Galileo High Accuracy Service (HAS)

GALILEO
Title	Galileo High Accuracy Service (HAS)
Edited by	European Commission
Level	Basic
Year of Publication	2026

The GALILEO System is an independent, global, European-controlled, satellite-based navigation system and provides a number of services to users equipped with Galileo-compatible receivers.

The GALILEO High Accuracy Service (HAS) provides free of charge high-accuracy PPP corrections, in the Galileo E6-B data component and by terrestrial means, for Galileo and GPS (single and multi-frequency) to achieve real-time improved user positioning performances (positioning error of less than two decimetres in nominal conditions).

The Galileo High Accuracy Service resulted from the re-scoping of the former Galileo Commercial Service (CS). The Galileo HAS Initial Service (Phase 1) was declared operational in January 2023. Further evolutions are being developed in HAS Phase 2.

Target Applications

Galileo HAS Civil Application

The High Accuracy Service (HAS) is aimed at applications requiring higher performance than that offered by the Open Service. It is provided on a free of charge basis, with content and format of data publicly and openly available on a global scale. Developing applications using the HAS signals opens a wide range of possibilities. The worldwide coverage brings a strong advantage for applications requiring global availability, even in areas with limited wireless communications coverage.

Applications of Galileo HAS span a wide range of land, sea, and air domains. They include high‑precision GIS and mapping, cadastral and hydrographic surveying. Galileo HAS can also support advanced mobility and automation, powering applications such as automated driving, machinery guidance and autonomous surface vessel navigation. Other applications are robotics, port operations, and even smartphone‑based mapping and navigation support for visually impaired users, demonstrating the service’s versatility across professional and societal needs.

Precise Point Positioning

Multiple approaches have been developed to provide positioning accuracy at the decimetre level or better: real time kinematic (RTK), precise point positioning (PPP), and more recently PPP-RTK. The main advantage of using PPP instead of RTK is that it provides a global and absolute positioning and timing service without the need for nearby reference stations. PPP is based on the derivation of accurate GNSS satellite orbits and clock data as well as biases (i.e. code and phase biases) using a sparse, globally distributed network of reference stations. Receivers apply this data to estimate a user position based on carrier phase measurements. The ionospheric delays are typically estimated by the PPP receiver or removed by performing the ionosphere-free combination. However, atmospheric data may be supplied to reduce the convergence time and to improve the accuracy for single-frequency users. In Galileo HAS, PPP data is distributed through the Galileo system itself.

Galileo HAS Data

Galileo HAS data are transmitted using the data (E6-B) component in the E6 band. E6 signals are modulated using binary phase shift keying BPSK(5) at a carrier frequency of 1278.75 MHz, which is used by all satellites and shared through a code division multiple access (CDMA) RF channel access method. Therefore, the signal main lobe and most of the signal power is in the 1273.75-1283.75 MHz band. The HAS data are transmitted within the C/NAV navigation message in the E6-B signal component at a rate of 448 bps.

The Galileo E6-B channel is well suited to transmit PPP information. The available rate of 448 bps per satellite allows the transmission of PPP data at an adequate update rate to provide accuracy at the centimetre level. The HAS message also uses a specific outer-layer coding technique developed for optimally transmitting long messages from satellite constellations, called HPVRS (High Parity Vertical Reed-Solomon). The Galileo HAS corrections are also available through a terrestrial link as an addition dissemination channel.

High accuracy corrections follow a similar format to Compact-State Space Representation (CSSR). Note that the High Accuracy Service does not offer integrity information.

Galileo Signal Frequencies

Galileo HAS Service Levels

The HAS comprises two services levels:

• Service Level 1 (SL1) with global coverage, providing high accuracy corrections (orbits, clocks) and biases (code and phase) for Galileo E1/E5b/E5a/E6 and E5AltBOC and GPS L1/L5/L2 signals.
• Service Level 2 (SL2) with regional coverage, providing SL1 corrections plus ionospheric corrections.

The next table summarizes the main characteristics for each of the Galileo HAS Service levels:

Table 1- Main HAS characteristics and target performances

HAS	Service Level 1	Service Level 2
COVERAGE	Global	European Coverage Area (ECA)
TYPE OF CORRECTIONS	PPP - orbit, clock, biases (code and phase)	PPP - orbit, clock, biases (code and phase) incl. atmospheric corrections
FORMAT OF CORRECTIONS	Open format similar to Compact-SSR (CSSR)	Open format similar to Compact-SSR (CSSR), plus Galileo HAS ionospheric correction message
DISSEMINATION OF CORRECTIONS	Galileo E6-B using 448 bits per satellite per second / terrestrial (internet)	Galileo E6-B using 448 bits per satellite per second / terrestrial (internet)
SUPPORTED CONSTELLATIONS	Galileo, GPS	Galileo, GPS
SUPPORTED FREQUENCIES	E1/E5a/E5b/E6/E5 (AltBOC), L1/L5/L2C	E1/E5a/E5b/E6/E5 (AltBOC), L1/L5/L2C
HORIZONTAL ACCURACY 95%	< 20 cm	< 20 cm
VERTICAL ACCURACY 95%	< 40 cm	< 40 cm
CONVERGENCE TIME	< 300 s	< 100 s
AVAILABILITY	99%	99%
USER HELPDESK	24/7	24/7

The HAS Initial Service is currently providing Service Level 1 with reduced coverage and performance compared to the Full Service. The Minimum Performance Levels (MPLs) are defined in the Galileo HAS Service Definition Document. Performance reports are published on a quarterly basis.

System Level Implementation

Galileo HAS High Level Architecture

The Galileo system elements involved in the provision of the Galileo High Accuracy Service are:

• High Accuracy Data Generator (HADG), located at the GSC (European GNSS Service Centre), receives data from the Galileo Sensor Stations (GSS) and generates corrections for Galileo and GPS. Note that additional reference station networks of Galileo Experimental Sensor Stations (GESS), from the Galileo System Test Bed, and RIMS from EGNOS, will be incorporated in Phase 2.
• The High Accuracy (HA) corrections are sent in real time to the Galileo core infrastructure.
• The Galileo core infrastructure receives the HA data and compiles the information in one single message of 448 bits per second and per connected satellite.
• The Galileo core infrastructure uploads the HA data to the Galileo satellites through the Uplink Stations (ULS).
• Galileo satellites broadcast HA data through the Galileo E6-B signal component.
• HA data is also provided through the terrestrial link, accessible to the users through the Internet.
• Users receive the HA data and implement PPP algorithms to apply HA corrections to the Galileo and GPS navigation data.

HAS High Level Architecture

Galileo HAS Roadmap

The Galileo High Accuracy Service is implemented in a stepped approach:

• Phase 0 (HA testing and experimentation) focused on activities aimed at validating Galileo’s dissemination capabilities through the E6-B channel and performing initial high-accuracy testing. Internal testing started in 2019. HAS SiS tests were executed from Q1 2021.
• Phase 1 (HA Initial Service). Provision of an initial Galileo High Accuracy Service resulting from the implementation of a high-accuracy data generation system processing Galileo system data only. The HA initial service is available since 24/01/2023 and delivers Service Level 1 performance.
• Phase 2 (HA Full Service). Full provision of the Galileo High Accuracy Service, including Service Level 1 and Service Level 2, fulfilling its target performance. In Phase 2, additional stations are added to improve performance and the HAS data will also support additional features such as the authentication of the HAS data.
• Phase X (HA Evolution). Implementation of HAS Evolutions in the frame of Galileo 2^nd generation developments, addressing the HAS users’ feedback and lessons learned from the previous phases.

Galileo HAS Roadmap

Galileo HAS Adoption

Following its Initial Service Declaration in January 2023, the High Accuracy Service started to be integrated by major high-precision receiver manufacturers. A growing number of GNSS receivers now incorporate HAS as part of their precise point positioning (PPP) solutions for applications including precision agriculture, transportation, autonomous systems and other professional markets. EUSPA maintains a non-exhaustive list of receivers supporting HAS as part of their list of Galileo compatible devices.

Credits

The information of this article has been compiled based on public information from the Galileo HAS Info Note and other sources as indicated through the references. The initial (2011) version of this article was edited by GMV.