RTK vs Smartphone High-Precision GPS: Which Can Be Used in the Field?

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 in the field?

• Practical use of simplified surveying with LRTK

• FAQ

Accurate position information is indispensable for surveying and stakeout work in the field. Traditionally, one of the positioning technologies used for this purpose is RTK (Real Time Kinematic). In recent years, however, smartphone-based high-precision GPS positioning has emerged, raising expectations that “precise positioning could be done easily with a phone.” So which is actually more reliable for outdoor work sites: RTK or smartphone high-precision GPS? This article compares the characteristics, differences, advantages, and disadvantages of both and explains their practicality on-site. Finally, it touches on simplified surveying using the new surveying solution LRTK and offers tips for improving fieldwork 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 can have errors of several meters (several ft), RTK uses data from a reference station (a fixed receiver) to correct positioning errors. A rover (the mobile receiver) receives correction information from the reference station in real time and, by comparing the phases of satellite signals, can compute its position with centimeter-level accuracy (half-inch accuracy).

There are generally two configurations for performing RTK positioning. One is to provide your own set of reference and rover receivers, and the other is to obtain correction information over the internet by using nationwide continuous reference stations or commercial reference networks—so-called network RTK (VRS, etc.). In either case, the strength of RTK is that high-precision coordinates are available in real time. RTK has long been used in surveying for boundary determination, as-built control in civil engineering, machine guidance, and other situations where high accuracy is required.

What is smartphone high-precision GPS?

Smartphone high-precision GPS refers to methods and technologies for performing high-precision positioning using a smartphone. Traditionally, positioning with a smartphone’s built-in GPS commonly had errors of several meters (several ft). This is due to signal errors from satellites, atmospheric effects, and reception limits caused by the smartphone’s small antenna. However, recent advances in smartphone technology and the expansion of positioning services have made higher-precision positioning on phones increasingly feasible.

Modern smartphones are equipped with multi-GNSS chips that can use not only GPS but also GLONASS, Galileo, and Michibiki (QZSS). Some models can receive signals on multiple frequency bands such as L1 and L5, which helps reduce errors like ionospheric delay. In Japan, by using the centimeter-level augmentation service (CLAS) provided by the Michibiki quasi-zenith satellites, it is possible to correct the positioning data received by a smartphone and achieve accuracies from several tens of centimeters to several centimeters (several ft to a few in). In this way, smartphones alone can now substantially improve positioning accuracy with the right measures.

Also noteworthy is the emergence of compact high-precision GNSS receivers that can work with smartphones. By using an external GNSS unit that connects via the phone’s charging port or Bluetooth, the positional information obtained by the smartphone can be dramatically improved. For example, attaching an RTK-capable receiver to a smartphone can enable the phone—normally subject to meter-level errors—to achieve centimeter-level accuracy after correction. Miniature RTK-GNSS devices that attach to a smartphone, such as LRTK, are also appearing, making it possible to perform high-precision positioning with a smartphone even without specialized equipment.

RTK advantages and disadvantages

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

● Main advantages of RTK:

• Extremely high accuracy: Horizontal positions can be within a few centimeters (a few in), and vertical errors can be on the order of a few centimeters to several tens of centimeters (a few in to tens of in), meeting the strict accuracy standards required in surveying and construction design. It is reliable in situations where absolute accuracy is important, such as establishing control points and as-built control of structures.

• Immediate results: Because positioning is performed by applying correction information in real time, coordinates can be obtained on the spot. You can immediately confirm the coordinates of measured points and quickly make on-site decisions for the next steps.

• Track record and reliability: RTK has been used for many years by professional surveyors and construction engineers. Dedicated equipment is rugged 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 initial cost: Equipping a full RTK surveying system requires a substantial investment. In addition to the receiver units, you need base station equipment, communication devices, survey poles/tripods, field tablets, and other gear. Even when using network RTK, there may be running costs such as fees for commercial correction services.

• Operation requires effort and expertise: Preparing and configuring equipment, setting up reference stations, and adjusting coordinate systems require specialized knowledge and experience. In some cases two or more people are needed to operate (for setting up equipment or holding prisms), so RTK is less convenient. It is difficult for a beginner to use effectively without training, and it takes time to become proficient.

• Dependence on communications and environment: Network RTK requires the rover to be within communication range to receive correction data. It may be unusable in mountainous areas or places with no signal. Also, in environments where the sky is obscured—such as in dense urban canyons or forests—satellite signals can be blocked, and RTK may fail to obtain a solution.

Smartphone high-precision GPS advantages and disadvantages

Next, let’s look at the advantages and challenges of using smartphones for high-precision positioning. This discussion covers both standalone smartphones and cases combining a phone with a small GNSS receiver.

● Main advantages of smartphone high-precision GPS:

• Ease of use and high mobility: Smartphones are carried by everyone in daily life and are far more compact and lightweight than dedicated equipment. You can survey while walking the site with just a smartphone, without separately carrying an antenna or controller. There is no need to carry heavy tripods or batteries, and the ability to quickly take out your phone and start measuring when needed provides strong mobility for fieldwork.

• Low barrier to operation: Surveying via smartphone apps enables intuitive touch operations for recording positions and creating drawings. Thanks to familiar smartphone UIs, people with limited expertise can handle them easily. On the app you can view maps or aerial photos in the background and plot measured points in real time, making it a user-friendly surveying method anyone can use.

• Real-time collaboration and digitization: Smartphones are typically always connected to the internet, allowing you to upload positioning data to the cloud on-site or issue sharing links for real-time data sharing with team members. You can connect measured points on the app to instantly generate simple drawings—something unique to smartphones. Immediate digitalization of measurements enables sharing the latest information with stakeholders before returning to the office, speeding up reporting and review.

• Low introduction cost: A major advantage is that you can use a smartphone you already own instead of buying dedicated surveying instruments. All you may need is a surveying app and, in some cases, an affordable external GNSS receiver, allowing you to try high-precision positioning with low upfront cost. Also, Michibiki’s CLAS can be used without extra fees, offering operational cost benefits.

● Main disadvantages of smartphone high-precision GPS:

• Limits to accuracy and stability: A smartphone’s built-in GNSS antenna is small and limited in performance; used alone it can produce errors of several to tens of meters (several to tens of ft). Achieving high precision often requires access to external correction information or external hardware, and without the right conditions a smartphone may not reach RTK-level accuracy. Handheld use also introduces motion and posture-related errors during measurement. Compared to dedicated equipment, smartphone-based positioning can be inferior in result stability.

• Time to converge to accurate positioning: When performing high-precision positioning with a standalone smartphone—using CLAS or other satellite augmentation methods, for example—it may take time for the accuracy to converge (on the order of minutes). Network-based RTK corrections can achieve high precision relatively quickly, but then you become dependent on communications. Depending on the method, you may not obtain the same responsiveness as RTK.

• Influence of radio conditions: Smartphone GPS becomes unstable in building shadows or forests. In environments where buildings or terrain block satellite visibility, even high-end smartphones can fail to position or show large errors. Even when using an external receiver that connects via Bluetooth, the phone must be within communication range; receiving network corrections such as Ntrip requires cellular coverage. Like RTK, smartphone performance is heavily influenced by radio conditions and sky visibility, but because smartphone antennas are weaker, performance in challenging environments tends to degrade more readily.

Which is usable in the field?

Having considered the characteristics of RTK and smartphone high-precision GPS, which is more reliable for actual outdoor work? The conclusion is that it is wise to use both depending on site conditions and objectives. The cases best suited to each method are summarized below.

• Smartphone high-precision positioning is advantageous when out of cellular range or for wide-area surveys: In mountainous or remote sites where mobile signals are unavailable, PPP-RTK methods (e.g., Michibiki’s CLAS) that do not require a local reference station can be very effective. With a smartphone plus a small receiver that can receive CLAS, centimeter-level positioning (half-inch accuracy) is possible anywhere nationwide even without internet. For drone-based large-scale surveys or broad patrol surveys, smartphone positioning that requires no complex communication setup is more convenient and lowers running costs.

• RTK is reassuring when precision and responsiveness are required: In severely obstructed environments where satellite visibility is poor—such as under tree cover or between tall buildings—the proven stability of RTK may provide more reliable positioning. The initialization to a fixed RTK solution (network RTK) also tends to be faster, so in sites where “you need to know an accurate position one second sooner,” dedicated RTK equipment is dependable. For establishing control points or official boundary surveys where absolute reliability is critical, RTK is still often chosen.

In short, rather than asking which is superior, it is important to choose the optimal method according to site conditions. Consider radio conditions, required accuracy, budget, and personnel, and use RTK and smartphone positioning where each performs best.

Recently, there has been a trend to combine the strengths of smartphones and RTK to revolutionize fieldwork. A leading example is the simplified surveying approach using LRTK described next.

Practical use of simplified surveying with LRTK

Traditional high-precision positioning has involved trade-offs such as “large-scale equipment” and the need for specialized skills. However, with the latest smartphone surveying solution LRTK, simplified surveying that balances accuracy and ease of use can be realized on-site. LRTK is a pocket-sized RTK-GNSS receiver that can be attached to a smartphone, instantly transforming the phone into a surveying device capable of centimeter-level accuracy (half-inch accuracy).

Attach the LRTK to your smartphone and launch the dedicated app—no complex equipment setup or difficult operations are required. Anyone can use it intuitively, and it functions as a one-person-per-smartphone surveying tool on-site. The compact device weighs just a few hundred grams, so it can be carried at all times and taken out to start measuring whenever needed. The smartphone GPS errors that used to be around 5–10 m (16.4–32.8 ft) can be reduced to a few centimeters (a few in) by LRTK’s high-precision corrections, making it sufficiently accurate for routine construction management and as-built checks.

Moreover, LRTK supports cloud sharing of positioning data in conjunction with the smartphone and allows measured points to be recorded with photos and notes—features suited to the field DX era. Without carrying paper drawings or lots of equipment, surveying, drawing creation, and data sharing can all be completed with just a smartphone and LRTK, dramatically improving on-site productivity. On sites without permanent surveying staff, construction managers or workers themselves can quickly measure and check as needed, speeding up decision-making.

By using LRTK, anyone can perform centimeter-level accuracy (half-inch accuracy) positioning with a single smartphone and obtain highly reliable survey results on site immediately. The lightweight responsiveness of being able to measure and digitalize drawings on the spot without relying on heavy machinery or expert technicians will be an indispensable asset for strengthening field capabilities going forward. Frontline construction workers and engineers should consider actively adopting such cutting-edge technologies. The smartphone + LRTK combination can greatly enhance the speed and accuracy of surveying and measurement and take your fieldwork to the next level.

FAQ

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

Q: How accurate is smartphone GPS? A: Typical accuracy of a smartphone’s built-in GPS is on the order of several meters (several ft). In good outdoor reception conditions, errors may be around 2–5 m (6.6–16.4 ft), but inside buildings or in dense urban canyons errors can exceed 10 m (32.8 ft). However, recent smartphones support multiple constellations and multiple frequencies, and by using dedicated correction services, accuracy can be improved to under 1 m in some cases. Nevertheless, it remains difficult for a standalone smartphone to consistently achieve centimeter-level accuracy, so limitations remain.

Q: Can a smartphone achieve RTK-like high-precision positioning? A: Yes, it is possible. By combining a smartphone with an external high-precision GNSS receiver, using network RTK corrections, or using satellite augmentation services, a smartphone can achieve RTK-equivalent accuracy. For example, using an attachable RTK receiver such as LRTK allows a smartphone to perform centimeter-level RTK surveying. You can also receive Michibiki’s CLAS or paid correction services through a smartphone app to correct the built-in GPS. However, environmental conditions can affect stability, so ensuring adequate satellite reception and availability of correction information is important when using on-site.

Q: Which is more suitable for field surveying: smartphone or RTK? A: It depends on the purpose and conditions. For formal control point surveys or situations requiring strict accuracy management, conventional RTK surveying equipment is more reliable. For routine construction management and progress checks where sufficiently high accuracy is acceptable, the convenience of smartphone + high-precision positioning is extremely useful. In sites with poor communications, CLAS and similar smartphone-available services are effective, and in labor-short environments, smartphone surveying that anyone can use can improve efficiency. Considering both technologies’ characteristics, 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 (positioning device) that attaches to a smartphone. It works in tandem with the phone to measure high-precision coordinates in real time. In other words, it is a device that turns a smartphone into a centimeter-level positioning survey instrument (half-inch accuracy), weighing only a few hundred grams. Used with a dedicated app, it is designed so one person can easily perform surveying and stakeout tasks.

Q: Can anyone perform surveying using LRTK? A: Yes. LRTK is designed to be easy to use even for those without specialized knowledge. Simply attach it to the smartphone and operate the app; the device automatically handles everything from acquiring correction information to computing positions, so no complicated settings are required. Measured data can be displayed on a map or saved to the cloud, eliminating the need for sketches on paper. Tasks that previously required experienced personnel can be quickly handled by anyone on site using LRTK. Of course, for advanced survey planning or cases requiring rigorous accuracy control, expert judgment is still necessary, but for routine simplified surveys LRTK is a powerful ally for anyone to use.