed at a known location) and a rover (the device whose position you want to determine) simultaneously, and by sending the satellite positioning error information captured by the reference station to the rover and applying corrections, dramatically improves positioning accuracy in real time. With this method, GPS positioning, which typically has errors of several meters, can be reduced at once to errors within a few centimeters. When centimeter-level positioning becomes possible, you obtain information that goes beyond mere location awareness and is sufficient for precise surveying work. For example, in scenarios where accurate position information is required—such as measuring farmland area, determining elevation differences, or improving the accuracy of drone photogrammetry—RTK becomes an indispensable foundational technology.

Traditionally, achieving RTK positioning required preparing dedicated high-performance GNSS receivers for both the base and rover stations and conducting measurements while communicating via radio or the Internet. The equipment—tripods, poles, large batteries, and control terminals—was also bulky, making it hard work just to bring everything to the site. Furthermore, there was an "initialization wait" of several minutes (time until FIX) before high-precision information could be obtained from the satellites, so one had to patiently wait for positioning to stabilize. Additionally, this equipment was extremely expensive, with substantial acquisition and maintenance costs, making it out of reach for small operators and individuals.

Easy high-precision positioning realized with 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 compact GNSS receiver that can be attached to the back of a smartphone (particularly high-end iPhones), they turn the phone itself into a surveying instrument with centimeter-level accuracy. GPS on a smartphone alone can have errors of several meters, but by combining it with an external RTK-capable receiver, accuracy of a few centimeters can be achieved. For example, if you attach a GNSS antenna to an iPhone via a dedicated case or attachment and connect it via Bluetooth or the like, the smartphone can continuously measure its own position with high accuracy.

The advantage of this iPhone RTK unit lies in its ease of use. The receiver is lightweight at only a few hundred grams, thin, and pocketable. With a built-in battery and no need for cumbersome wiring, you can quickly attach it to your smartphone on site and start measuring immediately. By launching the dedicated app and configuring it to receive correction information from a reference station over the network (connecting to a distribution service called Ntrip) or by selecting the reception mode for Japan’s Quasi-Zenith Satellite System “Michibiki” centimeter-level augmentation service (CLAS), high-precision positioning can begin within a few tens of seconds. Even in mountainous areas or farms where signals don’t reach, a CLAS-compatible device can obtain correction signals directly from satellites, so maintaining stable centimeter-level accuracy even outside of communication coverage is a major strength.

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

Low-cost, one-per-person surveying devices become a reality

One reason smartphone surveying using iPhone RTK devices is attracting attention is its low cost and ease of adoption. Traditionally, centimeter-accuracy surveying equipment required investments on the order of several million yen, and on-site it was common for teams to operate while sharing a single expensive device. Because equipment was limited, there were often waits and personnel adjustments, and many situations where work couldn't proceed efficiently. That situation is changing dramatically with the advent of smartphone RTK. Devices like the LRTK discussed later are priced lower than traditional units, and have even been described as "surprisingly affordable." If every individual can have their own high-precision positioning device, there will be no need to vie for equipment at each survey, creating an environment where you can measure whenever you want.

This "one surveying device per person" offers immeasurable benefits. On sites facing staff shortages and an aging workforce, wide areas must be managed with a limited number of people, but if everyone can carry a surveying device that fits in a pocket, it directly leads to staff reductions and labor savings. In fact, there have been reports that tasks that once took two people half a day can be completed by one person in about two hours, resulting in significant reductions in working time and labor costs. Coordination of multiple schedules becomes unnecessary, and because it creates the mobility to go to the site and take measurements immediately when needed, it can contribute to shortening overall project timelines and enabling faster decision-making.

Furthermore, smartphone-based systems have refined UIs (user interfaces) that anyone can operate without difficulty, which also helps drive adoption. By enabling stable measurement accuracy even for non-expert surveyors, they are expected to ease issues such as the loss of know-how caused by the retirement of veteran professionals. In other words, through reduced costs and simplified operation, the user base expands, and surveying will no longer be the exclusive domain of specialized experts.

Real-time coordination between the field and the office via cloud sharing

Another innovative feature of the iPhone RTK terminal is data integration through cloud sharing. Positioning data and photos captured with the smartphone can be uploaded to the cloud on-site and shared. Point coordinates, notes, photos, and other items measured by field workers are stored in the cloud in real time, allowing staff in the office and other team members to immediately view that information. As a result, information that previously had to be taken back from the field, compiled into reports, and could not be conveyed until the next day is now shared instantly, eliminating the time lag.

Cloud integration offers various advantages. First, because data is centrally managed, the risk of data being 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, data in the cloud can be exported as CSV or image files and can be immediately used for import into other analysis software or for report preparation. For example, at a soil survey site, sharing soil data and photos from each location via the cloud enables all stakeholders to understand the results and issue the next instructions immediately after the survey is completed. The boundary between the field and the office disappears, leading to faster decision-making and early detection of mistakes.

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

Examples of Applications and Benefits in Agriculture

High-precision positioning technology using smartphone RTK brings many benefits to agricultural sites. For example, in field development (such as reorganizing plots of farmland and paddies and leveling the ground), there are tasks like measuring ground elevation and recording the locations of waterways and field ridges. Ground elevation surveys that used to require a two-person team using leveling instruments or total stations and repeatedly repositioning equipment over long periods can be completed quickly by a single person with an RTK-capable smartphone. As a result, it is possible to efficiently survey vast agricultural land, contributing to the alleviation of labor shortages.

Also, for as-built management of agricultural irrigation and drainage channels (post-construction finish verification), it is necessary to accurately measure heights and slopes, but with smartphone RTK the construction personnel themselves can take measurements on site immediately and share the data to the cloud. This reduces the time lag of 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 introduction of digital technologies will become increasingly important going forward. Affordable and easy-to-carry smartphone RTK devices are precisely the right tools to serve that need.

With the introduction of smartphone RTK, visualization in the agricultural sector also advances. By using a smartphone's camera and LiDAR to capture three-dimensional field data (point clouds) and adding the position coordinates obtained from RTK, it becomes possible to generate a terrain model of farmland on site. For example, visualizing a field's slopes and low-lying areas prone to water pooling in a 3D model helps with planning drainage measures and improvement works. In addition, using AR (augmented reality) technology allows you to confirm the placement of planned drainage channels on site through the smartphone screen. Because the completed image, which was hard to grasp from drawings alone, can be shared at the site, building consensus among stakeholders is likely to proceed more smoothly. In this way, smartphone RTK contributes to the maintenance and advanced planning of agricultural infrastructure and serves as a technology that plays a part in smart agriculture.

Applications and Benefits of Drone Surveying

Surveying using drones (photogrammetry and laser surveying) has rapidly spread in recent years in the construction and civil engineering sectors, and is also expanding into agriculture and environmental fields. In drone surveying, numerous images captured from the air are analyzed to create high-precision topographic maps and 3D models, but ensuring positional accuracy is a major challenge. Standard consumer drone–mounted GPS can have errors of several meters, causing the generated maps to be misaligned if used as is. For high-precision surveying, it has been necessary to use RTK-capable drones or to establish ground control points (Ground Control Point) on the ground to provide accurate coordinates. The former faces the issue that RTK-equipped industrial drones are costly and their adoption is limited, while the latter is not simple, as it requires surveying knowledge and effort.

That's where smartphone RTK shines. By using a handheld iPhone RTK device to measure the coordinates of multiple ground points to centimeter-level accuracy and using those as control points for drone image processing, you can generate highly accurate 3D maps even with ordinary drones that lack RTK. For example, when mapping crop growth across an entire field with drone imagery, if you record the coordinates of the field's four corners and reference points with a smartphone RTK, you can correct positional offsets on the map. As a result, the resulting orthophotos and terrain models align with real-world coordinate systems (latitude and longitude or planar coordinates), enabling area calculations and slope analyses to be performed with high reliability.

Furthermore, when combined with services that upload on-site photo data to the cloud for automated processing, it becomes possible to handle everything from drone photography to point cloud model generation in a one-stop workflow. Because photo analysis is completed on the cloud side even without a high-performance PC, you can obtain results quickly even when working remotely. As the foundation that supports such workflows, smartphone RTK plays the role of ensuring accuracy.

The combination of drone surveying and smartphone RTK proves powerful even for surveys of steep mountain forests and wide-area farmland. Drones can safely acquire data from places people cannot enter, and when reliable positional accuracy is added, downstream data utilization (for example, calculating earthwork volumes or reflecting results in cropping plans) becomes smoother. In addition, by cross-checking drone survey results with on-site survey points obtained via smartphone RTK, data reliability checks can be performed on the spot. Because deliverables can be shared in real time between the field and the office, flexible responses—such as immediately instructing additional imaging or measurements—are also possible. This series of processes dramatically shortens surveying work that previously took several days and helps drive on-site DX (digital transformation).

New Possibilities Opened 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 on-site operations. One of these is visualization through 3D measurement and AR. The latest iPhones are equipped with LiDAR scanners and high-performance cameras, and when fused with high-precision RTK positioning, anyone can 3D-scan their surroundings on-site and assign accurate coordinates to the resulting point cloud data. Previously, positional errors of the smartphone could accumulate during scanning and distort the model, but with RTK support all acquired point clouds can be assigned Earth coordinates (latitude, longitude, height), making it easy to integrate and compare data acquired at different locations or at different times. For example, analyses such as periodically measuring subsidence of farmland to track long-term changes, 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 a key appeal of smartphone surveying. By overlaying lines from design drawings and models of planned structures onto the real-world scene displayed on the smartphone screen, you can intuitively grasp the finished image while on site. For example, when laying a new water channel, showing the virtual location 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 practice of marking the ground with stakes or chalk. It enables safe positioning even in areas with poor footing or on paved surfaces, contributing to improved worker safety. Visual information provided by AR also helps in explaining plans to clients and local residents, facilitating smoother consensus building.

By leveraging digital technologies centered on smartphone RTK in this way, the field becomes more "visible" state than ever. Information that could not be fully shared with drawings and numbers alone can now be shared in forms that anyone can intuitively understand through 3D models and AR. If photos and comments are linked to collected data, you can reproduce past site conditions in detail at your desk without revisiting the site later. Because aspects that relied on veteran intuition and experience can be supplemented with data, this also aids knowledge transfer and error prevention. The new form of fieldwork that smartphone surveying is opening up can truly be described as the shape of the next-generation smart agriculture and smart construction.

Enabling Simple Smartphone Surveying with LRTK

Finally, as a concrete solution that makes it easy to achieve such high-precision positioning with smartphone RTK, we introduce LRTK. LRTK (El-are-tee-kay) is a series of compact RTK-GNSS receivers developed by a venture company originating from the Tokyo Institute of Technology. It can be attached to an iPhone via a dedicated smartphone case, and despite weighing about 150 g, enables centimeter-level positioning. It runs on a built-in battery and connects to the smartphone via Bluetooth, allowing cable-free handling. LRTK supports CLAS, the Japanese GPS augmentation signal mentioned above, and can perform high-precision satellite-based positioning even in locations where cellular signals do not reach. In practice, there are examples of iPhones equipped with LRTK proving useful in field surveys of farmland in mountainous areas and at disaster sites where communications infrastructure was cut off.

Attach the LRTK to an iPhone and launch the dedicated app, and anyone can immediately begin simple smartphone surveying. At the point you want to measure, simply hold up the smartphone and tap the button in the app to record the location. 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 if they are not on site. If you take photos, the photo’s location and orientation are saved as metadata, so when you review them later it is immediately obvious what was photographed and in which direction. There is no longer any need to hand-mark paper drawings or paste photos into ledgers and write explanations.

In this way, LRTK-enabled smartphone surveying is a new surveying style where "anyone can pull it out of their pocket and measure anytime." There is no need to transport and assemble heavy equipment as before, and you can start measurements instantly whenever the need arises. Once one device per person becomes the norm, you will be able to respond immediately to measurement needs that occur on site, dramatically improving both productivity and accuracy. Because it can be operated without special skills, it is dependable even at sites that lack specialist surveyors. The 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. Be sure to experience this simple surveying at your site and realize a next-generation smart workflow.

Frequently Asked Questions (FAQ)

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

Q: What is an iPhone RTK terminal? A: An iPhone RTK terminal is a compact, high-precision GNSS receiver that attaches to and is used with smartphones such as the iPhone. By pairing it with a smartphone, you can use the phone as a centimeter-level positioning device. Simply attaching the dedicated device and using a compatible app makes it easy to perform high-precision surveying that previously required specialized equipment.

Q: Can a smartphone alone really achieve centimeter-level accuracy? A: Yes, under favorable conditions, a smartphone combined with an RTK receiver can achieve approximately ±1–2 cm accuracy in horizontal position and about ±3 cm in elevation. This is comparable to the accuracy of professional surveying equipment. However, accuracy is affected by surrounding visibility (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 necessary to use smartphone RTK? A: Basically, you need an RTK-capable GNSS receiver (a device attached 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 via the internet (using an Ntrip service), or directly receiving the CLAS signal from the Quasi-Zenith Satellite System "Michibiki." Using the latter allows corrections even in areas without cellular coverage, such as mountainous regions. Within Japan, CLAS is available in many areas.

Q: What are the benefits of supporting cloud sharing? A: With a smartphone RTK system that supports cloud sharing, you can save field-measured data to the cloud on the spot and share it with the entire team. This eliminates waiting for reports to be sent from the field to the office, allowing you to grasp the situation in real time and give instructions. Because the data are 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, preventing omissions or mix-ups of information.

Q: What can RTK specifically be used for in agriculture? A: In the agricultural sector, RTK can be used for measuring elevation differences across fields, calculating plot areas, and surveying the layout of irrigation channels and field ridges. For example, it can be applied to measure rice paddy elevations in detail to improve drainage, or to create high-precision maps of fields for autonomous tractor operation. With smartphone RTK, agricultural workers can survey fields themselves and immediately share the data, making the planning of field improvement projects and the input of data into smart agriculture systems smooth and efficient.

Q: Why is RTK necessary for drone surveying? A: When creating maps or models from aerial photographs taken by drones, it is important that each photo is tagged with accurate positional information. Ordinary GPS has large errors, so using it as‑is introduces misalignments into the generated models. Using RTK can reduce errors to a few centimeters, dramatically improving the accuracy of drone surveying. While one option is to use RTK‑equipped drones, because they are costly, a low‑cost approach that has gained attention is measuring ground points with smartphone RTK to serve as control points and applying corrections to photos taken by standard drones.

Q: Can smartphone RTK be used deep in the mountains where there is no cellular coverage? A: Yes—if you use a receiver that supports CLAS (Centimeter-Level Augmentation Service), it can obtain correction information directly from satellites even in areas 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, non-CLAS-compatible devices require corrections via the internet, so their accuracy may degrade outside cellular coverage.

Q: If you use smartphone RTK, will conventional surveying instruments become unnecessary? A: Smartphone RTK can now address many surveying needs, but there remain situations where conventional instruments are still advantageous. For example, precise construction measurements that require millimeter-level accuracy, or measurements using total stations equipped with specific sensors. However, for general positioning, terrain surveying, and as-built/quality control management, there are increasing cases where smartphone RTK is sufficient, and its role as the primary tool on site is certainly 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, enabling immediate cloud sharing of data collected on site. With LRTK, you can carry out everyday surveying tasks without owning specialized surveying equipment.