[Difx-users] ITRF realisations {External}

[Leonid Petrov]

Chris,

   I looked at sched-12.0. I found that internally it uses UTC(t)
function as time. It assumes UT1(t) = UTC(t), see for instance
schgeo.f. This can introduce an error that is equivalent to an
error in position of mid-latitude sites at a level of several
hundreds meters.

   In that context difference in several centimeters between different
station catalogues is irrelevant.

Leonid
2025.07.04_08:47:11

> On 2025-07-04 01:02, Phillips, Chris (S&A, Marsfield) via Difx-users 
> wrote:
> Hi all,
> 
> I have just learned that ITRF (which we use as the XYZ coordinate
> system of our telescopes) has multiple realisations (ITRF2000,
> ITRF2014 etc).
> 
> There was approx a 9cm change between around ITRF2005, which is huge.
> 
> The “Frame” detail in Sched is light on details and vex2difx make
> no mention of frame.
> 
> Does anyone know what ITRF frame Sched expects?
> 
> Thanks
> 
> Chris
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