NMEA-0183 message: GNS

Related Topics

GNSS fix data

GNSS capable receivers will always output this message with the GN talker ID

GNSS capable receivers will also output this message with the GP and/or GL talker ID when using more than one constellation for the position fix

An example of the GNS message output from a GNSS capable receiver is:

$GNGNS,014035.00,4332.69262,S,17235.48549,E,RR,13,0.9,25.63,11.24,,*70<CR><LF>

$GPGNS,014035.00,,,,,,8,,,,1.0,23*76<CR><LF>

$GLGNS,014035.00,,,,,,5,,,,1.0,23*67<CR><LF>

GNS message fields

Field Meaning
0 Message ID $--GNS

Talker ID can be:

GP: To provide information specific to the GPS constellation when more than one constellation is used for the differential position fix

GL: To provide information specific to the GLONASS constellation when more than one constellation is used for the differential position fix
GN: GNSS position fix from more than one constellation (eg. GPS + GLONASS)

1 UTC of position fix
2 Latitude
3 Direction of latitude:

N: North

S: South

4 Longitude
5 Direction of longitude:

E: East

W: West

6 Mode indicator:
  • Variable character field with one character for each supported constellation.
  • First character is for GPS
  • Second character is for GLONASS
  • Subsequent characters will be added for new constellation

Each character will be one of the following:

N = No fix. Satellite system not used in position fix, or fix not valid

A = Autonomous. Satellite system used in non-differential mode in position fix

D = Differential (including all OmniSTAR services). Satellite system used in differential mode in position fix

P = Precise. Satellite system used in precision mode. Precision mode is defined as: no deliberate degradation (such as Selective Availability) and higher resolution code (P-code) is used to compute position fix

R = Real Time Kinematic. Satellite system used in RTK mode with fixed integers

F = Float RTK. Satellite system used in real time kinematic mode with floating integers

E = Estimated (dead reckoning) Mode

M = Manual Input Mode

S = Simulator Mode

7 Number of SVs in use, range 00–99
8 HDOP calculated using all the satellites (GPS, GLONASS, and any future satellites) used in computing the solution reported in each GNS sentence.
9 Orthometric height in meters (MSL reference)
10 Geoidal separation in meters - the difference between the earth ellipsoid surface and mean-sea-level (geoid) surface defined by the reference datum used in the position solution

“-” = mean-sea-level surface below ellipsoid.

11 Age of differential data - Null if talker ID is GN, additional GNS messages follow with GP and/or GL Age of differential data
12 Reference station ID1, range 0000-4095

- Null if talker ID is GN, additional GNS messages follow with GP and/or GL Reference station ID

13 The checksum data, always begins with *

Note – If a user-defined geoid model, or an inclined plane is loaded into the receiver, then the height output in the NMEA GNS string is always the orthometric height (height above a geoid). The orthometric height is output even if no user-defined geoid is loaded (there is a simplified default geoid in the receiver), or if a user-defined geoid is loaded, or if an inclined plane is used.