Ignore this, I think.
Just found the answer...
VTG - Velocity made good. The gps receiver may use the LC prefix instead of GP if it is emulating Loran output.
$GPVTG,054.7,T,034.4,M,005.5,N,010.2,K*48
where:
VTG Track made good and ground speed
054.7,T True...