What is noRTK? A new positioning technology that achieves centimeter-level accuracy without base stations

Table of contents

• Challenges of high-precision positioning and the RTK method

• What is base-station-free "noRTK"?

• How the technologies that enable noRTK work

• Benefits of high-precision positioning without base stations

• Application areas and use cases where noRTK shines

• Summary: Simple surveying with LRTK is changing the field

• Frequently Asked Questions (FAQ)

In recent years, the construction and surveying fields have seen growing demand for high-precision positioning technologies that can pinpoint locations with errors down to a few centimeters. Conventional GNSS positioning, such as GPS, can produce errors of several meters, so achieving centimeter-level accuracy required special correction methods. The representative method is known as RTK positioning (Real-Time Kinematic). In RTK, a base station and a rover simultaneously receive satellite signals and cancel errors by differencing the two observations. This method can reduce errors that were on the order of 5-10 m (16.4-32.8 ft) in standalone positioning to horizontal and vertical errors of a few centimeters. However, RTK positioning carries the precondition that correction data must always be received from a base station, and that requirement brought several operational challenges in the field.

Challenges of high-precision positioning and the RTK method

When using the RTK method on site, the following constraints and pain points were common.

• Need to install base station equipment: For standalone RTK, you must set up your own GNSS receiver as a base station near the survey area and transmit correction information to the rover via radio. Even though this is done to obtain a high-precision positional reference, carrying and setting up the full kit—including large tripods and batteries—is no small task. Also, positioning is possible only within the range of the base station’s radio (on the order of several km to 10 km), so in large areas multiple setups and relocations could be required.

• Dependence on communications infrastructure: An alternative to deploying a local base station is network RTK, where correction data from national or commercial reference station networks is received over the internet (for example, via Ntrip). In that case, the rover must maintain a constant mobile data connection. In mountainous or disaster-stricken areas where mobile coverage is unavailable, network RTK cannot be used, and real-time high-precision positioning may be impossible. There are also service fees and communication charges, which present cost burdens.

• Operational costs and personnel burden: Sustaining RTK operations requires various costs, including high-precision GNSS receivers for base stations, communication modems, and positioning service subscriptions. On site, personnel must be assigned to set up and dismantle base stations and manage equipment. The time and monetary costs and the operational workload, traded off against the accuracy benefits, have been barriers to wider RTK adoption.

What is base-station-free "noRTK"?

To address the dependence on base stations, a new positioning technology called noRTK has emerged in recent years. As the name implies, noRTK aims to enable centimeter-level positioning without placing a base station on site. Concretely, noRTK uses high-precision correction information provided via satellite communications in addition to GNSS satellite signals, allowing a single receiver to compute centimeter-level positions in real time. Because it does not require the previously essential “correction data distribution from a base station,” high-precision positioning is possible even where there is no terrestrial communication coverage. Technically, this approach is also referred to as the PPP-RTK method, which combines Precise Point Positioning and RTK: error information generated from reference-station networks (satellite orbit/clock errors and ionospheric delays, etc.) is distributed via satellites and used for correction.

How the technologies that enable noRTK work

So how is it possible to obtain high-precision correction information without a base station on site? The key is Japan’s Quasi-Zenith Satellite System “Michibiki,” which provides the Centimeter-Level Augmentation Service (CLAS). CLAS aggregates error information observed by the Geospatial Information Authority of Japan’s Continuously Operating Reference Stations (GEONET) and transmits it as augmentation signals on Michibiki (QZSS) satellite broadcasts. noRTK-capable GNSS receivers directly receive this augmentation signal on a dedicated L6 band and apply the corrections to their position solution in real time. As a result, users can obtain centimeter-level accuracy with a single rover receiver without installing their own base station or acquiring correction data via the internet.

Positioning using CLAS also offers uniform accuracy across Japan as a major advantage. Since the correction information broadcast from the satellites covers the entire service area, centimeter-level positioning is possible anywhere—plains, mountains, remote islands, or at sea—provided there is a clear view of the sky. There is no need to worry about accuracy degradation due to “distance from the base station,” as with local RTK. Furthermore, because Michibiki’s augmentation signals are provided by the government free of charge, users with compatible receivers can use the service without additional subscription fees, which is appealing. The ability to operate without mobile data connectivity means no concerns about communication charges, enabling truly field-contained high-precision positioning.

Moreover, the time to initial convergence for high accuracy has been shortened in recent devices. Multi-GNSS, multi-frequency receivers can simultaneously receive signals from GPS, GLONASS, Galileo, Michibiki, and other constellations, and the positioning solution can stabilize within tens of seconds to a few minutes. Once a fixed solution (integer centimeter-level fix) is obtained, centimeter-level positioning can be maintained even while moving. Measured horizontal accuracy is within a few centimeters, and vertical errors are typically under 10 cm (under 3.9 in) to several tens of centimeters, reaching accuracy levels comparable to conventional RTK (in some environments RTK may be slightly more accurate, but for normal use the accuracy is entirely sufficient).

Benefits of high-precision positioning without base stations

The emergence of noRTK technology has greatly lowered the barriers to achieving centimeter-level positioning in the field. Here are the main benefits of eliminating the need for base stations.

• Simplified field preparation: Without the need to set up a base station, the time from arrival on site to starting positioning is dramatically reduced. Previously, conducting remote RTK surveys required installing base station equipment and checking the communication environment in advance. With noRTK-compatible devices, high-precision positioning can begin simply by powering on the receiver. The ease of getting to work immediately without complex equipment configuration is a major advantage.

• Consistent accuracy anywhere: Satellite-based corrections provide nearly uniform accuracy across Japan. Without concern for distance from a base station or radio coverage, large-area surveys and tasks involving movement can maintain centimeter-level accuracy. Places where high-precision positioning was previously impractical—mountains, remote islands—can be surveyed on site immediately with noRTK.

• Independence from communication environment: When using satellite augmentation such as CLAS, there is no need to connect to a mobile network on site. High-precision positioning is possible even in areas without mobile coverage or in disaster situations where networks are down, reducing opportunity loss for surveying. Eliminating communication charges is an economic benefit as well. The hassle of obtaining special radio licenses or adjusting frequencies for base-station transmissions is also removed.

• Cost reduction and labor savings: Without the need for in-house base station equipment or paid correction services, initial investment and running costs are reduced. Devices have become smaller and lighter—for example, pocket-sized GNSS receivers that attach to smartphones or tablets are now available. There is no need to carry heavy tripods or large batteries, and a single person can transport equipment to the site. This leads to reduced staffing and lower workload, enabling more efficient positioning operations.

These benefits are transforming centimeter-level positioning from a specialized operation into an everyday tool. noRTK is becoming an accessible infrastructure not only for survey professionals but also for various engineers and field workers.

Application areas and use cases where noRTK shines

Where does base-station-free high-precision positioning truly excel in practice? Below are key fields and scenarios where noRTK is being applied.

Construction and surveying: In civil engineering and surveying, noRTK is beginning to change work styles on site. High-precision work traditionally required two-person surveying teams or pre-installed base stations. However, the advent of small high-precision GNSS devices (for example, smartphone-attachable LRTK receivers) has increased opportunities for one-person surveys. Benchmarks and as-built checks can be done in real time, and survey results can be immediately shared to the cloud for construction management, creating smart construction workflows. As a cutting-edge technology aligned with the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction initiative, noRTK has strong potential to boost field productivity and quality.

Disaster response and mitigation: Large-scale disasters can sever communication infrastructure, but noRTK remains effective in such conditions. With a CLAS-compatible GNSS receiver, responders can record the precise locations of damage on the spot even in mountainous landslide sites or rubble-strewn disaster areas. For example, collapsed buildings or ground fissures can be surveyed on foot and the data later shared with headquarters via satellite communications or mobile base stations. Generating 3D damage maps on site and sharing them with remote specialists can dramatically speed up initial response and recovery planning. noRTK, which keeps positioning running even when communications are difficult, is a powerful tool for disaster response.

Agriculture and autonomous vehicles: High-precision positioning is essential in agriculture, forestry, and for autonomous construction machinery. Traditionally, RTK base stations had to be installed for each field or site to guide farm machinery or construction equipment. Recently, however, high-precision positioning services that combine mobile networks and satellite augmentation have become more common. For example, network RTK services provided by domestic telecom operators let users receive correction data without providing their own reference stations, enabling agricultural robots and unmanned construction equipment to navigate with centimeter accuracy. The noRTK approach is applicable to industrial machinery automation, helping reduce manual labor and enabling unmanned operations with improved safety. In aerial surveying with drones, systems have begun appearing that allow aircraft to receive high-precision corrections without pre-deploying base stations, which is expected to further streamline wide-area mapping operations.

Summary: Simple surveying with LRTK is changing the field

noRTK technology has broken the conventional reliance on base stations and greatly expanded the possibilities for centimeter-level positioning. In particular, the emergence of Japan’s CLAS and compatible LRTK series devices marks the dawn of an era in which “anyone, anywhere can easily survey.” With a pocket-sized receiver and a smartphone, you can obtain high-precision position information at the push of a button—even deep in the mountains or on remote islands.

This innovative technology not only dramatically improves the efficiency and convenience of surveying but also opens the door to users who previously did not utilize high-precision positioning. From construction technicians to agricultural workers and municipal officers, non-specialists are increasingly able to use centimeter-level positioning as a standard tool. Michibiki is expected to be augmented further, and with services like Europe’s Galileo high-accuracy offerings beginning, base-station-free positioning technologies will expand globally.

The combination of always-carryable devices like LRTK and noRTK technology has the potential to transform field work styles and workflows. Tasks that were once impractical in harsh environments or required cumbersome benchmark setups will become markedly easier. Take this opportunity to experience state-of-the-art noRTK technology and see how its convenience can change your field work.

Frequently Asked Questions (FAQ)

Q: What is noRTK? How does it differ from conventional RTK positioning? A: noRTK is a new GNSS positioning technology that achieves centimeter-level accuracy without using the correction data from a base station that was previously required. Conventional RTK required the user to either set up a nearby base station or receive correction information over a network. noRTK uses correction information obtained directly from satellites, such as the CLAS signal from Michibiki, so real-time high-precision positioning is possible without a base station or an internet connection.

Q: Do I need an internet connection or a paid subscription to use noRTK? A: No, generally you do not. The CLAS augmentation signal that enables noRTK in Japan is provided free from the satellite, so there is no need to connect to mobile networks or subscribe to costly positioning services. However, in environments where satellite augmentation cannot be received, you may still need to use network RTK services as before (in which case a communication link and service subscription would be necessary).

Q: What level of accuracy can actually be achieved? A: Under good conditions, horizontal position errors of a few centimeters and vertical accuracy on the order of approximately 10-20 cm (3.9-7.9 in) can be expected. This is comparable to typical RTK positioning. Compared to standalone GNSS positioning (errors of several meters), the improvement is dramatic and is practically sufficient for surveying and machine guidance. However, because noRTK uses GNSS signals, accuracy may be somewhat unstable in locations surrounded by tall buildings or dense forests. As with other GNSS methods, open sky conditions yield the most stable high accuracy.

Q: What equipment is needed to use noRTK? Can I use it with a smartphone? A: You need a GNSS receiver that can receive satellite augmentation signals such as CLAS. Specifically, a high-precision receiver that supports the L6 band CLAS signal and multi-frequency GNSS is connected to a smartphone or tablet. Portable receivers that pair with smartphones (for example, LRTK devices) are commercially available; they include antennas and batteries and are easy to carry. By installing a dedicated app on a smartphone, you can intuitively start positioning and record/share measurement data. Large fixed base stations or bulky equipment are not required, so you can readily begin centimeter-level positioning.

Q: Can noRTK position in forests or mountainous areas where satellite visibility is poor? A: Positioning is possible as long as some sky view is available. noRTK-capable receivers calculate positions by tracking multiple satellite constellations, so even in forest interiors or valleys, centimeter-level accuracy can be achieved if there is a small opening in the sky overhead. However, in extremely signal-poor dense forests or directly beneath cliffs, accuracy may degrade or positioning may become unstable. Even in such cases, you do not need the long line-of-sight required by optical surveying; moving to points with sky visibility and measuring while relocating can cover these situations. As a result, surveying in mountainous areas that was previously difficult can now be performed with practical accuracy.

Q: How long does it take from powering on to achieving centimeter-level accuracy? A: With a multi-frequency GNSS receiver, the initial convergence of position error completes relatively quickly. In good conditions, an RTK fixed solution can start to be obtained within tens of seconds to about one minute after powering on. Once a high-precision solution is established, centimeter-level accuracy can be maintained while moving. Depending on the environment it can take a few minutes, but compared with traditional PPP positioning, practical accuracy is reached in a much shorter time.

Q: Can noRTK be used outside Japan? A: Currently, the CLAS augmentation signals that form the core of noRTK are available only within Japan. Devices designed for the domestic market, such as LRTK, assume reception of Michibiki signals, so centimeter-level positioning is generally possible across Japan from Hokkaido to Okinawa and remote islands, but not overseas where Michibiki signals do not reach. That said, services such as Europe’s Galileo High Accuracy Service (HAS) are starting to roll out, and similar base-station-free positioning services are emerging worldwide. As such services expand, technologies equivalent to noRTK will become available outside Japan in the future.