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EtherCATTiming
Time Synchronisation Without GPS Belowdecks
By Engineering — Platform · January 5, 2026 · 5 min read
A red-state event has to be timestamped to within milliseconds across all sensor cells. Belowdecks, GPS is not available. PTP over the EtherCAT ring is.
A coherence check is only valid if all the cells being compared are reporting on the same clock. Belowdecks on a steel-hulled vessel, GPS is unavailable or unreliable, and we needed a synchronisation source that did not depend on it. PTP-over-EtherCAT solves the problem inside the ring.
Where the clock comes from
- Segment master holds the deck reference clock, disciplined from vessel time at the bridge.
- PTP messages propagate around the ring with per-node compensation for the link delay.
- Each cell holds local time to within ~1 µs of the master across normal operation.
- Cells log a sequence number alongside the timestamp so out-of-order arrivals are detectable.
GPS belowdecks is a polite fiction. PTP-over-EtherCAT is the actual answer, and it is the same standard the rest of the industrial-automation world uses.
Related reading
Continue the thread
EtherCATNetworking
Apr 30, 2026 · 9 min read
Why We Chose EtherCAT Ring Topology for Marine Sensor Networks
Star-topology fieldbuses fail open when a single run is damaged. Ring topology with redundancy keeps the segment master talking to every node, even with a cut cable.
By Engineering — NetworksRead
ArchitectureLatency
Feb 22, 2026 · 7 min read
The Data Pipeline From Deck Sensor to Bridge Console
A walk-through of every hop the data takes — sensor cell, segment master, vessel server, bridge console — and the latency budget at each.
By Engineering — PlatformRead