Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://www.atnf.csiro.au/vlbi/dokuwiki/lib/exe/fetch.php/difx/socorro2010/jmgeodesy.pdf Äàòà èçìåíåíèÿ: Tue Nov 16 20:47:46 2010 Äàòà èíäåêñèðîâàíèÿ: Tue Apr 12 12:35:23 2016 Êîäèðîâêà: koi8-r Ïîèñêîâûå ñëîâà: ðåëÿòèâèñòñêîå äâèæåíèå

DiFX for geodesy/Geodesy tools for DiFX

PCal extraction in DiFX

Verification

Bug Reports and Testing

References

Improving Accuracy in DiFX
John Morgan (ICRAR, Perth, Australia)

DiFX Workshop Socorro Monday 15 November 2010


DiFX for geodesy/Geodesy tools for DiFX

PCal extraction in DiFX

Verification

Bug Reports and Testing

References

Overview

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DiFX for geodesy/Geodesy tools for DiFX PCal extraction in DiFX Verification Bug Reports and Testing Unit testing

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DiFX for geodesy/Geodesy tools for DiFX

PCal extraction in DiFX

Verification

Bug Reports and Testing

References

difx2mark4

· It works! · Some tidying up of the code to be done · four fit reference time · obser vation number (different from the alphanumeric obscode) · lots of scope for sharing code with difx2fits · Move code from difx2fits to difxio · Generalise · Multiple scans conver ted at once · Multiple scans in a job


DiFX for geodesy/Geodesy tools for DiFX

PCal extraction in DiFX

Verification

Bug Reports and Testing

References

Fourfit

· Highly desirable for geodesy work · Also extremely useful for data checking · supercharged sniffer


DiFX for geodesy/Geodesy tools for DiFX

PCal extraction in DiFX

Verification

Bug Reports and Testing

References

PCal extraction
(typically) 1µs pulses injected (for 1 MHz picket fence in frequency space)
· VLBA (and field system?) extract tone amplitudes and phases

at the station
· Most geodetic correlators (e.g. Bonn mk4) extract the tones

from the baseband data during correlation
· 1 or 2 tones per sub-band (as specified in vex file1 )

DiFX now supports pcal tone extraction!
· All tones in bandpass · Same integration time (accumulation period) as the visibilities

1

bug in sched?


DiFX for geodesy/Geodesy tools for DiFX

PCal extraction in DiFX

Verification

Bug Reports and Testing

References

PCal and fourfit

· fourfit already handles multiple (>2) tones per subband · seems to be fine


DiFX for geodesy/Geodesy tools for DiFX

PCal extraction in DiFX

Verification

Bug Reports and Testing

References

PCal and difx2fits

· AIPS expects two tones per IF · If there are more it uses the outer two tones · This may not be desirable · Idea is to have difx2fits select the only two tones to write out

to fits
· This is suppor ted in the input file format and in a branch of

difx2fits
· Missing link is to have vex2difx read the correct tones from

the vex file

Better may be to modify AIPS to allow selection of pcal tones to be used by PCCOR


DiFX for geodesy/Geodesy tools for DiFX

PCal extraction in DiFX

Verification

Bug Reports and Testing

References

Advanced PCal

· Useful to be able to plot pcal amplitude vs. phase · Useful to be able to plot pcal amplitude against Tsys · Use all pcals to contribute to the solution · avoids necessity to fringe fit in PCCOR · Use pcal amplitudes for amplitude calibration? · Global VLBI correlated at Socorro · EVN correlated in Bonn


DiFX for geodesy/Geodesy tools for DiFX

PCal extraction in DiFX

Verification

Bug Reports and Testing

References

Loose Ends

· Cable Cal. · Works OK for VLBA (vestigal `pcal' file) · Sampler statistics etc. · Getting a version of HOPS which is compatible with DiFX · DiFX subversion repositor y??


DiFX for geodesy/Geodesy tools for DiFX

PCal extraction in DiFX

Verification

Bug Reports and Testing

References

Verifying DiFX for Geodesy
· Tingay et al. (2009) verified amplitude and phase · 1 minute of data from the middle of a fringe finder scan for a few VLBA antennas · central 50% of the bandpass · almost per fect agreement in amplitude and phase · Petrov has done some verification (seems to be happy) · Would be good to do a direct comparison of Mark4 and

DiFX
· All data contributing to solution · PCal extraction · Model accountability

· Compare the final geodesy product (CALC/SOLVE database)


DiFX for geodesy/Geodesy tools for DiFX

PCal extraction in DiFX

Verification

Bug Reports and Testing

References

Full Audit of differences between Mark4 and DiFX

· Sync'ing at the start of reading a baseband file · Handling of errors in baseband data · Integration times


DiFX for geodesy/Geodesy tools for DiFX

PCal extraction in DiFX

Verification

Bug Reports and Testing

References

Questions?


DiFX for geodesy/Geodesy tools for DiFX

PCal extraction in DiFX

Verification

Bug Reports and Testing

References

Bug Reports

· Please can we have a bug report system? · Web-based inter face for repor ting bugs · Email goes to all relevant developers · Assign priority · Feature requests? · resolutions posted to an FAQs? · Really useful for beginners, advanced users and developers


DiFX for geodesy/Geodesy tools for DiFX Unit testing

PCal extraction in DiFX

Verification

Bug Reports and Testing

References

Unit testing

A set of tests built in to the source code to test for correct behaviour
· Bad for high-level tests (Adam's stuff covers this) · Bad for performance testing · Good for low-level tests (configuration, correctness of

individual functions) "Test-driven" or "Extreme Programming" (probably not what we want to do)
· Write the tests before the code


DiFX for geodesy/Geodesy tools for DiFX Unit testing

PCal extraction in DiFX

Verification

Bug Reports and Testing

References

Making a start with Unit testing

· Choose a framework2 · Start with some tests to check for model ac · mpifxcorr and difx2fits use different code model (e.g. combining clock and CALC d · Not likely that mpifxcorr will adapt to use

countability
to calculate the elay) difxio (?)

· devise same tests for mpifxcorr and difxio · this would provide a check

· Integrate with Autotools (make check) · Integrate with Subversion?

See üüò »» ºâñûæ ñæ ºð ü» ñ » üÿï» ¾º üÿï for an overview. Also Wettzell have their own system, available on request.
2


DiFX for geodesy/Geodesy tools for DiFX Unit testing

PCal extraction in DiFX

Verification

Bug Reports and Testing

References

Continuing with Unit testing

· Developers can add tests when they submit/triage/fix bugs · Core developers will inevitably make assumptions which

may break for some power users
· VLBI2010 developers (for example) can add tests to avoid

these problems


DiFX for geodesy/Geodesy tools for DiFX Unit testing

PCal extraction in DiFX

Verification

Bug Reports and Testing

References

References

Tingay, S. J., Alef, W., Graham, D., & Deller, A. T. 2009, Journal of Geodesy, 83, 1061