Leica GPS1200 Series Technical Reference Manual page 1357

Examples
NMEA Message Formats
Field Description
x.x Altitude of position marker as local ellipsoidal height. If the local ellipsoidal
height is not available, the WGS 1984 ellipsoidal height will be exported.
M Units of altitude as fixed text M
*hh Checksum
<CR> Carriage Return
<LF> Line Feed
Standard Talker ID
$PTNL,GGK,113616.00,041006,4724.5248557,N,00937.1063064,E,3,12,1.5,EHT1171.74
2,M*4C
User defined Talker ID = GN
$PTNL,GGK,113806.00,041006,4724.5248557,N,00937.1063064,E,3,13,1.2,EHT1171.74
6,M*43
GPS1200 1357