RTK vs Network RTK: Comparing the Differences Between a Single Base Station and VRS

On construction and surveying sites, a positional deviation of only a few centimeters (a few in) can have serious consequences. In situations where accurate positional information determines quality and safety—such as highway and railway construction, land boundary surveys, and building construction management—the usual GPS positioning error of several meters (several ft) is insufficient. The technology that emerged to eliminate that error is RTK positioning (Real Time Kinematic, real-time kinematic positioning). RTK corrects GPS errors in real time, enabling immediate centimeter-level (cm level accuracy, half-inch accuracy) high-precision positioning.

In this article, we compare and explain the differences between the traditional RTK method (single reference station method) and the network RTK method (VRS method), which has become mainstream in recent years. We will explain, in an easy-to-understand way for surveying beginners and site supervisors, each method’s mechanism, positioning accuracy, operational conditions, advantages and disadvantages, cost structure, and applicable scenarios.

Table of Contents

• What is RTK (single-base station method)

• What is network-type RTK (VRS method)

• Comparison of mechanisms, accuracy, and operational conditions of RTK and VRS

• Advantages and disadvantages of RTK and VRS

• Differences in cost structure

• Application scenarios and selection points

• Summary

• FAQ

• Introduction to LRTK products

RTK (Single Reference Station Method)

RTK stands for Real Time Kinematic (real-time kinematic) and is a type of relative positioning using two GNSS receivers. In Japanese it is also called "real-time dynamic positioning." Specifically, first a receiver that will serve as a reference station (base station) is installed at a known point with precisely known coordinates. Then a second receiver is placed at the point to be surveyed (the unknown point), and this is called the mobile station (rover). Both the reference station and the mobile station simultaneously receive GNSS signals from 4 or more satellites, and each independently computes its own position.

Because the reference station knows its precise position (known-point coordinates), it can calculate in real time the error between that and the position determined by GNSS positioning. The reference station transmits that error (correction information) to the rover sequentially by radio or other means. The rover applies the received correction information to its own positioning data and cancels out the errors contained in the satellite signals in real time. With this mechanism, positioning errors that are normally several meters (several ft) are canceled out, allowing the current position to be determined with centimeter-level accuracy (half-inch accuracy). When properly operated, RTK positioning yields horizontal errors of about 1-2 cm (0.4-0.8 in), and vertical errors on the order of several centimeters to a dozen or so centimeters (several in to a dozen or so in).

It should be noted that the accuracy of RTK positioning is greatly affected by the distance between the reference station and the rover (the baseline). When the two stations are close, many error sources—such as signal delay errors caused by the ionosphere and troposphere—are common to both and can be canceled out, but as distance increases, differences in atmospheric conditions introduce errors that cannot be fully corrected. For this reason, in typical RTK setups the reference station is placed as close as possible to the survey work area (ideally within a few km (a few miles)), and correction information is transmitted to the rover using UHF-band low-power radios or long-range radios. When operated correctly, it can achieve on-site accuracy that sets it apart from conventional standalone positioning (positioning with a single GNSS receiver). However, this method has the constraint that a reference station must be set up on site each time, and it has the drawback of requiring effort for transporting equipment and setting it up on known points.

What is network RTK (VRS method)?

The method that eliminates the effort and constraints of placing a reference station on-site is called network RTK. A representative scheme of this is called VRS (Virtual Reference Station, virtual reference point method). In network RTK, a network is constructed by installing a large number of fixed reference stations (electronic reference points) in a country or region in advance, and correction data are generated as if a virtual reference station exists near the user.

As an overview of the mechanism, the network's operation server acquires the user's (mobile station's) approximate current position and performs integrated analysis of observation data from several fixed reference stations (electronic reference points) around it. It then simulates “what satellite signals would be observed if a reference station were placed very close to the user” and generates correction information corresponding to that location.

The correction information for the generated virtual reference point is delivered to the rover via an Internet connection, such as a mobile phone (typically delivered using the Ntrip protocol). On the rover side, RTK calculations can be performed under the same conditions as if a reference station were located right next to it, resulting in centimeter-level accuracy (cm level accuracy, half-inch accuracy) comparable to that of a single-reference-station method. With the advent of the VRS method, the convenience of RTK positioning has dramatically improved. All that is required on-site is a single rover receiver, and because the complicated work of setting up a reference station is no longer necessary, surveying can begin immediately upon arrival. Because a virtual reference point is always established near the survey point, the accuracy degradation due to baseline length is almost eliminated, allowing uniform high-precision positioning even when moving over wide areas.

The Geospatial Information Authority of Japan has established an electronic reference point network (GEONET) at approximately 1,300 sites nationwide, and a real-time correction service using this network is provided. By using this service, users can obtain high-precision coordinates in the Japanese geodetic datum (World Geodetic System) on site without having to provide their own reference station. Network RTK services offered by private companies have also become widespread in recent years. By using these wide-area reference station networks, if within mobile phone coverage, almost anywhere in Japan, stable centimeter-level positioning (cm level accuracy, half-inch accuracy) has become possible.

Comparison of the Mechanisms, Accuracy, and Operational Conditions of RTK and VRS

RTK (single-base-station method) and network RTK (VRS method) can both achieve centimeter-level accuracy with appropriate measures. However, there are significant differences in the equipment and operational procedures required. The main differences are summarized below.

• Required equipment: Conventional RTK requires two GNSS receivers, one for the base station and one for the rover, and also a radio unit (transceiver) to connect the two stations. On the other hand, with the VRS method positioning is possible with only a single receiver on the rover side (a communication terminal for receiving correction data is required).

• Initial setup and effort: With the RTK method you must install a base station at each site, set up a tripod and level the equipment, and position it to match known-point coordinates, so preparing to start work takes time and effort. With the VRS method base station installation is unnecessary, so you can start surveying immediately by simply powering on the receiver and connecting to the network. The waiting time from arrival on site to the start of work is greatly reduced.

• Positioning coverage: With standalone RTK accuracy decreases the farther you are from the base station, so there is a practical limit to the area that can be covered. Also, when sending correction information by radio, the upper limit of the positioning area is the radio reach (on the order of several km to a dozen-odd km). With the VRS method, as long as the cellular network is available it can cover an entire region, and virtual reference points are generated close to the user’s position, so high accuracy is maintained even when moving over a wide area.

• Operating costs: With RTK you need to provide your own base station equipment, but once the equipment is in place there are no ongoing running costs for use itself (if you use license-exempt radios there is no radio usage fee). However, the purchase cost of high-performance GNSS receivers and radios is high. With the VRS method, instead of owning your own base station you need to contract with government or commercial network RTK service providers to receive correction information (service usage fees apply). In recent years these services have become cheaper, and what used to cost several tens of thousands of yen per month has fallen to a monthly fee of several thousand yen. There are increasing cases of minimizing equipment purchase costs and contracting for services only for the required period.

• Positioning accuracy: When used properly, the obtainable positioning accuracy is nearly the same for both methods. Horizontal positions are within a few centimeters (a few inches), and vertical errors are within several tens of centimeters (several inches to a few feet). However, while RTK’s accuracy gradually decreases as you move far from the base station, VRS always has a virtual reference point nearby, so it excels in the uniformity of positioning accuracy over wide areas. Conversely, in locations where the communication environment is poor and network RTK services cannot be used, VRS cannot be used and you must switch to a conventional self-owned RTK.

• Coordinate reference: With standalone RTK you position relative to the base station you installed yourself, so unless you align the base station’s position with a known public coordinate, the obtained coordinates will be in a local arbitrary coordinate system (local coordinates). Converting later to the national coordinate datum (World Geodetic System) may require extra work. With the VRS method, the network of electronic reference points underpinning the correction information is tied to the national coordinate system, so the positioning results obtained are from the outset in a public coordinate system such as Japan Geodetic Datum 2011. This makes it easy to directly compare survey points with public survey results or to integrate with GIS data.

The differences above can be briefly summarized in the following table.

Advantages and disadvantages of RTK and VRS

RTK (standalone base-station method) advantages

• It does not depend on communications infrastructure and can be operated even at sites outside mobile phone coverage or without Internet access.

• Once the base station equipment is purchased, there are no running costs, so long-term expenses can be reduced.

• Because the base station can be installed at any location to suit local conditions, an independent positioning system that does not rely on other services can be established.

Disadvantages of RTK (single base-station method)

• The initial acquisition cost for base-station equipment (high-precision GNSS receivers, mounting tripods, radios, etc.) is high.

• Each time work is performed, the setup and takedown of the base station are required, which means it takes time from arriving on site to starting positioning.

• If radio communication with the base station is interrupted, positioning becomes impossible, so care must be taken regarding radio conditions and securing line of sight. Additionally, the measurement range is limited to the vicinity of the base station.

Benefits of Network RTK (VRS method)

• The equipment configuration is simple, requiring only one GNSS receiver to carry. There is no need to transport heavy base station equipment or radios, and no on-site equipment setup is required.

• The convenience of being able to start measuring immediately upon arrival at the site directly improves fieldwork efficiency. Because complex setup or coordinate-alignment procedures are unnecessary, even beginners can start work without hesitation.

• Stable accuracy is maintained even when moving across wide areas. For example, when a single person surveys points across a large development site, they can achieve the same accuracy everywhere. There is no need to worry that “accuracy might become questionable from here…”.

• Conversion of control points (coordinates) to a public coordinate system is unnecessary, and obtained positioning results can be directly compared with coordinates on drawings or in GIS.

• No manpower is required for base station installation or management, enabling efficient one-person operations. Also, using a network service instead of purchasing expensive equipment reduces the initial investment burden.

Disadvantages of Network RTK (VRS method)

• Because an Internet connection is required, it cannot be used in areas with no mobile coverage. Also, if radio conditions are unstable, reception of correction data may be interrupted, which can interrupt positioning.

• A subscription and usage fees for the correction information service are required. Over the long term, costs may exceed those of purchasing equipment, so it is necessary to take measures such as selecting a plan according to usage frequency.

• Because it depends on the systems of network RTK service providers, there is a risk that the service will be unavailable during outages or maintenance (however, such events are rare).

Differences in Cost Structure

RTK and network RTK (VRS) differ in the structure of required equipment expenses and running costs. In terms of initial capital outlay, the RTK method requires purchasing two high-precision GNSS receivers—two units: a base station and a rover—so the initial investment is large. High-performance GNSS surveying instruments often cost several hundred thousand to more than 1,000,000 yen per unit, and when accessories such as radios and tripods are included, a conventional RTK set can cost on the order of several million yen. By contrast, with the VRS method you only need to provide a single rover unit, so equipment costs can be greatly reduced. Recently, low-cost GNSS receivers that can be used in conjunction with smartphones have appeared, making it possible to start centimeter-level positioning at a cost below several hundred thousand yen.

Next, in terms of running costs, with the RTK method, since you operate your own base station, monthly fees are basically not incurred. If you use license-exempt low-power radio or specified low-power radio, radio usage fees are also unnecessary. On the other hand, with the VRS method, a correction information distribution service usage fee—such as for a private service—is required. Service prices vary depending on the provider and contract, but in recent years competition has driven prices down, and more plans are becoming available that can be used for a few thousand yen to about 10,000 yen per month. If usage frequency is high and use is long-term, total costs may increase, but you can keep costs down by using short-term plans that allow contracting only for the required period or by using any regional free services if available.

Overall, in terms of keeping initial investment low and being able to start immediately, the VRS method is easier to adopt, while if you will use it frequently over a long period, the RTK method tends to be more advantageous in terms of running costs. However, in recent years the falling prices of equipment and reductions in service fees have been progressing, making it increasingly easier for small businesses and beginners to adopt high-precision positioning.

Use Cases and Selection Points

The RTK method and the network RTK method each have their suitable use cases. In general, if an environment where mobile communications are available exists, the VRS method is recommended for its ease and efficiency. When surveying over wide areas or moving between multiple sites for observations, the advantage of VRS—no need to repeatedly set up base stations—becomes particularly apparent. Also, even on sites without specialized surveying technicians, the VRS method’s simple setup makes it easy to handle and has the benefit that beginners can operate it.

On the other hand, in mountainous or remote areas where communications infrastructure is not developed the signal may not reach even if you want to use VRS, so there are cases where you have no choice but to position with conventional RTK (an in-house base station). In such situations, a portable GNSS base station device is set up on site and operated. Also, if the area to be surveyed is very limited and you repeatedly measure in the same location, fixing the base station in place can eliminate the preparation each time, so the RTK method may not be that much of a hassle. For example, if repeated surveys are carried out over a long period at a large construction site, you could fixedly install a base station on the roof of the site office and operate using in-house RTK within that site (providing stable corrections without communication costs).

When making a choice, it is a good idea to consider the following points.

• 通信環境: Whether the work site is within or outside mobile network coverage. If it is outside coverage, your own RTK is the only option.

• 測定範囲・移動: Whether the survey points cover a wide area or consist of multiple dispersed sites. For wide areas, VRS is advantageous; for a single, confined site, RTK can also be sufficient.

• 利用頻度と期間: Whether it is a temporary/short-term project or will be used frequently over the long term. For short-term work, using a service rather than buying equipment is lower cost; for long-term use, purchasing equipment can sometimes pay off.

• 予算と人員: If the initial budget is limited, starting with VRS + a low-cost receiver is realistic. Conversely, if you have available funds and want to own surveying equipment as an asset, purchasing RTK equipment is an option. Also consider whether you have personnel knowledgeable about equipment setup. VRS is easier to operate without specialized knowledge.

The optimal solution depends on site conditions and the desired mode of operation, but in recent years the spread of network RTK services has led to the VRS method being increasingly adopted in many surveying tasks. However, as a precaution you may consider preparing an in‑house simple reference station so you can switch to it if radio signals are lost, and operating by switching between the two methods as the situation requires.

Summary

RTK and network RTK (VRS) are both technologies that correct satellite positioning errors to achieve centimeter-level accuracy. Single-reference-station RTK is an established technology long used at surveying sites and has the advantage of enabling high-precision positioning without relying on communications infrastructure. In contrast, the VRS method leverages a network of reference stations to dramatically increase convenience, proving especially effective for large-area surveys and tasks involving frequent movement. There is no significant difference in positioning accuracy itself between the two, but from the perspectives of operational cost and ease of use, surveying using the VRS method is becoming mainstream.

That said, the optimal method depends on the site environment and the intended application. As explained in this article, it is important to choose the approach that fits your needs by taking into account conditions such as the communication environment, cost, work scope, and frequency. Advances in technology have recently brought compact, low-cost devices and inexpensive correction services. High-precision positioning is becoming accessible not only to surveying professionals but also to site supervisors and construction managers. The use of RTK and network RTK will increasingly enable more efficient and higher-quality surveying and construction going forward.

FAQ

Q: Which is more accurate, the RTK method or the VRS method? A: The basic positioning accuracy (on the order of a few centimeters) is equivalent for both methods when properly operated. Both RTK and VRS can achieve errors within a few centimeters when stationary. However, whereas RTK's accuracy degrades as you get farther from the reference station, VRS always has a virtual reference point nearby, so accuracy remains stable even at long distances. Also, if environmental factors are the same, it is not that standalone RTK inherently has lower accuracy; any accuracy differences stem from differences in operational conditions.

Q: How should positioning be performed in areas such as mountain regions where there is no network connectivity? A: In areas where cellular signal does not reach, unfortunately you cannot use the VRS system. In that case, you need to set up your own base station on site and perform positioning using the conventional RTK method. Also, within Japan you can use a system called Michibiki (QZSS) CLAS, which allows direct reception of correction signals from satellites without network communication (a compatible receiver is required). For example, devices that support CLAS reception, such as the LRTK Pro2, can continue centimeter-level positioning via satellite augmentation even outside communication coverage.

Q: What is needed to start RTK positioning? Can it be done with just a smartphone? A: To perform centimeter-level RTK positioning, a compatible GNSS receiver is required. The GPS built into typical smartphones does not provide sufficient accuracy and cannot acquire the positioning data required for RTK (such as carrier phase). Therefore, first obtain an RTK-capable GNSS receiver (rover). For the RTK method, set up another receiver as a base station and establish a system to transmit correction information wirelessly. For the VRS method, corrections are received via the Internet, so you must subscribe to a network RTK service and have a communication method (smartphone tethering or a built-in SIM, etc.). Recently, various small GNSS receivers that can connect to smartphones have been released; using those allows you to connect to correction services via a smartphone app and easily achieve high-precision positioning.

Q: すでに自社でGNSS基準局を運用している場合でも、VRSを使うメリットはありますか？ A: Yes. Even if you already operate your own reference station, there are benefits to using a VRS service. For example, when surveying multiple distant sites, VRS is efficient because you can measure immediately at each site with just one receiver without having to relocate your own reference station each time. VRS, which can cover wide areas, is also well suited to long-distance surveys that your own station cannot fully cover and to continuous positioning while moving (e.g., vehicle or drone measurements). Some companies treat their existing reference stations as backups or as support when out of communication range, switching routine operations to VRS to improve work efficiency. However, if you already own reference stations, you also have the advantage of being able to use your in-house RTK as before in locations without communication coverage. Ideally, you should use both depending on the situation.

Introduction to LRTK products

Conventional RTK equipment was expensive and required specialized knowledge, but the recently introduced LRTK (an RTK positioning solution developed by Refixia) has greatly lowered that barrier. LRTK is an ultra-compact GNSS receiver series based on the concept of a “pocket-sized RTK surveying device that anyone can use on site.” Weighing approximately 125 g, and with a thickness of just about 13 mm (0.51 in), the device integrates an antenna, GNSS receiver, battery, and wireless communication module, and by attaching this single unit to a smartphone and launching the app, centimeter-level positioning (cm level accuracy (half-inch accuracy)) can be started easily. Communication links to the smartphone via Bluetooth or Wi-Fi allow reception of correction information and cloud transmission of positioning results through the phone, eliminating the need for complicated cable connections. Its mobility for easy transport to the field and intuitive operation via a smartphone app make it easy to use even for those who are not surveying professionals.

Despite its compact size, the LRTK series delivers professional-grade performance. The higher-end LRTK Pro2 supports the centimeter-level augmentation service (CLAS) provided by Japan’s Quasi-Zenith Satellite System "Michibiki", enabling high-precision positioning using only augmentation signals from satellites even in mountainous areas outside mobile network coverage.

Also, the LRTK series features tilt-compensation functionality, automatically correcting for slight tilts of the antenna at the tip of the surveying pole to obtain accurate coordinates directly beneath it. It’s a groundbreaking feature that lets you measure without positional offset even when you must tilt the antenna to avoid obstacles. Furthermore, its rugged dustproof and waterproof design allows reliable use even in the harsh environments of civil engineering sites.

By utilizing LRTK in this way, advanced positioning technologies such as RTK and network RTK can be brought to the field more easily than ever before. LRTK is a solution that contributes to improving the efficiency and sophistication of surveying and construction management by making high-precision position information available to everyone. If you are interested, please check the details of LRTK products. It will surely transform on-site positioning work.