Threemiles,
Data are from Air Data Computer. No data are calculated outside the airframe. Most likely recorded FDR data will appear 100% the same, albeit at a higher sampling rate.
MSL altitiude is from GPS (height over ellipsoid) and transmitted as an offset to QNE baro altitude.
Open remains the source of VS. There are two options: GPS or Baro. Depends on the supplier of the avionics.
Thanks for that. Great explanation. BTW, have you noticed how on the TCAS display how the an aircraft ahead can jump around in azimuth and also how a level aircraft ahead can show alternating climbs and descents with changes of around 100ft?