Subject: [ids.analysis.forum] Proposals for a SOLUTION/DISCONTINUITY block
From: Laurent soudarin <[email-masked]>
To: [email-masked]
Date: Thu, 01 Sep 2011 10:51:50 +0200

Dear colleagues,

FYI, here is another discussion within the IERS Working Group on SINEX,
where Guilhem and I are the IDS representatives.
This one concerns the handling of the discontinuities.
Please send your comments to the forum that I will compile
and send to the WG.

Best regards
Laurent

>Subject: Re: Proposals for a SOLUTION/DISCONTINUITY block
>From: "Paul Rebischung" <[email-masked]>
>To: <[email-masked]>
>Cc: <[email-masked]>, <[email-masked]>,
>         <[email-masked]>, <[email-masked]>
>Date: Wed, 31 Aug 2011 17:06:11 +0200
>
>
>Dear all,
>
>Thanks for your comments and suggestions. I compiled those which require
>further discussion below and inserted some answers.
>
>Best regards,
>
>Paul
>
>
>
>1) Jim: "Concerning option 1, another advantage is that there is
>flexibility to retain or remove the equality constraints without having
>to restack the entire long-term solution."
>
> > This is an advantage of the parameterization used, not of option 1
>over option 2. The usual parameterization (one position+velocity set per
>time period; equality constraints between successive velocities) is
>still possible with option 2.
>
>
>
>2) Extension of 7th column, suggested by Jim and Daniela, in order to
>keep information about the nature of discontinuities (in option 1) or to
>make this information more easily readable (in option 2). Example:
>
>BDOS  A    1 P 00:000:00000 04:225:00000 PVAS     Unknown
>BDOS  A    2 P 04:225:00000 07:333:68419 P        Martinique EQ
>BDOS  A    3 P 07:333:68419 00:000:00000 PV
>
> > This possibility can work in principle with both options 1 and 2.
>(Note that the meaning of the example would differ with the option. With
>option 1, there would be 3 velocities and we would know from the
>discontinuity block that velocities 1 and 2 are constrained. With option
>2, this block would indicate that there are only two velocities, the
>first one being valid over periods 1 and 2.)
>
>Admittedly, the extended 7th column makes all the discontinuity
>information interpretable at a (human) glance. On the other hand, it
>would make life more difficult for programmers: the correspondence
>between parameters and their validity periods would not be
>straightforward.
>
>As other suggestions will show below, there is generally a trade-off
>between the human readability of the discontinuity block and the
>straightforwardness of the correspondence between parameters and their
>validity periods.
>
>
>
>3) Daniela: "Would it be an option to define the block only with one
>epoch instead of an interval? [...] Of course, the solution numbers are
>then obsolete."
>
>Example 1:
>BDOS  A P 04:225:00000 P Unknown
>BDOS  A P 07:333:68419 P Martinique EQ
>BDOS  A P 07:333:68419 V Martinique EQ
>
>Example 2:
>BDOS  A P 04:225:00000 P    Unknown
>BDOS  A P 07:333:68419 PV   Martinique EQ
>
> > With positions and velocities only, these possibilities work in
>principle, although the correspondence between parameters and their
>validity periods is now completely hidden/implicit. However, with this
>option, I can't see an easy way to deal with LOG or EXP parameters, for
>which a validity period is really needed.
>
>
>
>4) A third option: Sylvain pointed out that the issue of discontinuities
>does not only concern station-related parameters, but also satellite
>phase center offsets, dynamical orbital parameters, gravity field
>coefficients, etc. That's why he suggests that, instead of grouping
>parameters as proposed in option 2, each individual parameter could
>appear in both validity and epoch blocks. In that way, the extension to
>any type of parameters would be straightforward. A restricted example:
>
>+SOLUTION/VALIDITY
>      1 STAX   BDOS  A    1 00:000:00000 04:225:00000 Unknown
>      2 STAY   BDOS  A    1 00:000:00000 04:225:00000 Unknown
>      3 STAZ   BDOS  A    1 00:000:00000 04:225:00000 Unknown
>      4 STAX   BDOS  A    2 04:225:00000 07:333:68419 Martinique EQ
>      5 STAY   BDOS  A    2 04:225:00000 07:333:68419 Martinique EQ
>      6 STAZ   BDOS  A    2 04:225:00000 07:333:68419 Martinique EQ
>      7 VELX   BDOS  A    1 00:000:00000 07:333:68419 Martinique EQ
>      8 VELY   BDOS  A    1 00:000:00000 07:333:68419 Martinique EQ
>      9 VELZ   BDOS  A    1 00:000:00000 07:333:68419 Martinique EQ
>     10 STAX   BDOS  A    3 07:333:68419 00:000:00000
>     11 STAY   BDOS  A    3 07:333:68419 00:000:00000
>     12 STAZ   BDOS  A    3 07:333:68419 00:000:00000
>     13 VELX   BDOS  A    2 07:333:68419 00:000:00000
>     14 VELY   BDOS  A    2 07:333:68419 00:000:00000
>     15 VELZ   BDOS  A    2 07:333:68419 00:000:00000
>-SOLUTION/VALIDITY
>+SOLUTION/EPOCHS
>      1 STAX   BDOS  A    1 04:163:00000 04:223:00000 04:193:00000
>      2 STAY   BDOS  A    1 04:163:00000 04:223:00000 04:193:00000
>      3 STAZ   BDOS  A    1 04:163:00000 04:223:00000 04:193:00000
>      4 STAX   BDOS  A    2 05:156:00000 07:336:00000 06:246:00000
>      5 STAY   BDOS  A    2 05:156:00000 07:336:00000 06:246:00000
>      6 STAZ   BDOS  A    2 05:156:00000 07:336:00000 06:246:00000
>      7 VELX   BDOS  A    1 04:163:00000 07:336:00000 06:066:43200
>      8 VELY   BDOS  A    1 04:163:00000 07:336:00000 06:066:43200
>      9 VELZ   BDOS  A    1 04:163:00000 07:336:00000 06:066:43200
>     10 STAX   BDOS  A    3 07:336:00000 11:220:00000 09:277:43200
>     11 STAY   BDOS  A    3 07:336:00000 11:220:00000 09:277:43200
>     12 STAZ   BDOS  A    3 07:336:00000 11:220:00000 09:277:43200
>     13 VELX   BDOS  A    2 07:336:00000 11:220:00000 09:277:43200
>     14 VELY   BDOS  A    2 07:336:00000 11:220:00000 09:277:43200
>     15 VELZ   BDOS  A    2 07:336:00000 11:220:00000 09:277:43200
>-SOLUTION/EPOCHS
>
> > I like this third option, for it makes the correspondence between
>parameters and their validity periods crystal clear! On the other hand,
>the reading gets more complicated for a human.
>
>
>
>5) Back to option 2: Alvaro noticed that the correspondence between the
>soln types and the initial letters of parameter names (e.g. "V" for
>VELX/VELY/VELZ) was not fulfilled for the position parameters. So, he
>suggests to rename the STAX/STAY/STAZ parameters into POSX/POSY/POSZ.
>
>
>
>6) RÃ©mi suggested two additional changes to the SOLUTION/EPOCHS block:
>replacement of the mean epochs by epochs of minimum variance; addition
>of another column to indicate the number of observations (i.e.
>instantaneous positions) used to estimate each position/velocity.
>
>
>
>7) RÃ©mi has a number of other suggestions that are not directly related
>to this discussion, but are worthy of note:
>- For ease of reading, station-related parameters could be provided in
>topocentric (ENH) frames rather than in a geocentric frame.
>- Still for ease of reading, an amplitude+phase parameterization could
>be adopted rather than the cos+sin one for periodic station motions. It
>would require a strict definition of phases.
>- For periodic station motions, he suggests the following parameter
>names: A1AMX/A1AMY/A1AMZ (annual amplitudes), A1PEX/A1PEY/A1PEZ (annual
>phases), A2AMX/A2AMY/A2AMZ (semi-annual amplitudes)... This could be
>extended until A9 if needed.
>
>
>
>
>
>On mar., 2011-08-30 at 10:34 +0200, Paul Rebischung wrote:
> > Dear colleagues,
> >
> > Following our discussion in Vienna, we started thinking about an
> > official inclusion of the SOLUTION/DISCONTINUITY block into the SINEX
> > format. It turned out to be more subtle than expected and raised several
> > questions, in particular about the exact definition of "solution
> > numbers". Our thoughts are summarized in the attached document. Of
> > course, this discussion is only relevant for long-term (cumulative)
> > solutions.
> >
> > You are all invited to send comments.
> >
> > Best regards,
> >
> > Paul, Zuheir, Xavier

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