Table of Contents

• What is RTK?

• What is smartphone high-precision GPS?

• RTK advantages and disadvantages

• Smartphone high-precision GPS advantages and disadvantages

• Which is usable on site?

• Using LRTK for simple surveying

• FAQ

High-precision position information is indispensable for on-site surveying and staking-out work. Traditionally, one of the positioning techniques used for this purpose is Real Time Kinematic, or RTK. In recent years, however, high-precision GPS positioning using smartphones has also emerged, raising expectations that precise positioning might be achievable easily with a phone. So which is more reliable for actual outdoor field work: RTK or smartphone high-precision GPS? This article compares the characteristics, differences, advantages, and disadvantages of both, and explains their practical usability on site. Finally, we touch on a new surveying solution, LRTK, for simple surveying and offer tips to improve field work efficiency.

What is RTK?

RTK (Real Time Kinematic) is one of the high-precision positioning methods that uses GNSS (Global Navigation Satellite Systems). While ordinary GPS positioning typically has errors of several meters, RTK uses data from a reference station (a fixed receiver) to correct positioning errors. A rover (the mobile receiver) receives real-time correction information from the reference station and compares satellite signal phases to compute its position with centimeter-level accuracy.

There are generally two RTK configurations. One is to prepare your own set of a reference station and a rover, and the other is to obtain correction information over the internet from nationwide geodetic control points or private reference station networks, known as network RTK (e.g., VRS). In either case, the strength of RTK is that it provides highly accurate coordinates in real time. On surveying sites, RTK has been widely used where high accuracy is required, such as establishing boundary markers, managing as-built conditions in civil engineering, and machine guidance.

What is smartphone high-precision GPS?

“Smartphone high-precision GPS” refers broadly to methods and technologies for obtaining high-precision positioning using a smartphone. Traditionally, positioning with a smartphone’s built-in GPS had errors on the order of several meters. This was due to satellite signal errors, atmospheric effects, and the reception limits of the smartphone’s small antenna. However, recent advances in smartphone technology and expanded positioning services are making higher-precision positioning on phones increasingly possible.

Modern smartphones include chips that support multi-GNSS—using not only GPS but GLONASS, Galileo, and QZSS (Michibiki). Some models can also receive satellite signals on multiple frequency bands such as L1 and L5, reducing errors like ionospheric delay. Furthermore, in Japan, using the centimeter-level augmentation service (CLAS) broadcast from the QZSS “Michibiki” satellites allows correction of positioning data received by a phone to achieve accuracies on the order of tens of centimeters to several centimeters. In this way, with the right measures, a smartphone alone can significantly improve positioning accuracy.

Also noteworthy is the advent of small high-precision GNSS receivers that can pair with smartphones. Using an external GNSS unit that connects via the phone’s charging port or Bluetooth can dramatically improve the positional data obtained by the phone. For example, attaching an RTK-capable receiver to a smartphone can enable centimeter-level accuracy after correction, even though a phone’s GPS alone normally has errors of several meters. Ultra-compact RTK-GNSS devices that attach to a smartphone—such as those used in LRTK—have also appeared, making it increasingly possible to perform high-precision positioning with a phone without specialized equipment.

RTK advantages and disadvantages

Let’s organize the strengths and weaknesses of the RTK method.

● Main advantages of RTK:

• Extremely high accuracy: Horizontal positions are accurate to several centimeters, and elevations are within several centimeters to several tens of centimeters, meeting strict accuracy standards required in surveying and design. RTK is reliable in situations where absolute accuracy is important, such as establishing control points and managing the as-built condition of structures.

• Immediate results: Because corrections are applied in real time, you can obtain coordinate values on the spot. You can immediately check the coordinates of measured points and quickly move on to the next task on site.

• Proven track record and reliability: RTK has been used for many years by professional surveyors and construction engineers. Dedicated equipment is built ruggedly and designed specifically for positioning, so it tends to operate stably even in harsh field conditions (heat, cold, rain, vibration, etc.).

● Main disadvantages of RTK:

• High introduction cost: Equipping a full RTK survey setup requires a significant investment. In addition to the receiver itself, you need base station equipment, communication devices, survey poles and tripods, and field tablets. Using network RTK may also incur running costs such as subscription fees for private correction services.

• Operational effort and specialized knowledge required: Preparing and configuring equipment, setting up reference stations, and aligning coordinate systems require technical knowledge and experience. Some tasks may require more than one person (for setting up equipment or holding prisms), so RTK is less convenient in that sense. It can be difficult for newcomers to use immediately, and training takes time.

• Dependence on communication and environment: Network RTK requires the rover to be within communication range to receive correction data. In mountainous areas or places without signal coverage, it may not be usable. Also, in areas where the sky is obstructed by tall buildings or forests, satellite signals can be blocked and RTK may not yield a solution (i.e., positioning can fail).

Smartphone high-precision GPS advantages and disadvantages

Next, let’s look at the benefits and challenges of using a smartphone for high-precision positioning. This section considers both smartphone-only use and combinations of a smartphone with a small GNSS receiver.

● Main advantages of smartphone high-precision GPS:

• Easy and highly mobile: Smartphones are tools that people carry daily and are far lighter and more compact than dedicated equipment. You can perform surveying while walking around with just a smartphone, without separately carrying an antenna or controller. There is no need to lug heavy tripods or batteries, and you can quickly take out your phone and start measuring when needed—an operational advantage on site.

• Low barrier to operation: Surveying via smartphone apps allows intuitive touch operations for position logging and drawing. Thanks to familiar smartphone UIs, people with little specialist knowledge can operate them easily. You can view maps or aerial photographs as a background and plot measured points in real time on an app, so it’s a surveying method that is easy for anyone to use.

• Real-time collaboration and digitization: Smartphones are usually connected to the internet, making it easy to upload positioning data to the cloud on site or issue shareable links for real-time data sharing with other team members. You can link measured points into lines in the app and instantly generate simple drawings—something only possible with a smartphone. Immediate digitization of measurements and sharing with stakeholders before returning to the office speeds up reporting and review.

• Low introduction cost: A major advantage is that you can use an existing smartphone rather than purchasing dedicated survey equipment. All you may need is a survey app and, in some cases, an affordable external GNSS receiver, so you can try high-precision positioning with low initial investment. Also, Michibiki’s CLAS is available without additional fees, offering operational cost benefits.

● Main disadvantages of smartphone high-precision GPS:

• Limits to accuracy and stability: The GNSS antenna built into a smartphone is small and limited in performance, so standalone use can result in errors from several meters up to tens of meters. Achieving high accuracy often requires access to external correction information or external hardware, and without the right conditions, you may not reach RTK-level accuracy. Because smartphones are handheld and used while moving, measurement jitter and posture-related errors can also affect results. Compared to dedicated equipment, smartphones can be inferior in the stability of positioning results.

• Time to converge to high accuracy: When performing high-precision positioning with a smartphone alone—such as using CLAS or other satellite augmentation methods—it can take time for accuracy to stabilize (on the order of several minutes). Receiving RTK corrections over the network can provide high accuracy more quickly, but that approach depends on communications. In some methods, you may not achieve the same responsiveness as RTK.

• Affected by radio conditions: Smartphone GPS becomes unstable in building shadows or under tree cover. In environments where satellites cannot be sufficiently captured due to buildings or terrain, even high-end smartphones may fail to position or produce large errors. When using an external receiver connected via Bluetooth, that link must be maintained, and receiving network corrections requires cellular coverage. The performance is heavily influenced by field radio conditions and sky visibility, a challenge shared with RTK, but because smartphone antennas are weaker, they tend to struggle more in severe environments.

Which is usable on site?

So far we have reviewed the characteristics of RTK and smartphone high-precision GPS—so which is more reliable for actual outdoor fieldwork? The conclusion is that it is wise to use both depending on the situation and purpose. The following summarizes the situations each method is suited to.

• Smartphone high-precision positioning is advantageous for areas without network coverage or for wide-area surveys: In mountainous or remote sites where mobile signals are unavailable, PPP-RTK methods that do not require reference station radio (e.g., Michibiki’s CLAS) demonstrate their true value. With a smartphone and a small receiver capable of receiving CLAS, centimeter-level positioning is possible anywhere nationwide without internet connectivity. For large-scale drone surveys or wide-area patrol surveys, smartphone-based positioning is easier to use and has lower running costs because complex communication setup is unnecessary.

• RTK is reliable when precision and responsiveness are required: In severely obstructed environments such as under trees or between high-rise buildings—where satellite capture is difficult—RTK, with its long-established track record, can be more stable. RTK (especially network RTK) also tends to initialize to a fixed solution faster, so in critical situations where “you need accurate position one second sooner,” dedicated RTK equipment is dependable. For establishing control points or official boundary surveys where absolute reliability is essential, RTK is still often the chosen method.

In short, rather than asking which is superior, it is important to choose the optimal method for the site conditions. Consider radio conditions, required accuracy, budget, and personnel, and apply RTK and smartphone positioning where each method’s strengths can be leveraged.

Recently, there is a trend to combine the strengths of smartphones and RTK to innovate field operations. A prime example of this is the simple surveying approach using LRTK, introduced next.

Using LRTK for simple surveying

Traditional high-precision positioning has required bulky equipment and specialist skills in exchange for accuracy. However, using the latest smartphone surveying solution, LRTK, enables simple surveying on site that balances accuracy and ease of use. LRTK (Light RTK) is a pocket-sized RTK-GNSS receiver that can be attached to a smartphone, instantly turning a phone into a centimeter-level surveying instrument.

Attach an LRTK to a smartphone and launch the dedicated app: no complex equipment setup or difficult operations are required. Anyone can use it intuitively, making it a one-person-per-smartphone surveying tool on site. The compact device weighs only a few hundred grams, so it can be carried at all times and taken out for measurement as needed. Errors in smartphone GPS that used to be around 5–10 m (16.4–32.8 ft) can be reduced to several centimeters with LRTK’s high-precision corrections, providing sufficient accuracy for routine construction management and as-built checks.

Moreover, LRTK integrates with smartphones to share positioning data to the cloud, attach photos and notes to measured points, and offers functions suited to the era of field digital transformation. With just a smartphone and LRTK, you can complete everything from surveying to drawing and data sharing without paper maps or numerous devices, dramatically improving on-site productivity. Even on sites without dedicated surveying staff, construction managers and workers can quickly measure and verify when needed, speeding decision-making.

By leveraging LRTK, anyone can perform centimeter-accurate positioning with just a smartphone and obtain reliable survey results on site immediately. The nimbleness of being able to measure and digitize on the spot—even without heavy machinery or expert operators—is an indispensable advantage for strengthening future field capabilities. Frontline constructors and technicians should consider proactively adopting such technologies. The combination of smartphone + LRTK can dramatically improve the speed and accuracy of surveying and measurement, taking your field operations to the next level.

FAQ

Q: What is RTK? A: RTK stands for Real Time Kinematic. It is a technique that uses correction information from a reference station to correct GNSS positioning errors in real time. Standalone GPS can have errors of several meters, but with RTK you can measure positions with errors of only a few centimeters. It is widely used where high precision is required, such as surveying and positioning control for construction machinery.

Q: How accurate is smartphone GPS? A: Typical accuracy of a smartphone’s built-in GPS is on the order of several meters. In good reception conditions outdoors, errors may be around 2–5 m (6.6–16.4 ft), but in buildings or dense urban canyons, deviations of 10 m (32.8 ft) or more can occur. Recent smartphones support multiple satellite systems and multiple frequencies, and using dedicated correction services can improve accuracy to under 1 m (<3.3 ft) in some cases. That said, it is still difficult for a smartphone alone to consistently achieve centimeter-level accuracy.

Q: Can a smartphone achieve RTK-like high-precision positioning? A: Yes. Not with the smartphone alone in most cases, but by combining an external high-precision GNSS receiver, using network RTK corrections, or using satellite augmentation you can achieve RTK-equivalent accuracy with a smartphone. For example, using an attachable RTK receiver (such as LRTK) enables a smartphone to perform centimeter-level RTK positioning. Alternatively, receiving CLAS from Michibiki or paid correction services via a smartphone app can correct the phone’s built-in GPS. However, accuracy may still be unstable depending on environmental conditions, so ensuring sufficient satellite reception and correction information on site is important.

Q: For on-site surveying, which is more suitable: smartphone or RTK? A: It depends on the purpose and conditions. For formal control point surveys or situations requiring strict accuracy control, conventional RTK surveying is the reliable choice. For everyday construction management or progress checks where “reasonably high accuracy” is sufficient, the convenience of smartphone-based high-precision positioning is highly beneficial. In areas with poor connectivity, CLAS and similar smartphone-receivable services are effective, and in labor-short sites, smartphone surveying that anyone can use improves efficiency. Considering the characteristics of both, choose RTK when accuracy is paramount and smartphone surveying when efficiency is the priority.

Q: What is LRTK? A: LRTK is a small RTK-GNSS receiver that attaches to a smartphone. It works with the phone to measure high-precision coordinates in real time—essentially “turning a smartphone into a centimeter-level GPS surveying instrument.” It weighs only a few hundred grams and is very compact. Combined with a dedicated app, it is designed so that one person can easily perform surveying and staking-out tasks.

Q: Can anyone survey using LRTK? A: Yes. LRTK is designed to be easy to use even for those without specialist knowledge. You simply attach it to a smartphone and operate the app; it handles correction acquisition and positioning calculations automatically, so no difficult configuration is needed. Measured data can be displayed on a map or saved to the cloud, eliminating the need for paper and pencil-like sketching. Tasks that previously required experienced personnel can now be carried out quickly by site staff using LRTK. Of course, for complex surveying plans or where strict accuracy control is required, expert judgment is still necessary, but for routine on-site simple surveying, LRTK is a powerful ally anyone can use.