I get Position Fix Indicator = 6 in GGA / $GPGGA sentences: what does it mean?As of NMEA version 2.3 (and later), the
Position Fix Indicator field in NMEA GGA / $GPGGA sentences can also take the value of 6 = "Dead Reckoning Mode, fix valid".
See here for further reference:
http://www.gpsinformation.org/dale/nmea.htm#GGA
Quote
Fix quality: 0 = invalid
1 = GPS fix (SPS)
2 = DGPS fix
3 = PPS fix
4 = Real Time Kinematic
5 = Float RTK
6 = estimated (dead reckoning) (2.3 feature)
7 = Manual input mode
8 = Simulation mode