[LEAPSECS] Leap smear

[Keith Winstein]

On Fri, Sep 30, 2011 at 2:59 AM, mike cook <michael.cook at sfr.fr> wrote:

>> Both GPS and VLBI require knowledge of UTC and UT1 for implementation. How

>> does the GPS pick up the UT1 corrections?  VLBI, at least when I was

>> involved with it many years ago, depends on the IERS circular.

>>

> GPS doesn't transmit DUT1 as far as I can see. It just tells you how to get

> from GPS time to UTC .


? The GPS navigation message includes a complete set of earth
orientation parameters (as determined by USNO, who also publishes IERS
Bulletin A). The receiver needs the earth orientation to be able to
translate from XYZ (earth-centered inertial) coordinates (which is how
the satellite ephemerides are specified) to earth-centered,
earth-fixed coordinates and then to WGS84 latitude and longitude.

DUT1 gets 31 bits, including the sign, and is in units of 2^(-24)
second. They also give a rate of change so it can be approximated to
first order by the receiver.

-Keith