What is MADOCA-PPP? Explaining a high-precision positioning mechanism that works anywhere in the world without communication

Introduction

In recent years, demand for higher-precision satellite positioning has been rapidly increasing. Situations such as autonomous vehicles and drone navigation, automatic steering of agricultural machinery, precision surveying, and infrastructure inspection increasingly require centimeter-level position accuracy (cm level accuracy (half-inch accuracy)). The accuracy of standalone positioning using GNSS (Global Navigation Satellite Systems) such as conventional GPS is on the order of several meters, which makes it difficult to meet the requirements of these advanced applications.

Conventional technologies for achieving high-precision positioning have included RTK (Real-Time Kinematic) positioning and national augmentation services (for example Japan’s Continuously Operating Reference Stations or the US WAAS). RTK can provide centimeter-level accuracy immediately through relative positioning with a reference station, but it requires communication with the base station and a distance condition within on the order of several tens of km. It also requires dedicated communication lines or internet connection, making it difficult to use in off-grid environments such as mountainous areas or at sea. To solve these problems, recent efforts around the world have aimed to provide augmentation signals widely from satellites to improve accuracy. For example, Europe’s Galileo system began operating a High Accuracy Service (HAS) in 2022, and similar services are being considered for other GNSSs including the United States. MADOCA-PPP is a Japanese-launched, communication-free, global high-precision positioning service in this global trend, and it has attracted considerable attention since its introduction.

What is MADOCA-PPP?

MADOCA-PPP is one of the high-precision positioning augmentation services provided by Japan’s Quasi-Zenith Satellite System (QZSS, “Michibiki”). “MADOCA” stands for Multi-GNSS Advanced Orbit and Clock Augmentation and is the name of the satellite orbit and clock correction technology developed by JAXA (Japan Aerospace Exploration Agency). “PPP” stands for Precise Point Positioning, known in Japanese as 精密単独測位 or high-precision standalone positioning. As the name implies, the PPP method enables centimeter-level positioning using only a single GNSS receiver, and it is characterized by not requiring the conventional reference station (base station).

In MADOCA-PPP, orbit and clock errors originating from GNSS satellites are computed with high accuracy based on data from global GNSS observation networks (such as IGS and domestic and international reference station networks), and those correction data are broadcast from the Michibiki QZSS satellites. Users can receive real-time high-precision PPP positioning by receiving the Michibiki-transmitted L6-band radio signal with a compatible receiver. In other words, the revolutionary aspect of MADOCA-PPP is that a single receiver can determine an absolute position with high accuracy using only augmentation signals from satellites, without relying on terrestrial communication infrastructure.

In Japan, trial broadcasts of MADOCA-PPP began in September 2022, and full operational service started in April 2024. The service is designed to be usable not only within Japan but across the Asia-Oceania region, with use at sea and overseas in mind. For example, whereas the centimeter-level augmentation service CLAS had been limited to Japan, MADOCA-PPP allows high-precision positioning anywhere that Michibiki signals can be received, making it attractive for companies expanding internationally and for maritime applications.

Technical features

The technical features of MADOCA-PPP can be summarized as follows.

• Positioning accuracy and convergence time: PPP positioning using MADOCA-PPP achieves horizontal accuracy on the order of several tens of centimeters (95% confidence under 30 cm (11.8 in)), and vertical accuracy on the order of 50 cm (19.7 in). However, obtaining this high accuracy requires an initial convergence time of about 20–30 minutes. Continued observation gradually improves accuracy, and once sufficiently converged, centimeter-level accuracy can be approached. In the future, providing additional correction information such as ionospheric corrections via satellite broadcasts is planned to significantly shorten convergence times and further improve accuracy (achieving centimeter accuracy through resolution of integer ambiguities).

• Supported satellite positioning systems: MADOCA-PPP is a multi-GNSS augmentation service. Correction data support multiple GNSSs such as GPS, GLONASS, Galileo, and QZSS (Michibiki), and positioning is performed using multiple-frequency signals (L1/L2/L5, etc.) from these systems. Note that achieving a high-precision PPP solution requires multi-frequency observations (two or more frequencies); single-frequency-only receivers cannot adequately correct ionospheric errors to meet the required accuracy. By supporting multi-GNSS, the service can track more than 20 satellites continuously without relying on a single satellite system, enabling stable positioning (in an open-sky environment where many satellites are visible).

• Frequencies and signal format: Correction information is transmitted from Michibiki on the L6 band (around 1.2 GHz). Michibiki’s L6 signal includes both the Japan-targeted centimeter-level service (CLAS) and the MADOCA-PPP messages. MADOCA-PPP messages conform to the international RTCM-SSR format, and high-precision GNSS receivers interpret this format to perform positioning computations. Because the L6 signal from the satellite can be received directly even in the absence of terrestrial communication infrastructure, MADOCA-PPP truly enables “high-precision positioning usable anywhere.” The signal specifications and formats for this service are publicly available, and with the appropriate receiving environment, data processing can be performed using open-source PPP analysis software.

• Real-time capability: MADOCA-PPP correction data are broadcast continuously in real time, and receivers update PPP solutions sequentially. Once accuracy has converged, a moving platform can maintain high-precision real-time positioning as long as signal reception is not interrupted. While traditional PPP methods have been associated with static positioning or post-processing, MADOCA-PPP is a real-time service that can meet the needs of dynamic navigation applications.

• Differences from other methods (RTK and CLAS): - Difference from RTK positioning: RTK achieves immediate high accuracy through relative positioning with regional base stations via simultaneous observations, but it has limitations such as the need for communication with the base station and distance limits (generally within several tens of km). Because MADOCA-PPP does not require a reference station, it offers the advantage of providing high accuracy independently in remote mountains, on isolated islands, or at sea. However, the time required to achieve high accuracy is longer than RTK, so it takes time from startup until high-precision operation. In summary: “RTK gives instant centimeter-level accuracy but with limited range; PPP is globally applicable but requires convergence time.” - Difference from CLAS: CLAS (Centimeter-Level Augmentation Service) is also provided via Michibiki’s L6 signal, but it operates only within Japan and uses the domestic Continuously Operating Reference Station network to provide centimeter-level accuracy in a short time. MADOCA-PPP, by contrast, is designed for wider-area use (including outside Japan) and uses global satellite correction information without relying on a local reference station network. Although MADOCA-PPP requires time for accuracy convergence, its ability to be used overseas and at sea is an advantage that CLAS does not have.

Use cases

The communication-free nature of MADOCA-PPP is valuable in many scenarios where conventional methods made positioning difficult. Representative use cases include:

• Surveying and construction in off-grid environments: MADOCA-PPP enables high-precision positioning in mountainous areas, remote islands, and forests outside of mobile network coverage. For example, in forest surveying or mountain tunnel construction, accurate position information can be obtained using only a single GNSS receiver without installing base stations or setting up long-range radio links.

• High-precision positioning at sea and offshore: The service enables high-precision ship navigation and marine surveys on the open ocean. Ships beyond the range of terrestrial base stations that cannot receive ground communications can receive MADOCA-PPP satellite augmentation signals and determine their positions to within several tens of centimeters. This is useful for oceanographic survey vessels conducting marine surveys or for precise alignment during offshore platform construction. Traditionally, DGPS using coastal stations provided meter-level accuracy, but MADOCA-PPP can maintain higher accuracy independently on the open ocean.

• Smart agriculture and forestry: In vast farmlands and deep forests, MADOCA-PPP enables guidance of autonomous tractors and forestry machinery with high-precision position information. Even on farms or in woodlands without cellular connectivity, machinery can operate while receiving satellite correction signals to automate seeding and harvesting or to precisely control pesticide spraying. In the context of ICT agriculture and smart forestry, MADOCA-PPP serves as a reliable foundational technology.

• Machine guidance for construction equipment: Centimeter-level positioning is essential for machine guidance of heavy equipment and for construction quality control. Traditionally, sites used local base stations or VRS network contracts, which can be difficult in mountainous or overseas projects. With MADOCA-PPP–compatible machine navigation systems, equipment can be guided by satellite augmentation signals regardless of the country, reducing the complicated preparation required for each site.

• Infrastructure maintenance and inspection: High-precision position logging is important for inspection of long infrastructure such as power lines, pipelines, roads, and railways. By equipping patrol vehicles or inspection drones with MADOCA-PPP–compatible GNSS devices, inspections can be conducted while consistently recording positions in a unified coordinate system, even in remote areas. This supports wide-area infrastructure management including areas outside communication coverage.

• Disaster and emergency response: Immediately after a large-scale disaster, when communication infrastructure may be disrupted, satellite-only positioning can support situational awareness and recovery efforts. With MADOCA-PPP–compatible equipment, responders can rapidly record locations of collapsed structures and create damage maps without setting up reference stations or relying on cellular networks. Using this service for drone surveys and situational assessment in communication-denied environments can greatly improve the efficiency of initial responses. Where previously high-precision positioning was difficult when communications failed, MADOCA-PPP dramatically increases the resilience of positional information in emergencies.

• International projects and overseas deployment: The ability to use domestically developed high-precision positioning technology overseas is a major advantage. For example, when a Japanese surveying company conducts construction surveys abroad, there is no need to establish local reference stations or rely on local services. Bringing a MADOCA-PPP–compatible receiver allows reproduction of the same high-precision positioning as in Japan in most places around the world. This reduces the time and cost of negotiating various correction service contracts in different countries and facilitates international expansion.

Requirements and notes

Key conditions and precautions to effectively use MADOCA-PPP are summarized below.

• A compatible GNSS receiver is required: As a prerequisite, you need equipment that can receive the L6 signal and perform PPP computations. Typical single-frequency (L1-only) GNSS chips or smartphones are not compatible; a high-precision dual-frequency GNSS receiver (supporting L1/L5 or L1/L2) for surveying is required. Fortunately, compact modules supporting QZSS L6-band augmentation have appeared recently, making the devices more accessible compared to traditional expensive surveying equipment. For example, using a MADOCA-PPP–compatible high-precision GNSS receiver such as the LRTK series, centimeter-level positioning can be achieved without specialized surveying instruments.

• Satellite signal reception environment: Because the service relies on satellite correction signals, a stable reception environment for both GNSS satellites and Michibiki satellites is required. It is desirable to operate in an open-sky environment where at least one Michibiki satellite is visible (service availability requires at least one Michibiki with an elevation angle of 10 degrees or more to be visible within the service area). In forests or urban canyons with tall buildings, signals may be blocked, degrading accuracy and increasing re-convergence time, so attention should be paid to antenna placement and operations. Also note that an L6-band–compatible antenna is required.

• Time required for initial convergence: As mentioned above, obtaining a high-precision solution after powering on or after a long interruption in reception requires time. A general guideline is to continue stable reception for about 20–30 minutes, so operational measures such as powering equipment before starting work or waiting for positioning to stabilize before moving are recommended. This convergence time may vary depending on satellite geometry and observation environment. Once converged, continuous reception of corrections maintains accuracy, but if signal reception is lost and corrections resume later, re-convergence will require time.

• How to obtain correction information: The primary intended operation is to receive the L6 signal directly from the satellite, but correction data can also be obtained via the internet. The Cabinet Office’s QZSS official site provides an NTRIP service for MADOCA-PPP correction messages for research and development use (application required). This allows obtaining the same data via a network as from the satellite, which can be useful for testing PPP in areas where Michibiki is not visible. However, since the advantage of MADOCA-PPP is that communication is not required, it is generally simplest to operate by receiving the satellite directly in the field unless there are special circumstances.

• Free to use: The MADOCA-PPP satellite broadcast service itself is provided as an official service of Michibiki (QZSS) and is basically free of charge. Previously, obtaining centimeter-level accuracy often required subscribing to commercial paid augmentation services, but MADOCA-PPP has appeared as an open government-provided service. Users can obtain high-precision correction information without additional costs by simply providing compatible equipment, lowering the barrier to high-precision positioning. The reduced cost barrier is expected to accelerate adoption in infrastructure projects in emerging countries and among small and medium-sized enterprises.

Conclusion

MADOCA-PPP is a groundbreaking technology that promotes the “democratization of high-precision positioning” by being usable widely without the need for communication. Across many industries with growing demand, it makes a future in which anyone can obtain centimeter-level position information regardless of location a realistic possibility. Precision positioning that previously required specialized surveyors, expensive equipment, and communication infrastructure becomes markedly more accessible with MADOCA-PPP–compatible devices.

For example, the latest high-precision GNSS product lines, including the LRTK series, can achieve simple centimeter-level positioning with pocket-sized devices by utilizing MADOCA-PPP, enabling non-experts to perform tasks that once required specialists. This helps resolve labor shortages and cost constraints on surveying and construction sites and directly contributes to productivity improvements. Tasks that previously required two people with a total station can be completed by one person in a short time with LRTK, contributing to workforce reduction on site. With the advent of MADOCA-PPP, high-precision positioning is shifting from something special to an everyday infrastructure. Future increases in Michibiki satellites and technical improvements are expected to further enhance performance and make the technology even more convenient and accessible. Although the full-scale service began operation in 2024, the range of fields benefiting from it will continue to expand. Consider leveraging this new high-precision positioning mechanism to support next-generation field operations that can obtain reliable position information anywhere in the world.