High precision computer logger

Replace ntpd with chronyd:

• http://chrony.tuxfamily.org/

Then, also add gpsd:

• http://www.catb.org/gpsd/gpsd-time-service-howto.html
• In addition to gpsd you will need to modify the default configuration so that the gpsd daemon starts looking for the gps at start up:

root@turkey:/etc/default# cat /etc/default/gpsd
# Default settings for the gpsd init script and the hotplug wrapper.

# Start the gpsd daemon automatically at boot time
START_DAEMON="true"

# Use USB hotplugging to add new USB devices automatically to the daemon
USBAUTO="true"

# Devices gpsd should collect to at boot time.
# They need to be read/writeable, either by user gpsd or the group dialout.
DEVICES="/dev/ttyUSB0"

# Other options you want to pass to gpsd
GPSD_OPTIONS="-G -n"

Doing those two things will get you a computer that will keep time with good precision when connected to a gps & unable to access network time for extended periods. NTP works best in always connected environments.