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EGNOS Receivers
| EGNOS | |
|---|---|
| Title | EGNOS Receivers |
| Author(s) | GMV. |
| Level | Basic |
| Year of Publication | 2011 |
EGNOS-enabled receiver depend on the targeted application, the EGNOS functions that will be used and the integration constraints. In choosing a receiver, users should establish whether it correctly supports EGNOS, then select the interface type. Check if the protocols supported by the receiver allow retrieval of the data required for the targeted application.[1]
Receiver types
EGNOS-enabled receivers can be designed using a chipset, hybrid component or auxiliary card.
- Chipset: consists of one or two components that must be installed on a circuit board. The routing of the RF part is sensitive. This compact solution is also the least expensive.
- Hybrid component: consists of a single component integrating the RF and signal processing parts to be installed on a circuit board. Routing is easier compared to chipsets. The price is higher than for the chipset solution.
- Auxiliary card (piggyback): all the receiver and peripheral components are integrated on a ready-to-use card connected to the final product’s main circuit board. It is an ideal solution for prototyping embedded applications. This is the most expensive solution.
Communications protocols
Manufacturers generally use proprietary protocols which give access to almost all the data (pseudoranges, satellite navigation messages, SBAS messages, etc.) associated with a standardised protocol, NMEA 0183. Some receivers also generate data in RINEX (Receiver INdependent EXchange) format.
RINEX is an exchange format that is independent of the receiver. It was developed by the Astronomical Institute of the University of Bern in order to provide data in a single format that has been collected in proprietary formats by different brands of receiver. This format is generally supported by professional receivers. It is also used by IGS servers for supplying GNSS data. In this format, the GNSS data are provided as text files. A description of this format described by the University of Bern is available free of charge on http://igscb.jpl.nasa.gov/igscb/data/format/rinex210.txt.
Manufacturer’s specifications
Although some manufacturers clearly specify that EGNOS is supported, others indicate that their receivers are “WAAS Capable” or “WAAS Enabled”, with WAAS referring to both the North American satellite-based augmentation system (SBAS) and the SBAS standard. In practice, “WAAS Capable” means that the receiver can use SBAS services but the user must activate this function once only, or each time it starts up. “WAAS Enabled” usually means that the receiver activates SBAS reception by default.
It is important to bear in mind that there is no guarantee a “WAAS Capable” or “WAAS Enabled” receiver will support EGNOS (this is due in particular to the MT0/2 message which is sometimes interpreted as MT0).