See NMEA GSV definition http://www.nmea.de/nmea0183datensaetze.html#gsv
The GSV string transmits the pseudo random number (PRN) for every single satellite in view and the signal-to noise-ratio (SNR) in dB.
In addition the vertical angle (elevation) and the horizontal angle (azimuth) of the satellite are given by the GSV string.
The last column of the list shows the satellite system and a flag if the satellite is used for the calculation of the position.
Supported satellite systems are
- GPS (USA)
- GLONASS (Russia)
- GALILEO (European Union)
- BEIDOU (China)
- IRNSS (India)
- QZSS (Japan)
- SBAS (worldwide)
additional satellite-broadcast messages.