From: Poul-Henning Kamp <>
Date: Sat, 27 Dec 2003 21:05:17 +0100

In message <>, Steve Allen writes:
>On Wed 2003-12-24T13:33:37 -0800, Steve Allen hath writ:
>> The current downlink data format for the GPS satellites stores the
>> difference between GPS system time and UTC using 8-bits.
>oops. I've just re-read the GPS Interface Control Document.
>Those 8-bits are a signed quantity. It can count to 127.
>The current GPS data format will fail in approximately 2057, 2079, or
>2095 for decelerations of 42, 31, or 25.6 s/cy2, respectively.
>In terms of deployed systems, that's Real Soon Now.

Steve, I fundamentally agree with you I think, but you are starting
to sound a bit shrill.

53 years is an exceedingly improbable lifetime for any deployed

Few of todays semiconductors have reliability figures which gives
us any reason to think they will work 20 years from now, and in
particular, there is plenty of time to augment the GPS signal format
several times over before before 2057.

Can we turn the alarmist tone down a bit ?


Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
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Never attribute to malice what can adequately be explained by incompetence.
Received on Sat Dec 27 2003 - 12:05:33 PST

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