- For a given period (usually 14 days) arrange the data (per beam) into 10m intervals, based upon the sidereal time.
- Take the median of the 600 samples.
- For each interval sort the data.
- Discard the largest value as it may be corrupted by interference (e.g. lightning, solar radio emissions) or scintillation.
- Take the mean of the next two largest values.
- Repeat for each beam and each 10m interval in the sidereal day.
An alternative method sometimes is employed is based on the above, but with a sliding median of 1s resolution data. Thus 86164 blocks, per beam, per sidereal day, are considered.