NTPviz GPS graph

[NTPfiend]

Having been running classic ntp for many years, the last 2 years on a
dedicated R Pi B, I was interested to come across NTPsec by means of the
"Stratum-1-Microserver HOWTO". I've had it all up and running since
about 4 Dec with no problems. Great software.

NTPviz is suitably impressive and my results all get cronjobbed to a
website. However, I'm stumped as to how to get "a log file named gpsd in
the log file directory"; what produces this log file ? I've googled
merrily but to little avail, principally as NTPviz is so new. Some
pointers would be good.