What Is a Cloud-Based RTK Service?
As mentioned at the outset, a cloud‐based RTK service is a system that delivers GNSS correction information over the Internet. In traditional RTK (Real Time Kinematic) positioning, two receivers—a reference station and a rover—exchange data, using error information from the base station to refine the rover’s position in real time to centimeter‐level accuracy.

In a cloud‐based RTK service, the role of the reference station is fulfilled by a service provider’s cloud infrastructure. The provider maintains a network of fixed reference stations across the country and generates correction data based on the GNSS signals they receive. The user (the rover) then receives those corrections in real time via the Internet (typically over cellular networks) and applies them to their own GNSS positioning.

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One major advantage of this system is that users no longer need to deploy their own base station. For example, with traditional RTK you could only achieve centimeter-level positioning within a few to several dozen kilometers of a tripod-mounted base station at the survey site. With cloud RTK, however, you can get high-precision coordinates anywhere inside the service area without placing a base station on site. This eliminates the labor and time required to set up and dismantle equipment, dramatically improving work efficiency. In addition, because an unlimited number of rovers can access the same network corrections simultaneously, multiple machines or drones used for construction management and surveying can all share identical correction data and operate without positional discrepancies.

Cloud-based RTK services primarily use the Ntrip (Networked Transport of RTCM via Internet Protocol) communication protocol to deliver correction data. After subscribing, users receive an Ntrip ID and password, which they configure in their GNSS receiver or positioning app. Some providers also offer dedicated communication terminals or apps, but the basic mechanism remains the same. Most services transmit corrections over mobile networks (3G/LTE/5G), although any Internet connection—such as Wi-Fi—will work. Conversely, the UHF-radio correction links commonly required for standalone base stations become unnecessary in a cloud-based setup.

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Introduction to Major Domestic Cloud-Based RTK Services
Currently, the primary cloud-based RTK services available in Japan fall into three categories: SoftBank’s “ichimill,” NTT Docomo’s GNSS Correction Information Service, and privately offered VRS services. Although each is operated by a different provider and delivered in a slightly different format, they all share the same core capability: real-time delivery of GNSS correction data via the cloud, enabling centimeter-level positioning accuracy.

Below is an overview of each service in turn.

・ichimill – SoftBank
SoftBank Corp. offers ichimill as a cloud-based RTK service. Leveraging the locations of its nationwide mobile‐network base stations, SoftBank has installed over 3,300 proprietary GNSS reference points. The signals from these stations are integrated in SoftBank’s “Positioning Core System” to generate real-time correction data. Users receive this RTCM-formatted correction information via SoftBank’s Internet network and perform RTK positioning on their rovers.Within cellular coverage, ichimill provides stable, wide-area centimeter-level accuracy and is used for applications such as autonomous operation of agricultural and construction machinery, drone navigation, and precision surveying. Thanks to the very high density of reference points, handovers between correction sources occur smoothly even during continuous movement, helping maintain accuracy over long distances. Support is provided through FAQs and an inquiry form, and users are issued an Ntrip ID and password—just enter these into a compatible GNSS receiver or app to get started.

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・NTT Docomo’s High-Precision GNSS Correction Service
NTT Docomo (and its group company NTT Communications) offers a cloud-based RTK service officially called the “docomo IoT High-Precision GNSS Positioning Service.” It combines the Geospatial Information Authority of Japan’s network of approximately 1,300 electronic reference stations with Docomo’s own GNSS reference points to achieve nationwide coverage. In areas where the density of electronic reference stations is insufficient, Docomo’s proprietary stations fill the gaps, enabling stable, centimeter-level positioning throughout Japan.As a rover moves, the system automatically switches to correction data from the nearest reference station, ensuring continuous high-precision positioning even over long distances. Like ichimill, this service uses the Ntrip protocol: after subscribing, you configure the issued Ntrip ID in your GNSS receiver. Applications are handled via the Docomo Business Online Shop, and the service is targeted at corporate users.Docomo provides robust support, including a business concierge desk, inquiry forms, and detailed user manuals. Although the service leverages Docomo’s mobile network, correction data can also be received over other carriers’ SIMs or via Wi-Fi, offering flexibility regardless of your choice of communications provider.

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・Privately Offered VRS Services (e.g., ALES VRS, Trimble VRS Now):
In addition to carrier-based offerings, there are cloud-based RTK services provided by private companies and surveying-equipment manufacturers. Representative examples include ALES Inc.’s centimeter-class positioning service and Trimble’s globally deployed VRS Now.

ALES VRS: ALES, in partnership with SoftBank, generates and distributes correction data using SoftBank’s proprietary reference-station observations. Offered to individual users, its core technical specifications mirror those of ichimill, delivering RTK correction streams via the Ntrip protocol. Within network RTK, it is classified as an RRS (Real Reference Station) service—providing data from actual nearby reference stations—and adds unique crustal-deformation correction technology to achieve horizontal accuracy on the order of 1–5 cm. Individuals can subscribe easily via a web form, and support is available online. The service is not aimed at corporate clients; large-volume users are instead directed to SoftBank’s ichimill.

Trimble VRS Now: Trimble VRS Now is a cloud-based RTK service offered by Trimble, a leading surveying-equipment manufacturer, in many countries worldwide. In Japan, it is available in certain regions and is typically bundled with Trimble GNSS receivers. As its name implies, it uses the VRS (Virtual Reference Station) method, creating virtual base-station corrections near the user from a permanent network of reference stations. It delivers stable, real-time RTK corrections and is widely used in agriculture and surveying overseas. Japanese coverage and pricing are limited, but usage rights may be included for a period with new equipment purchases or via annual contracts through authorized dealers. Other manufacturers—such as Leica and Topcon—also offer their own network RTK services and solutions, giving users a range of options depending on their hardware and location.

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The above provides an overview of the major domestic cloud-based RTK services. Now, let’s compare their correction methods, fees, and service coverage.

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Differences Between Cloud-Based RTK Services
Among Japan’s major offerings, the VRS method is most common, but users can take advantage of it without needing to be aware of the underlying technology. From the comparison above, you can see that carrier-based services like ichimill and Docomo provide a low-cost, standard cloud RTK solution usable anywhere in the country, whereas privately offered VRS services offer a wider variety of options tailored to specific applications and hardware.

In particular, services from established surveying-equipment manufacturers are characterized by tight integration with their own receivers and broad, often global, coverage. On the pricing side, the emergence of carrier-based offerings has driven costs down across the board—network RTK, which once cost tens of thousands of yen per month, can now be used for just a few thousand yen. With so many choices available, it’s important for users to identify the service that best matches their own workflow and requirements.

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Combining with LRTK
Finally, we introduce how to leverage our LRTK devices in combination with cloud-based RTK services. LRTK—a high-precision RTK-GNSS smart device—is a compact, RTK-enabled GNSS receiver that attaches to smartphones or tablets, allowing easy centimeter-level positioning and 3D measurements in the field. Although LRTK includes a high-performance receiver and antenna and can perform standalone GNSS positioning, using correction information is key to achieving even higher accuracy.

How to Use Cloud-Based RTK Services:Because LRTK connects to the internet via a smartphone, it can seamlessly utilize any of the cloud-based RTK services discussed above. For example, you configure Ntrip settings in the LRTK app on your phone and connect to the ichimill or Docomo correction server. Real-time corrections are then applied to the GNSS data captured by LRTK, delivering centimeter-level accuracy that standalone positioning cannot achieve. The LRTK app supports external correction input—simply enter the Ntrip ID and password provided after subscribing (see each service provider’s manual for detailed setup). In the field, correction data are automatically retrieved and applied over your phone’s 4G/5G connection, enabling pocket-sized LRTK to match the accuracy of traditional fixed receivers.