Exclusions from DuchampΒΆ

Selavy does not implement all of the features available in Duchamp. This is due to a number of factors:

  • We do not have the Duchamp graphics capabilities enabled, since pgplot is not included in the askapsoft code tree.
  • The FDR method is not implemented. This method uses all the data to find the optimum threshold, and it is not completely clear how this works in the distributed case, when a given worker only sees part of the data. It could potentially be included in the variable-threshold option, but would be very expensive computationally.
  • The baseline-subtraction option has not been impelemented - it would require additional work to pass the baseline values between the workers and the master, and has not been a priority.
  • Trimming of blank pixels has not been implemented.
  • Reading previously-created smoothed or reconstructed versions of the image has not been implemented.
  • Writing of FITS images (smoothed / reconstructed / mask / moment mask) is allowed, but only in the case of serial operation and when the input image is a FITS image (due to the way the code works - rewriting this has not been a priority). This was implemented to allow the export of the mask file in particular, to allow testing and comparison of the new algorithms.
  • Reprocessing a source list from a previous Duchamp/Selavy run has not been made available, although it is possible to write the catalogue to a binary catalogue that can be used in Duchamp (to, for instance, examine the graphical output for detected sources).

The following table lists Duchamp input parameters that will not work in Selavy - if they are included in the input parameter set, a warning message will be written to the log.

Parameter Reason for exclusion
flagPlotSpectra No graphics capabilities
flagPlotIndividualSpectra No graphics capabilities
spectraFile No graphics capabilities
flagMaps No graphics capabilities
detectMap No graphics capabilities
momentMap No graphics capabilities
flagXOutput No graphics capabilities
drawBlankEdges No graphics capabilities
spectralMethod No graphics capabilities
flagFDR FDR method not implemented
alphaFDR FDR method not implemented
FDRnumCorChan FDR method not implemented
flagBaseline Baseline-subtraction not impelemented
baselineType Baseline-subtraction not impelemented
baselineBoxWidth Baseline-subtraction not impelemented
flagOutputBaseline Baseline-subtraction not impelemented
fileOutputBaseline Baseline-subtraction not impelemented
flagReconExists Reading of previously-made FITS files not implemented
reconFile Reading of previously-made FITS files not implemented
flagSmoothExists Reading of previously-made FITS files not implemented
smoothFile Reading of previously-made FITS files not implemented
flagTrim Trimming not implemented
newFluxUnits Not implemented - not used in the ASKAP context.