GPS devices without PPS signal


El-Cheapo devices, like USB attached GPS units

Timestamping is done at the initial '$' character of the $GPRMC message

This is a "wild guess" and a compromise at best, but what else can we do?

The skew between tty- and soft-timestamping is between 0.03s and 0.05s on i386 (a value that - for some reason - is reasonable ;)