Richard,
Faros uses a precise time of day to determine the time it took for the
beacon signal to reach your location. It uses this info to determine if the
path was the short path, or the long path.
The NCDXF beacons use a GPS receiver to determine a very accurate time of
day, and to start their transmission at a precise time. Faros looks at the
clock time when it hears the signal arriving at the receiver it’s listening
with. It knows the exact location of the transmitter and your exact
location. Form there, it can calculate the spherical distance, both the
“short path” and the “long path”. With the distance known, and the delay in
receiving the signal, Faros can then determine if the signal arrived at your
location via the short path, or the long path (or both!).
Faros gets the correct time of day, by using it’s own built in NTP. It has
a list of NTP servers, and it uses the NTP algorithm to determine the
“delay” to that server. Faros ranks the quality of the NTP servers by
delay.
An interesting experiment is to tell Faros a location that’s much different
than where it’s receive really is located.
KR
================================
Kevin,
From that I would expect the receiver & PC to have a good sub-millisecond
accuracy, and the best way to achieve that would be to run the whole lot on
Linux, to be honest! Given that it's Windows software:
- ensure you're running Windows-10 as it has more precise time functions.
- ask the developer to check for and use the
"GetSystemTimePreciseAsFileTime" function to take advantage of the
increased precision.
- use a GPS with a PPS feed and ideally a PC with a real COM port, or at
least a 3rd-party COM port. NOT a COM port over USB!
- install the reference version of NTP (which includes PPS support for
Windows). It does a lot more than a simple NTP client will do. I have some
notes to help configure here:
https://www.satsignal.eu/ntp/Sure-GPS.htm
That's using a board which is no longer available, but a cheap Chinese GPS
board with PPS output will suffice, possible needing a TTL to RS-232 level
converter. Search that page for "loopback-ppsapi-provider.dll" as the
original method of replacing the serial port driver no longer works under
the current Windows-10.
- leave the PC 24x7 on at as near constant temperature you can get.
Have fun!
Cheers,
David
--
SatSignal Software - Quality software for you
Web: http://www.satsignal.eu
Email: [email protected]
Twitter: @gm8arv
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