MADOCA-PPP vs RTK: A Thorough Comparison and How to Choose High‑Precision Positioning According to Communication Conditions

Introduction

In recent years, demand for centimeter‑level high‑precision GNSS positioning has rapidly increased in practical fields such as surveying, construction, agriculture, and infrastructure management. Two representative technologies for achieving high‑precision positioning are RTK (Real‑Time Kinematic) using reference stations and MADOCA‑PPP (high‑precision positioning augmentation service) provided via the Quasi‑Zenith Satellite System "Michibiki." This article explains in detail the fundamental differences and performance comparisons between MADOCA‑PPP and RTK, and discusses how to choose the optimal positioning method according to communication environments and use cases.

What is MADOCA‑PPP? — High‑precision stand‑alone positioning

MADOCA‑PPP is a service based on Precise Point Positioning (PPP) that enables high‑precision positioning with a single GNSS receiver. PPP reduces standalone positioning errors, which were traditionally on the order of meters, by precisely correcting for satellite orbit and clock errors. MADOCA‑PPP is an augmentation service provided by Japan’s Quasi‑Zenith Satellite System "Michibiki," covering the Asia‑Oceania region and achieving positioning accuracy of approximately 10 cm (3.9 in).

MADOCA‑PPP widely broadcasts correction information for orbit and clock errors—computed from data of GNSS observation stations around the world—via Michibiki’s L6‑band communications. Users can perform real‑time high‑precision PPP positioning by using an L6‑capable multi‑band GNSS receiver that can receive this augmentation signal. A key feature is that users do not need to install their own reference stations, and uniform accuracy can be obtained over a wide area. Therefore, it is expected to be a high‑precision positioning option usable even in areas lacking ground infrastructure—such as at sea, in mountainous regions, or overseas.

However, PPP has the drawback that initial convergence takes time. For MADOCA‑PPP, obtaining a high‑precision position requires about 15–30 minutes of observation time (convergence time). This is because long observations are needed to resolve the ionosphere and integer biases (ambiguities) of carrier‑phase measurements. That said, technical developments are progressing; for example, the Japan‑only PPP service CLAS (Centimeter‑Level Augmentation Service) achieves convergence in about 1–2 minutes and about 7 cm (2.8 in) accuracy by introducing local corrections and ambiguity resolution techniques (PPP‑AR). MADOCA‑PPP itself is also planning future reductions in convergence time, such as the introduction of wide‑area ionospheric corrections. PPP methods are improving day by day and will become increasingly practical.

What is RTK? — High‑precision relative positioning

RTK (Real Time Kinematic) is a method that achieves high‑precision positioning in real time by canceling errors using two or more GNSS receivers—a reference station and a rover. The reference station is installed at a known, precise coordinate position, and the rover is attached to the object to be positioned. Both receivers simultaneously receive signals from the same satellites; the reference station computes error information and continuously sends it to the rover so the rover performs differential positioning by removing those errors from its own observations. This effectively eliminates the several‑meter errors typical of standalone positioning, allowing immediate horizontal accuracy of a few centimeters.

RTK requires exchange of raw GNSS data (carrier‑phase) and real‑time computation to achieve high precision, so external communication is essential. Communication methods for sending correction data from the reference to the rover include radio links or Internet connections (e.g., NTRIP using cellular networks). RTK can be implemented as a standalone RTK where users provide their own reference station, or as network RTK (e.g., VRS) that utilizes existing permanent reference station networks. With network RTK, users can subscribe to correction data from public or private reference station networks without installing their own base, enabling RTK positioning over a wide area (though subscription fees or monthly charges may apply).

A major advantage of RTK is that initial position fixing (the fix) is extremely fast. With the latest multi‑band RTK receivers, integer ambiguity resolution can be completed in a matter of seconds to about 30 seconds in good environments, yielding centimeter‑level positions almost immediately. Once a fix is obtained, high‑precision positions can be updated in real time while moving, making RTK well suited for dynamic measurements and machine control. However, RTK requires a maintained communication link with the reference station; in mountainous or maritime areas where communication is unavailable, standard RTK is usually impractical. In those cases, PPP (described above) or static surveying (long observations followed by post‑processing) must be used.

Comparison table: MADOCA‑PPP vs RTK

Let’s compare the characteristics of MADOCA‑PPP and RTK across major items.

*The current positioning accuracy of MADOCA‑PPP is the present value and may improve with future enhancements.*

As the table shows, both MADOCA‑PPP and RTK provide centimeter‑level positioning, but their characteristics differ significantly. RTK’s strength is immediacy—obtaining high‑precision positions on site instantly—making it suitable for precision tasks and dynamic control that tolerate virtually no deviation. MADOCA‑PPP requires time to converge but offers the flexibility of maintaining a consistent level of accuracy anywhere the augmentation signal is received. Also, while RTK depends on local reference stations, PPP operates with global satellite corrections, making it suitable for areas without established reference points or for cross‑border positioning.

Notably, RTK results follow the coordinate system of the reference station. In other words, if the reference station’s coordinates are set to national or custom control points, the rover’s results will be in that system, enabling positioning directly tied to site survey control points. PPP (MADOCA‑PPP), however, calculates absolute positions in global coordinate systems (e.g., WGS84 or ITRF), which is advantageous when existing control points have moved due to crustal deformation, because PPP yields positions aligned with global coordinates. This difference is important in geodesy, but from a user perspective it can usually be handled by conversion or adjustment as needed; fundamentally, choose between systems based on required accuracy and work requirements.

Use cases: Which positioning method should you choose?

Here are recommendations for MADOCA‑PPP vs RTK in specific use cases. It is important to select the appropriate method based on communication availability, accuracy requirements, and operational conditions.

• Communication‑outage mountain or remote island positioning: In remote areas or islands without cellular coverage, receiving correction data from reference stations is difficult, so MADOCA‑PPP is a practical choice. For example, in topographic surveys or establishing survey control points, as long as Michibiki’s augmentation signals can be received, standalone high‑precision positioning is possible, greatly improving surveying efficiency (there are cases where MADOCA‑PPP was used on remote islands to establish control points with RTK‑comparable accuracy). RTK could be used by setting up your own reference station and communicating by radio, but given the effort of setup and transport, PPP that completes everything via satellite communication is often preferable.

• Real‑time machine control in urban areas: For urban applications requiring real‑time centimeter accuracy—such as machine guidance for construction equipment or autonomous vehicle control—network RTK is suitable. Where cellular correction services are available, RTK provides high‑precision positions within seconds, enabling automatic control of heavy machinery and precision construction. While PPP can achieve usable final accuracy, the wait for convergence and re‑convergence issues when satellite augmentation signals are temporarily blocked by buildings make RTK superior in scenarios demanding real‑time performance.

• Simple surveying / short‑duration point measurements: For quick point‑by‑point coordinate acquisition, RTK is more convenient. If you can connect to a network RTK service, you can obtain centimeter accuracy within seconds of setup, allowing rapid measurement of many points. PPP is less suitable for short‑duration spot surveying because of its long stabilization time (though if there are few points and no communication, you could use PPP and spend tens of minutes per point).

• Guidance for agricultural machinery / agriculture: In agriculture, choice depends on required accuracy and communication conditions. For automatic driving of tractors over large fields, MADOCA‑PPP’s 10 cm (3.9 in)‑class accuracy is often sufficiently practical. In areas with unstable communications, satellite‑based PPP can provide consistent guidance. However, for tasks like precision seeding or autonomous harvesting robots that require deviations under a few centimeters, network RTK with reliable communications is more certain. Network RTK base station networks are increasingly being deployed in agriculture, enabling high‑precision autonomous operation within fields where base stations exist. Overall, agriculture uses a mix of PPP and RTK depending on communication availability and accuracy requirements.

Conclusion: A new trend of high‑precision positioning using both technologies

MADOCA‑PPP and RTK are high‑precision positioning technologies with different strengths. For practitioners, the key is to skillfully use both depending on the use case. In areas with established communication infrastructure, RTK can provide instantaneous centimeter accuracy, while in communication‑outage environments or emergencies PPP (MADOCA‑PPP) provides stable positioning via wide‑area satellite augmentation—making hybrid operations realistic.

In fact, solutions that integrate the advantages of both methods have appeared. For example, the GNSS receiver for smartphones [LRTK series](https://lrtk.lefixea.com) uses network RTK while in coverage to achieve centimeter accuracy, and automatically switches to Michibiki’s CLAS/MADOCA augmentation signals when leaving cellular coverage to maintain high‑precision positioning. Products like this allow field staff without specialized knowledge to use high‑precision positioning optimally without complex configuration. High‑precision GNSS technology is becoming an accessible tool for many sites, not just specialists. By wisely using both MADOCA‑PPP and RTK, you can improve efficiency and accuracy across a variety of fields.