At Earth Signal we reconcile the monitor and baseline surveys in receiver line, receiver station, shot line, shot station, elevation, and recording patches. During reconciliation, different station skid allowances are tested to see the resulting CMP fold outputs. Without proper fold and geometry reconciliation, differences between the stacks cannot necessarily be attributed to 4D time-lapse effects. Therefore, to achieve consistent 4D responses, the baseline and monitor surveys need to have 4D geometry reconciliation applied every time a new survey is acquired. Our iterative NRMS Amplitude QC measures the repeatability of the traces between the baseline and monitor. RMS amplitudes can be sensitive to phase, static and amplitude differences so it is important to run NRMS QC’s after every process to make sure we are not introducing a time lapse response that is due to a processing artifact. Low NRMS values indicate high repeatability between surveys.