A quick example on what $GPTRF messages are. Keep in mind that the sentence Identifier can also be displayed as $GNTRF. The message is the same but some GNSS receivers use this format.
Transit Fix Data
Time, date, position, and information related to a TRANSIT Fix.
hhmmss.ss = UTC of position fix
xxxxxx = Date: dd/mm/yy
llll.ll,a = Latitude of position fix, N/S
yyyyy.yy,a = Longitude of position fix, E/W
x.x = Elevation angle
x.x = Number of iterations
x.x = Number of Doppler intervals
x.x = Update distance, nautical miles
x.x = Satellite ID