What is Galileo HAS?
The Galileo High Accuracy Service (HAS) will provide free of charge high accuracy Precise Point Positioning (PPP) corrections through the Galileo signal (E6-B) and by terrestrial means (Internet). Galileo HAS will offer real-time improved user positioning performances with accuracy less than two decimetres (in nominal conditions).
The main characteristics of the Galileo HAS are:
- HAS corrections: high accuracy corrections are composed by orbits, clocks, code and phase biases per each satellite. The HAS full service will include atmospheric corrections too.
- Accessible: high accuracy corrections will be accessible through two dissemination channels: E6-B Signal in Space (SiS) and a terrestrial link, which provides an alternate source to the SiS through the Internet.
- Multi-constellation and multi-frequency: high accuracy corrections are computed for Galileo E1/E5a/E5b/E6; E5 AltBOC and GPS L1/L5; L2C.
- Open format: high accuracy corrections follow a similar format to Compact-State Space Representation (CSSR).
Additional details about service description, potential target markets, technical details and evolution of the HAS services can be found in Galileo High Accuracy Service Info Note.
Galileo HAS service levels
Two service levels are defined for the provision of high accuracy PPP corrections:
- Service Level 1 (SL1): with a global coverage availability, provides high accuracy corrections (orbits, clocks) and biases (code and phase) for Galileo E1/E5b/E5a/E6 and E5AltBOC and GPS L1/L5/L2C signals.
- Service Level 2 (SL2): with a regional coverage availability, over the European Coverage Area (ECA), provides SL1 corrections plus atmospheric (at least ionospheric) corrections and potential additional biases.
The target performances for both SL1 and SL2, at full service capabilities, are presented in the table below:
Table 1: Target performances for Galileo HAS Service Level 1 (SL1) and Service Level 2 (SL2)
Additional details about description and target performances for Galileo HAS service levels can be found in Galileo High Accuracy Service Info Note.
Galileo HAS high-level architecture
The generation, provision and exploitation of high accuracy corrections involve several Galileo system elements:
Figure 1: Galileo system elements involved in the generation, provision and exploitation of Galileo HAS
- The High Accuracy Data Generator (HADG) module receives data from the Galileo Sensor Stations (GSS) and generates corrections for Galileo and GPS. The High Accuracy (HA) corrections are relayed 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, through the Uplink Stations (ULS), uploads the HA data to the satellites.
- Galileo satellites broadcast HA data through the Galileo E6-B signal component. Main specification of the Galileo E6-B and E6-C codes are accessible in the E6B/C Signal In Space Technical Note.
- HA data is also provided through the terrestrial link, accessible to the users through the Internet.
- User receivers implement PPP algorithms to apply HA corrections to the Open Service navigation data received via E1-B signal.
Additional details about HAS system high-level architecture can be found in the Galileo High Accuracy Service Info Note.
Galileo HAS roadmap
The implementation of the Galileo HAS is following a staggered approach based on the 3 phases depicted in figure below:
Figure 2: Galileo HAS implementation roadmap
In line with the Galileo HAS roadmap, key milestones are planned for a continuous service development. More details on the relevant milestones can be found in the Galileo High Accuracy Service Info Note.
Galileo HAS target markets
The following picture provides an overview of the most relevant applications that can benefit from Galileo HAS.
Figure 3: Summary of most relevant Galileo HAS target applications
Additional details about target applications which will benefit from Galileo HAS can be found in the Galileo High Accuracy Service Info Note.
A compilation of the most common questions on Galileo HAS can be found in the Frequently Asked Questions (FAQ) section of the GSC web portal. If you require additional information, please contact our Galileo Helpdesk at firstname.lastname@example.org or directly through the Galileo helpdesk form.