Hey Guest!
smilie in place of the real @
Pretty Please - add it to our Events forum(s) and add to the calendar! >> Here's How << 
Is it a type of weather station? PJ
I'm not familiar with WHO, but I beleive the machine is a tidal calculator for determining which days and times would have offer tides most favorable for a landing, and ensuring that subsequent tides would be lesser and not wash the army off the beach the next cycle.