[LEAPSECS] temporal turf wars

[Tom Van Baak]

> An interesting NIST document from 2000 gives insight into the turf wars

> about precision time scales.

> 

> http://tf.nist.gov/general/pdf/1429.pdf

> 

> The document makes it clear that GPS time was never designed to follow

> UTC(USNO) (and by implication, TAI).


I think you're misreading that sentence. GPS is in fact steered to
the USNO MC which is steered to UTC. But I think the steering
parameters are quite different between the two though. I also
suspect there have been improvements in the past ten years.
Demetrios can explain more, if needed.


> The document also clarifies the distinction between (raw) GPS time and

> GPS time corrected by the offset given in subframe 4 page 18.


The GPS ICD 200 describes the A0 and A1 correction. I believe
most (all?) GPS timing receiver implement the correction. Steve, you'd
have fun with a GPS timing receiver like a Thunderbolt or an M12;
all those subframe parameters can be dumped over the serial port
and played with.


> The document also coins the term UTC(GPS) with very interesting

> footnotes disclaiming the validity of the use of such a term.


I doubt Al coined that term; I recall seeing it long before. But like
the editor implies, people realized it was not a valid term and so
you rarely see it any more. Maybe marketing people still use it.
I remember being gently corrected by the BIPM and I stopped
using it myself. I think UTC(tvb) is ok, though ;-)

/tvb