NTRIP vs VRS: Differences and When to Use Each

Table of Contents

• What is RTK?

• What is NTRIP?

• What is VRS?

• Differences between NTRIP and VRS

• When to use NTRIP and VRS

• Simple surveying with LRTK

• FAQ

What is RTK? Basic overview of high-precision positioning

RTK (Real Time Kinematic) is a technique that corrects GNSS (such as GPS) errors in real time to enable centimeter-level high-precision positioning. Standalone GNSS positioning typically has errors of several meters, but RTK uses two receivers called a reference station (base) and a rover (mobile) and cancels errors by comparing satellite signal data received simultaneously. As a result, current position can be determined with dramatically higher accuracy — on the order of about 1-2 cm (0.4-0.8 in) horizontally.

The principle of RTK positioning is that the reference station computes the error amount (correction information) from the difference between its pre-determined accurate coordinates and the positioning results from the satellites, and transmits that to the rover continuously. The rover applies the received correction information to its own positioning data, thereby correcting many error sources in real time such as satellite orbit errors and atmospheric delays. This method improves position accuracy that would normally be off by several meters down to a few centimeters.

However, RTK positioning accuracy is greatly affected by the distance between the reference station and the rover (baseline length). The closer they are, the more atmospheric errors and other effects are common and the higher the accuracy can be maintained; as the distance increases, errors that cannot be fully corrected increase and accuracy gradually degrades. Therefore, traditionally it has been common practice to install the reference station as close to the survey site as possible (ideally within a few km) and operate by transmitting correction information via radio. If operated properly, centimeter-level real-time accuracy can be obtained, but a major drawback has been the burden of “having to place a reference station on site each time.”

What is NTRIP? Internet-based distribution of correction data

NTRIP stands for “Networked Transport of RTCM via Internet Protocol” and is a standard communication protocol for sending and receiving GNSS correction data over the Internet. Simply put, it is a method for distributing and receiving correction information from reference stations used in RTK via an Internet connection. NTRIP itself is a communication mechanism (protocol) and not the name of a specific positioning service. Nevertheless, it has become an indispensable foundational technology for modern high-precision GNSS positioning, and many surveying instruments and services support NTRIP.

In traditional RTK, reference station data was transmitted via UHF radio, but with the advent of NTRIP, RTK using cellular networks became possible. Specifically, the base side prepares an NTRIP-compatible server (NTRIP caster), and users (rovers) connect to the Internet data distribution service via an NTRIP client installed on a smartphone or surveying instrument. Correction data can be received by specifying an identifier called a “mount point,” and is delivered to the rover in real time. NTRIP is based on the HTTP protocol and allows relatively lightweight and stable streaming, making it suitable for continuous positioning on moving platforms.

An important point is that NTRIP is merely the name of the communication method, not the name of the correction data service itself. In practice, various correction services (reference station networks or single base station data, etc.) use NTRIP to distribute data. From a user perspective, “connecting via NTRIP to receive corrections = performing RTK positioning over the Internet,” so it is often referred to as the “NTRIP method” to distinguish it from conventional radio RTK.

What is VRS? Network RTK using a virtual reference station

VRS stands for “Virtual Reference Station,” known in Japanese as the virtual reference point method, and is a high-precision positioning technique. VRS is a representative method of network RTK that computes a virtual reference station near the user from multiple reference station data and generates correction information for that location.

In conventional RTK, an actual reference station was placed on site, but VRS leverages existing reference station networks such as the Geospatial Information Authority of Japan’s Continuously Operating Reference Stations (approximately 1,300 fixed stations nationwide). The user (rover) sends their approximate position to a server, which integrates and analyzes observational data from multiple fixed reference stations around that area. The server then simulates “what the corrections would be if a reference station were placed right next to the user” and generates correction data that is equivalent to having a reference station adjacent to the site.

The generated virtual reference station correction data is distributed via the Internet (often using the NTRIP protocol), and the rover receives it to perform RTK computations. As a result, because the condition of being very close to a reference station is reproduced wherever you are within a wide area, accuracy degradation due to distance is almost eliminated. Also, because there is no need to physically install a base station on site, centimeter-level positioning is possible with only a single rover receiver, greatly reducing the preparation and installation effort. In short, VRS combines the high precision of RTK with the convenience of “no base station required” and the “stable accuracy over wide areas.”

In Japan, real-time correction services using the Geospatial Information Authority’s CORS network (commonly known as GEONET) are provided and used for public surveys. Private telecom companies and positioning service providers have also recently rolled out network RTK services, and as cellular coverage expands, environments where centimeter-level accuracy can be obtained nationwide wherever mobile signals reach are becoming increasingly available.

Differences between NTRIP and VRS

NTRIP and VRS are often compared, but they are different in nature. NTRIP is a communication protocol (method), while VRS is a method for generating correction data. They are not inherently opposing concepts, but in practical operations the difference typically appears as the choice between “connecting your own single base station via NTRIP” and “using a VRS service based on a reference station network.” Below is a summary of the differences in characteristics between the two.

• Reference station installation: In conventional RTK or single-base station methods, the user installs a physical reference station on site. In contrast, VRS uses an existing network of reference stations, so there is no need to place a new station at the site.

• Source of correction data: In the single-base station method, data from one reference station is used as-is. VRS, on the other hand, integrates data from multiple reference stations to generate virtual correction values. The latter reflects the surrounding conditions comprehensively, yielding uniform accuracy over a wide area.

• Communication method: Even when using a single reference station today, NTRIP is increasingly used to distribute data over the Internet (direct local radio is still possible but has range limitations). When using VRS services, correction data is also typically received via NTRIP. In other words, both methods commonly use NTRIP for communications. However, VRS requires two-way communication such as transmitting the user’s position to the server, which is a distinguishing feature.

• Positioning accuracy: The ultimate positioning accuracy that can be achieved is comparable: a single-base station method can reach centimeter-level accuracy if the baseline is short, and VRS likewise always creates conditions equivalent to a short baseline. Thus, there is no significant difference in accuracy in principle. However, the single-base station method will inevitably suffer accuracy degradation (an increase of several cm or more) as distance from the base station grows, whereas VRS can virtually eliminate distance-related errors and thus maintain stable accuracy over large areas.

• Required equipment: With a single-base station method, the user must prepare a base-station GNSS receiver and communication equipment. When using VRS, only a rover receiver and a communication terminal are needed. Thus, VRS requires less equipment to bring to the field.

• Introduction cost: If you purchase and install your own base station equipment for the single-base method, you may not incur subsequent usage fees (there are also cases where free public reference station data can be used). In contrast, using a VRS service generally requires a contract with a service provider, with monthly or annual usage fees. Initial equipment costs are typically lower for VRS, but service fees become an ongoing running cost in the long term.

• Communication environment: Because NTRIP is used in both methods, an Internet connection such as a cellular network is required. VRS in particular depends on server two-way communication, so it cannot be used if communications are unstable. In mountainous areas, underground locations, or other places outside coverage, NTRIP-based RTK positioning (both single-base and VRS) becomes difficult. In such cases, alternative measures like radio RTK or satellite communications augmentation should be considered.

When to use NTRIP and VRS

How should you choose between NTRIP (single-base station method) and VRS services at actual sites? Here are some points to consider based on use and environment.

• Scale of the survey area: If the survey area is relatively small and there is a place where you can install a reference station, a single-base station + NTRIP operation can provide high accuracy without issue. If one base station can cover the area (a radius of a few km to about 10 km), self-operated base station use is cost-effective. Conversely, if the area is wide-ranging or you frequently survey while moving, using a VRS network is advantageous because it can cover the entire area without re-installing base stations.

• Infrastructure environment: If the site is in an urban area with stable cellular coverage, use network RTK over NTRIP (including VRS) without hesitation. In mountainous or out-of-coverage areas where NTRIP communications cannot be ensured, you need to choose conventional RTK with an on-site base station and radio operation. Recently, methods that can receive augmentation directly from satellites (for example, Japan’s quasi-zenith satellite CLAS) have become available as an option where communications infrastructure is lacking.

• Initial investment and running costs: If you already own RTK base station equipment or have an in-house station, you can reduce costs by distributing corrections via NTRIP. Conversely, for beginners or small operators without equipment, subscribing to a high-precision positioning service (VRS) is easier to introduce because it requires almost no initial investment. For short-term projects that need high precision for a limited period, VRS subscriptions offer the flexibility to use the service only for the required period.

• Intended use of positioning data: If conformity to official coordinate reference systems is required for public surveys, correction data using the Geospatial Information Authority’s CORS is often used. In that case, choose a VRS service certified for public use. When using a single-base station, calibrations at known points or post-processing to align with official coordinate systems may be necessary. Which option is more suitable depends on the specific requirements of the work.

In summary, the basic guideline is to choose conventional single-base RTK (NTRIP one-to-one distribution) when the area is small, existing equipment is available, or communications are poor; choose network RTK (VRS services) when you prioritize wide-area coverage, ease of use, and have good communications without your own equipment. Both have pros and cons, so select the best method based on your site conditions, required accuracy, and costs.

Simple surveying enabled by LRTK

Although RTK and VRS technologies have dramatically improved positioning accuracy, traditional high-precision GNSS equipment has required specialized skills and has been large and expensive. A new generation solution that addresses this is LRTK. LRTK is a pocket-sized RTK positioning device developed by the startup Reflexia, designed to enable anyone on site to perform centimeter-level surveying easily by linking with a smartphone.

The LRTK device integrates an antenna, GNSS receiver, battery, and communication module into a small enclosure that fits in the palm of your hand, and weighs about 125 g. By attaching this device to a smartphone (e.g., an iPhone) on site and connecting via Bluetooth or Wi‑Fi, real-time RTK positioning begins through a dedicated app on the phone. No complex cabling is required, and the device is characterized by portability and ease of operation.

With LRTK, work that used to require specialist teams and expensive equipment can be performed by site supervisors or workers themselves using “surveying with a smartphone.” For example, ground elevation measurements, post-construction as-built checks, or equipment position verification can all be performed immediately with smartphone + LRTK, and results can be shared with the office via the cloud. By linking positioning data with photos and comments, LRTK promotes DX (digital transformation) of surveying and inspection operations.

Higher-end models in the LRTK series also support Japan’s quasi-zenith satellite system “Michibiki” centimeter-class augmentation service (CLAS), allowing centimeter-level positioning from satellite augmentation alone even in mountainous areas without Internet access. The device also includes an tilt compensation function, enabling acquisition of accurate coordinates directly beneath the antenna even when the pole is tilted to avoid obstacles. It is designed with dustproof, waterproof, and shock-resistant robustness so it can be used reliably in harsh civil engineering and construction environments.

Thus, LRTK realizes the simplification, miniaturization, and cost reduction of RTK positioning, greatly broadening access to high-precision positioning. The price is also much more affordable than conventional surveying GNSS equipment, and LRTK can be said to be a true “democratization of RTK surveying.” In addition to the technical choice of “NTRIP vs VRS,” using easy solutions like LRTK will further improve efficiency and sophistication of field surveying. LRTK is gaining attention as a new option that anyone can handle when high-precision positioning is required.

FAQ

Q: Which is more accurate, NTRIP or VRS? A: If used correctly, both approaches can achieve centimeter-level positioning accuracy. NTRIP-based single-base station RTK can be very accurate when the base station is nearby, and VRS also produces near-base-station conditions to deliver high accuracy. Differences become apparent over wide areas: the single-base method experiences some accuracy degradation at long distances, whereas VRS maintains uniform accuracy over large areas.

Q: What do I need to use a VRS service? A: To use a VRS service you need a compatible GNSS receiver (rover) and a communication terminal (a controller with a SIM or a smartphone, etc.). You also need to sign a contract with a provider that offers VRS. After contracting, configure the specified NTRIP connection information (server URL, mount point, login credentials) in your receiver, send your position information, and receive the correction data. A cellular network (or mobile Wi‑Fi router, etc.) must be available at the site.

Q: Can I do RTK positioning in areas without coverage? A: NTRIP-based methods (both single-base and VRS) that rely on Internet communication cannot be used in real time where cellular coverage is not available. Alternatives include direct radio RTK using radio devices or augmentations via satellite (SBAS, CLAS, or offline PPP positioning). For example, in Japan, devices that can receive Michibiki’s CLAS can achieve centimeter-level accuracy even without communications coverage.

Q: How do I distribute my own base station data via NTRIP? A: To distribute an existing GNSS base station over the Internet, you need to set up an NTRIP caster server and broadcast the base station data. Commercial NTRIP-compatible receivers and software allow you to distribute base station data through an in-house server or public services. Recently, free open NTRIP caster services have emerged, so small-scale operations can use those to share their base station’s correction data over the Internet.

Q: Which is easier for beginners to adopt? A: For beginners unfamiliar with specialized equipment, VRS services are recommended because they require minimal device preparation. Once you have a receiver and communications, subscribing to a service lets you start high-precision surveying without complicated base station setup. If you have skilled technicians and equipment or want to minimize long-term running costs, your own base station + NTRIP is also an option. LRTK and similar solutions that allow RTK via just a smartphone are also emerging, so consider the best option based on your intended use.