hours output marker pulses

[Mike Watterson]

GPS is a bad idea for anything not needing navigation. It needs reception and is vulnerable. It's stupidly used  for loads of commercial applications simply to save less €200 on a €10K+ system so next decent Solar Flare like in 19th C there will be no Mobile, DTT or DAB most places.

NTP is a bad idea except to update occasionally as it needs the Internet, and thus has at least two vulnerabilities.

Both sweeping statements that I really have to pick up on. It may well be that this sort of accuracy is not needed, but to sweepingly dismiss both technologies in such a cavalier manner is, IMHO, unreasonable and incorrect.

You are totally missing the point. It's when it's designed definite failure simply to cut costs. Failure is a "when" not "if". It's about the wrong sort of reliance on certain technologies that reduces uptime simply to save an install cost.
My statements only seem sweeping and cavalier. Misuse of technolgy, particularly of GPS, is a threat.

Obviously if the system using NTP or GPS is either able to work without (not possible for GPS used intsead of an accurate reference in DAB, DTT, Mobile rather than timekeeping) or the system failure isn't important, then it doesn't matter.

A different sort of stupidity is using proprietary internet servers so that the DRM, lock, doorbell, speech recognition, local media player, smoke alarm, burglar alarm or thermostat doesn't work at all without the Internet or the server.

GPS is very useful for navigation & location to feed an explicit & legal tracker.
NTP is needed for Servers on the Internet. Any computer clock should still work meantime if the NTP is lost, it's not a substitute for a quartz clock, but a synchronisation scheme.

I've used both technologies appropriately. They are both inappropriate for the OP, though the GPS could be used to initialise location on a portable unit and NTP used if the sesomgraph sensor was only used via a remote server on the Internet. But the actual logging should not use either, except on initialisation or a remote signal to synchronise time and date.

[Doodlebug]

I've just bought a quartz chiming clock movement.
Here is a shot of it chiming on one of 3 seismograph outputs. At present it overwhelms the o/p of a seismo during chiming but unless
this happens at time of a quake, then it's of no matter.
I just connected the loudspeaker of the clock to the seismo recorder !

I'm quite pleased with this non tech, simple solution.
   

[ppppenguin]

The simplest solutions are often the best. Well done.

[BusyBee]

Well done! There is always more than one way to skin a cat

Tracy