and 
NMEA GSA message
Popular NMEA messages
GNSS DOP and active satellites (GSA)
| Message | NMEA-Standard-GSA GNSS DOP and active satellites |
| Comment | The GNSS receiver operating mode, satellites used for navigation, and DOP values. • If less than 12 SVs are used for navigation, the remaining fields are left empty. If more than 12 SVs are used for navigation, only the IDs of the first 12 are output. • The SV numbers (fields 'svid') are in the range of 1 to 32 for GPS satellites, and 33 to 64 for SBAS satellites (33 = SBAS PRN 120, 34 = SBAS PRN 121, and so on) In a multi-GNSS system this message will be output multiple times, once for each GNSS. |
| Information | Number of fields: 21 |
| Structure | $xxGSA,opMode,navMode{,svid},PDOP,HDOP,VDOP,systemId*cs\r\n |
| Example | $GPGSA,A,3,23,29,07,08,09,18,26,28,,,,,1.94,1.18,1.54,1*0D\r\n |
Payload
| Field | Name | Format | Unit | Example | Description |
|---|---|---|---|---|---|
| 0 | xxGSA | string | - | $GPGSA | GSA Message ID (xx = current Talker ID) |
| 1 | opMode | character | - | A | Operation mode: • M = Manually set to operate in 2D or 3D mode • A = Automatically switching between 2D or 3D mode |
| 2 | navMode | digit | - | 3 | Navigation mode, see position fix flags description |
| Start of repeated group (12 times) | |||||
| 3 + n | svid | numeric | - | 29 | Satellite number |
| End of repeated group (12 times) | |||||
| 15 | PDOP | numeric | - | 1.94 | Position dilution of precision |
| 16 | HDOP | numeric | - | 1.18 | Horizontal dilution of precision |
| 17 | VDOP | numeric | - | 1.54 | Vertical dilution of precision |
| 18 | systemId | hexadecimal | - | 1 | NMEA-defined GNSS system ID |
| 19 | cs | hexadecimal | - | *0D | Checksum |
| 20 | CRLF | character | - | - | Carriage return and line feed |
Based on NMEA documentation provided by u-blox.
Learn more about NMEA protocol:
