help calculating $GPRMB value

Hi everyone,

In the $GPRMB data string, the 11th byte gives the "true bearing to
destination". I need to verify this parameter and was wondering how to
calculate it based on the LAT and LONG data. I have come across a
variey of formulas on the web:

TB1 =
acos((sin(LAT_DEST)-sin(LAT_START)*cos(D))/(sin(D)*cos(LAT_START)))
TB2 = 360 -
acos((sin(LAT_DEST)-sin(LAT_START)*cos(D))/(sin(D)*cos(LAT_START)))
TB3 = atan2((LAT_DEST - LAT_START),(LONG_DEST - LONG_START))

I think TB2 (law of cosines) is probably the most accurate and
efficient way to calculate this value, right?

Thanks in advance,
weg