Scantable vs MS

Issues

• changing ASAP to use MS underneath means rewriting almost all methods
  • everything is based on row/Vector operations
• Scantable stores polarisations individually, MS stores them in a matrix
  • no referencing possible - requires copying
• Scantables stores Coordinates (per band), MS stores per channel information
• MS is overkill for SD data

Solutions

• change Scantable schema closer to MS to allow future move.
• write direct MS -> Scantable filler
  • only copy when necessary
  • faster
  • both are based on casa::Table so clever things can be done
  • all non-asap relevant information could be copied/referenced
• write Scantable -> MS writer
  • preserve all (most) information/meta-data
• don't use MS, use ALMA to Scantable Filler ;-)
• trial implementation of complex functions e.g. freqAlign/polarimetry against MS. Keep api.