On 04/03/2021 00:01, Martin Gregorie wrote:
And the inability of long-stored GPS units to figure out which "epoch"
they really are in is another form of planned obsolescence.

I think its more case of volatile memory (RAM) with a coin battery for
backup being more reliable and supporting many more read/write cycles
that the EEPROM that was available when the 1st gen GPS receivers were
built.

I have some very old Garmin GPSs that work just fine, except that some
of them are confused about the epoch.

That depended on the device. O lot of 1st epoch GPSes couldn't resync if
the epoch counter was zeroed by total power loss. IIRC my GPS II+ units
are in that group, which is why I keep them continuously powered except
for 30 seconds every 9-12 months whe n their alkalines are changed.

That's not a problem unless the device is also a flight recorder
(logger) since it will stamp your flight log with the wrong date
(off by about 11 years).

It can be more than that - some early receivers could not rsync with the
GPS constellation from epoch 1 onward if power loss zeroed their epoch
counter - I believe this design fault wasn't recognised until after the
first epoch rollover, at which point it was too late for recovery.


IF the GPS transmissions that we use included data on which the current
epoch is, there would not be a problem, but they don't.

Most GPS engines will reset to the epoch in which they were made, not
necessarily epoch 0.