My First GPS (AmbiCom GPS Navigation Receiver GPS-USB)

(tags timekeeping, GPS, hardware, Windows)

 The GPS unit I ordered, the AmbiCom GPS Navigation Receiver, came in today. Yes! Let's setup a NTP server!

Mount it outside:

It's a USB device, so hook it up to the computer and install the drivers. (The included CD is useless...) It's (virtually) connected to the COM3 serial port, woopie:

Test it out. Can you see satellites? Does it output NMEA 0813 messages?

Yes, it's not a dud! It's tracking a bunch of satellites, I think. At least the time is right and the lat/long is what I expect.

Let's move it over to the stable computer, Project Asobi, and set up the NTP server. The relevant configuration is in the ntp.conf file.

## Local GPS clock
# AmbiCom GP Navigation Receiver GPS-USB
server 127.127.20.3 prefer mode 7
fudge 127.127.20.3 stratum 0

## Statistic settings
# Windows example:
driftfile "D:\Program Files\NTP\etc\ntp.drift"
enable stats
statsdir "D:\Program Files\NTP\stats\"
# stupid statsdir needs the backslash
# quote is here for stupid emacs"
statistics loopstats clockstats

## Allowed NTP clients
restrict default ignore
restrict 127.0.0.1
restrict 192.168.0.0 mask 255.255.0.0


(info and guidance from zaitcev, thanks)

And... let's debug it on the command line first:

z:\Cliff>"D:\Program Files\NTP\bin\ntpd.exe" -n -M -g
  -c "D:\Program Files\NTP\etc\ntp.conf"
  -l "D:\Program Files\NTP\stats\general-log.txt"

Will the reference NTP server software ported by Meinburg recognize this serial device and use it to sync?

Yes! No problem! Let's sync the whole network to it.

Wait, from my other computer, it's about two seconds off from their reported NTP time:

Z:\Cliff>ntpq -p
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
 ring.aist.go.jp .INIT.          16 u    -   64    0    0.000    0.000   0.000
 ring.sakura.ad. .INIT.          16 u    -   64    0    0.000    0.000   0.000
 ring.yamanashi. .INIT.          16 u    -   64    0    0.000    0.000   0.000
xasobi           .GPS.            1 u   39   64  377    0.413  -99.557  26.489
 SUGAR           .INIT.          16 u    -   64    0    0.000    0.000   0.000
xrabic           xxx.xxx.xxx.xx   3 u   49   64  377    2.491  1932.77  14.958

The problems are shown in underline. The "x" at the very front means that this computer's NTP server disregarded the foreign server's time info. Why?!? Don't tell me I have to set a time offset calibration factor or reverse the polarity (Star Trek joke).

Well I haven't resolved the problem, but it's a start. Unfortunately, I'm outta time! Tune back next time and maybe I'll have figured out why this is not in agreement.