I have a measurement challenge: 3 different locations to meaure at, all app 1 mile apart (1.5 km). No way to use GPS to establish clock synchronisation, since it is underground.
I was hoping to network it together using fiberoptic and the bran new ethercat 9144 expansion module for cRIO, but I fear hardware availability.
So my question is:
How would you synchronize 3 measurement locations without cabling between them, using a cRIO, laptop or Fieldpoint on each location, no access to internet or GPS. Measurement time is limited, so I would be satisfied to have the clocks synchronized up front if the realtime clock or PC clock drift stay limited to msecs per day
