[daip] FRING in TST, bug fix 13398 has no effect
Thomas Krichbaum
tkrichbaum at mpifr-bonn.mpg.de
Fri Sep 16 11:13:43 EDT 2011
Hi Eric,
I now also tested the version 'old' fringing runing it with exactly the same parameters.
Also the 'old' version suffers from the same problem in the sense that messages
with phases above 360 deg and **** appear.
When I compare the SN-tables from NEW (SN5) and OLD (SN6),
I see fewer and less extreme outliers in SN5 from TST,
which indicates that FRING in the TSTversion already works better. Still
it continues to produced the funny solutions.
I attach some screenshots for rate and delay (showing IF2 out of 4).
SN5 -> FRING(tst)
SN6 -> FRING(Old)
I got the impression, that in exhaustive baseline search mode, FRINGE is
not able to deal correctly with the rereferencing of the delay. POSSM shows
large residual delays in one polarisation, but not in the other,
although the data were already fringe fitted.
If I fringe fit with a different Refant's and/or a different station
sequence in the SEARCH parameter, scans which were good in one choice become
bad in another choice. So it is an effect which cannot be attributed to a particular
station. It looks to me as if FRINGE has perhaps a problem when fringes are
found in one polarisation to the refant, but not at the same time also for the
other polarisation. There may be also a problem in the subsequent combination of
the solutions from different ref-antennas.
best regards, Thomas
On Thursday 15 September 2011, Eric Greisen wrote:
> Thomas Krichbaum wrote:
> > Hi
> >
> > I did some more test using FRING in version 'new' and 'tst' using ap9=1.
> >
> > The SN-tables produced by both versions are identical. The bug fix
> > mentioned in CHANGE.DOC (13398. January 21, 2011) seems to
> > have no affect in our TST version (31DEC11).
> >
> > Can you please check, if the correct version of FRING is implemented under TST.
> >
>
> The bug fix mentioned in 13398 is mentioned in that number in both TST
> and NEW - a patch was performed for this bug, so the two versions should
> be the same. It appears that there are additional difficulties. If you
> wish to compare versions use OLD in Bonn at least in this case.
>
> I will take a look at this code again but I am quite sure that the
> January fix is in place.
>
> Eric Greisen
>
>
> > best regards
> > Thomas
> >
> >
> > here a more extreme example:
> >
> > 1 2 14-SEP-2011 20:26:37 FRING Time= 0/ 19 05 29, Polarization = 2
> >
> > 1 3 14-SEP-2011 20:26:59 FRING Ant(01): Phas=****** rate= 6.69 delay= 347.87 SNR= 10.3
> > 1 3 14-SEP-2011 20:26:59 FRING Ant(02): Phas=****** rate= -42.26 delay= 196.57 SNR= 7.8
> > 1 3 14-SEP-2011 20:26:59 FRING Ant(03): Phas=****** rate= -24.21 delay= 367.99 SNR= 10.7
> > 1 3 14-SEP-2011 20:26:59 FRING Ant(04): Phas=3271.6 rate= -75.26 delay= -211.49 SNR= 12.0
> > 1 3 14-SEP-2011 20:26:59 FRING Ant(06): Phas=****** rate= -112.27 delay= 312.61 SNR= 9.6
> > 1 3 14-SEP-2011 20:26:59 FRING Ant(07): Phas=****** rate= -26.83 delay= 342.43 SNR= 6.4
> > 1 3 14-SEP-2011 20:26:59 FRING Ant(08): Phas=-670.8 rate= -24.45 delay= 146.65 SNR= 9.2
> > 1 3 14-SEP-2011 20:26:59 FRING Ant(09): Phas=****** rate= -33.23 delay= 134.15 SNR= 7.7
> > 1 3 14-SEP-2011 20:26:59 FRING Ant(10): Phas=-720.6 rate= -5.82 delay= 295.55 SNR= 8.1
> > 1 3 14-SEP-2011 20:26:59 FRING Ant(11): Phas=****** rate= -24.56 delay= 190.89 SNR= 7.8
> > 1 3 14-SEP-2011 20:26:59 FRING Ant(12): Phas=****** rate= -2.80 delay= 311.55 SNR= 10.4
> > 1 3 14-SEP-2011 20:26:59 FRING Ant(13): Phas=-342.8 rate= -40.83 delay= 189.65 SNR= 7.8
> >
> >
> >
> >
> >
> > ---------- Forwarded Message ----------
> >
> > Subject: Fringe, exhaustive baseline search gives wrong solution
> > Date: Wednesday 14 September 2011
> > From: Thomas Krichbaum <tkrichbaum at mpifr-bonn.mpg.de>
> > To: "aips, daip" <daip at nrao.edu>
> >
> > Hi,
> >
> > I use FRING in version 'new' and 'tst'. I run it in the exhaustive baseline search mode using ap5=1 and ap7=1.
> > This is necessary since the data have low SNR (3mm-VLBI).
> >
> > The parms are set like this:
> > REFANT 5
> > SEARCH 12 11 3 4 13 2 0
> > SOLINT 4
> > SOLSUB 2
> > SOLMIN 1
> > APARM 2 0 0 0 1 2 4 0 1 0
> > DPARM 2 500 500 1 0 0 1 0
> >
> > As in some earlier versions, I again encounter 'wrong' solutions, which appear occassionally.
> > I thought that bug was fixed some time ago.
> >
> > In the coarse search I see phases above 360 deg or even with "****".
> >
> > The POSSM plot shows that the delays on some baselines come out wrongly.
> >
> > When I switch off exhaustive mode (set aparm9=0) the effect seems to dissappear. However
> > that mode gives too few solutions, since FRINGE does not cycle through the full antenna list.
> >
> > Here the prtmsg output for a particular scan:
> >
> > 1 3 14-SEP-2011 19:12:29 FRING IF number = 1 Poln. = 1
> > 1 3 14-SEP-2011 19:12:29 FRING Fitted phases, rates, delays and SNR: [ P = phase(deg),
> > 1 3 14-SEP-2011 19:12:29 FRING R = rate(mHz), D = Single-Band Delay(nsec), S = SNR ]
> > 1 3 14-SEP-2011 19:12:29 FRING R = rate(mHz), D = Single-Band Delay(nsec), S = SNR ]
> > 1 3 14-SEP-2011 19:12:29 FRING Ant(01): Phas=-959.6 rate= -1.81 delay= 2.86 SNR= 20.4
> > 1 3 14-SEP-2011 19:12:29 FRING Ant(03): Phas=****** rate= 27.16 delay= -11.47 SNR= 21.6
> > 1 3 14-SEP-2011 19:12:29 FRING Ant(04): Phas=****** rate= 0.74 delay= 3.06 SNR= 21.4
> > 1 3 14-SEP-2011 19:12:29 FRING Ant(07): Phas=****** rate= 17.50 delay= 2.02 SNR= 20.2
> > 1 3 14-SEP-2011 19:12:29 FRING Ant(08): Phas=-958.2 rate= -24.19 delay= -0.23 SNR= 18.6
> > 1 3 14-SEP-2011 19:12:29 FRING Ant(10): Phas=****** rate= -2.38 delay= 1.83 SNR= 21.5
> > 1 3 14-SEP-2011 19:12:29 FRING Ant(11): Phas=****** rate= 2.69 delay= 2.66 SNR= 22.1
> > 1 3 14-SEP-2011 19:12:29 FRING Ant(12): Phas=****** rate= -4.39 delay= 3.46 SNR= 22.1
> > 1 3 14-SEP-2011 19:12:29 FRING Standard RMS errors (deg, mHz, nsec):
> >
> >
> > Is this a bug ?
> >
> >
> > best regards, Thomas
> >
> >
> >
>
>
--
Thomas P. Krichbaum
Max-Planck-Institut für Radioastronomie
Auf dem Hügel 69
D-53121 Bonn / Germany
Tel. : (Germany +49)-228-525-295
Fax : (Germany +49)-228-525-229
e-mail: tkrichbaum at mpifr-bonn.mpg.de
URL: http://www.mpifr-bonn.mpg.de/staff/tkrichbaum
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