USS Fitzgerald

[Bruce_in_Oz]

Aussie 48: Correct about the "time-zone" thing in Oz military use.

All our comms-centre logs were in Zulu and there was always a "master clock" kept on that time and labeled as such. Some types even wore two watches, each neatly labeled with a time zone. The advent of digital watches with adjustable display formats greatly simplified that matter.

Daily routine on the ground; reveille, mess times, duty times, etc, were in "local" time, but all comms were tagged in Zulu.

The advent of the US GPS system changed a LOT of things. A flock of polar-orbiting satellites, each transmitting time-code, provides amazing precision in timing and navigation. "Mil-spec" system initially could locate you within ten metres accuracy or better, anywhere on the face of the planet. This is because the "good gear' uses two frequencies as opposed to the "civilian" units using one. "Civilian" ones were initially limited to 100metres accuracy, but that seems to have been improved, lately. Now, for example, GPS-enabled smartphones are typically accurate to within 5m circle. Major constraints or causes of error are blocking, reflection or absorption from large building in the vicinity or heavy, wet, tree canopy cover.

The accuracy of the "on-board' maps in a GPS receiver is also critical. If the folk who wrote the code that drives the maps, leave out minor roads, random geographical features, etc. things can get untidy fairly quickly. This is akin to the practice of some purveyors of paper maps for car-drivers, of leaving out minor roads. So, as you are driving at the limit, from Las Vegas to catch a flight at LAX, and counting exits etc., rally style, a "missing" road can rapidly land you in all sorts of geographical embarrassment. Having your domestic GPS receiver on the dash of the car, with no external antenna, also greatly slows down the ability of the unit to update at highway speeds, because the car's body is a pretty good Faraday cage, and thus blocks or seriously attenuates some of the signals.

I'm also ancient enough to have monitored the old "National Bureau of Standards" time signals on short wave radio; a voice droning on endlessly; "At the tone, it will be nine-forty-eight and ten seconds, precisely". and incrementally so on, every five seconds, twenty-four hours a day. They are now called WWV and are still very active, transmitting from near Fort Collins, Colorado.

See here: WWV and WWVH Digital Time Code and Broadcast Format | NIST

These days, you can synchronise your PC or portable device to a "master clock" via the internet and stay in sync / re-sync when re-connected.