Your site's time starts 20,200 km up.
Every relay timestamp trusts a satellite. What else is listening — and talking?
Scroll to fall from orbit to the fence — past the satellites your clocks trust, past a van with a long-range antenna, to the radio footprint around one OT site.
Signals reach your site from every direction.
GPS satellites about 20,200 km up give every relay and clock its time. Low-orbit broadband about 550 km up can put an internet link anywhere — including inside your fence.
SOURCES · GPS.GOV SPACE SEGMENT · FCC APPROVAL OF 550 km STARLINK SHELL (VIA SATELLITE, 2019)
A directional antenna doesn’t need to be close.
A van in a lay-by with a high-gain dish on a roof mast can hold a two-way Wi-Fi link for kilometres, line of sight — to a device on site, and back again. The fence stops people. It does not stop radio.
Your fence isn’t your perimeter.
Inside the fence: what the asset register knows. Around it: a radio footprint about three times the fenced area — the road, the car park, the houses. Unexplained is not the same as hostile.
How the clock can be misled — or simply fail.
SCENARIOS · ILLUSTRATIVE · NOT OBSERVATIONS OF ANY SITE
Every timestamp trusts one antenna.
Satellites, a roof antenna, a station clock, then PTP over the station bus to every relay. Lose the fix and the clock drifts in holdover; spoof it and it can be confidently wrong. Omnisight’s own receiver watches the same sky — off the OT network.
A second, independent view of the sky.
The sensor samples signal strength per satellite, fix quality and its own known position, compares this hour with the usual, and records events with the readings that caused them.
EVENTS IN SOURCE INCLUDE GNSS NO FIX SUSTAINED · POSITION ANCHOR RESIDUAL HIGH
One site. Five views.
The sky, the approach, the site, the air around it and the time it keeps. Your drawings show the middle one. Omnisight adds the rest.
- Where might a timing dependency matter?
- What raised the timing question?
- What could establish the facts?
ILLUSTRATIVE · GNSS AND TIMING-INTEGRITY OBSERVATIONS · SCOPED IN THE EVALUATION
